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Message-ID: <20170703070104.bxy27otaalvv3ii3@gmail.com>
Date: Mon, 3 Jul 2017 09:01:04 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, Josh Poimboeuf <jpoimboe@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
"H. Peter Anvin" <hpa@...or.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [GIT PULL] objtool changes for v4.13
Linus,
Please pull the latest core-objtool-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core-objtool-for-linus
# HEAD: 2513cbf9d622d85268655bfd787d4f004342cfc9 objtool: Silence warnings for functions which use IRET
This is an extensive rewrite of the objdump tool to track all stack pointer
modifications through the machine instructions of disassembled functions found in
kernel .o files.
This re-design removes the prior dependency on CONFIG_FRAME_POINTERS=y, with the
goal to prepare the tool to generate kernel debuginfo data in the future. There's
also an increase in checking/tracking robustness as a side effect as well.
No (intended) changes to existing functionality.
Thanks,
Ingo
------------------>
Josh Poimboeuf (4):
objtool: Move checking code to check.c
objtool, x86: Add several functions and files to the objtool whitelist
objtool: Implement stack validation 2.0
objtool: Silence warnings for functions which use IRET
arch/x86/crypto/Makefile | 2 +
arch/x86/crypto/sha1-mb/Makefile | 2 +
arch/x86/crypto/sha256-mb/Makefile | 2 +
arch/x86/kernel/Makefile | 1 +
arch/x86/kernel/acpi/Makefile | 2 +
arch/x86/kernel/kprobes/opt.c | 9 +-
arch/x86/kernel/reboot.c | 2 +
arch/x86/kvm/svm.c | 2 +
arch/x86/kvm/vmx.c | 3 +
arch/x86/lib/msr-reg.S | 8 +-
arch/x86/net/Makefile | 2 +
arch/x86/platform/efi/Makefile | 1 +
arch/x86/power/Makefile | 2 +
arch/x86/xen/Makefile | 3 +
kernel/kexec_core.c | 4 +-
tools/objtool/Build | 1 +
tools/objtool/Documentation/stack-validation.txt | 153 +-
tools/objtool/Makefile | 2 +-
tools/objtool/arch.h | 64 +-
tools/objtool/arch/x86/decode.c | 400 +++++-
tools/objtool/builtin-check.c | 1281 +----------------
tools/objtool/cfi.h | 55 +
tools/objtool/check.c | 1655 ++++++++++++++++++++++
tools/objtool/check.h | 66 +
tools/objtool/elf.c | 59 +-
tools/objtool/elf.h | 6 +-
tools/objtool/special.c | 6 +-
tools/objtool/warn.h | 10 +
28 files changed, 2352 insertions(+), 1451 deletions(-)
create mode 100644 tools/objtool/cfi.h
create mode 100644 tools/objtool/check.c
create mode 100644 tools/objtool/check.h
diff --git a/arch/x86/crypto/Makefile b/arch/x86/crypto/Makefile
index 34b3fa2889d1..9e32d40d71bd 100644
--- a/arch/x86/crypto/Makefile
+++ b/arch/x86/crypto/Makefile
@@ -2,6 +2,8 @@
# Arch-specific CryptoAPI modules.
#
+OBJECT_FILES_NON_STANDARD := y
+
avx_supported := $(call as-instr,vpxor %xmm0$(comma)%xmm0$(comma)%xmm0,yes,no)
avx2_supported := $(call as-instr,vpgatherdd %ymm0$(comma)(%eax$(comma)%ymm1\
$(comma)4)$(comma)%ymm2,yes,no)
diff --git a/arch/x86/crypto/sha1-mb/Makefile b/arch/x86/crypto/sha1-mb/Makefile
index 2f8756375df5..2e14acc3da25 100644
--- a/arch/x86/crypto/sha1-mb/Makefile
+++ b/arch/x86/crypto/sha1-mb/Makefile
@@ -2,6 +2,8 @@
# Arch-specific CryptoAPI modules.
#
+OBJECT_FILES_NON_STANDARD := y
+
avx2_supported := $(call as-instr,vpgatherdd %ymm0$(comma)(%eax$(comma)%ymm1\
$(comma)4)$(comma)%ymm2,yes,no)
ifeq ($(avx2_supported),yes)
diff --git a/arch/x86/crypto/sha256-mb/Makefile b/arch/x86/crypto/sha256-mb/Makefile
index 41089e7c400c..45b4fca6c4a8 100644
--- a/arch/x86/crypto/sha256-mb/Makefile
+++ b/arch/x86/crypto/sha256-mb/Makefile
@@ -2,6 +2,8 @@
# Arch-specific CryptoAPI modules.
#
+OBJECT_FILES_NON_STANDARD := y
+
avx2_supported := $(call as-instr,vpgatherdd %ymm0$(comma)(%eax$(comma)%ymm1\
$(comma)4)$(comma)%ymm2,yes,no)
ifeq ($(avx2_supported),yes)
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 4b994232cb57..3c7c419c4e3e 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -29,6 +29,7 @@ OBJECT_FILES_NON_STANDARD_head_$(BITS).o := y
OBJECT_FILES_NON_STANDARD_relocate_kernel_$(BITS).o := y
OBJECT_FILES_NON_STANDARD_ftrace_$(BITS).o := y
OBJECT_FILES_NON_STANDARD_test_nx.o := y
+OBJECT_FILES_NON_STANDARD_paravirt_patch_$(BITS).o := y
# If instrumentation of this dir is enabled, boot hangs during first second.
# Probably could be more selective here, but note that files related to irqs,
diff --git a/arch/x86/kernel/acpi/Makefile b/arch/x86/kernel/acpi/Makefile
index 26b78d86f25a..85a9e17e0dbc 100644
--- a/arch/x86/kernel/acpi/Makefile
+++ b/arch/x86/kernel/acpi/Makefile
@@ -1,3 +1,5 @@
+OBJECT_FILES_NON_STANDARD_wakeup_$(BITS).o := y
+
obj-$(CONFIG_ACPI) += boot.o
obj-$(CONFIG_ACPI_SLEEP) += sleep.o wakeup_$(BITS).o
obj-$(CONFIG_ACPI_APEI) += apei.o
diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index 901c640d152f..69ea0bc1cfa3 100644
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -28,6 +28,7 @@
#include <linux/kdebug.h>
#include <linux/kallsyms.h>
#include <linux/ftrace.h>
+#include <linux/frame.h>
#include <asm/text-patching.h>
#include <asm/cacheflush.h>
@@ -94,6 +95,7 @@ static void synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val)
}
asm (
+ "optprobe_template_func:\n"
".global optprobe_template_entry\n"
"optprobe_template_entry:\n"
#ifdef CONFIG_X86_64
@@ -131,7 +133,12 @@ asm (
" popf\n"
#endif
".global optprobe_template_end\n"
- "optprobe_template_end:\n");
+ "optprobe_template_end:\n"
+ ".type optprobe_template_func, @function\n"
+ ".size optprobe_template_func, .-optprobe_template_func\n");
+
+void optprobe_template_func(void);
+STACK_FRAME_NON_STANDARD(optprobe_template_func);
#define TMPL_MOVE_IDX \
((long)&optprobe_template_val - (long)&optprobe_template_entry)
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 2544700a2a87..67393fc88353 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -9,6 +9,7 @@
#include <linux/sched.h>
#include <linux/tboot.h>
#include <linux/delay.h>
+#include <linux/frame.h>
#include <acpi/reboot.h>
#include <asm/io.h>
#include <asm/apic.h>
@@ -123,6 +124,7 @@ void __noreturn machine_real_restart(unsigned int type)
#ifdef CONFIG_APM_MODULE
EXPORT_SYMBOL(machine_real_restart);
#endif
+STACK_FRAME_NON_STANDARD(machine_real_restart);
/*
* Some Apple MacBook and MacBookPro's needs reboot=p to be able to reboot
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index ba9891ac5c56..33460fcdeef9 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -36,6 +36,7 @@
#include <linux/slab.h>
#include <linux/amd-iommu.h>
#include <linux/hashtable.h>
+#include <linux/frame.h>
#include <asm/apic.h>
#include <asm/perf_event.h>
@@ -4906,6 +4907,7 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
mark_all_clean(svm->vmcb);
}
+STACK_FRAME_NON_STANDARD(svm_vcpu_run);
static void svm_set_cr3(struct kvm_vcpu *vcpu, unsigned long root)
{
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index ca5d2b93385c..1b469b6c762f 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -33,6 +33,7 @@
#include <linux/slab.h>
#include <linux/tboot.h>
#include <linux/hrtimer.h>
+#include <linux/frame.h>
#include "kvm_cache_regs.h"
#include "x86.h"
@@ -8652,6 +8653,7 @@ static void vmx_handle_external_intr(struct kvm_vcpu *vcpu)
);
}
}
+STACK_FRAME_NON_STANDARD(vmx_handle_external_intr);
static bool vmx_has_high_real_mode_segbase(void)
{
@@ -9028,6 +9030,7 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
vmx_recover_nmi_blocking(vmx);
vmx_complete_interrupts(vmx);
}
+STACK_FRAME_NON_STANDARD(vmx_vcpu_run);
static void vmx_switch_vmcs(struct kvm_vcpu *vcpu, struct loaded_vmcs *vmcs)
{
diff --git a/arch/x86/lib/msr-reg.S b/arch/x86/lib/msr-reg.S
index c81556409bbb..10ffa7e8519f 100644
--- a/arch/x86/lib/msr-reg.S
+++ b/arch/x86/lib/msr-reg.S
@@ -13,14 +13,14 @@
.macro op_safe_regs op
ENTRY(\op\()_safe_regs)
pushq %rbx
- pushq %rbp
+ pushq %r12
movq %rdi, %r10 /* Save pointer */
xorl %r11d, %r11d /* Return value */
movl (%rdi), %eax
movl 4(%rdi), %ecx
movl 8(%rdi), %edx
movl 12(%rdi), %ebx
- movl 20(%rdi), %ebp
+ movl 20(%rdi), %r12d
movl 24(%rdi), %esi
movl 28(%rdi), %edi
1: \op
@@ -29,10 +29,10 @@ ENTRY(\op\()_safe_regs)
movl %ecx, 4(%r10)
movl %edx, 8(%r10)
movl %ebx, 12(%r10)
- movl %ebp, 20(%r10)
+ movl %r12d, 20(%r10)
movl %esi, 24(%r10)
movl %edi, 28(%r10)
- popq %rbp
+ popq %r12
popq %rbx
ret
3:
diff --git a/arch/x86/net/Makefile b/arch/x86/net/Makefile
index 90568c33ddb0..fefb4b619598 100644
--- a/arch/x86/net/Makefile
+++ b/arch/x86/net/Makefile
@@ -1,4 +1,6 @@
#
# Arch-specific network modules
#
+OBJECT_FILES_NON_STANDARD_bpf_jit.o += y
+
obj-$(CONFIG_BPF_JIT) += bpf_jit.o bpf_jit_comp.o
diff --git a/arch/x86/platform/efi/Makefile b/arch/x86/platform/efi/Makefile
index f1d83b34c329..2f56e1ed61c3 100644
--- a/arch/x86/platform/efi/Makefile
+++ b/arch/x86/platform/efi/Makefile
@@ -1,4 +1,5 @@
OBJECT_FILES_NON_STANDARD_efi_thunk_$(BITS).o := y
+OBJECT_FILES_NON_STANDARD_efi_stub_$(BITS).o := y
obj-$(CONFIG_EFI) += quirks.o efi.o efi_$(BITS).o efi_stub_$(BITS).o
obj-$(CONFIG_EARLY_PRINTK_EFI) += early_printk.o
diff --git a/arch/x86/power/Makefile b/arch/x86/power/Makefile
index a6a198c33623..05041871ac90 100644
--- a/arch/x86/power/Makefile
+++ b/arch/x86/power/Makefile
@@ -1,3 +1,5 @@
+OBJECT_FILES_NON_STANDARD_hibernate_asm_$(BITS).o := y
+
# __restore_processor_state() restores %gs after S3 resume and so should not
# itself be stack-protected
nostackp := $(call cc-option, -fno-stack-protector)
diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
index fffb0a16f9e3..bced7a369a11 100644
--- a/arch/x86/xen/Makefile
+++ b/arch/x86/xen/Makefile
@@ -1,3 +1,6 @@
+OBJECT_FILES_NON_STANDARD_xen-asm_$(BITS).o := y
+OBJECT_FILES_NON_STANDARD_xen-pvh.o := y
+
ifdef CONFIG_FUNCTION_TRACER
# Do not profile debug and lowlevel utilities
CFLAGS_REMOVE_spinlock.o = -pg
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index ae1a3ba24df5..154ffb489b93 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -38,6 +38,7 @@
#include <linux/syscore_ops.h>
#include <linux/compiler.h>
#include <linux/hugetlb.h>
+#include <linux/frame.h>
#include <asm/page.h>
#include <asm/sections.h>
@@ -874,7 +875,7 @@ int kexec_load_disabled;
* only when panic_cpu holds the current CPU number; this is the only CPU
* which processes crash_kexec routines.
*/
-void __crash_kexec(struct pt_regs *regs)
+void __noclone __crash_kexec(struct pt_regs *regs)
{
/* Take the kexec_mutex here to prevent sys_kexec_load
* running on one cpu from replacing the crash kernel
@@ -896,6 +897,7 @@ void __crash_kexec(struct pt_regs *regs)
mutex_unlock(&kexec_mutex);
}
}
+STACK_FRAME_NON_STANDARD(__crash_kexec);
void crash_kexec(struct pt_regs *regs)
{
diff --git a/tools/objtool/Build b/tools/objtool/Build
index d6cdece5e58b..6f2e1987c4d9 100644
--- a/tools/objtool/Build
+++ b/tools/objtool/Build
@@ -1,5 +1,6 @@
objtool-y += arch/$(SRCARCH)/
objtool-y += builtin-check.o
+objtool-y += check.o
objtool-y += elf.o
objtool-y += special.o
objtool-y += objtool.o
diff --git a/tools/objtool/Documentation/stack-validation.txt b/tools/objtool/Documentation/stack-validation.txt
index 55a60d331f47..17c1195f11f4 100644
--- a/tools/objtool/Documentation/stack-validation.txt
+++ b/tools/objtool/Documentation/stack-validation.txt
@@ -127,28 +127,13 @@ b) 100% reliable stack traces for DWARF enabled kernels
c) Higher live patching compatibility rate
- (NOTE: This is not yet implemented)
-
- Currently with CONFIG_LIVEPATCH there's a basic live patching
- framework which is safe for roughly 85-90% of "security" fixes. But
- patches can't have complex features like function dependency or
- prototype changes, or data structure changes.
-
- There's a strong need to support patches which have the more complex
- features so that the patch compatibility rate for security fixes can
- eventually approach something resembling 100%. To achieve that, a
- "consistency model" is needed, which allows tasks to be safely
- transitioned from an unpatched state to a patched state.
-
- One of the key requirements of the currently proposed livepatch
- consistency model [*] is that it needs to walk the stack of each
- sleeping task to determine if it can be transitioned to the patched
- state. If objtool can ensure that stack traces are reliable, this
- consistency model can be used and the live patching compatibility
- rate can be improved significantly.
-
- [*] https://lkml.kernel.org/r/cover.1423499826.git.jpoimboe@redhat.com
+ Livepatch has an optional "consistency model", which is needed for
+ more complex patches. In order for the consistency model to work,
+ stack traces need to be reliable (or an unreliable condition needs to
+ be detectable). Objtool makes that possible.
+ For more details, see the livepatch documentation in the Linux kernel
+ source tree at Documentation/livepatch/livepatch.txt.
Rules
-----
@@ -201,80 +186,84 @@ Rules
return normally.
-Errors in .S files
-------------------
+Objtool warnings
+----------------
-If you're getting an error in a compiled .S file which you don't
-understand, first make sure that the affected code follows the above
-rules.
+For asm files, if you're getting an error which doesn't make sense,
+first make sure that the affected code follows the above rules.
+
+For C files, the common culprits are inline asm statements and calls to
+"noreturn" functions. See below for more details.
+
+Another possible cause for errors in C code is if the Makefile removes
+-fno-omit-frame-pointer or adds -fomit-frame-pointer to the gcc options.
Here are some examples of common warnings reported by objtool, what
they mean, and suggestions for how to fix them.
-1. asm_file.o: warning: objtool: func()+0x128: call without frame pointer save/setup
+1. file.o: warning: objtool: func()+0x128: call without frame pointer save/setup
The func() function made a function call without first saving and/or
- updating the frame pointer.
-
- If func() is indeed a callable function, add proper frame pointer
- logic using the FRAME_BEGIN and FRAME_END macros. Otherwise, remove
- its ELF function annotation by changing ENDPROC to END.
+ updating the frame pointer, and CONFIG_FRAME_POINTER is enabled.
- If you're getting this error in a .c file, see the "Errors in .c
- files" section.
+ If the error is for an asm file, and func() is indeed a callable
+ function, add proper frame pointer logic using the FRAME_BEGIN and
+ FRAME_END macros. Otherwise, if it's not a callable function, remove
+ its ELF function annotation by changing ENDPROC to END, and instead
+ use the manual CFI hint macros in asm/undwarf.h.
+ If it's a GCC-compiled .c file, the error may be because the function
+ uses an inline asm() statement which has a "call" instruction. An
+ asm() statement with a call instruction must declare the use of the
+ stack pointer in its output operand. For example, on x86_64:
-2. asm_file.o: warning: objtool: .text+0x53: return instruction outside of a callable function
-
- A return instruction was detected, but objtool couldn't find a way
- for a callable function to reach the instruction.
+ register void *__sp asm("rsp");
+ asm volatile("call func" : "+r" (__sp));
- If the return instruction is inside (or reachable from) a callable
- function, the function needs to be annotated with the ENTRY/ENDPROC
- macros.
+ Otherwise the stack frame may not get created before the call.
- If you _really_ need a return instruction outside of a function, and
- are 100% sure that it won't affect stack traces, you can tell
- objtool to ignore it. See the "Adding exceptions" section below.
+2. file.o: warning: objtool: .text+0x53: unreachable instruction
-3. asm_file.o: warning: objtool: func()+0x9: function has unreachable instruction
+ Objtool couldn't find a code path to reach the instruction.
- The instruction lives inside of a callable function, but there's no
- possible control flow path from the beginning of the function to the
- instruction.
+ If the error is for an asm file, and the instruction is inside (or
+ reachable from) a callable function, the function should be annotated
+ with the ENTRY/ENDPROC macros (ENDPROC is the important one).
+ Otherwise, the code should probably be annotated with the CFI hint
+ macros in asm/undwarf.h so objtool and the unwinder can know the
+ stack state associated with the code.
- If the instruction is actually needed, and it's actually in a
- callable function, ensure that its function is properly annotated
- with ENTRY/ENDPROC.
+ If you're 100% sure the code won't affect stack traces, or if you're
+ a just a bad person, you can tell objtool to ignore it. See the
+ "Adding exceptions" section below.
If it's not actually in a callable function (e.g. kernel entry code),
change ENDPROC to END.
-4. asm_file.o: warning: objtool: func(): can't find starting instruction
+4. file.o: warning: objtool: func(): can't find starting instruction
or
- asm_file.o: warning: objtool: func()+0x11dd: can't decode instruction
+ file.o: warning: objtool: func()+0x11dd: can't decode instruction
- Did you put data in a text section? If so, that can confuse
+ Does the file have data in a text section? If so, that can confuse
objtool's instruction decoder. Move the data to a more appropriate
section like .data or .rodata.
-5. asm_file.o: warning: objtool: func()+0x6: kernel entry/exit from callable instruction
-
- This is a kernel entry/exit instruction like sysenter or sysret.
- Such instructions aren't allowed in a callable function, and are most
- likely part of the kernel entry code.
+5. file.o: warning: objtool: func()+0x6: unsupported instruction in callable function
- If the instruction isn't actually in a callable function, change
- ENDPROC to END.
+ This is a kernel entry/exit instruction like sysenter or iret. Such
+ instructions aren't allowed in a callable function, and are most
+ likely part of the kernel entry code. They should usually not have
+ the callable function annotation (ENDPROC) and should always be
+ annotated with the CFI hint macros in asm/undwarf.h.
-6. asm_file.o: warning: objtool: func()+0x26: sibling call from callable instruction with changed frame pointer
+6. file.o: warning: objtool: func()+0x26: sibling call from callable instruction with modified stack frame
- This is a dynamic jump or a jump to an undefined symbol. Stacktool
+ This is a dynamic jump or a jump to an undefined symbol. Objtool
assumed it's a sibling call and detected that the frame pointer
wasn't first restored to its original state.
@@ -282,24 +271,28 @@ they mean, and suggestions for how to fix them.
destination code to the local file.
If the instruction is not actually in a callable function (e.g.
- kernel entry code), change ENDPROC to END.
+ kernel entry code), change ENDPROC to END and annotate manually with
+ the CFI hint macros in asm/undwarf.h.
-7. asm_file: warning: objtool: func()+0x5c: frame pointer state mismatch
+7. file: warning: objtool: func()+0x5c: stack state mismatch
The instruction's frame pointer state is inconsistent, depending on
which execution path was taken to reach the instruction.
- Make sure the function pushes and sets up the frame pointer (for
- x86_64, this means rbp) at the beginning of the function and pops it
- at the end of the function. Also make sure that no other code in the
- function touches the frame pointer.
+ Make sure that, when CONFIG_FRAME_POINTER is enabled, the function
+ pushes and sets up the frame pointer (for x86_64, this means rbp) at
+ the beginning of the function and pops it at the end of the function.
+ Also make sure that no other code in the function touches the frame
+ pointer.
+ Another possibility is that the code has some asm or inline asm which
+ does some unusual things to the stack or the frame pointer. In such
+ cases it's probably appropriate to use the CFI hint macros in
+ asm/undwarf.h.
-Errors in .c files
-------------------
-1. c_file.o: warning: objtool: funcA() falls through to next function funcB()
+8. file.o: warning: objtool: funcA() falls through to next function funcB()
This means that funcA() doesn't end with a return instruction or an
unconditional jump, and that objtool has determined that the function
@@ -318,22 +311,6 @@ Errors in .c files
might be corrupt due to a gcc bug. For more details, see:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70646
-2. If you're getting any other objtool error in a compiled .c file, it
- may be because the file uses an asm() statement which has a "call"
- instruction. An asm() statement with a call instruction must declare
- the use of the stack pointer in its output operand. For example, on
- x86_64:
-
- register void *__sp asm("rsp");
- asm volatile("call func" : "+r" (__sp));
-
- Otherwise the stack frame may not get created before the call.
-
-3. Another possible cause for errors in C code is if the Makefile removes
- -fno-omit-frame-pointer or adds -fomit-frame-pointer to the gcc options.
-
-Also see the above section for .S file errors for more information what
-the individual error messages mean.
If the error doesn't seem to make sense, it could be a bug in objtool.
Feel free to ask the objtool maintainer for help.
diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index 27e019c09bd2..0e2765e243c0 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -25,7 +25,7 @@ OBJTOOL_IN := $(OBJTOOL)-in.o
all: $(OBJTOOL)
INCLUDES := -I$(srctree)/tools/include -I$(srctree)/tools/arch/$(HOSTARCH)/include/uapi
-CFLAGS += -Wall -Werror $(EXTRA_WARNINGS) -fomit-frame-pointer -O2 -g $(INCLUDES)
+CFLAGS += -Wall -Werror $(EXTRA_WARNINGS) -Wno-switch-default -Wno-switch-enum -fomit-frame-pointer -O2 -g $(INCLUDES)
LDFLAGS += -lelf $(LIBSUBCMD)
# Allow old libelf to be used:
diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
index a59e061c0b4a..21aeca874edb 100644
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -19,25 +19,63 @@
#define _ARCH_H
#include <stdbool.h>
+#include <linux/list.h>
#include "elf.h"
+#include "cfi.h"
-#define INSN_FP_SAVE 1
-#define INSN_FP_SETUP 2
-#define INSN_FP_RESTORE 3
-#define INSN_JUMP_CONDITIONAL 4
-#define INSN_JUMP_UNCONDITIONAL 5
-#define INSN_JUMP_DYNAMIC 6
-#define INSN_CALL 7
-#define INSN_CALL_DYNAMIC 8
-#define INSN_RETURN 9
-#define INSN_CONTEXT_SWITCH 10
-#define INSN_NOP 11
-#define INSN_OTHER 12
+#define INSN_JUMP_CONDITIONAL 1
+#define INSN_JUMP_UNCONDITIONAL 2
+#define INSN_JUMP_DYNAMIC 3
+#define INSN_CALL 4
+#define INSN_CALL_DYNAMIC 5
+#define INSN_RETURN 6
+#define INSN_CONTEXT_SWITCH 7
+#define INSN_STACK 8
+#define INSN_NOP 9
+#define INSN_OTHER 10
#define INSN_LAST INSN_OTHER
+enum op_dest_type {
+ OP_DEST_REG,
+ OP_DEST_REG_INDIRECT,
+ OP_DEST_MEM,
+ OP_DEST_PUSH,
+ OP_DEST_LEAVE,
+};
+
+struct op_dest {
+ enum op_dest_type type;
+ unsigned char reg;
+ int offset;
+};
+
+enum op_src_type {
+ OP_SRC_REG,
+ OP_SRC_REG_INDIRECT,
+ OP_SRC_CONST,
+ OP_SRC_POP,
+ OP_SRC_ADD,
+ OP_SRC_AND,
+};
+
+struct op_src {
+ enum op_src_type type;
+ unsigned char reg;
+ int offset;
+};
+
+struct stack_op {
+ struct op_dest dest;
+ struct op_src src;
+};
+
+void arch_initial_func_cfi_state(struct cfi_state *state);
+
int arch_decode_instruction(struct elf *elf, struct section *sec,
unsigned long offset, unsigned int maxlen,
unsigned int *len, unsigned char *type,
- unsigned long *displacement);
+ unsigned long *immediate, struct stack_op *op);
+
+bool arch_callee_saved_reg(unsigned char reg);
#endif /* _ARCH_H */
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c
index 6ac99e3266eb..a36c2eba64e7 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -27,6 +27,17 @@
#include "../../arch.h"
#include "../../warn.h"
+static unsigned char op_to_cfi_reg[][2] = {
+ {CFI_AX, CFI_R8},
+ {CFI_CX, CFI_R9},
+ {CFI_DX, CFI_R10},
+ {CFI_BX, CFI_R11},
+ {CFI_SP, CFI_R12},
+ {CFI_BP, CFI_R13},
+ {CFI_SI, CFI_R14},
+ {CFI_DI, CFI_R15},
+};
+
static int is_x86_64(struct elf *elf)
{
switch (elf->ehdr.e_machine) {
@@ -40,24 +51,50 @@ static int is_x86_64(struct elf *elf)
}
}
+bool arch_callee_saved_reg(unsigned char reg)
+{
+ switch (reg) {
+ case CFI_BP:
+ case CFI_BX:
+ case CFI_R12:
+ case CFI_R13:
+ case CFI_R14:
+ case CFI_R15:
+ return true;
+
+ case CFI_AX:
+ case CFI_CX:
+ case CFI_DX:
+ case CFI_SI:
+ case CFI_DI:
+ case CFI_SP:
+ case CFI_R8:
+ case CFI_R9:
+ case CFI_R10:
+ case CFI_R11:
+ case CFI_RA:
+ default:
+ return false;
+ }
+}
+
int arch_decode_instruction(struct elf *elf, struct section *sec,
unsigned long offset, unsigned int maxlen,
unsigned int *len, unsigned char *type,
- unsigned long *immediate)
+ unsigned long *immediate, struct stack_op *op)
{
struct insn insn;
- int x86_64;
- unsigned char op1, op2, ext;
+ int x86_64, sign;
+ unsigned char op1, op2, rex = 0, rex_b = 0, rex_r = 0, rex_w = 0,
+ modrm = 0, modrm_mod = 0, modrm_rm = 0, modrm_reg = 0,
+ sib = 0;
x86_64 = is_x86_64(elf);
if (x86_64 == -1)
return -1;
- insn_init(&insn, (void *)(sec->data + offset), maxlen, x86_64);
+ insn_init(&insn, sec->data->d_buf + offset, maxlen, x86_64);
insn_get_length(&insn);
- insn_get_opcode(&insn);
- insn_get_modrm(&insn);
- insn_get_immediate(&insn);
if (!insn_complete(&insn)) {
WARN_FUNC("can't decode instruction", sec, offset);
@@ -73,67 +110,323 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
op1 = insn.opcode.bytes[0];
op2 = insn.opcode.bytes[1];
+ if (insn.rex_prefix.nbytes) {
+ rex = insn.rex_prefix.bytes[0];
+ rex_w = X86_REX_W(rex) >> 3;
+ rex_r = X86_REX_R(rex) >> 2;
+ rex_b = X86_REX_B(rex);
+ }
+
+ if (insn.modrm.nbytes) {
+ modrm = insn.modrm.bytes[0];
+ modrm_mod = X86_MODRM_MOD(modrm);
+ modrm_reg = X86_MODRM_REG(modrm);
+ modrm_rm = X86_MODRM_RM(modrm);
+ }
+
+ if (insn.sib.nbytes)
+ sib = insn.sib.bytes[0];
+
switch (op1) {
- case 0x55:
- if (!insn.rex_prefix.nbytes)
- /* push rbp */
- *type = INSN_FP_SAVE;
+
+ case 0x1:
+ case 0x29:
+ if (rex_w && !rex_b && modrm_mod == 3 && modrm_rm == 4) {
+
+ /* add/sub reg, %rsp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
+ op->dest.type = OP_SRC_REG;
+ op->dest.reg = CFI_SP;
+ }
+ break;
+
+ case 0x50 ... 0x57:
+
+ /* push reg */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG;
+ op->src.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
+ op->dest.type = OP_DEST_PUSH;
+
break;
- case 0x5d:
- if (!insn.rex_prefix.nbytes)
- /* pop rbp */
- *type = INSN_FP_RESTORE;
+ case 0x58 ... 0x5f:
+
+ /* pop reg */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_POP;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
+
+ break;
+
+ case 0x68:
+ case 0x6a:
+ /* push immediate */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_CONST;
+ op->dest.type = OP_DEST_PUSH;
break;
case 0x70 ... 0x7f:
*type = INSN_JUMP_CONDITIONAL;
break;
+ case 0x81:
+ case 0x83:
+ if (rex != 0x48)
+ break;
+
+ if (modrm == 0xe4) {
+ /* and imm, %rsp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_AND;
+ op->src.reg = CFI_SP;
+ op->src.offset = insn.immediate.value;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+ }
+
+ if (modrm == 0xc4)
+ sign = 1;
+ else if (modrm == 0xec)
+ sign = -1;
+ else
+ break;
+
+ /* add/sub imm, %rsp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_SP;
+ op->src.offset = insn.immediate.value * sign;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+
case 0x89:
- if (insn.rex_prefix.nbytes == 1 &&
- insn.rex_prefix.bytes[0] == 0x48 &&
- insn.modrm.nbytes && insn.modrm.bytes[0] == 0xe5)
- /* mov rsp, rbp */
- *type = INSN_FP_SETUP;
+ if (rex == 0x48 && modrm == 0xe5) {
+
+ /* mov %rsp, %rbp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG;
+ op->src.reg = CFI_SP;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_BP;
+ break;
+ }
+ /* fallthrough */
+ case 0x88:
+ if (!rex_b &&
+ (modrm_mod == 1 || modrm_mod == 2) && modrm_rm == 5) {
+
+ /* mov reg, disp(%rbp) */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG;
+ op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
+ op->dest.type = OP_DEST_REG_INDIRECT;
+ op->dest.reg = CFI_BP;
+ op->dest.offset = insn.displacement.value;
+
+ } else if (rex_w && !rex_b && modrm_rm == 4 && sib == 0x24) {
+
+ /* mov reg, disp(%rsp) */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG;
+ op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
+ op->dest.type = OP_DEST_REG_INDIRECT;
+ op->dest.reg = CFI_SP;
+ op->dest.offset = insn.displacement.value;
+ }
+
+ break;
+
+ case 0x8b:
+ if (rex_w && !rex_b && modrm_mod == 1 && modrm_rm == 5) {
+
+ /* mov disp(%rbp), reg */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG_INDIRECT;
+ op->src.reg = CFI_BP;
+ op->src.offset = insn.displacement.value;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
+
+ } else if (rex_w && !rex_b && sib == 0x24 &&
+ modrm_mod != 3 && modrm_rm == 4) {
+
+ /* mov disp(%rsp), reg */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_REG_INDIRECT;
+ op->src.reg = CFI_SP;
+ op->src.offset = insn.displacement.value;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
+ }
+
break;
case 0x8d:
- if (insn.rex_prefix.nbytes &&
- insn.rex_prefix.bytes[0] == 0x48 &&
- insn.modrm.nbytes && insn.modrm.bytes[0] == 0x2c &&
- insn.sib.nbytes && insn.sib.bytes[0] == 0x24)
- /* lea %(rsp), %rbp */
- *type = INSN_FP_SETUP;
+ if (rex == 0x48 && modrm == 0x65) {
+
+ /* lea -disp(%rbp), %rsp */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_BP;
+ op->src.offset = insn.displacement.value;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+ }
+
+ if (rex == 0x4c && modrm == 0x54 && sib == 0x24 &&
+ insn.displacement.value == 8) {
+
+ /*
+ * lea 0x8(%rsp), %r10
+ *
+ * Here r10 is the "drap" pointer, used as a stack
+ * pointer helper when the stack gets realigned.
+ */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_SP;
+ op->src.offset = 8;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_R10;
+ break;
+ }
+
+ if (rex == 0x4c && modrm == 0x6c && sib == 0x24 &&
+ insn.displacement.value == 16) {
+
+ /*
+ * lea 0x10(%rsp), %r13
+ *
+ * Here r13 is the "drap" pointer, used as a stack
+ * pointer helper when the stack gets realigned.
+ */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_SP;
+ op->src.offset = 16;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_R13;
+ break;
+ }
+
+ if (rex == 0x49 && modrm == 0x62 &&
+ insn.displacement.value == -8) {
+
+ /*
+ * lea -0x8(%r10), %rsp
+ *
+ * Restoring rsp back to its original value after a
+ * stack realignment.
+ */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_R10;
+ op->src.offset = -8;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+ }
+
+ if (rex == 0x49 && modrm == 0x65 &&
+ insn.displacement.value == -16) {
+
+ /*
+ * lea -0x10(%r13), %rsp
+ *
+ * Restoring rsp back to its original value after a
+ * stack realignment.
+ */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_ADD;
+ op->src.reg = CFI_R13;
+ op->src.offset = -16;
+ op->dest.type = OP_DEST_REG;
+ op->dest.reg = CFI_SP;
+ break;
+ }
+
+ break;
+
+ case 0x8f:
+ /* pop to mem */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_POP;
+ op->dest.type = OP_DEST_MEM;
break;
case 0x90:
*type = INSN_NOP;
break;
+ case 0x9c:
+ /* pushf */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_CONST;
+ op->dest.type = OP_DEST_PUSH;
+ break;
+
+ case 0x9d:
+ /* popf */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_POP;
+ op->dest.type = OP_DEST_MEM;
+ break;
+
case 0x0f:
+
if (op2 >= 0x80 && op2 <= 0x8f)
*type = INSN_JUMP_CONDITIONAL;
else if (op2 == 0x05 || op2 == 0x07 || op2 == 0x34 ||
op2 == 0x35)
+
/* sysenter, sysret */
*type = INSN_CONTEXT_SWITCH;
+
else if (op2 == 0x0d || op2 == 0x1f)
+
/* nopl/nopw */
*type = INSN_NOP;
- else if (op2 == 0x01 && insn.modrm.nbytes &&
- (insn.modrm.bytes[0] == 0xc2 ||
- insn.modrm.bytes[0] == 0xd8))
- /* vmlaunch, vmrun */
- *type = INSN_CONTEXT_SWITCH;
+
+ else if (op2 == 0xa0 || op2 == 0xa8) {
+
+ /* push fs/gs */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_CONST;
+ op->dest.type = OP_DEST_PUSH;
+
+ } else if (op2 == 0xa1 || op2 == 0xa9) {
+
+ /* pop fs/gs */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_POP;
+ op->dest.type = OP_DEST_MEM;
+ }
break;
- case 0xc9: /* leave */
- *type = INSN_FP_RESTORE;
+ case 0xc9:
+ /*
+ * leave
+ *
+ * equivalent to:
+ * mov bp, sp
+ * pop bp
+ */
+ *type = INSN_STACK;
+ op->dest.type = OP_DEST_LEAVE;
+
break;
- case 0xe3: /* jecxz/jrcxz */
+ case 0xe3:
+ /* jecxz/jrcxz */
*type = INSN_JUMP_CONDITIONAL;
break;
@@ -158,14 +451,27 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
break;
case 0xff:
- ext = X86_MODRM_REG(insn.modrm.bytes[0]);
- if (ext == 2 || ext == 3)
+ if (modrm_reg == 2 || modrm_reg == 3)
+
*type = INSN_CALL_DYNAMIC;
- else if (ext == 4)
+
+ else if (modrm_reg == 4)
+
*type = INSN_JUMP_DYNAMIC;
- else if (ext == 5) /*jmpf */
+
+ else if (modrm_reg == 5)
+
+ /* jmpf */
*type = INSN_CONTEXT_SWITCH;
+ else if (modrm_reg == 6) {
+
+ /* push from mem */
+ *type = INSN_STACK;
+ op->src.type = OP_SRC_CONST;
+ op->dest.type = OP_DEST_PUSH;
+ }
+
break;
default:
@@ -176,3 +482,21 @@ int arch_decode_instruction(struct elf *elf, struct section *sec,
return 0;
}
+
+void arch_initial_func_cfi_state(struct cfi_state *state)
+{
+ int i;
+
+ for (i = 0; i < CFI_NUM_REGS; i++) {
+ state->regs[i].base = CFI_UNDEFINED;
+ state->regs[i].offset = 0;
+ }
+
+ /* initial CFA (call frame address) */
+ state->cfa.base = CFI_SP;
+ state->cfa.offset = 8;
+
+ /* initial RA (return address) */
+ state->regs[16].base = CFI_CFA;
+ state->regs[16].offset = -8;
+}
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 5f66697fe1e0..365c34ecab26 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -1,5 +1,5 @@
/*
- * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@...hat.com>
+ * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@...hat.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
@@ -25,1287 +25,32 @@
* For more information, see tools/objtool/Documentation/stack-validation.txt.
*/
-#include <string.h>
-#include <stdlib.h>
#include <subcmd/parse-options.h>
-
#include "builtin.h"
-#include "elf.h"
-#include "special.h"
-#include "arch.h"
-#include "warn.h"
-
-#include <linux/hashtable.h>
-#include <linux/kernel.h>
-
-#define STATE_FP_SAVED 0x1
-#define STATE_FP_SETUP 0x2
-#define STATE_FENTRY 0x4
-
-struct instruction {
- struct list_head list;
- struct hlist_node hash;
- struct section *sec;
- unsigned long offset;
- unsigned int len, state;
- unsigned char type;
- unsigned long immediate;
- bool alt_group, visited, dead_end;
- struct symbol *call_dest;
- struct instruction *jump_dest;
- struct list_head alts;
- struct symbol *func;
-};
-
-struct alternative {
- struct list_head list;
- struct instruction *insn;
-};
-
-struct objtool_file {
- struct elf *elf;
- struct list_head insn_list;
- DECLARE_HASHTABLE(insn_hash, 16);
- struct section *rodata, *whitelist;
- bool ignore_unreachables, c_file;
-};
-
-const char *objname;
-static bool nofp;
-
-static struct instruction *find_insn(struct objtool_file *file,
- struct section *sec, unsigned long offset)
-{
- struct instruction *insn;
-
- hash_for_each_possible(file->insn_hash, insn, hash, offset)
- if (insn->sec == sec && insn->offset == offset)
- return insn;
-
- return NULL;
-}
-
-static struct instruction *next_insn_same_sec(struct objtool_file *file,
- struct instruction *insn)
-{
- struct instruction *next = list_next_entry(insn, list);
-
- if (&next->list == &file->insn_list || next->sec != insn->sec)
- return NULL;
-
- return next;
-}
-
-static bool gcov_enabled(struct objtool_file *file)
-{
- struct section *sec;
- struct symbol *sym;
-
- list_for_each_entry(sec, &file->elf->sections, list)
- list_for_each_entry(sym, &sec->symbol_list, list)
- if (!strncmp(sym->name, "__gcov_.", 8))
- return true;
-
- return false;
-}
-
-#define for_each_insn(file, insn) \
- list_for_each_entry(insn, &file->insn_list, list)
-
-#define func_for_each_insn(file, func, insn) \
- for (insn = find_insn(file, func->sec, func->offset); \
- insn && &insn->list != &file->insn_list && \
- insn->sec == func->sec && \
- insn->offset < func->offset + func->len; \
- insn = list_next_entry(insn, list))
-
-#define func_for_each_insn_continue_reverse(file, func, insn) \
- for (insn = list_prev_entry(insn, list); \
- &insn->list != &file->insn_list && \
- insn->sec == func->sec && insn->offset >= func->offset; \
- insn = list_prev_entry(insn, list))
-
-#define sec_for_each_insn_from(file, insn) \
- for (; insn; insn = next_insn_same_sec(file, insn))
-
-
-/*
- * Check if the function has been manually whitelisted with the
- * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted
- * due to its use of a context switching instruction.
- */
-static bool ignore_func(struct objtool_file *file, struct symbol *func)
-{
- struct rela *rela;
- struct instruction *insn;
-
- /* check for STACK_FRAME_NON_STANDARD */
- if (file->whitelist && file->whitelist->rela)
- list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) {
- if (rela->sym->type == STT_SECTION &&
- rela->sym->sec == func->sec &&
- rela->addend == func->offset)
- return true;
- if (rela->sym->type == STT_FUNC && rela->sym == func)
- return true;
- }
-
- /* check if it has a context switching instruction */
- func_for_each_insn(file, func, insn)
- if (insn->type == INSN_CONTEXT_SWITCH)
- return true;
-
- return false;
-}
-
-/*
- * This checks to see if the given function is a "noreturn" function.
- *
- * For global functions which are outside the scope of this object file, we
- * have to keep a manual list of them.
- *
- * For local functions, we have to detect them manually by simply looking for
- * the lack of a return instruction.
- *
- * Returns:
- * -1: error
- * 0: no dead end
- * 1: dead end
- */
-static int __dead_end_function(struct objtool_file *file, struct symbol *func,
- int recursion)
-{
- int i;
- struct instruction *insn;
- bool empty = true;
-
- /*
- * Unfortunately these have to be hard coded because the noreturn
- * attribute isn't provided in ELF data.
- */
- static const char * const global_noreturns[] = {
- "__stack_chk_fail",
- "panic",
- "do_exit",
- "do_task_dead",
- "__module_put_and_exit",
- "complete_and_exit",
- "kvm_spurious_fault",
- "__reiserfs_panic",
- "lbug_with_loc",
- "fortify_panic",
- };
-
- if (func->bind == STB_WEAK)
- return 0;
-
- if (func->bind == STB_GLOBAL)
- for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
- if (!strcmp(func->name, global_noreturns[i]))
- return 1;
-
- if (!func->sec)
- return 0;
-
- func_for_each_insn(file, func, insn) {
- empty = false;
-
- if (insn->type == INSN_RETURN)
- return 0;
- }
-
- if (empty)
- return 0;
-
- /*
- * A function can have a sibling call instead of a return. In that
- * case, the function's dead-end status depends on whether the target
- * of the sibling call returns.
- */
- func_for_each_insn(file, func, insn) {
- if (insn->sec != func->sec ||
- insn->offset >= func->offset + func->len)
- break;
-
- if (insn->type == INSN_JUMP_UNCONDITIONAL) {
- struct instruction *dest = insn->jump_dest;
- struct symbol *dest_func;
-
- if (!dest)
- /* sibling call to another file */
- return 0;
-
- if (dest->sec != func->sec ||
- dest->offset < func->offset ||
- dest->offset >= func->offset + func->len) {
- /* local sibling call */
- dest_func = find_symbol_by_offset(dest->sec,
- dest->offset);
- if (!dest_func)
- continue;
-
- if (recursion == 5) {
- WARN_FUNC("infinite recursion (objtool bug!)",
- dest->sec, dest->offset);
- return -1;
- }
-
- return __dead_end_function(file, dest_func,
- recursion + 1);
- }
- }
-
- if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts))
- /* sibling call */
- return 0;
- }
-
- return 1;
-}
-
-static int dead_end_function(struct objtool_file *file, struct symbol *func)
-{
- return __dead_end_function(file, func, 0);
-}
-
-/*
- * Call the arch-specific instruction decoder for all the instructions and add
- * them to the global instruction list.
- */
-static int decode_instructions(struct objtool_file *file)
-{
- struct section *sec;
- struct symbol *func;
- unsigned long offset;
- struct instruction *insn;
- int ret;
-
- list_for_each_entry(sec, &file->elf->sections, list) {
-
- if (!(sec->sh.sh_flags & SHF_EXECINSTR))
- continue;
-
- for (offset = 0; offset < sec->len; offset += insn->len) {
- insn = malloc(sizeof(*insn));
- memset(insn, 0, sizeof(*insn));
-
- INIT_LIST_HEAD(&insn->alts);
- insn->sec = sec;
- insn->offset = offset;
-
- ret = arch_decode_instruction(file->elf, sec, offset,
- sec->len - offset,
- &insn->len, &insn->type,
- &insn->immediate);
- if (ret)
- return ret;
-
- if (!insn->type || insn->type > INSN_LAST) {
- WARN_FUNC("invalid instruction type %d",
- insn->sec, insn->offset, insn->type);
- return -1;
- }
-
- hash_add(file->insn_hash, &insn->hash, insn->offset);
- list_add_tail(&insn->list, &file->insn_list);
- }
-
- list_for_each_entry(func, &sec->symbol_list, list) {
- if (func->type != STT_FUNC)
- continue;
-
- if (!find_insn(file, sec, func->offset)) {
- WARN("%s(): can't find starting instruction",
- func->name);
- return -1;
- }
-
- func_for_each_insn(file, func, insn)
- if (!insn->func)
- insn->func = func;
- }
- }
-
- return 0;
-}
-
-/*
- * Find all uses of the unreachable() macro, which are code path dead ends.
- */
-static int add_dead_ends(struct objtool_file *file)
-{
- struct section *sec;
- struct rela *rela;
- struct instruction *insn;
- bool found;
-
- sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
- if (!sec)
- return 0;
-
- list_for_each_entry(rela, &sec->rela_list, list) {
- if (rela->sym->type != STT_SECTION) {
- WARN("unexpected relocation symbol type in %s", sec->name);
- return -1;
- }
- insn = find_insn(file, rela->sym->sec, rela->addend);
- if (insn)
- insn = list_prev_entry(insn, list);
- else if (rela->addend == rela->sym->sec->len) {
- found = false;
- list_for_each_entry_reverse(insn, &file->insn_list, list) {
- if (insn->sec == rela->sym->sec) {
- found = true;
- break;
- }
- }
-
- if (!found) {
- WARN("can't find unreachable insn at %s+0x%x",
- rela->sym->sec->name, rela->addend);
- return -1;
- }
- } else {
- WARN("can't find unreachable insn at %s+0x%x",
- rela->sym->sec->name, rela->addend);
- return -1;
- }
-
- insn->dead_end = true;
- }
-
- return 0;
-}
-
-/*
- * Warnings shouldn't be reported for ignored functions.
- */
-static void add_ignores(struct objtool_file *file)
-{
- struct instruction *insn;
- struct section *sec;
- struct symbol *func;
-
- list_for_each_entry(sec, &file->elf->sections, list) {
- list_for_each_entry(func, &sec->symbol_list, list) {
- if (func->type != STT_FUNC)
- continue;
-
- if (!ignore_func(file, func))
- continue;
-
- func_for_each_insn(file, func, insn)
- insn->visited = true;
- }
- }
-}
-
-/*
- * Find the destination instructions for all jumps.
- */
-static int add_jump_destinations(struct objtool_file *file)
-{
- struct instruction *insn;
- struct rela *rela;
- struct section *dest_sec;
- unsigned long dest_off;
-
- for_each_insn(file, insn) {
- if (insn->type != INSN_JUMP_CONDITIONAL &&
- insn->type != INSN_JUMP_UNCONDITIONAL)
- continue;
-
- /* skip ignores */
- if (insn->visited)
- continue;
-
- rela = find_rela_by_dest_range(insn->sec, insn->offset,
- insn->len);
- if (!rela) {
- dest_sec = insn->sec;
- dest_off = insn->offset + insn->len + insn->immediate;
- } else if (rela->sym->type == STT_SECTION) {
- dest_sec = rela->sym->sec;
- dest_off = rela->addend + 4;
- } else if (rela->sym->sec->idx) {
- dest_sec = rela->sym->sec;
- dest_off = rela->sym->sym.st_value + rela->addend + 4;
- } else {
- /* sibling call */
- insn->jump_dest = 0;
- continue;
- }
-
- insn->jump_dest = find_insn(file, dest_sec, dest_off);
- if (!insn->jump_dest) {
-
- /*
- * This is a special case where an alt instruction
- * jumps past the end of the section. These are
- * handled later in handle_group_alt().
- */
- if (!strcmp(insn->sec->name, ".altinstr_replacement"))
- continue;
-
- WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
- insn->sec, insn->offset, dest_sec->name,
- dest_off);
- return -1;
- }
- }
-
- return 0;
-}
-
-/*
- * Find the destination instructions for all calls.
- */
-static int add_call_destinations(struct objtool_file *file)
-{
- struct instruction *insn;
- unsigned long dest_off;
- struct rela *rela;
-
- for_each_insn(file, insn) {
- if (insn->type != INSN_CALL)
- continue;
-
- rela = find_rela_by_dest_range(insn->sec, insn->offset,
- insn->len);
- if (!rela) {
- dest_off = insn->offset + insn->len + insn->immediate;
- insn->call_dest = find_symbol_by_offset(insn->sec,
- dest_off);
- if (!insn->call_dest) {
- WARN_FUNC("can't find call dest symbol at offset 0x%lx",
- insn->sec, insn->offset, dest_off);
- return -1;
- }
- } else if (rela->sym->type == STT_SECTION) {
- insn->call_dest = find_symbol_by_offset(rela->sym->sec,
- rela->addend+4);
- if (!insn->call_dest ||
- insn->call_dest->type != STT_FUNC) {
- WARN_FUNC("can't find call dest symbol at %s+0x%x",
- insn->sec, insn->offset,
- rela->sym->sec->name,
- rela->addend + 4);
- return -1;
- }
- } else
- insn->call_dest = rela->sym;
- }
-
- return 0;
-}
-
-/*
- * The .alternatives section requires some extra special care, over and above
- * what other special sections require:
- *
- * 1. Because alternatives are patched in-place, we need to insert a fake jump
- * instruction at the end so that validate_branch() skips all the original
- * replaced instructions when validating the new instruction path.
- *
- * 2. An added wrinkle is that the new instruction length might be zero. In
- * that case the old instructions are replaced with noops. We simulate that
- * by creating a fake jump as the only new instruction.
- *
- * 3. In some cases, the alternative section includes an instruction which
- * conditionally jumps to the _end_ of the entry. We have to modify these
- * jumps' destinations to point back to .text rather than the end of the
- * entry in .altinstr_replacement.
- *
- * 4. It has been requested that we don't validate the !POPCNT feature path
- * which is a "very very small percentage of machines".
- */
-static int handle_group_alt(struct objtool_file *file,
- struct special_alt *special_alt,
- struct instruction *orig_insn,
- struct instruction **new_insn)
-{
- struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump;
- unsigned long dest_off;
-
- last_orig_insn = NULL;
- insn = orig_insn;
- sec_for_each_insn_from(file, insn) {
- if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
- break;
-
- if (special_alt->skip_orig)
- insn->type = INSN_NOP;
-
- insn->alt_group = true;
- last_orig_insn = insn;
- }
-
- if (!next_insn_same_sec(file, last_orig_insn)) {
- WARN("%s: don't know how to handle alternatives at end of section",
- special_alt->orig_sec->name);
- return -1;
- }
-
- fake_jump = malloc(sizeof(*fake_jump));
- if (!fake_jump) {
- WARN("malloc failed");
- return -1;
- }
- memset(fake_jump, 0, sizeof(*fake_jump));
- INIT_LIST_HEAD(&fake_jump->alts);
- fake_jump->sec = special_alt->new_sec;
- fake_jump->offset = -1;
- fake_jump->type = INSN_JUMP_UNCONDITIONAL;
- fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
-
- if (!special_alt->new_len) {
- *new_insn = fake_jump;
- return 0;
- }
-
- last_new_insn = NULL;
- insn = *new_insn;
- sec_for_each_insn_from(file, insn) {
- if (insn->offset >= special_alt->new_off + special_alt->new_len)
- break;
-
- last_new_insn = insn;
-
- if (insn->type != INSN_JUMP_CONDITIONAL &&
- insn->type != INSN_JUMP_UNCONDITIONAL)
- continue;
-
- if (!insn->immediate)
- continue;
-
- dest_off = insn->offset + insn->len + insn->immediate;
- if (dest_off == special_alt->new_off + special_alt->new_len)
- insn->jump_dest = fake_jump;
-
- if (!insn->jump_dest) {
- WARN_FUNC("can't find alternative jump destination",
- insn->sec, insn->offset);
- return -1;
- }
- }
-
- if (!last_new_insn) {
- WARN_FUNC("can't find last new alternative instruction",
- special_alt->new_sec, special_alt->new_off);
- return -1;
- }
-
- list_add(&fake_jump->list, &last_new_insn->list);
-
- return 0;
-}
-
-/*
- * A jump table entry can either convert a nop to a jump or a jump to a nop.
- * If the original instruction is a jump, make the alt entry an effective nop
- * by just skipping the original instruction.
- */
-static int handle_jump_alt(struct objtool_file *file,
- struct special_alt *special_alt,
- struct instruction *orig_insn,
- struct instruction **new_insn)
-{
- if (orig_insn->type == INSN_NOP)
- return 0;
-
- if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
- WARN_FUNC("unsupported instruction at jump label",
- orig_insn->sec, orig_insn->offset);
- return -1;
- }
-
- *new_insn = list_next_entry(orig_insn, list);
- return 0;
-}
-
-/*
- * Read all the special sections which have alternate instructions which can be
- * patched in or redirected to at runtime. Each instruction having alternate
- * instruction(s) has them added to its insn->alts list, which will be
- * traversed in validate_branch().
- */
-static int add_special_section_alts(struct objtool_file *file)
-{
- struct list_head special_alts;
- struct instruction *orig_insn, *new_insn;
- struct special_alt *special_alt, *tmp;
- struct alternative *alt;
- int ret;
-
- ret = special_get_alts(file->elf, &special_alts);
- if (ret)
- return ret;
-
- list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
- alt = malloc(sizeof(*alt));
- if (!alt) {
- WARN("malloc failed");
- ret = -1;
- goto out;
- }
-
- orig_insn = find_insn(file, special_alt->orig_sec,
- special_alt->orig_off);
- if (!orig_insn) {
- WARN_FUNC("special: can't find orig instruction",
- special_alt->orig_sec, special_alt->orig_off);
- ret = -1;
- goto out;
- }
+#include "check.h"
- new_insn = NULL;
- if (!special_alt->group || special_alt->new_len) {
- new_insn = find_insn(file, special_alt->new_sec,
- special_alt->new_off);
- if (!new_insn) {
- WARN_FUNC("special: can't find new instruction",
- special_alt->new_sec,
- special_alt->new_off);
- ret = -1;
- goto out;
- }
- }
+bool nofp;
- if (special_alt->group) {
- ret = handle_group_alt(file, special_alt, orig_insn,
- &new_insn);
- if (ret)
- goto out;
- } else if (special_alt->jump_or_nop) {
- ret = handle_jump_alt(file, special_alt, orig_insn,
- &new_insn);
- if (ret)
- goto out;
- }
-
- alt->insn = new_insn;
- list_add_tail(&alt->list, &orig_insn->alts);
-
- list_del(&special_alt->list);
- free(special_alt);
- }
-
-out:
- return ret;
-}
-
-static int add_switch_table(struct objtool_file *file, struct symbol *func,
- struct instruction *insn, struct rela *table,
- struct rela *next_table)
-{
- struct rela *rela = table;
- struct instruction *alt_insn;
- struct alternative *alt;
-
- list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
- if (rela == next_table)
- break;
-
- if (rela->sym->sec != insn->sec ||
- rela->addend <= func->offset ||
- rela->addend >= func->offset + func->len)
- break;
-
- alt_insn = find_insn(file, insn->sec, rela->addend);
- if (!alt_insn) {
- WARN("%s: can't find instruction at %s+0x%x",
- file->rodata->rela->name, insn->sec->name,
- rela->addend);
- return -1;
- }
-
- alt = malloc(sizeof(*alt));
- if (!alt) {
- WARN("malloc failed");
- return -1;
- }
-
- alt->insn = alt_insn;
- list_add_tail(&alt->list, &insn->alts);
- }
-
- return 0;
-}
-
-/*
- * find_switch_table() - Given a dynamic jump, find the switch jump table in
- * .rodata associated with it.
- *
- * There are 3 basic patterns:
- *
- * 1. jmpq *[rodata addr](,%reg,8)
- *
- * This is the most common case by far. It jumps to an address in a simple
- * jump table which is stored in .rodata.
- *
- * 2. jmpq *[rodata addr](%rip)
- *
- * This is caused by a rare GCC quirk, currently only seen in three driver
- * functions in the kernel, only with certain obscure non-distro configs.
- *
- * As part of an optimization, GCC makes a copy of an existing switch jump
- * table, modifies it, and then hard-codes the jump (albeit with an indirect
- * jump) to use a single entry in the table. The rest of the jump table and
- * some of its jump targets remain as dead code.
- *
- * In such a case we can just crudely ignore all unreachable instruction
- * warnings for the entire object file. Ideally we would just ignore them
- * for the function, but that would require redesigning the code quite a
- * bit. And honestly that's just not worth doing: unreachable instruction
- * warnings are of questionable value anyway, and this is such a rare issue.
- *
- * 3. mov [rodata addr],%reg1
- * ... some instructions ...
- * jmpq *(%reg1,%reg2,8)
- *
- * This is a fairly uncommon pattern which is new for GCC 6. As of this
- * writing, there are 11 occurrences of it in the allmodconfig kernel.
- *
- * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
- * ensure the same register is used in the mov and jump instructions.
- */
-static struct rela *find_switch_table(struct objtool_file *file,
- struct symbol *func,
- struct instruction *insn)
-{
- struct rela *text_rela, *rodata_rela;
- struct instruction *orig_insn = insn;
-
- text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
- if (text_rela && text_rela->sym == file->rodata->sym) {
- /* case 1 */
- rodata_rela = find_rela_by_dest(file->rodata,
- text_rela->addend);
- if (rodata_rela)
- return rodata_rela;
-
- /* case 2 */
- rodata_rela = find_rela_by_dest(file->rodata,
- text_rela->addend + 4);
- if (!rodata_rela)
- return NULL;
- file->ignore_unreachables = true;
- return rodata_rela;
- }
-
- /* case 3 */
- func_for_each_insn_continue_reverse(file, func, insn) {
- if (insn->type == INSN_JUMP_DYNAMIC)
- break;
-
- /* allow small jumps within the range */
- if (insn->type == INSN_JUMP_UNCONDITIONAL &&
- insn->jump_dest &&
- (insn->jump_dest->offset <= insn->offset ||
- insn->jump_dest->offset > orig_insn->offset))
- break;
-
- /* look for a relocation which references .rodata */
- text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
- insn->len);
- if (!text_rela || text_rela->sym != file->rodata->sym)
- continue;
-
- /*
- * Make sure the .rodata address isn't associated with a
- * symbol. gcc jump tables are anonymous data.
- */
- if (find_symbol_containing(file->rodata, text_rela->addend))
- continue;
-
- return find_rela_by_dest(file->rodata, text_rela->addend);
- }
-
- return NULL;
-}
-
-static int add_func_switch_tables(struct objtool_file *file,
- struct symbol *func)
-{
- struct instruction *insn, *prev_jump = NULL;
- struct rela *rela, *prev_rela = NULL;
- int ret;
-
- func_for_each_insn(file, func, insn) {
- if (insn->type != INSN_JUMP_DYNAMIC)
- continue;
-
- rela = find_switch_table(file, func, insn);
- if (!rela)
- continue;
-
- /*
- * We found a switch table, but we don't know yet how big it
- * is. Don't add it until we reach the end of the function or
- * the beginning of another switch table in the same function.
- */
- if (prev_jump) {
- ret = add_switch_table(file, func, prev_jump, prev_rela,
- rela);
- if (ret)
- return ret;
- }
-
- prev_jump = insn;
- prev_rela = rela;
- }
-
- if (prev_jump) {
- ret = add_switch_table(file, func, prev_jump, prev_rela, NULL);
- if (ret)
- return ret;
- }
-
- return 0;
-}
-
-/*
- * For some switch statements, gcc generates a jump table in the .rodata
- * section which contains a list of addresses within the function to jump to.
- * This finds these jump tables and adds them to the insn->alts lists.
- */
-static int add_switch_table_alts(struct objtool_file *file)
-{
- struct section *sec;
- struct symbol *func;
- int ret;
-
- if (!file->rodata || !file->rodata->rela)
- return 0;
-
- list_for_each_entry(sec, &file->elf->sections, list) {
- list_for_each_entry(func, &sec->symbol_list, list) {
- if (func->type != STT_FUNC)
- continue;
-
- ret = add_func_switch_tables(file, func);
- if (ret)
- return ret;
- }
- }
-
- return 0;
-}
-
-static int decode_sections(struct objtool_file *file)
-{
- int ret;
-
- ret = decode_instructions(file);
- if (ret)
- return ret;
-
- ret = add_dead_ends(file);
- if (ret)
- return ret;
-
- add_ignores(file);
-
- ret = add_jump_destinations(file);
- if (ret)
- return ret;
-
- ret = add_call_destinations(file);
- if (ret)
- return ret;
-
- ret = add_special_section_alts(file);
- if (ret)
- return ret;
-
- ret = add_switch_table_alts(file);
- if (ret)
- return ret;
-
- return 0;
-}
-
-static bool is_fentry_call(struct instruction *insn)
-{
- if (insn->type == INSN_CALL &&
- insn->call_dest->type == STT_NOTYPE &&
- !strcmp(insn->call_dest->name, "__fentry__"))
- return true;
-
- return false;
-}
-
-static bool has_modified_stack_frame(struct instruction *insn)
-{
- return (insn->state & STATE_FP_SAVED) ||
- (insn->state & STATE_FP_SETUP);
-}
-
-static bool has_valid_stack_frame(struct instruction *insn)
-{
- return (insn->state & STATE_FP_SAVED) &&
- (insn->state & STATE_FP_SETUP);
-}
-
-static unsigned int frame_state(unsigned long state)
-{
- return (state & (STATE_FP_SAVED | STATE_FP_SETUP));
-}
-
-/*
- * Follow the branch starting at the given instruction, and recursively follow
- * any other branches (jumps). Meanwhile, track the frame pointer state at
- * each instruction and validate all the rules described in
- * tools/objtool/Documentation/stack-validation.txt.
- */
-static int validate_branch(struct objtool_file *file,
- struct instruction *first, unsigned char first_state)
-{
- struct alternative *alt;
- struct instruction *insn;
- struct section *sec;
- struct symbol *func = NULL;
- unsigned char state;
- int ret;
-
- insn = first;
- sec = insn->sec;
- state = first_state;
-
- if (insn->alt_group && list_empty(&insn->alts)) {
- WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
- sec, insn->offset);
- return 1;
- }
-
- while (1) {
- if (file->c_file && insn->func) {
- if (func && func != insn->func) {
- WARN("%s() falls through to next function %s()",
- func->name, insn->func->name);
- return 1;
- }
-
- func = insn->func;
- }
-
- if (insn->visited) {
- if (frame_state(insn->state) != frame_state(state)) {
- WARN_FUNC("frame pointer state mismatch",
- sec, insn->offset);
- return 1;
- }
-
- return 0;
- }
-
- insn->visited = true;
- insn->state = state;
-
- list_for_each_entry(alt, &insn->alts, list) {
- ret = validate_branch(file, alt->insn, state);
- if (ret)
- return 1;
- }
-
- switch (insn->type) {
-
- case INSN_FP_SAVE:
- if (!nofp) {
- if (state & STATE_FP_SAVED) {
- WARN_FUNC("duplicate frame pointer save",
- sec, insn->offset);
- return 1;
- }
- state |= STATE_FP_SAVED;
- }
- break;
-
- case INSN_FP_SETUP:
- if (!nofp) {
- if (state & STATE_FP_SETUP) {
- WARN_FUNC("duplicate frame pointer setup",
- sec, insn->offset);
- return 1;
- }
- state |= STATE_FP_SETUP;
- }
- break;
-
- case INSN_FP_RESTORE:
- if (!nofp) {
- if (has_valid_stack_frame(insn))
- state &= ~STATE_FP_SETUP;
-
- state &= ~STATE_FP_SAVED;
- }
- break;
-
- case INSN_RETURN:
- if (!nofp && has_modified_stack_frame(insn)) {
- WARN_FUNC("return without frame pointer restore",
- sec, insn->offset);
- return 1;
- }
- return 0;
-
- case INSN_CALL:
- if (is_fentry_call(insn)) {
- state |= STATE_FENTRY;
- break;
- }
-
- ret = dead_end_function(file, insn->call_dest);
- if (ret == 1)
- return 0;
- if (ret == -1)
- return 1;
-
- /* fallthrough */
- case INSN_CALL_DYNAMIC:
- if (!nofp && !has_valid_stack_frame(insn)) {
- WARN_FUNC("call without frame pointer save/setup",
- sec, insn->offset);
- return 1;
- }
- break;
-
- case INSN_JUMP_CONDITIONAL:
- case INSN_JUMP_UNCONDITIONAL:
- if (insn->jump_dest) {
- ret = validate_branch(file, insn->jump_dest,
- state);
- if (ret)
- return 1;
- } else if (has_modified_stack_frame(insn)) {
- WARN_FUNC("sibling call from callable instruction with changed frame pointer",
- sec, insn->offset);
- return 1;
- } /* else it's a sibling call */
-
- if (insn->type == INSN_JUMP_UNCONDITIONAL)
- return 0;
-
- break;
-
- case INSN_JUMP_DYNAMIC:
- if (list_empty(&insn->alts) &&
- has_modified_stack_frame(insn)) {
- WARN_FUNC("sibling call from callable instruction with changed frame pointer",
- sec, insn->offset);
- return 1;
- }
-
- return 0;
-
- default:
- break;
- }
-
- if (insn->dead_end)
- return 0;
-
- insn = next_insn_same_sec(file, insn);
- if (!insn) {
- WARN("%s: unexpected end of section", sec->name);
- return 1;
- }
- }
-
- return 0;
-}
-
-static bool is_kasan_insn(struct instruction *insn)
-{
- return (insn->type == INSN_CALL &&
- !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
-}
-
-static bool is_ubsan_insn(struct instruction *insn)
-{
- return (insn->type == INSN_CALL &&
- !strcmp(insn->call_dest->name,
- "__ubsan_handle_builtin_unreachable"));
-}
-
-static bool ignore_unreachable_insn(struct symbol *func,
- struct instruction *insn)
-{
- int i;
-
- if (insn->type == INSN_NOP)
- return true;
-
- /*
- * Check if this (or a subsequent) instruction is related to
- * CONFIG_UBSAN or CONFIG_KASAN.
- *
- * End the search at 5 instructions to avoid going into the weeds.
- */
- for (i = 0; i < 5; i++) {
-
- if (is_kasan_insn(insn) || is_ubsan_insn(insn))
- return true;
-
- if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest) {
- insn = insn->jump_dest;
- continue;
- }
-
- if (insn->offset + insn->len >= func->offset + func->len)
- break;
- insn = list_next_entry(insn, list);
- }
-
- return false;
-}
-
-static int validate_functions(struct objtool_file *file)
-{
- struct section *sec;
- struct symbol *func;
- struct instruction *insn;
- int ret, warnings = 0;
-
- list_for_each_entry(sec, &file->elf->sections, list) {
- list_for_each_entry(func, &sec->symbol_list, list) {
- if (func->type != STT_FUNC)
- continue;
-
- insn = find_insn(file, sec, func->offset);
- if (!insn)
- continue;
-
- ret = validate_branch(file, insn, 0);
- warnings += ret;
- }
- }
-
- list_for_each_entry(sec, &file->elf->sections, list) {
- list_for_each_entry(func, &sec->symbol_list, list) {
- if (func->type != STT_FUNC)
- continue;
-
- func_for_each_insn(file, func, insn) {
- if (insn->visited)
- continue;
-
- insn->visited = true;
-
- if (file->ignore_unreachables || warnings ||
- ignore_unreachable_insn(func, insn))
- continue;
-
- /*
- * gcov produces a lot of unreachable
- * instructions. If we get an unreachable
- * warning and the file has gcov enabled, just
- * ignore it, and all other such warnings for
- * the file.
- */
- if (!file->ignore_unreachables &&
- gcov_enabled(file)) {
- file->ignore_unreachables = true;
- continue;
- }
-
- WARN_FUNC("function has unreachable instruction", insn->sec, insn->offset);
- warnings++;
- }
- }
- }
-
- return warnings;
-}
-
-static int validate_uncallable_instructions(struct objtool_file *file)
-{
- struct instruction *insn;
- int warnings = 0;
-
- for_each_insn(file, insn) {
- if (!insn->visited && insn->type == INSN_RETURN) {
- WARN_FUNC("return instruction outside of a callable function",
- insn->sec, insn->offset);
- warnings++;
- }
- }
-
- return warnings;
-}
-
-static void cleanup(struct objtool_file *file)
-{
- struct instruction *insn, *tmpinsn;
- struct alternative *alt, *tmpalt;
-
- list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
- list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
- list_del(&alt->list);
- free(alt);
- }
- list_del(&insn->list);
- hash_del(&insn->hash);
- free(insn);
- }
- elf_close(file->elf);
-}
-
-const char * const check_usage[] = {
+static const char * const check_usage[] = {
"objtool check [<options>] file.o",
NULL,
};
+const struct option check_options[] = {
+ OPT_BOOLEAN('f', "no-fp", &nofp, "Skip frame pointer validation"),
+ OPT_END(),
+};
+
int cmd_check(int argc, const char **argv)
{
- struct objtool_file file;
- int ret, warnings = 0;
-
- const struct option options[] = {
- OPT_BOOLEAN('f', "no-fp", &nofp, "Skip frame pointer validation"),
- OPT_END(),
- };
+ const char *objname;
- argc = parse_options(argc, argv, options, check_usage, 0);
+ argc = parse_options(argc, argv, check_options, check_usage, 0);
if (argc != 1)
- usage_with_options(check_usage, options);
+ usage_with_options(check_usage, check_options);
objname = argv[0];
- file.elf = elf_open(objname);
- if (!file.elf) {
- fprintf(stderr, "error reading elf file %s\n", objname);
- return 1;
- }
-
- INIT_LIST_HEAD(&file.insn_list);
- hash_init(file.insn_hash);
- file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard");
- file.rodata = find_section_by_name(file.elf, ".rodata");
- file.ignore_unreachables = false;
- file.c_file = find_section_by_name(file.elf, ".comment");
-
- ret = decode_sections(&file);
- if (ret < 0)
- goto out;
- warnings += ret;
-
- ret = validate_functions(&file);
- if (ret < 0)
- goto out;
- warnings += ret;
-
- ret = validate_uncallable_instructions(&file);
- if (ret < 0)
- goto out;
- warnings += ret;
-
-out:
- cleanup(&file);
-
- /* ignore warnings for now until we get all the code cleaned up */
- if (ret || warnings)
- return 0;
- return 0;
+ return check(objname, nofp);
}
diff --git a/tools/objtool/cfi.h b/tools/objtool/cfi.h
new file mode 100644
index 000000000000..443ab2c69992
--- /dev/null
+++ b/tools/objtool/cfi.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@...hat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _OBJTOOL_CFI_H
+#define _OBJTOOL_CFI_H
+
+#define CFI_UNDEFINED -1
+#define CFI_CFA -2
+#define CFI_SP_INDIRECT -3
+#define CFI_BP_INDIRECT -4
+
+#define CFI_AX 0
+#define CFI_DX 1
+#define CFI_CX 2
+#define CFI_BX 3
+#define CFI_SI 4
+#define CFI_DI 5
+#define CFI_BP 6
+#define CFI_SP 7
+#define CFI_R8 8
+#define CFI_R9 9
+#define CFI_R10 10
+#define CFI_R11 11
+#define CFI_R12 12
+#define CFI_R13 13
+#define CFI_R14 14
+#define CFI_R15 15
+#define CFI_RA 16
+#define CFI_NUM_REGS 17
+
+struct cfi_reg {
+ int base;
+ int offset;
+};
+
+struct cfi_state {
+ struct cfi_reg cfa;
+ struct cfi_reg regs[CFI_NUM_REGS];
+};
+
+#endif /* _OBJTOOL_CFI_H */
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
new file mode 100644
index 000000000000..fea222192c57
--- /dev/null
+++ b/tools/objtool/check.c
@@ -0,0 +1,1655 @@
+/*
+ * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@...hat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <string.h>
+#include <stdlib.h>
+
+#include "check.h"
+#include "elf.h"
+#include "special.h"
+#include "arch.h"
+#include "warn.h"
+
+#include <linux/hashtable.h>
+#include <linux/kernel.h>
+
+struct alternative {
+ struct list_head list;
+ struct instruction *insn;
+};
+
+const char *objname;
+static bool nofp;
+struct cfi_state initial_func_cfi;
+
+static struct instruction *find_insn(struct objtool_file *file,
+ struct section *sec, unsigned long offset)
+{
+ struct instruction *insn;
+
+ hash_for_each_possible(file->insn_hash, insn, hash, offset)
+ if (insn->sec == sec && insn->offset == offset)
+ return insn;
+
+ return NULL;
+}
+
+static struct instruction *next_insn_same_sec(struct objtool_file *file,
+ struct instruction *insn)
+{
+ struct instruction *next = list_next_entry(insn, list);
+
+ if (!next || &next->list == &file->insn_list || next->sec != insn->sec)
+ return NULL;
+
+ return next;
+}
+
+static bool gcov_enabled(struct objtool_file *file)
+{
+ struct section *sec;
+ struct symbol *sym;
+
+ for_each_sec(file, sec)
+ list_for_each_entry(sym, &sec->symbol_list, list)
+ if (!strncmp(sym->name, "__gcov_.", 8))
+ return true;
+
+ return false;
+}
+
+#define func_for_each_insn(file, func, insn) \
+ for (insn = find_insn(file, func->sec, func->offset); \
+ insn && &insn->list != &file->insn_list && \
+ insn->sec == func->sec && \
+ insn->offset < func->offset + func->len; \
+ insn = list_next_entry(insn, list))
+
+#define func_for_each_insn_continue_reverse(file, func, insn) \
+ for (insn = list_prev_entry(insn, list); \
+ &insn->list != &file->insn_list && \
+ insn->sec == func->sec && insn->offset >= func->offset; \
+ insn = list_prev_entry(insn, list))
+
+#define sec_for_each_insn_from(file, insn) \
+ for (; insn; insn = next_insn_same_sec(file, insn))
+
+#define sec_for_each_insn_continue(file, insn) \
+ for (insn = next_insn_same_sec(file, insn); insn; \
+ insn = next_insn_same_sec(file, insn))
+
+/*
+ * Check if the function has been manually whitelisted with the
+ * STACK_FRAME_NON_STANDARD macro, or if it should be automatically whitelisted
+ * due to its use of a context switching instruction.
+ */
+static bool ignore_func(struct objtool_file *file, struct symbol *func)
+{
+ struct rela *rela;
+ struct instruction *insn;
+
+ /* check for STACK_FRAME_NON_STANDARD */
+ if (file->whitelist && file->whitelist->rela)
+ list_for_each_entry(rela, &file->whitelist->rela->rela_list, list) {
+ if (rela->sym->type == STT_SECTION &&
+ rela->sym->sec == func->sec &&
+ rela->addend == func->offset)
+ return true;
+ if (rela->sym->type == STT_FUNC && rela->sym == func)
+ return true;
+ }
+
+ /* check if it has a context switching instruction */
+ func_for_each_insn(file, func, insn)
+ if (insn->type == INSN_CONTEXT_SWITCH)
+ return true;
+
+ return false;
+}
+
+/*
+ * This checks to see if the given function is a "noreturn" function.
+ *
+ * For global functions which are outside the scope of this object file, we
+ * have to keep a manual list of them.
+ *
+ * For local functions, we have to detect them manually by simply looking for
+ * the lack of a return instruction.
+ *
+ * Returns:
+ * -1: error
+ * 0: no dead end
+ * 1: dead end
+ */
+static int __dead_end_function(struct objtool_file *file, struct symbol *func,
+ int recursion)
+{
+ int i;
+ struct instruction *insn;
+ bool empty = true;
+
+ /*
+ * Unfortunately these have to be hard coded because the noreturn
+ * attribute isn't provided in ELF data.
+ */
+ static const char * const global_noreturns[] = {
+ "__stack_chk_fail",
+ "panic",
+ "do_exit",
+ "do_task_dead",
+ "__module_put_and_exit",
+ "complete_and_exit",
+ "kvm_spurious_fault",
+ "__reiserfs_panic",
+ "lbug_with_loc",
+ "fortify_panic",
+ };
+
+ if (func->bind == STB_WEAK)
+ return 0;
+
+ if (func->bind == STB_GLOBAL)
+ for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)
+ if (!strcmp(func->name, global_noreturns[i]))
+ return 1;
+
+ if (!func->sec)
+ return 0;
+
+ func_for_each_insn(file, func, insn) {
+ empty = false;
+
+ if (insn->type == INSN_RETURN)
+ return 0;
+ }
+
+ if (empty)
+ return 0;
+
+ /*
+ * A function can have a sibling call instead of a return. In that
+ * case, the function's dead-end status depends on whether the target
+ * of the sibling call returns.
+ */
+ func_for_each_insn(file, func, insn) {
+ if (insn->sec != func->sec ||
+ insn->offset >= func->offset + func->len)
+ break;
+
+ if (insn->type == INSN_JUMP_UNCONDITIONAL) {
+ struct instruction *dest = insn->jump_dest;
+ struct symbol *dest_func;
+
+ if (!dest)
+ /* sibling call to another file */
+ return 0;
+
+ if (dest->sec != func->sec ||
+ dest->offset < func->offset ||
+ dest->offset >= func->offset + func->len) {
+ /* local sibling call */
+ dest_func = find_symbol_by_offset(dest->sec,
+ dest->offset);
+ if (!dest_func)
+ continue;
+
+ if (recursion == 5) {
+ WARN_FUNC("infinite recursion (objtool bug!)",
+ dest->sec, dest->offset);
+ return -1;
+ }
+
+ return __dead_end_function(file, dest_func,
+ recursion + 1);
+ }
+ }
+
+ if (insn->type == INSN_JUMP_DYNAMIC && list_empty(&insn->alts))
+ /* sibling call */
+ return 0;
+ }
+
+ return 1;
+}
+
+static int dead_end_function(struct objtool_file *file, struct symbol *func)
+{
+ return __dead_end_function(file, func, 0);
+}
+
+static void clear_insn_state(struct insn_state *state)
+{
+ int i;
+
+ memset(state, 0, sizeof(*state));
+ state->cfa.base = CFI_UNDEFINED;
+ for (i = 0; i < CFI_NUM_REGS; i++)
+ state->regs[i].base = CFI_UNDEFINED;
+ state->drap_reg = CFI_UNDEFINED;
+}
+
+/*
+ * Call the arch-specific instruction decoder for all the instructions and add
+ * them to the global instruction list.
+ */
+static int decode_instructions(struct objtool_file *file)
+{
+ struct section *sec;
+ struct symbol *func;
+ unsigned long offset;
+ struct instruction *insn;
+ int ret;
+
+ for_each_sec(file, sec) {
+
+ if (!(sec->sh.sh_flags & SHF_EXECINSTR))
+ continue;
+
+ for (offset = 0; offset < sec->len; offset += insn->len) {
+ insn = malloc(sizeof(*insn));
+ if (!insn) {
+ WARN("malloc failed");
+ return -1;
+ }
+ memset(insn, 0, sizeof(*insn));
+ INIT_LIST_HEAD(&insn->alts);
+ clear_insn_state(&insn->state);
+
+ insn->sec = sec;
+ insn->offset = offset;
+
+ ret = arch_decode_instruction(file->elf, sec, offset,
+ sec->len - offset,
+ &insn->len, &insn->type,
+ &insn->immediate,
+ &insn->stack_op);
+ if (ret)
+ return ret;
+
+ if (!insn->type || insn->type > INSN_LAST) {
+ WARN_FUNC("invalid instruction type %d",
+ insn->sec, insn->offset, insn->type);
+ return -1;
+ }
+
+ hash_add(file->insn_hash, &insn->hash, insn->offset);
+ list_add_tail(&insn->list, &file->insn_list);
+ }
+
+ list_for_each_entry(func, &sec->symbol_list, list) {
+ if (func->type != STT_FUNC)
+ continue;
+
+ if (!find_insn(file, sec, func->offset)) {
+ WARN("%s(): can't find starting instruction",
+ func->name);
+ return -1;
+ }
+
+ func_for_each_insn(file, func, insn)
+ if (!insn->func)
+ insn->func = func;
+ }
+ }
+
+ return 0;
+}
+
+/*
+ * Find all uses of the unreachable() macro, which are code path dead ends.
+ */
+static int add_dead_ends(struct objtool_file *file)
+{
+ struct section *sec;
+ struct rela *rela;
+ struct instruction *insn;
+ bool found;
+
+ sec = find_section_by_name(file->elf, ".rela.discard.unreachable");
+ if (!sec)
+ return 0;
+
+ list_for_each_entry(rela, &sec->rela_list, list) {
+ if (rela->sym->type != STT_SECTION) {
+ WARN("unexpected relocation symbol type in %s", sec->name);
+ return -1;
+ }
+ insn = find_insn(file, rela->sym->sec, rela->addend);
+ if (insn)
+ insn = list_prev_entry(insn, list);
+ else if (rela->addend == rela->sym->sec->len) {
+ found = false;
+ list_for_each_entry_reverse(insn, &file->insn_list, list) {
+ if (insn->sec == rela->sym->sec) {
+ found = true;
+ break;
+ }
+ }
+
+ if (!found) {
+ WARN("can't find unreachable insn at %s+0x%x",
+ rela->sym->sec->name, rela->addend);
+ return -1;
+ }
+ } else {
+ WARN("can't find unreachable insn at %s+0x%x",
+ rela->sym->sec->name, rela->addend);
+ return -1;
+ }
+
+ insn->dead_end = true;
+ }
+
+ return 0;
+}
+
+/*
+ * Warnings shouldn't be reported for ignored functions.
+ */
+static void add_ignores(struct objtool_file *file)
+{
+ struct instruction *insn;
+ struct section *sec;
+ struct symbol *func;
+
+ for_each_sec(file, sec) {
+ list_for_each_entry(func, &sec->symbol_list, list) {
+ if (func->type != STT_FUNC)
+ continue;
+
+ if (!ignore_func(file, func))
+ continue;
+
+ func_for_each_insn(file, func, insn)
+ insn->ignore = true;
+ }
+ }
+}
+
+/*
+ * Find the destination instructions for all jumps.
+ */
+static int add_jump_destinations(struct objtool_file *file)
+{
+ struct instruction *insn;
+ struct rela *rela;
+ struct section *dest_sec;
+ unsigned long dest_off;
+
+ for_each_insn(file, insn) {
+ if (insn->type != INSN_JUMP_CONDITIONAL &&
+ insn->type != INSN_JUMP_UNCONDITIONAL)
+ continue;
+
+ if (insn->ignore)
+ continue;
+
+ rela = find_rela_by_dest_range(insn->sec, insn->offset,
+ insn->len);
+ if (!rela) {
+ dest_sec = insn->sec;
+ dest_off = insn->offset + insn->len + insn->immediate;
+ } else if (rela->sym->type == STT_SECTION) {
+ dest_sec = rela->sym->sec;
+ dest_off = rela->addend + 4;
+ } else if (rela->sym->sec->idx) {
+ dest_sec = rela->sym->sec;
+ dest_off = rela->sym->sym.st_value + rela->addend + 4;
+ } else {
+ /* sibling call */
+ insn->jump_dest = 0;
+ continue;
+ }
+
+ insn->jump_dest = find_insn(file, dest_sec, dest_off);
+ if (!insn->jump_dest) {
+
+ /*
+ * This is a special case where an alt instruction
+ * jumps past the end of the section. These are
+ * handled later in handle_group_alt().
+ */
+ if (!strcmp(insn->sec->name, ".altinstr_replacement"))
+ continue;
+
+ WARN_FUNC("can't find jump dest instruction at %s+0x%lx",
+ insn->sec, insn->offset, dest_sec->name,
+ dest_off);
+ return -1;
+ }
+ }
+
+ return 0;
+}
+
+/*
+ * Find the destination instructions for all calls.
+ */
+static int add_call_destinations(struct objtool_file *file)
+{
+ struct instruction *insn;
+ unsigned long dest_off;
+ struct rela *rela;
+
+ for_each_insn(file, insn) {
+ if (insn->type != INSN_CALL)
+ continue;
+
+ rela = find_rela_by_dest_range(insn->sec, insn->offset,
+ insn->len);
+ if (!rela) {
+ dest_off = insn->offset + insn->len + insn->immediate;
+ insn->call_dest = find_symbol_by_offset(insn->sec,
+ dest_off);
+ if (!insn->call_dest) {
+ WARN_FUNC("can't find call dest symbol at offset 0x%lx",
+ insn->sec, insn->offset, dest_off);
+ return -1;
+ }
+ } else if (rela->sym->type == STT_SECTION) {
+ insn->call_dest = find_symbol_by_offset(rela->sym->sec,
+ rela->addend+4);
+ if (!insn->call_dest ||
+ insn->call_dest->type != STT_FUNC) {
+ WARN_FUNC("can't find call dest symbol at %s+0x%x",
+ insn->sec, insn->offset,
+ rela->sym->sec->name,
+ rela->addend + 4);
+ return -1;
+ }
+ } else
+ insn->call_dest = rela->sym;
+ }
+
+ return 0;
+}
+
+/*
+ * The .alternatives section requires some extra special care, over and above
+ * what other special sections require:
+ *
+ * 1. Because alternatives are patched in-place, we need to insert a fake jump
+ * instruction at the end so that validate_branch() skips all the original
+ * replaced instructions when validating the new instruction path.
+ *
+ * 2. An added wrinkle is that the new instruction length might be zero. In
+ * that case the old instructions are replaced with noops. We simulate that
+ * by creating a fake jump as the only new instruction.
+ *
+ * 3. In some cases, the alternative section includes an instruction which
+ * conditionally jumps to the _end_ of the entry. We have to modify these
+ * jumps' destinations to point back to .text rather than the end of the
+ * entry in .altinstr_replacement.
+ *
+ * 4. It has been requested that we don't validate the !POPCNT feature path
+ * which is a "very very small percentage of machines".
+ */
+static int handle_group_alt(struct objtool_file *file,
+ struct special_alt *special_alt,
+ struct instruction *orig_insn,
+ struct instruction **new_insn)
+{
+ struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump;
+ unsigned long dest_off;
+
+ last_orig_insn = NULL;
+ insn = orig_insn;
+ sec_for_each_insn_from(file, insn) {
+ if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
+ break;
+
+ if (special_alt->skip_orig)
+ insn->type = INSN_NOP;
+
+ insn->alt_group = true;
+ last_orig_insn = insn;
+ }
+
+ if (!next_insn_same_sec(file, last_orig_insn)) {
+ WARN("%s: don't know how to handle alternatives at end of section",
+ special_alt->orig_sec->name);
+ return -1;
+ }
+
+ fake_jump = malloc(sizeof(*fake_jump));
+ if (!fake_jump) {
+ WARN("malloc failed");
+ return -1;
+ }
+ memset(fake_jump, 0, sizeof(*fake_jump));
+ INIT_LIST_HEAD(&fake_jump->alts);
+ clear_insn_state(&fake_jump->state);
+
+ fake_jump->sec = special_alt->new_sec;
+ fake_jump->offset = -1;
+ fake_jump->type = INSN_JUMP_UNCONDITIONAL;
+ fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
+ fake_jump->ignore = true;
+
+ if (!special_alt->new_len) {
+ *new_insn = fake_jump;
+ return 0;
+ }
+
+ last_new_insn = NULL;
+ insn = *new_insn;
+ sec_for_each_insn_from(file, insn) {
+ if (insn->offset >= special_alt->new_off + special_alt->new_len)
+ break;
+
+ last_new_insn = insn;
+
+ if (insn->type != INSN_JUMP_CONDITIONAL &&
+ insn->type != INSN_JUMP_UNCONDITIONAL)
+ continue;
+
+ if (!insn->immediate)
+ continue;
+
+ dest_off = insn->offset + insn->len + insn->immediate;
+ if (dest_off == special_alt->new_off + special_alt->new_len)
+ insn->jump_dest = fake_jump;
+
+ if (!insn->jump_dest) {
+ WARN_FUNC("can't find alternative jump destination",
+ insn->sec, insn->offset);
+ return -1;
+ }
+ }
+
+ if (!last_new_insn) {
+ WARN_FUNC("can't find last new alternative instruction",
+ special_alt->new_sec, special_alt->new_off);
+ return -1;
+ }
+
+ list_add(&fake_jump->list, &last_new_insn->list);
+
+ return 0;
+}
+
+/*
+ * A jump table entry can either convert a nop to a jump or a jump to a nop.
+ * If the original instruction is a jump, make the alt entry an effective nop
+ * by just skipping the original instruction.
+ */
+static int handle_jump_alt(struct objtool_file *file,
+ struct special_alt *special_alt,
+ struct instruction *orig_insn,
+ struct instruction **new_insn)
+{
+ if (orig_insn->type == INSN_NOP)
+ return 0;
+
+ if (orig_insn->type != INSN_JUMP_UNCONDITIONAL) {
+ WARN_FUNC("unsupported instruction at jump label",
+ orig_insn->sec, orig_insn->offset);
+ return -1;
+ }
+
+ *new_insn = list_next_entry(orig_insn, list);
+ return 0;
+}
+
+/*
+ * Read all the special sections which have alternate instructions which can be
+ * patched in or redirected to at runtime. Each instruction having alternate
+ * instruction(s) has them added to its insn->alts list, which will be
+ * traversed in validate_branch().
+ */
+static int add_special_section_alts(struct objtool_file *file)
+{
+ struct list_head special_alts;
+ struct instruction *orig_insn, *new_insn;
+ struct special_alt *special_alt, *tmp;
+ struct alternative *alt;
+ int ret;
+
+ ret = special_get_alts(file->elf, &special_alts);
+ if (ret)
+ return ret;
+
+ list_for_each_entry_safe(special_alt, tmp, &special_alts, list) {
+ alt = malloc(sizeof(*alt));
+ if (!alt) {
+ WARN("malloc failed");
+ ret = -1;
+ goto out;
+ }
+
+ orig_insn = find_insn(file, special_alt->orig_sec,
+ special_alt->orig_off);
+ if (!orig_insn) {
+ WARN_FUNC("special: can't find orig instruction",
+ special_alt->orig_sec, special_alt->orig_off);
+ ret = -1;
+ goto out;
+ }
+
+ new_insn = NULL;
+ if (!special_alt->group || special_alt->new_len) {
+ new_insn = find_insn(file, special_alt->new_sec,
+ special_alt->new_off);
+ if (!new_insn) {
+ WARN_FUNC("special: can't find new instruction",
+ special_alt->new_sec,
+ special_alt->new_off);
+ ret = -1;
+ goto out;
+ }
+ }
+
+ if (special_alt->group) {
+ ret = handle_group_alt(file, special_alt, orig_insn,
+ &new_insn);
+ if (ret)
+ goto out;
+ } else if (special_alt->jump_or_nop) {
+ ret = handle_jump_alt(file, special_alt, orig_insn,
+ &new_insn);
+ if (ret)
+ goto out;
+ }
+
+ alt->insn = new_insn;
+ list_add_tail(&alt->list, &orig_insn->alts);
+
+ list_del(&special_alt->list);
+ free(special_alt);
+ }
+
+out:
+ return ret;
+}
+
+static int add_switch_table(struct objtool_file *file, struct symbol *func,
+ struct instruction *insn, struct rela *table,
+ struct rela *next_table)
+{
+ struct rela *rela = table;
+ struct instruction *alt_insn;
+ struct alternative *alt;
+
+ list_for_each_entry_from(rela, &file->rodata->rela->rela_list, list) {
+ if (rela == next_table)
+ break;
+
+ if (rela->sym->sec != insn->sec ||
+ rela->addend <= func->offset ||
+ rela->addend >= func->offset + func->len)
+ break;
+
+ alt_insn = find_insn(file, insn->sec, rela->addend);
+ if (!alt_insn) {
+ WARN("%s: can't find instruction at %s+0x%x",
+ file->rodata->rela->name, insn->sec->name,
+ rela->addend);
+ return -1;
+ }
+
+ alt = malloc(sizeof(*alt));
+ if (!alt) {
+ WARN("malloc failed");
+ return -1;
+ }
+
+ alt->insn = alt_insn;
+ list_add_tail(&alt->list, &insn->alts);
+ }
+
+ return 0;
+}
+
+/*
+ * find_switch_table() - Given a dynamic jump, find the switch jump table in
+ * .rodata associated with it.
+ *
+ * There are 3 basic patterns:
+ *
+ * 1. jmpq *[rodata addr](,%reg,8)
+ *
+ * This is the most common case by far. It jumps to an address in a simple
+ * jump table which is stored in .rodata.
+ *
+ * 2. jmpq *[rodata addr](%rip)
+ *
+ * This is caused by a rare GCC quirk, currently only seen in three driver
+ * functions in the kernel, only with certain obscure non-distro configs.
+ *
+ * As part of an optimization, GCC makes a copy of an existing switch jump
+ * table, modifies it, and then hard-codes the jump (albeit with an indirect
+ * jump) to use a single entry in the table. The rest of the jump table and
+ * some of its jump targets remain as dead code.
+ *
+ * In such a case we can just crudely ignore all unreachable instruction
+ * warnings for the entire object file. Ideally we would just ignore them
+ * for the function, but that would require redesigning the code quite a
+ * bit. And honestly that's just not worth doing: unreachable instruction
+ * warnings are of questionable value anyway, and this is such a rare issue.
+ *
+ * 3. mov [rodata addr],%reg1
+ * ... some instructions ...
+ * jmpq *(%reg1,%reg2,8)
+ *
+ * This is a fairly uncommon pattern which is new for GCC 6. As of this
+ * writing, there are 11 occurrences of it in the allmodconfig kernel.
+ *
+ * TODO: Once we have DWARF CFI and smarter instruction decoding logic,
+ * ensure the same register is used in the mov and jump instructions.
+ */
+static struct rela *find_switch_table(struct objtool_file *file,
+ struct symbol *func,
+ struct instruction *insn)
+{
+ struct rela *text_rela, *rodata_rela;
+ struct instruction *orig_insn = insn;
+
+ text_rela = find_rela_by_dest_range(insn->sec, insn->offset, insn->len);
+ if (text_rela && text_rela->sym == file->rodata->sym) {
+ /* case 1 */
+ rodata_rela = find_rela_by_dest(file->rodata,
+ text_rela->addend);
+ if (rodata_rela)
+ return rodata_rela;
+
+ /* case 2 */
+ rodata_rela = find_rela_by_dest(file->rodata,
+ text_rela->addend + 4);
+ if (!rodata_rela)
+ return NULL;
+ file->ignore_unreachables = true;
+ return rodata_rela;
+ }
+
+ /* case 3 */
+ func_for_each_insn_continue_reverse(file, func, insn) {
+ if (insn->type == INSN_JUMP_DYNAMIC)
+ break;
+
+ /* allow small jumps within the range */
+ if (insn->type == INSN_JUMP_UNCONDITIONAL &&
+ insn->jump_dest &&
+ (insn->jump_dest->offset <= insn->offset ||
+ insn->jump_dest->offset > orig_insn->offset))
+ break;
+
+ /* look for a relocation which references .rodata */
+ text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
+ insn->len);
+ if (!text_rela || text_rela->sym != file->rodata->sym)
+ continue;
+
+ /*
+ * Make sure the .rodata address isn't associated with a
+ * symbol. gcc jump tables are anonymous data.
+ */
+ if (find_symbol_containing(file->rodata, text_rela->addend))
+ continue;
+
+ return find_rela_by_dest(file->rodata, text_rela->addend);
+ }
+
+ return NULL;
+}
+
+static int add_func_switch_tables(struct objtool_file *file,
+ struct symbol *func)
+{
+ struct instruction *insn, *prev_jump = NULL;
+ struct rela *rela, *prev_rela = NULL;
+ int ret;
+
+ func_for_each_insn(file, func, insn) {
+ if (insn->type != INSN_JUMP_DYNAMIC)
+ continue;
+
+ rela = find_switch_table(file, func, insn);
+ if (!rela)
+ continue;
+
+ /*
+ * We found a switch table, but we don't know yet how big it
+ * is. Don't add it until we reach the end of the function or
+ * the beginning of another switch table in the same function.
+ */
+ if (prev_jump) {
+ ret = add_switch_table(file, func, prev_jump, prev_rela,
+ rela);
+ if (ret)
+ return ret;
+ }
+
+ prev_jump = insn;
+ prev_rela = rela;
+ }
+
+ if (prev_jump) {
+ ret = add_switch_table(file, func, prev_jump, prev_rela, NULL);
+ if (ret)
+ return ret;
+ }
+
+ return 0;
+}
+
+/*
+ * For some switch statements, gcc generates a jump table in the .rodata
+ * section which contains a list of addresses within the function to jump to.
+ * This finds these jump tables and adds them to the insn->alts lists.
+ */
+static int add_switch_table_alts(struct objtool_file *file)
+{
+ struct section *sec;
+ struct symbol *func;
+ int ret;
+
+ if (!file->rodata || !file->rodata->rela)
+ return 0;
+
+ for_each_sec(file, sec) {
+ list_for_each_entry(func, &sec->symbol_list, list) {
+ if (func->type != STT_FUNC)
+ continue;
+
+ ret = add_func_switch_tables(file, func);
+ if (ret)
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
+static int decode_sections(struct objtool_file *file)
+{
+ int ret;
+
+ ret = decode_instructions(file);
+ if (ret)
+ return ret;
+
+ ret = add_dead_ends(file);
+ if (ret)
+ return ret;
+
+ add_ignores(file);
+
+ ret = add_jump_destinations(file);
+ if (ret)
+ return ret;
+
+ ret = add_call_destinations(file);
+ if (ret)
+ return ret;
+
+ ret = add_special_section_alts(file);
+ if (ret)
+ return ret;
+
+ ret = add_switch_table_alts(file);
+ if (ret)
+ return ret;
+
+ return 0;
+}
+
+static bool is_fentry_call(struct instruction *insn)
+{
+ if (insn->type == INSN_CALL &&
+ insn->call_dest->type == STT_NOTYPE &&
+ !strcmp(insn->call_dest->name, "__fentry__"))
+ return true;
+
+ return false;
+}
+
+static bool has_modified_stack_frame(struct insn_state *state)
+{
+ int i;
+
+ if (state->cfa.base != initial_func_cfi.cfa.base ||
+ state->cfa.offset != initial_func_cfi.cfa.offset ||
+ state->stack_size != initial_func_cfi.cfa.offset ||
+ state->drap)
+ return true;
+
+ for (i = 0; i < CFI_NUM_REGS; i++)
+ if (state->regs[i].base != initial_func_cfi.regs[i].base ||
+ state->regs[i].offset != initial_func_cfi.regs[i].offset)
+ return true;
+
+ return false;
+}
+
+static bool has_valid_stack_frame(struct insn_state *state)
+{
+ if (state->cfa.base == CFI_BP && state->regs[CFI_BP].base == CFI_CFA &&
+ state->regs[CFI_BP].offset == -16)
+ return true;
+
+ if (state->drap && state->regs[CFI_BP].base == CFI_BP)
+ return true;
+
+ return false;
+}
+
+static void save_reg(struct insn_state *state, unsigned char reg, int base,
+ int offset)
+{
+ if ((arch_callee_saved_reg(reg) ||
+ (state->drap && reg == state->drap_reg)) &&
+ state->regs[reg].base == CFI_UNDEFINED) {
+ state->regs[reg].base = base;
+ state->regs[reg].offset = offset;
+ }
+}
+
+static void restore_reg(struct insn_state *state, unsigned char reg)
+{
+ state->regs[reg].base = CFI_UNDEFINED;
+ state->regs[reg].offset = 0;
+}
+
+/*
+ * A note about DRAP stack alignment:
+ *
+ * GCC has the concept of a DRAP register, which is used to help keep track of
+ * the stack pointer when aligning the stack. r10 or r13 is used as the DRAP
+ * register. The typical DRAP pattern is:
+ *
+ * 4c 8d 54 24 08 lea 0x8(%rsp),%r10
+ * 48 83 e4 c0 and $0xffffffffffffffc0,%rsp
+ * 41 ff 72 f8 pushq -0x8(%r10)
+ * 55 push %rbp
+ * 48 89 e5 mov %rsp,%rbp
+ * (more pushes)
+ * 41 52 push %r10
+ * ...
+ * 41 5a pop %r10
+ * (more pops)
+ * 5d pop %rbp
+ * 49 8d 62 f8 lea -0x8(%r10),%rsp
+ * c3 retq
+ *
+ * There are some variations in the epilogues, like:
+ *
+ * 5b pop %rbx
+ * 41 5a pop %r10
+ * 41 5c pop %r12
+ * 41 5d pop %r13
+ * 41 5e pop %r14
+ * c9 leaveq
+ * 49 8d 62 f8 lea -0x8(%r10),%rsp
+ * c3 retq
+ *
+ * and:
+ *
+ * 4c 8b 55 e8 mov -0x18(%rbp),%r10
+ * 48 8b 5d e0 mov -0x20(%rbp),%rbx
+ * 4c 8b 65 f0 mov -0x10(%rbp),%r12
+ * 4c 8b 6d f8 mov -0x8(%rbp),%r13
+ * c9 leaveq
+ * 49 8d 62 f8 lea -0x8(%r10),%rsp
+ * c3 retq
+ *
+ * Sometimes r13 is used as the DRAP register, in which case it's saved and
+ * restored beforehand:
+ *
+ * 41 55 push %r13
+ * 4c 8d 6c 24 10 lea 0x10(%rsp),%r13
+ * 48 83 e4 f0 and $0xfffffffffffffff0,%rsp
+ * ...
+ * 49 8d 65 f0 lea -0x10(%r13),%rsp
+ * 41 5d pop %r13
+ * c3 retq
+ */
+static int update_insn_state(struct instruction *insn, struct insn_state *state)
+{
+ struct stack_op *op = &insn->stack_op;
+ struct cfi_reg *cfa = &state->cfa;
+ struct cfi_reg *regs = state->regs;
+
+ /* stack operations don't make sense with an undefined CFA */
+ if (cfa->base == CFI_UNDEFINED) {
+ if (insn->func) {
+ WARN_FUNC("undefined stack state", insn->sec, insn->offset);
+ return -1;
+ }
+ return 0;
+ }
+
+ switch (op->dest.type) {
+
+ case OP_DEST_REG:
+ switch (op->src.type) {
+
+ case OP_SRC_REG:
+ if (cfa->base == op->src.reg && cfa->base == CFI_SP &&
+ op->dest.reg == CFI_BP && regs[CFI_BP].base == CFI_CFA &&
+ regs[CFI_BP].offset == -cfa->offset) {
+
+ /* mov %rsp, %rbp */
+ cfa->base = op->dest.reg;
+ state->bp_scratch = false;
+ } else if (state->drap) {
+
+ /* drap: mov %rsp, %rbp */
+ regs[CFI_BP].base = CFI_BP;
+ regs[CFI_BP].offset = -state->stack_size;
+ state->bp_scratch = false;
+ } else if (!nofp) {
+
+ WARN_FUNC("unknown stack-related register move",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ break;
+
+ case OP_SRC_ADD:
+ if (op->dest.reg == CFI_SP && op->src.reg == CFI_SP) {
+
+ /* add imm, %rsp */
+ state->stack_size -= op->src.offset;
+ if (cfa->base == CFI_SP)
+ cfa->offset -= op->src.offset;
+ break;
+ }
+
+ if (op->dest.reg == CFI_SP && op->src.reg == CFI_BP) {
+
+ /* lea disp(%rbp), %rsp */
+ state->stack_size = -(op->src.offset + regs[CFI_BP].offset);
+ break;
+ }
+
+ if (op->dest.reg != CFI_BP && op->src.reg == CFI_SP &&
+ cfa->base == CFI_SP) {
+
+ /* drap: lea disp(%rsp), %drap */
+ state->drap_reg = op->dest.reg;
+ break;
+ }
+
+ if (state->drap && op->dest.reg == CFI_SP &&
+ op->src.reg == state->drap_reg) {
+
+ /* drap: lea disp(%drap), %rsp */
+ cfa->base = CFI_SP;
+ cfa->offset = state->stack_size = -op->src.offset;
+ state->drap_reg = CFI_UNDEFINED;
+ state->drap = false;
+ break;
+ }
+
+ if (op->dest.reg == state->cfa.base) {
+ WARN_FUNC("unsupported stack register modification",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ break;
+
+ case OP_SRC_AND:
+ if (op->dest.reg != CFI_SP ||
+ (state->drap_reg != CFI_UNDEFINED && cfa->base != CFI_SP) ||
+ (state->drap_reg == CFI_UNDEFINED && cfa->base != CFI_BP)) {
+ WARN_FUNC("unsupported stack pointer realignment",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ if (state->drap_reg != CFI_UNDEFINED) {
+ /* drap: and imm, %rsp */
+ cfa->base = state->drap_reg;
+ cfa->offset = state->stack_size = 0;
+ state->drap = true;
+
+ }
+
+ /*
+ * Older versions of GCC (4.8ish) realign the stack
+ * without DRAP, with a frame pointer.
+ */
+
+ break;
+
+ case OP_SRC_POP:
+ if (!state->drap && op->dest.type == OP_DEST_REG &&
+ op->dest.reg == cfa->base) {
+
+ /* pop %rbp */
+ cfa->base = CFI_SP;
+ }
+
+ if (regs[op->dest.reg].offset == -state->stack_size) {
+
+ if (state->drap && cfa->base == CFI_BP_INDIRECT &&
+ op->dest.type == OP_DEST_REG &&
+ op->dest.reg == state->drap_reg) {
+
+ /* drap: pop %drap */
+ cfa->base = state->drap_reg;
+ cfa->offset = 0;
+ }
+
+ restore_reg(state, op->dest.reg);
+ }
+
+ state->stack_size -= 8;
+ if (cfa->base == CFI_SP)
+ cfa->offset -= 8;
+
+ break;
+
+ case OP_SRC_REG_INDIRECT:
+ if (state->drap && op->src.reg == CFI_BP &&
+ op->src.offset == regs[op->dest.reg].offset) {
+
+ /* drap: mov disp(%rbp), %reg */
+ if (op->dest.reg == state->drap_reg) {
+ cfa->base = state->drap_reg;
+ cfa->offset = 0;
+ }
+
+ restore_reg(state, op->dest.reg);
+
+ } else if (op->src.reg == cfa->base &&
+ op->src.offset == regs[op->dest.reg].offset + cfa->offset) {
+
+ /* mov disp(%rbp), %reg */
+ /* mov disp(%rsp), %reg */
+ restore_reg(state, op->dest.reg);
+ }
+
+ break;
+
+ default:
+ WARN_FUNC("unknown stack-related instruction",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ break;
+
+ case OP_DEST_PUSH:
+ state->stack_size += 8;
+ if (cfa->base == CFI_SP)
+ cfa->offset += 8;
+
+ if (op->src.type != OP_SRC_REG)
+ break;
+
+ if (state->drap) {
+ if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
+
+ /* drap: push %drap */
+ cfa->base = CFI_BP_INDIRECT;
+ cfa->offset = -state->stack_size;
+
+ /* save drap so we know when to undefine it */
+ save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
+
+ } else if (op->src.reg == CFI_BP && cfa->base == state->drap_reg) {
+
+ /* drap: push %rbp */
+ state->stack_size = 0;
+
+ } else if (regs[op->src.reg].base == CFI_UNDEFINED) {
+
+ /* drap: push %reg */
+ save_reg(state, op->src.reg, CFI_BP, -state->stack_size);
+ }
+
+ } else {
+
+ /* push %reg */
+ save_reg(state, op->src.reg, CFI_CFA, -state->stack_size);
+ }
+
+ /* detect when asm code uses rbp as a scratch register */
+ if (!nofp && insn->func && op->src.reg == CFI_BP &&
+ cfa->base != CFI_BP)
+ state->bp_scratch = true;
+ break;
+
+ case OP_DEST_REG_INDIRECT:
+
+ if (state->drap) {
+ if (op->src.reg == cfa->base && op->src.reg == state->drap_reg) {
+
+ /* drap: mov %drap, disp(%rbp) */
+ cfa->base = CFI_BP_INDIRECT;
+ cfa->offset = op->dest.offset;
+
+ /* save drap so we know when to undefine it */
+ save_reg(state, op->src.reg, CFI_CFA, op->dest.offset);
+ }
+
+ else if (regs[op->src.reg].base == CFI_UNDEFINED) {
+
+ /* drap: mov reg, disp(%rbp) */
+ save_reg(state, op->src.reg, CFI_BP, op->dest.offset);
+ }
+
+ } else if (op->dest.reg == cfa->base) {
+
+ /* mov reg, disp(%rbp) */
+ /* mov reg, disp(%rsp) */
+ save_reg(state, op->src.reg, CFI_CFA,
+ op->dest.offset - state->cfa.offset);
+ }
+
+ break;
+
+ case OP_DEST_LEAVE:
+ if ((!state->drap && cfa->base != CFI_BP) ||
+ (state->drap && cfa->base != state->drap_reg)) {
+ WARN_FUNC("leave instruction with modified stack frame",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ /* leave (mov %rbp, %rsp; pop %rbp) */
+
+ state->stack_size = -state->regs[CFI_BP].offset - 8;
+ restore_reg(state, CFI_BP);
+
+ if (!state->drap) {
+ cfa->base = CFI_SP;
+ cfa->offset -= 8;
+ }
+
+ break;
+
+ case OP_DEST_MEM:
+ if (op->src.type != OP_SRC_POP) {
+ WARN_FUNC("unknown stack-related memory operation",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ /* pop mem */
+ state->stack_size -= 8;
+ if (cfa->base == CFI_SP)
+ cfa->offset -= 8;
+
+ break;
+
+ default:
+ WARN_FUNC("unknown stack-related instruction",
+ insn->sec, insn->offset);
+ return -1;
+ }
+
+ return 0;
+}
+
+static bool insn_state_match(struct instruction *insn, struct insn_state *state)
+{
+ struct insn_state *state1 = &insn->state, *state2 = state;
+ int i;
+
+ if (memcmp(&state1->cfa, &state2->cfa, sizeof(state1->cfa))) {
+ WARN_FUNC("stack state mismatch: cfa1=%d%+d cfa2=%d%+d",
+ insn->sec, insn->offset,
+ state1->cfa.base, state1->cfa.offset,
+ state2->cfa.base, state2->cfa.offset);
+
+ } else if (memcmp(&state1->regs, &state2->regs, sizeof(state1->regs))) {
+ for (i = 0; i < CFI_NUM_REGS; i++) {
+ if (!memcmp(&state1->regs[i], &state2->regs[i],
+ sizeof(struct cfi_reg)))
+ continue;
+
+ WARN_FUNC("stack state mismatch: reg1[%d]=%d%+d reg2[%d]=%d%+d",
+ insn->sec, insn->offset,
+ i, state1->regs[i].base, state1->regs[i].offset,
+ i, state2->regs[i].base, state2->regs[i].offset);
+ break;
+ }
+
+ } else if (state1->drap != state2->drap ||
+ (state1->drap && state1->drap_reg != state2->drap_reg)) {
+ WARN_FUNC("stack state mismatch: drap1=%d(%d) drap2=%d(%d)",
+ insn->sec, insn->offset,
+ state1->drap, state1->drap_reg,
+ state2->drap, state2->drap_reg);
+
+ } else
+ return true;
+
+ return false;
+}
+
+/*
+ * Follow the branch starting at the given instruction, and recursively follow
+ * any other branches (jumps). Meanwhile, track the frame pointer state at
+ * each instruction and validate all the rules described in
+ * tools/objtool/Documentation/stack-validation.txt.
+ */
+static int validate_branch(struct objtool_file *file, struct instruction *first,
+ struct insn_state state)
+{
+ struct alternative *alt;
+ struct instruction *insn;
+ struct section *sec;
+ struct symbol *func = NULL;
+ int ret;
+
+ insn = first;
+ sec = insn->sec;
+
+ if (insn->alt_group && list_empty(&insn->alts)) {
+ WARN_FUNC("don't know how to handle branch to middle of alternative instruction group",
+ sec, insn->offset);
+ return -1;
+ }
+
+ while (1) {
+ if (file->c_file && insn->func) {
+ if (func && func != insn->func) {
+ WARN("%s() falls through to next function %s()",
+ func->name, insn->func->name);
+ return 1;
+ }
+ }
+
+ func = insn->func;
+
+ if (insn->visited) {
+ if (!!insn_state_match(insn, &state))
+ return 1;
+
+ return 0;
+ }
+
+ insn->state = state;
+
+ insn->visited = true;
+
+ list_for_each_entry(alt, &insn->alts, list) {
+ ret = validate_branch(file, alt->insn, state);
+ if (ret)
+ return 1;
+ }
+
+ switch (insn->type) {
+
+ case INSN_RETURN:
+ if (func && has_modified_stack_frame(&state)) {
+ WARN_FUNC("return with modified stack frame",
+ sec, insn->offset);
+ return 1;
+ }
+
+ if (state.bp_scratch) {
+ WARN("%s uses BP as a scratch register",
+ insn->func->name);
+ return 1;
+ }
+
+ return 0;
+
+ case INSN_CALL:
+ if (is_fentry_call(insn))
+ break;
+
+ ret = dead_end_function(file, insn->call_dest);
+ if (ret == 1)
+ return 0;
+ if (ret == -1)
+ return 1;
+
+ /* fallthrough */
+ case INSN_CALL_DYNAMIC:
+ if (!nofp && func && !has_valid_stack_frame(&state)) {
+ WARN_FUNC("call without frame pointer save/setup",
+ sec, insn->offset);
+ return 1;
+ }
+ break;
+
+ case INSN_JUMP_CONDITIONAL:
+ case INSN_JUMP_UNCONDITIONAL:
+ if (insn->jump_dest) {
+ ret = validate_branch(file, insn->jump_dest,
+ state);
+ if (ret)
+ return 1;
+ } else if (func && has_modified_stack_frame(&state)) {
+ WARN_FUNC("sibling call from callable instruction with modified stack frame",
+ sec, insn->offset);
+ return 1;
+ } /* else it's a sibling call */
+
+ if (insn->type == INSN_JUMP_UNCONDITIONAL)
+ return 0;
+
+ break;
+
+ case INSN_JUMP_DYNAMIC:
+ if (func && list_empty(&insn->alts) &&
+ has_modified_stack_frame(&state)) {
+ WARN_FUNC("sibling call from callable instruction with modified stack frame",
+ sec, insn->offset);
+ return 1;
+ }
+
+ return 0;
+
+ case INSN_STACK:
+ if (update_insn_state(insn, &state))
+ return -1;
+
+ break;
+
+ default:
+ break;
+ }
+
+ if (insn->dead_end)
+ return 0;
+
+ insn = next_insn_same_sec(file, insn);
+ if (!insn) {
+ WARN("%s: unexpected end of section", sec->name);
+ return 1;
+ }
+ }
+
+ return 0;
+}
+
+static bool is_kasan_insn(struct instruction *insn)
+{
+ return (insn->type == INSN_CALL &&
+ !strcmp(insn->call_dest->name, "__asan_handle_no_return"));
+}
+
+static bool is_ubsan_insn(struct instruction *insn)
+{
+ return (insn->type == INSN_CALL &&
+ !strcmp(insn->call_dest->name,
+ "__ubsan_handle_builtin_unreachable"));
+}
+
+static bool ignore_unreachable_insn(struct instruction *insn)
+{
+ int i;
+
+ if (insn->ignore || insn->type == INSN_NOP)
+ return true;
+
+ /*
+ * Ignore any unused exceptions. This can happen when a whitelisted
+ * function has an exception table entry.
+ */
+ if (!strcmp(insn->sec->name, ".fixup"))
+ return true;
+
+ /*
+ * Check if this (or a subsequent) instruction is related to
+ * CONFIG_UBSAN or CONFIG_KASAN.
+ *
+ * End the search at 5 instructions to avoid going into the weeds.
+ */
+ if (!insn->func)
+ return false;
+ for (i = 0; i < 5; i++) {
+
+ if (is_kasan_insn(insn) || is_ubsan_insn(insn))
+ return true;
+
+ if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest) {
+ insn = insn->jump_dest;
+ continue;
+ }
+
+ if (insn->offset + insn->len >= insn->func->offset + insn->func->len)
+ break;
+ insn = list_next_entry(insn, list);
+ }
+
+ return false;
+}
+
+static int validate_functions(struct objtool_file *file)
+{
+ struct section *sec;
+ struct symbol *func;
+ struct instruction *insn;
+ struct insn_state state;
+ int ret, warnings = 0;
+
+ clear_insn_state(&state);
+
+ state.cfa = initial_func_cfi.cfa;
+ memcpy(&state.regs, &initial_func_cfi.regs,
+ CFI_NUM_REGS * sizeof(struct cfi_reg));
+ state.stack_size = initial_func_cfi.cfa.offset;
+
+ for_each_sec(file, sec) {
+ list_for_each_entry(func, &sec->symbol_list, list) {
+ if (func->type != STT_FUNC)
+ continue;
+
+ insn = find_insn(file, sec, func->offset);
+ if (!insn || insn->ignore)
+ continue;
+
+ ret = validate_branch(file, insn, state);
+ warnings += ret;
+ }
+ }
+
+ return warnings;
+}
+
+static int validate_reachable_instructions(struct objtool_file *file)
+{
+ struct instruction *insn;
+
+ if (file->ignore_unreachables)
+ return 0;
+
+ for_each_insn(file, insn) {
+ if (insn->visited || ignore_unreachable_insn(insn))
+ continue;
+
+ /*
+ * gcov produces a lot of unreachable instructions. If we get
+ * an unreachable warning and the file has gcov enabled, just
+ * ignore it, and all other such warnings for the file. Do
+ * this here because this is an expensive function.
+ */
+ if (gcov_enabled(file))
+ return 0;
+
+ WARN_FUNC("unreachable instruction", insn->sec, insn->offset);
+ return 1;
+ }
+
+ return 0;
+}
+
+static void cleanup(struct objtool_file *file)
+{
+ struct instruction *insn, *tmpinsn;
+ struct alternative *alt, *tmpalt;
+
+ list_for_each_entry_safe(insn, tmpinsn, &file->insn_list, list) {
+ list_for_each_entry_safe(alt, tmpalt, &insn->alts, list) {
+ list_del(&alt->list);
+ free(alt);
+ }
+ list_del(&insn->list);
+ hash_del(&insn->hash);
+ free(insn);
+ }
+ elf_close(file->elf);
+}
+
+int check(const char *_objname, bool _nofp)
+{
+ struct objtool_file file;
+ int ret, warnings = 0;
+
+ objname = _objname;
+ nofp = _nofp;
+
+ file.elf = elf_open(objname);
+ if (!file.elf)
+ return 1;
+
+ INIT_LIST_HEAD(&file.insn_list);
+ hash_init(file.insn_hash);
+ file.whitelist = find_section_by_name(file.elf, ".discard.func_stack_frame_non_standard");
+ file.rodata = find_section_by_name(file.elf, ".rodata");
+ file.ignore_unreachables = false;
+ file.c_file = find_section_by_name(file.elf, ".comment");
+
+ arch_initial_func_cfi_state(&initial_func_cfi);
+
+ ret = decode_sections(&file);
+ if (ret < 0)
+ goto out;
+ warnings += ret;
+
+ if (list_empty(&file.insn_list))
+ goto out;
+
+ ret = validate_functions(&file);
+ if (ret < 0)
+ goto out;
+ warnings += ret;
+
+ if (!warnings) {
+ ret = validate_reachable_instructions(&file);
+ if (ret < 0)
+ goto out;
+ warnings += ret;
+ }
+
+out:
+ cleanup(&file);
+
+ /* ignore warnings for now until we get all the code cleaned up */
+ if (ret || warnings)
+ return 0;
+ return 0;
+}
diff --git a/tools/objtool/check.h b/tools/objtool/check.h
new file mode 100644
index 000000000000..da85f5b00ec6
--- /dev/null
+++ b/tools/objtool/check.h
@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2017 Josh Poimboeuf <jpoimboe@...hat.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _CHECK_H
+#define _CHECK_H
+
+#include <stdbool.h>
+#include "elf.h"
+#include "cfi.h"
+#include "arch.h"
+#include <linux/hashtable.h>
+
+struct insn_state {
+ struct cfi_reg cfa;
+ struct cfi_reg regs[CFI_NUM_REGS];
+ int stack_size;
+ bool bp_scratch;
+ bool drap;
+ int drap_reg;
+};
+
+struct instruction {
+ struct list_head list;
+ struct hlist_node hash;
+ struct section *sec;
+ unsigned long offset;
+ unsigned int len;
+ unsigned char type;
+ unsigned long immediate;
+ bool alt_group, visited, dead_end, ignore;
+ struct symbol *call_dest;
+ struct instruction *jump_dest;
+ struct list_head alts;
+ struct symbol *func;
+ struct stack_op stack_op;
+ struct insn_state state;
+};
+
+struct objtool_file {
+ struct elf *elf;
+ struct list_head insn_list;
+ DECLARE_HASHTABLE(insn_hash, 16);
+ struct section *rodata, *whitelist;
+ bool ignore_unreachables, c_file;
+};
+
+int check(const char *objname, bool nofp);
+
+#define for_each_insn(file, insn) \
+ list_for_each_entry(insn, &file->insn_list, list)
+
+#endif /* _CHECK_H */
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index d897702ce742..1a7e8aa2af58 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -37,6 +37,9 @@
#define ELF_C_READ_MMAP ELF_C_READ
#endif
+#define WARN_ELF(format, ...) \
+ WARN(format ": %s", ##__VA_ARGS__, elf_errmsg(-1))
+
struct section *find_section_by_name(struct elf *elf, const char *name)
{
struct section *sec;
@@ -139,12 +142,12 @@ static int read_sections(struct elf *elf)
int i;
if (elf_getshdrnum(elf->elf, §ions_nr)) {
- perror("elf_getshdrnum");
+ WARN_ELF("elf_getshdrnum");
return -1;
}
if (elf_getshdrstrndx(elf->elf, &shstrndx)) {
- perror("elf_getshdrstrndx");
+ WARN_ELF("elf_getshdrstrndx");
return -1;
}
@@ -165,37 +168,36 @@ static int read_sections(struct elf *elf)
s = elf_getscn(elf->elf, i);
if (!s) {
- perror("elf_getscn");
+ WARN_ELF("elf_getscn");
return -1;
}
sec->idx = elf_ndxscn(s);
if (!gelf_getshdr(s, &sec->sh)) {
- perror("gelf_getshdr");
+ WARN_ELF("gelf_getshdr");
return -1;
}
sec->name = elf_strptr(elf->elf, shstrndx, sec->sh.sh_name);
if (!sec->name) {
- perror("elf_strptr");
+ WARN_ELF("elf_strptr");
return -1;
}
- sec->elf_data = elf_getdata(s, NULL);
- if (!sec->elf_data) {
- perror("elf_getdata");
+ sec->data = elf_getdata(s, NULL);
+ if (!sec->data) {
+ WARN_ELF("elf_getdata");
return -1;
}
- if (sec->elf_data->d_off != 0 ||
- sec->elf_data->d_size != sec->sh.sh_size) {
+ if (sec->data->d_off != 0 ||
+ sec->data->d_size != sec->sh.sh_size) {
WARN("unexpected data attributes for %s", sec->name);
return -1;
}
- sec->data = (unsigned long)sec->elf_data->d_buf;
- sec->len = sec->elf_data->d_size;
+ sec->len = sec->data->d_size;
}
/* sanity check, one more call to elf_nextscn() should return NULL */
@@ -232,15 +234,15 @@ static int read_symbols(struct elf *elf)
sym->idx = i;
- if (!gelf_getsym(symtab->elf_data, i, &sym->sym)) {
- perror("gelf_getsym");
+ if (!gelf_getsym(symtab->data, i, &sym->sym)) {
+ WARN_ELF("gelf_getsym");
goto err;
}
sym->name = elf_strptr(elf->elf, symtab->sh.sh_link,
sym->sym.st_name);
if (!sym->name) {
- perror("elf_strptr");
+ WARN_ELF("elf_strptr");
goto err;
}
@@ -322,8 +324,8 @@ static int read_relas(struct elf *elf)
}
memset(rela, 0, sizeof(*rela));
- if (!gelf_getrela(sec->elf_data, i, &rela->rela)) {
- perror("gelf_getrela");
+ if (!gelf_getrela(sec->data, i, &rela->rela)) {
+ WARN_ELF("gelf_getrela");
return -1;
}
@@ -362,12 +364,6 @@ struct elf *elf_open(const char *name)
INIT_LIST_HEAD(&elf->sections);
- elf->name = strdup(name);
- if (!elf->name) {
- perror("strdup");
- goto err;
- }
-
elf->fd = open(name, O_RDONLY);
if (elf->fd == -1) {
perror("open");
@@ -376,12 +372,12 @@ struct elf *elf_open(const char *name)
elf->elf = elf_begin(elf->fd, ELF_C_READ_MMAP, NULL);
if (!elf->elf) {
- perror("elf_begin");
+ WARN_ELF("elf_begin");
goto err;
}
if (!gelf_getehdr(elf->elf, &elf->ehdr)) {
- perror("gelf_getehdr");
+ WARN_ELF("gelf_getehdr");
goto err;
}
@@ -407,6 +403,12 @@ void elf_close(struct elf *elf)
struct symbol *sym, *tmpsym;
struct rela *rela, *tmprela;
+ if (elf->elf)
+ elf_end(elf->elf);
+
+ if (elf->fd > 0)
+ close(elf->fd);
+
list_for_each_entry_safe(sec, tmpsec, &elf->sections, list) {
list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {
list_del(&sym->list);
@@ -421,11 +423,6 @@ void elf_close(struct elf *elf)
list_del(&sec->list);
free(sec);
}
- if (elf->name)
- free(elf->name);
- if (elf->fd > 0)
- close(elf->fd);
- if (elf->elf)
- elf_end(elf->elf);
+
free(elf);
}
diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index 731973e1a3f5..343968b778cb 100644
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -37,10 +37,9 @@ struct section {
DECLARE_HASHTABLE(rela_hash, 16);
struct section *base, *rela;
struct symbol *sym;
- Elf_Data *elf_data;
+ Elf_Data *data;
char *name;
int idx;
- unsigned long data;
unsigned int len;
};
@@ -86,6 +85,7 @@ struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
struct symbol *find_containing_func(struct section *sec, unsigned long offset);
void elf_close(struct elf *elf);
-
+#define for_each_sec(file, sec) \
+ list_for_each_entry(sec, &file->elf->sections, list)
#endif /* _OBJTOOL_ELF_H */
diff --git a/tools/objtool/special.c b/tools/objtool/special.c
index bff8abb3a4aa..84f001d52322 100644
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -91,16 +91,16 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry,
alt->jump_or_nop = entry->jump_or_nop;
if (alt->group) {
- alt->orig_len = *(unsigned char *)(sec->data + offset +
+ alt->orig_len = *(unsigned char *)(sec->data->d_buf + offset +
entry->orig_len);
- alt->new_len = *(unsigned char *)(sec->data + offset +
+ alt->new_len = *(unsigned char *)(sec->data->d_buf + offset +
entry->new_len);
}
if (entry->feature) {
unsigned short feature;
- feature = *(unsigned short *)(sec->data + offset +
+ feature = *(unsigned short *)(sec->data->d_buf + offset +
entry->feature);
/*
diff --git a/tools/objtool/warn.h b/tools/objtool/warn.h
index ac7e07523e84..afd9f7a05f6d 100644
--- a/tools/objtool/warn.h
+++ b/tools/objtool/warn.h
@@ -18,6 +18,13 @@
#ifndef _WARN_H
#define _WARN_H
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include "elf.h"
+
extern const char *objname;
static inline char *offstr(struct section *sec, unsigned long offset)
@@ -57,4 +64,7 @@ static inline char *offstr(struct section *sec, unsigned long offset)
free(_str); \
})
+#define WARN_ELF(format, ...) \
+ WARN(format ": %s", ##__VA_ARGS__, elf_errmsg(-1))
+
#endif /* _WARN_H */
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