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Date: Fri, 25 Aug 2017 15:31:11 -0500
From: Josh Poimboeuf <jpoimboe@...hat.com>
To: Jiri Slaby <jslaby@...e.cz>
Cc: "x86@...nel.org" <x86@...nel.org>,
Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: WARNING: at arch/x86/kernel/stacktrace.c:132
save_stack_trace_tsk_reliable
On Fri, Aug 25, 2017 at 10:01:58AM -0500, Josh Poimboeuf wrote:
> On Fri, Aug 25, 2017 at 03:54:12PM +0200, Jiri Slaby wrote:
> > So now, there are two things:
> > 1) how to fix orc_find & unwind_init properly?
> > 2) how to generate an EMPTY hint for secondary_startup_64 and maybe
> > later REGS hint after the rsp setup there? The function seems to be a
> > pretty killer for orc generate (among others in head_64.S):
>
> I think the solution is to get head_64.S annotated properly. Then there
> won't be a gap between _stext and the first ORC entry, and we won't need
> to fix __orc_find().
>
> I can work up a patch for you to test with.
Can you try this?
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 287eac7d207f..e2315aecc441 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -26,7 +26,6 @@ KASAN_SANITIZE_dumpstack.o := n
KASAN_SANITIZE_dumpstack_$(BITS).o := n
KASAN_SANITIZE_stacktrace.o := n
-OBJECT_FILES_NON_STANDARD_head_$(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
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 513cbb012ecc..a0970b3bfd89 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -49,6 +49,7 @@ L3_START_KERNEL = pud_index(__START_KERNEL_map)
.code64
.globl startup_64
startup_64:
+ UNWIND_HINT_EMPTY
/*
* At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
* and someone has loaded an identity mapped page table
@@ -88,6 +89,7 @@ startup_64:
addq $(early_top_pgt - __START_KERNEL_map), %rax
jmp 1f
ENTRY(secondary_startup_64)
+ UNWIND_HINT_EMPTY
/*
* At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
* and someone has loaded a mapped page table.
@@ -132,6 +134,7 @@ ENTRY(secondary_startup_64)
movq $1f, %rax
jmp *%rax
1:
+ UNWIND_HINT_EMPTY
/* Check if nx is implemented */
movl $0x80000001, %eax
@@ -234,7 +237,8 @@ ENTRY(secondary_startup_64)
pushq %rax # target address in negative space
lretq
.Lafter_lret:
-ENDPROC(secondary_startup_64)
+ nop
+END(secondary_startup_64)
#include "verify_cpu.S"
@@ -246,6 +250,7 @@ ENDPROC(secondary_startup_64)
*/
ENTRY(start_cpu0)
movq initial_stack(%rip), %rsp
+ UNWIND_HINT_EMPTY
jmp .Ljump_to_C_code
ENDPROC(start_cpu0)
#endif
@@ -265,26 +270,24 @@ ENDPROC(start_cpu0)
.quad init_thread_union + THREAD_SIZE - SIZEOF_PTREGS
__FINITDATA
-bad_address:
- jmp bad_address
-
__INIT
ENTRY(early_idt_handler_array)
- # 104(%rsp) %rflags
- # 96(%rsp) %cs
- # 88(%rsp) %rip
- # 80(%rsp) error code
i = 0
.rept NUM_EXCEPTION_VECTORS
.ifeq (EXCEPTION_ERRCODE_MASK >> i) & 1
- pushq $0 # Dummy error code, to make stack frame uniform
+ UNWIND_HINT_IRET_REGS
+ pushq $0 # Dummy error code, to make stack frame uniform
+ .else
+ UNWIND_HINT_IRET_REGS offset=8
.endif
pushq $i # 72(%rsp) Vector number
jmp early_idt_handler_common
+ UNWIND_HINT_IRET_REGS
i = i + 1
.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
.endr
-ENDPROC(early_idt_handler_array)
+ UNWIND_HINT_IRET_REGS offset=16
+END(early_idt_handler_array)
early_idt_handler_common:
/*
@@ -312,6 +315,7 @@ early_idt_handler_common:
pushq %r13 /* pt_regs->r13 */
pushq %r14 /* pt_regs->r14 */
pushq %r15 /* pt_regs->r15 */
+ UNWIND_HINT_REGS
cmpq $14,%rsi /* Page fault? */
jnz 10f
@@ -327,7 +331,7 @@ early_idt_handler_common:
20:
decl early_recursion_flag(%rip)
jmp restore_regs_and_iret
-ENDPROC(early_idt_handler_common)
+END(early_idt_handler_common)
__INITDATA
@@ -434,7 +438,7 @@ ENTRY(phys_base)
EXPORT_SYMBOL(phys_base)
#include "../../x86/xen/xen-head.S"
-
+
__PAGE_ALIGNED_BSS
NEXT_PAGE(empty_zero_page)
.skip PAGE_SIZE
diff --git a/arch/x86/kernel/verify_cpu.S b/arch/x86/kernel/verify_cpu.S
index 014ea59aa153..3d3c2f71f617 100644
--- a/arch/x86/kernel/verify_cpu.S
+++ b/arch/x86/kernel/verify_cpu.S
@@ -33,7 +33,7 @@
#include <asm/cpufeatures.h>
#include <asm/msr-index.h>
-verify_cpu:
+ENTRY(verify_cpu)
pushf # Save caller passed flags
push $0 # Kill any dangerous flags
popf
@@ -139,3 +139,4 @@ verify_cpu:
popf # Restore caller passed flags
xorl %eax, %eax
ret
+ENDPROC(verify_cpu)
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index a7525e95d53f..8f9741cbb32f 100644
--- a/arch/x86/xen/xen-head.S
+++ b/arch/x86/xen/xen-head.S
@@ -19,6 +19,7 @@
#ifdef CONFIG_XEN_PV
__INIT
ENTRY(startup_xen)
+ UNWIND_HINT_EMPTY
cld
/* Clear .bss */
@@ -33,21 +34,24 @@ ENTRY(startup_xen)
mov $init_thread_union+THREAD_SIZE, %_ASM_SP
jmp xen_start_kernel
-
+END(startup_xen)
__FINIT
#endif
.pushsection .text
.balign PAGE_SIZE
ENTRY(hypercall_page)
- .skip PAGE_SIZE
+ .rept (PAGE_SIZE / 32)
+ UNWIND_HINT_EMPTY
+ .skip 32
+ .endr
#define HYPERCALL(n) \
.equ xen_hypercall_##n, hypercall_page + __HYPERVISOR_##n * 32; \
.type xen_hypercall_##n, @function; .size xen_hypercall_##n, 32
#include <asm/xen-hypercalls.h>
#undef HYPERCALL
-
+END(hypercall_page)
.popsection
ELFNOTE(Xen, XEN_ELFNOTE_GUEST_OS, .asciz "linux")
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 5d6a3be10aee..21b432e417df 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1765,11 +1765,13 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
if (insn->dead_end)
return 0;
- insn = next_insn;
- if (!insn) {
+ if (!next_insn) {
+ if (state.cfa.base == CFI_UNDEFINED)
+ return 0;
WARN("%s: unexpected end of section", sec->name);
return 1;
}
+ insn = next_insn;
}
return 0;
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