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Date: Thu, 15 Aug 2019 18:07:19 +0200
From: Borislav Petkov <bp@...en8.de>
To: Jiri Slaby <jslaby@...e.cz>
Cc: tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
x86@...nel.org, linux-arch@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 05/28] x86/asm: annotate local pseudo-functions
On Thu, Aug 08, 2019 at 12:38:31PM +0200, Jiri Slaby wrote:
> Use the newly added SYM_CODE_START_LOCAL* to annotate starts of all
> pseudo-functions (those ending END until now) which do not have ".globl"
> annotation. This is needed to balance END for tools that generate
> debuginfo. Note that we switch from END to SYM_CODE_END too so that
> everybody can see the pairing.
Please get rid of the "we" etc personal pronouns in the commit messages
and make them all impartial and passive.
> We are not annotating C-like functions (which handle frame ptr etc.)
> here, hence we use SYM_CODE_* macros here, not SYM_FUNC_*. Note that
> early_idt_handler_common already had ENDPROC -- switch that to
> SYM_CODE_END for the same reason as above.
>
> bogus_64_magic, bad_address, bad_get_user*, and bad_put_user are now
> aligned, as they are separate functions. They do not mind to be aligned
> -- no need to be compact there.
>
> early_idt_handler_common is aligned now too, as it is after
> early_idt_handler_array, so as well no need to be compact there.
>
> verify_cpu is self-standing and included in other .S files, so align it
> too.
>
> The others have alignment preserved to what it used to be (using the
> _NOALIGN variant of macros).
>
> [v3] annotate more functions
> [v4] describe the alignments changes
>
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: <x86@...nel.org>
> ---
> arch/x86/entry/entry_64.S | 3 ++-
> arch/x86/kernel/acpi/wakeup_64.S | 3 ++-
> arch/x86/kernel/head_32.S | 4 ++--
> arch/x86/kernel/head_64.S | 4 ++--
> arch/x86/kernel/verify_cpu.S | 4 ++--
> arch/x86/lib/getuser.S | 6 ++++--
> arch/x86/lib/putuser.S | 3 ++-
> 7 files changed, 16 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
> index 9701464341e4..68cb3a9ee65e 100644
> --- a/arch/x86/entry/entry_64.S
> +++ b/arch/x86/entry/entry_64.S
> @@ -1059,7 +1059,7 @@ EXPORT_SYMBOL(native_load_gs_index)
> _ASM_EXTABLE(.Lgs_change, bad_gs)
> .section .fixup, "ax"
> /* running with kernelgs */
> -bad_gs:
> +SYM_CODE_START_LOCAL_NOALIGN(bad_gs)
> SWAPGS /* switch back to user gs */
> .macro ZAP_GS
> /* This can't be a string because the preprocessor needs to see it. */
> @@ -1070,6 +1070,7 @@ bad_gs:
> xorl %eax, %eax
> movl %eax, %gs
> jmp 2b
> +SYM_CODE_END(bad_gs)
> .previous
>
That can be made a local label:
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index be9ca198c581..ed4f2b6e29d5 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1058,11 +1058,12 @@ ENTRY(native_load_gs_index)
ENDPROC(native_load_gs_index)
EXPORT_SYMBOL(native_load_gs_index)
- _ASM_EXTABLE(.Lgs_change, bad_gs)
+ _ASM_EXTABLE(.Lgs_change, .Lbad_gs)
.section .fixup, "ax"
/* running with kernelgs */
-bad_gs:
+.Lbad_gs:
SWAPGS /* switch back to user gs */
+
.macro ZAP_GS
/* This can't be a string because the preprocessor needs to see it. */
movl $__USER_DS, %eax
> /* Call softirq on interrupt stack. Interrupts are off. */
> diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
> index a142c5ee0d4f..9f1852428a2d 100644
> --- a/arch/x86/kernel/acpi/wakeup_64.S
> +++ b/arch/x86/kernel/acpi/wakeup_64.S
> @@ -37,8 +37,9 @@ ENTRY(wakeup_long64)
> jmp *%rax
> ENDPROC(wakeup_long64)
>
> -bogus_64_magic:
> +SYM_CODE_START_LOCAL(bogus_64_magic)
> jmp bogus_64_magic
> +SYM_CODE_END(bogus_64_magic)
That thing is not really needed if we do the below.
It even tries to say that the magic was bad in %rcx if you can inspect
registers when the endless loop happens...
:-)
diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S
index a142c5ee0d4f..2ae21cc5a67c 100644
--- a/arch/x86/kernel/acpi/wakeup_64.S
+++ b/arch/x86/kernel/acpi/wakeup_64.S
@@ -18,10 +18,16 @@ ENTRY(wakeup_long64)
movq saved_magic, %rax
movq $0x123456789abcdef0, %rdx
cmpq %rdx, %rax
- jne bogus_64_magic
+ je 2f
+ /* stop here on a saved_magic mismatch */
+ movq $0xbad0fa61c, %rcx
+1:
+ jmp 1b
+
+2:
movw $__KERNEL_DS, %ax
- movw %ax, %ss
+ movw %ax, %ss
movw %ax, %ds
movw %ax, %es
movw %ax, %fs
@@ -37,9 +43,6 @@ ENTRY(wakeup_long64)
jmp *%rax
ENDPROC(wakeup_long64)
-bogus_64_magic:
- jmp bogus_64_magic
-
ENTRY(do_suspend_lowlevel)
FRAME_BEGIN
subq $8, %rsp
>
> ENTRY(do_suspend_lowlevel)
> FRAME_BEGIN
> diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
> index d1e213da4782..0bae769b7b59 100644
> --- a/arch/x86/kernel/head_32.S
> +++ b/arch/x86/kernel/head_32.S
> @@ -409,7 +409,7 @@ ENTRY(early_idt_handler_array)
> .endr
> ENDPROC(early_idt_handler_array)
>
> -early_idt_handler_common:
> +SYM_CODE_START_LOCAL(early_idt_handler_common)
> /*
> * The stack is the hardware frame, an error code or zero, and the
> * vector number.
> @@ -460,7 +460,7 @@ early_idt_handler_common:
> decl %ss:early_recursion_flag
> addl $4, %esp /* pop pt_regs->orig_ax */
> iret
> -ENDPROC(early_idt_handler_common)
> +SYM_CODE_END(early_idt_handler_common)
>
> /* This is the default interrupt "handler" :-) */
> ENTRY(early_ignore_irq)
Can be a local label...
> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
> index 6c1bf7ae55ff..6fedcda37634 100644
> --- a/arch/x86/kernel/head_64.S
> +++ b/arch/x86/kernel/head_64.S
> @@ -291,7 +291,7 @@ ENTRY(early_idt_handler_array)
> UNWIND_HINT_IRET_REGS offset=16
> END(early_idt_handler_array)
>
> -early_idt_handler_common:
> +SYM_CODE_START_LOCAL(early_idt_handler_common)
> /*
> * The stack is the hardware frame, an error code or zero, and the
> * vector number.
> @@ -333,7 +333,7 @@ early_idt_handler_common:
> 20:
> decl early_recursion_flag(%rip)
> jmp restore_regs_and_return_to_kernel
> -END(early_idt_handler_common)
> +SYM_CODE_END(early_idt_handler_common)
>
> __INITDATA
>
Ditto:
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 6fedcda37634..68e8d0332873 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -283,7 +283,7 @@ ENTRY(early_idt_handler_array)
UNWIND_HINT_IRET_REGS offset=8
.endif
pushq $i # 72(%rsp) Vector number
- jmp early_idt_handler_common
+ jmp .Learly_idt_handler_common
UNWIND_HINT_IRET_REGS
i = i + 1
.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
@@ -291,7 +291,7 @@ ENTRY(early_idt_handler_array)
UNWIND_HINT_IRET_REGS offset=16
END(early_idt_handler_array)
-SYM_CODE_START_LOCAL(early_idt_handler_common)
+SYM_CODE_START_LOCAL(.Learly_idt_handler_common)
/*
* The stack is the hardware frame, an error code or zero, and the
* vector number.
@@ -333,7 +333,7 @@ SYM_CODE_START_LOCAL(early_idt_handler_common)
20:
decl early_recursion_flag(%rip)
jmp restore_regs_and_return_to_kernel
-SYM_CODE_END(early_idt_handler_common)
+SYM_CODE_END(.Learly_idt_handler_common)
__INITDATA
> diff --git a/arch/x86/kernel/verify_cpu.S b/arch/x86/kernel/verify_cpu.S
> index a024c4f7ba56..641f0fe1e5b4 100644
> --- a/arch/x86/kernel/verify_cpu.S
> +++ b/arch/x86/kernel/verify_cpu.S
> @@ -31,7 +31,7 @@
> #include <asm/cpufeatures.h>
> #include <asm/msr-index.h>
>
> -ENTRY(verify_cpu)
> +SYM_FUNC_START_LOCAL(verify_cpu)
> pushf # Save caller passed flags
> push $0 # Kill any dangerous flags
> popf
> @@ -137,4 +137,4 @@ ENTRY(verify_cpu)
> popf # Restore caller passed flags
> xorl %eax, %eax
> ret
> -ENDPROC(verify_cpu)
> +SYM_FUNC_END(verify_cpu)
All except this one can be local labels and be removed from vmlinux'
symtable:
$ readelf -a vmlinux | grep -E "(bad_(gs|(get|put)_user)|bogus_64_magic|early_idt_handler_common|verify_cpu)"
45: ffffffff810000e0 241 FUNC LOCAL DEFAULT 1 verify_cpu
$
--
Regards/Gruss,
Boris.
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