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SubjectRe: [PATCH] objtool: Detect assembly code falling through to INT3 padding
On Thu, May 17, 2018 at 08:49:34AM -0500, Josh Poimboeuf wrote:
> With the following commit:
>
> 51bad67ffbce ("x86/asm: Pad assembly functions with INT3 instructions")
>
> ... asm function alignments are padded with INT3, so it's no longer safe
> to fall through to an aligned function. Make sure we catch any such
> cases with objtool.
>
> Note this only adds checking for 64-bit, since objtool doesn't support
> x86-32.
>
> Suggested-by: Thomas Gleixner <tglx@linutronix.de>
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> ---
> arch/x86/kernel/head_64.S | 2 --
> tools/objtool/arch.h | 3 ++-
> tools/objtool/arch/x86/decode.c | 2 +-
> tools/objtool/check.c | 11 ++++++++++-
> 4 files changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
> index 8344dd2f310a..3ed8cec6e765 100644
> --- a/arch/x86/kernel/head_64.S
> +++ b/arch/x86/kernel/head_64.S
> @@ -285,11 +285,9 @@ ENTRY(early_idt_handler_array)
> .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
> - UNWIND_HINT_IRET_REGS offset=16
> END(early_idt_handler_array)
>
> early_idt_handler_common:

As noted on IRC; I got slightly confused what this was about.

Other than that:

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

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