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SubjectRe: [PATCH] objtool: Detect assembly code falling through to INT3 padding

* Josh Poimboeuf <jpoimboe@redhat.com> 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(-)

Ok, this is cool, it addresses the robustness problem that INT3 padding introduced
very nicely.

The concept of built-in kernel tooling working at the machine code level is just
so powerful - we should have added our own KCC compiler 20 years ago.

Thanks,

Ingo

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