Messages in this thread | ![/](/images/icornerl.gif) | | From | Song Liu <> | Date | Wed, 6 Sep 2023 13:02:45 -0700 | Subject | Re: [PATCH] x86/vmlinux: Fix linker fill bytes for ld.lld |
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On Wed, Sep 6, 2023 at 12:58 PM Peter Zijlstra <peterz@infradead.org> wrote: > > On Wed, Sep 06, 2023 at 10:52:15AM -0700, Song Liu wrote: > > With ":text =0xcccc", ld.lld fills unused text area with 0xcccc0000. > > Example objdump -D output: > > > > ffffffff82b04203: 00 00 add %al,(%rax) > > ffffffff82b04205: cc int3 > > ffffffff82b04206: cc int3 > > ffffffff82b04207: 00 00 add %al,(%rax) > > ffffffff82b04209: cc int3 > > ffffffff82b0420a: cc int3 > > > > Replace it with ":text =0xcccccccc", so we get the following instead: > > > > ffffffff82b04203: cc int3 > > ffffffff82b04204: cc int3 > > ffffffff82b04205: cc int3 > > ffffffff82b04206: cc int3 > > ffffffff82b04207: cc int3 > > ffffffff82b04208: cc int3 > > > > gcc/ld doesn't seem to have the same issue. The generated code stays the > > same for gcc/ld. > > > > Cc: Kees Cook <keescook@chromium.org> > > Cc: x86@kernel.org > > Signed-off-by: Song Liu <song@kernel.org> > > Please provide a Fixes tag, I'm thinking this (otherwise trivial commit) > wants to be backported for sanity.
I guess we need:
Fixes: 7705dc855797 ("x86/vmlinux: Use INT3 instead of NOP for linker fill bytes")
Thanks, Song
> > Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
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