Messages in this thread | | | Date | Wed, 6 Sep 2023 11:06:02 -0700 | From | Kees Cook <> | Subject | Re: [PATCH] x86/vmlinux: Fix linker fill bytes for ld.lld |
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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>
Ah! Thanks for the catch... I wonder if ld.lld should be fixed too? My understanding was that ":text =...." was defined as being explicitly u16?
Reviewed-by: Kees Cook <keescook@chromium.org>
-- Kees Cook
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