Messages in this thread | | | Date | Wed, 6 Sep 2023 21:58:14 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] x86/vmlinux: Fix linker fill bytes for ld.lld |
| |
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.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> --- > arch/x86/kernel/vmlinux.lds.S | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S > index 83d41c2601d7..41d56fb9bf92 100644 > --- a/arch/x86/kernel/vmlinux.lds.S > +++ b/arch/x86/kernel/vmlinux.lds.S > @@ -156,7 +156,7 @@ SECTIONS > ALIGN_ENTRY_TEXT_END > *(.gnu.warning) > > - } :text =0xcccc > + } :text =0xcccccccc > > /* End of text section, which should occupy whole number of pages */ > _etext = .; > -- > 2.34.1 >
| |