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x86/build: Fix linker fill bytes quirk/incompatibility for ld.lld

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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.

Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Fixes: 7705dc8557 ("x86/vmlinux: Use INT3 instead of NOP for linker fill bytes")
Link: https://lore.kernel.org/r/20230906175215.2236033-1-song@kernel.org
This commit is contained in:
Song Liu 2023-09-06 10:52:15 -07:00 committed by Ingo Molnar
parent 3f874c9b2a
commit 65e710899f
1 changed files with 1 additions and 1 deletions
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arch/x86/kernel/vmlinux.lds.S
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@ -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 = .;