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Message-ID: <20230906175215.2236033-1-song@kernel.org>
Date: Wed, 6 Sep 2023 10:52:15 -0700
From: Song Liu <song@...nel.org>
To: <linux-kernel@...r.kernel.org>
CC: <kernel-team@...a.com>, Song Liu <song@...nel.org>,
Kees Cook <keescook@...omium.org>, <x86@...nel.org>
Subject: [PATCH] x86/vmlinux: Fix linker fill bytes for ld.lld
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@...omium.org>
Cc: x86@...nel.org
Signed-off-by: Song Liu <song@...nel.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
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