linux-kernel - [tip: x86/urgent] x86/bug: Fix old GCC compile fails

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Message-ID: <176605579804.510.611059138660243857.tip-bot2@tip-bot2>
Date: Thu, 18 Dec 2025 11:03:18 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Jean Delvare <jdelvare@...e.de>, Uros Bizjak <ubizjak@...il.com>,
 stable@...nel.org, "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/bug: Fix old GCC compile fails

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     c56a12c71ad38f381105f6e5036dede64ad2dfee
Gitweb:        https://git.kernel.org/tip/c56a12c71ad38f381105f6e5036dede64ad2dfee
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Thu, 18 Dec 2025 11:47:38 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Thu, 18 Dec 2025 11:55:40 +01:00

x86/bug: Fix old GCC compile fails

For some mysterious reasons the GCC 8 and 9 preprocessor manages to
sporadically fumble _ASM_BYTES(0x0f, 0x0b):

$ grep ".byte[ ]*0x0f" defconfig-build/drivers/net/wireless/realtek/rtlwifi/base.s
        1:       .byte0x0f,0x0b ;
        1:       .byte 0x0f,0x0b ;

which makes the assembler upset and all that. While there are more
_ASM_BYTES() users (notably the NOP instructions), those don't seem
affected. Therefore replace the offending ASM_UD2 with one using the
ud2 mnemonic.

Reported-by: Jean Delvare <jdelvare@...e.de>
Suggested-by: Uros Bizjak <ubizjak@...il.com>
Fixes: 85a2d4a890dc ("x86,ibt: Use UDB instead of 0xEA")
Cc: stable@...nel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://patch.msgid.link/20251218104659.GT3911114@noisy.programming.kicks-ass.net
---
 arch/x86/include/asm/bug.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
index ee23b98..40de579 100644
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -15,7 +15,7 @@ extern void __WARN_trap(struct bug_entry *bug, ...);
 /*
  * Despite that some emulators terminate on UD2, we use it for WARN().
  */
-#define ASM_UD2		_ASM_BYTES(0x0f, 0x0b)
+#define ASM_UD2		__ASM_FORM(ud2)
 #define INSN_UD2	0x0b0f
 #define LEN_UD2		2