linux-kernel - [PATCH] LoongArch: Fix bitflag conflict for TIF

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Message-ID: <20250919125829.37951-1-ziyao@disroot.org>
Date: Fri, 19 Sep 2025 12:58:29 +0000
From: Yao Zi <ziyao@...root.org>
To: Huacai Chen <chenhuacai@...nel.org>,
	WANG Xuerui <kernel@...0n.name>,
	Thomas Huth <thuth@...hat.com>,
	Yao Zi <ziyao@...root.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Xi Ruoyao <xry111@...111.site>
Cc: loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH] LoongArch: Fix bitflag conflict for TIF_FIXADE

After LoongArch was converted to use the generic TIF bits in commit
f9629891d407 ("loongarch: Use generic TIF bits"), its TIF_FIXADE flag
takes the same bit with TIF_RESTORE_SIGMASK in thread_info.flags.

Such conflict causes TIF_FIXADE being considered cleared when
TIF_RESTORE_SIGMASK is cleared during deliver of a signal. And since
TIF_FIXADE determines whether unaligned access emulation works for a
task, userspace making use of unaligned access will receive unexpected
SIGBUS (and likely terminate) after receiving its first signal.

This conflict looks like a simple typo, let's just switch to a free bit.

Fixes: f9629891d407 ("loongarch: Use generic TIF bits")
Signed-off-by: Yao Zi <ziyao@...root.org>
---

Note the problematic commit is contained in next-20250918, but not
master.

 arch/loongarch/include/asm/thread_info.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/loongarch/include/asm/thread_info.h b/arch/loongarch/include/asm/thread_info.h
index def7cb14467e..4d7117fcdc78 100644
--- a/arch/loongarch/include/asm/thread_info.h
+++ b/arch/loongarch/include/asm/thread_info.h
@@ -77,7 +77,7 @@ register unsigned long current_stack_pointer __asm__("$sp");
 #define TIF_NOHZ		16	/* in adaptive nohz mode */
 #define TIF_USEDFPU		17	/* FPU was used by this task this quantum (SMP) */
 #define TIF_USEDSIMD		18	/* SIMD has been used this quantum */
-#define TIF_FIXADE		10	/* Fix address errors in software */
+#define TIF_FIXADE		19	/* Fix address errors in software */
 #define TIF_LOGADE		20	/* Log address errors to syslog */
 #define TIF_32BIT_REGS		21	/* 32-bit general purpose registers */
 #define TIF_32BIT_ADDR		22	/* 32-bit address space */
-- 
2.50.1