linux-kernel - [PATCH] LoongArch: Avoid using $r0/$r1 as "mask" for csrxchg

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Message-ID: <20250522125050.2215157-1-chenhuacai@loongson.cn>
Date: Thu, 22 May 2025 20:50:50 +0800
From: Huacai Chen <chenhuacai@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: loongarch@...ts.linux.dev,
	Xuefeng Li <lixuefeng@...ngson.cn>,
	Guo Ren <guoren@...nel.org>,
	Xuerui Wang <kernel@...0n.name>,
	Jiaxun Yang <jiaxun.yang@...goat.com>,
	linux-kernel@...r.kernel.org,
	Huacai Chen <chenhuacai@...ngson.cn>,
	stable@...r.kernel.org,
	WANG Rui <wangrui@...ngson.cn>
Subject: [PATCH] LoongArch: Avoid using $r0/$r1 as "mask" for csrxchg

When building kernel with LLVM there are occasionally such errors:

In file included from ./include/linux/spinlock.h:59:
In file included from ./include/linux/irqflags.h:17:
arch/loongarch/include/asm/irqflags.h:38:3: error: must not be $r0 or $r1
   38 |                 "csrxchg %[val], %[mask], %[reg]\n\t"
      |                 ^
<inline asm>:1:16: note: instantiated into assembly here
    1 |         csrxchg $a1, $ra, 0
      |                       ^

The "mask" of the csrxchg instruction should not be $r0 or $r1, but the
compiler cannot avoid generating such code currently. So force to use t0
in the inline asm, in order to avoid using $r0/$r1.

Cc: stable@...r.kernel.org
Suggested-by: WANG Rui <wangrui@...ngson.cn>
Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
---
 arch/loongarch/include/asm/irqflags.h | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/loongarch/include/asm/irqflags.h b/arch/loongarch/include/asm/irqflags.h
index 319a8c616f1f..003172b8406b 100644
--- a/arch/loongarch/include/asm/irqflags.h
+++ b/arch/loongarch/include/asm/irqflags.h
@@ -14,40 +14,48 @@
 static inline void arch_local_irq_enable(void)
 {
 	u32 flags = CSR_CRMD_IE;
+	register u32 mask asm("t0") = CSR_CRMD_IE;
+
 	__asm__ __volatile__(
 		"csrxchg %[val], %[mask], %[reg]\n\t"
 		: [val] "+r" (flags)
-		: [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
+		: [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
 		: "memory");
 }
 
 static inline void arch_local_irq_disable(void)
 {
 	u32 flags = 0;
+	register u32 mask asm("t0") = CSR_CRMD_IE;
+
 	__asm__ __volatile__(
 		"csrxchg %[val], %[mask], %[reg]\n\t"
 		: [val] "+r" (flags)
-		: [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
+		: [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
 		: "memory");
 }
 
 static inline unsigned long arch_local_irq_save(void)
 {
 	u32 flags = 0;
+	register u32 mask asm("t0") = CSR_CRMD_IE;
+
 	__asm__ __volatile__(
 		"csrxchg %[val], %[mask], %[reg]\n\t"
 		: [val] "+r" (flags)
-		: [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
+		: [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
 		: "memory");
 	return flags;
 }
 
 static inline void arch_local_irq_restore(unsigned long flags)
 {
+	register u32 mask asm("t0") = CSR_CRMD_IE;
+
 	__asm__ __volatile__(
 		"csrxchg %[val], %[mask], %[reg]\n\t"
 		: [val] "+r" (flags)
-		: [mask] "r" (CSR_CRMD_IE), [reg] "i" (LOONGARCH_CSR_CRMD)
+		: [mask] "r" (mask), [reg] "i" (LOONGARCH_CSR_CRMD)
 		: "memory");
 }
 
-- 
2.47.1