From: Liyuan Pang <pangliyuan1@huawei.com>
Date: Tue, 9 Dec 2025 02:19:45 +0000 (+0100)
Subject: ARM: 9464/1: fix input-only operand modification in load_unaligned_zeropad()
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=edb924a7211c9aa7a4a415e03caee4d875e46b8e;p=thirdparty%2Fkernel%2Flinux.git

ARM: 9464/1: fix input-only operand modification in load_unaligned_zeropad()

In the inline assembly inside load_unaligned_zeropad(), the "addr" is
constrained as input-only operand. The compiler assumes that on exit
from the asm statement these operands contain the same values as they
had before executing the statement, but when kernel page fault happened, the assembly fixup code "bic %2 %2, #0x3" modify the value of "addr", which may lead to an unexpected behavior.

Use a temporary variable "tmp" to handle it, instead of modifying the
input-only operand, just like what arm64's load_unaligned_zeropad()
does.

Fixes: b9a50f74905a ("ARM: 7450/1: dcache: select DCACHE_WORD_ACCESS for little-endian ARMv6+ CPUs")
Co-developed-by: Xie Yuanbin <xieyuanbin1@huawei.com>
Signed-off-by: Xie Yuanbin <xieyuanbin1@huawei.com>
Signed-off-by: Liyuan Pang <pangliyuan1@huawei.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---

diff --git a/arch/arm/include/asm/word-at-a-time.h b/arch/arm/include/asm/word-at-a-time.h
index f9a3897b06e7f..5023f98d8293d 100644
--- a/arch/arm/include/asm/word-at-a-time.h
+++ b/arch/arm/include/asm/word-at-a-time.h
@@ -67,7 +67,7 @@ static inline unsigned long find_zero(unsigned long mask)
  */
 static inline unsigned long load_unaligned_zeropad(const void *addr)
 {
-	unsigned long ret, offset;
+	unsigned long ret, tmp;
 
 	/* Load word from unaligned pointer addr */
 	asm(
@@ -75,9 +75,9 @@ static inline unsigned long load_unaligned_zeropad(const void *addr)
 	"2:\n"
 	"	.pushsection .text.fixup,\"ax\"\n"
 	"	.align 2\n"
-	"3:	and	%1, %2, #0x3\n"
-	"	bic	%2, %2, #0x3\n"
-	"	ldr	%0, [%2]\n"
+	"3:	bic	%1, %2, #0x3\n"
+	"	ldr	%0, [%1]\n"
+	"	and	%1, %2, #0x3\n"
 	"	lsl	%1, %1, #0x3\n"
 #ifndef __ARMEB__
 	"	lsr	%0, %0, %1\n"
@@ -90,7 +90,7 @@ static inline unsigned long load_unaligned_zeropad(const void *addr)
 	"	.align	3\n"
 	"	.long	1b, 3b\n"
 	"	.popsection"
-	: "=&r" (ret), "=&r" (offset)
+	: "=&r" (ret), "=&r" (tmp)
 	: "r" (addr), "Qo" (*(unsigned long *)addr));
 
 	return ret;