From: Kees Cook <kees@kernel.org>
Date: Mon, 23 Mar 2026 01:17:59 +0000 (+0000)
Subject: x86: Remove arch-specific strncpy() implementation
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=dfe05fcca83d794cd76da1b6deb2dcd082aa1174;p=thirdparty%2Flinux.git

x86: Remove arch-specific strncpy() implementation

strncpy() has no remaining callers in the kernel[1]. Remove the
x86-32-specific inline assembly implementation and __HAVE_ARCH_STRNCPY
define, falling back to the generic version in lib/string.c.

Link: https://github.com/KSPP/linux/issues/90 [1]
Signed-off-by: Kees Cook <kees@kernel.org>
---

diff --git a/arch/x86/include/asm/string_32.h b/arch/x86/include/asm/string_32.h
index e9cce169bb4cd..43ab6806ab539 100644
--- a/arch/x86/include/asm/string_32.h
+++ b/arch/x86/include/asm/string_32.h
@@ -9,9 +9,6 @@
 #define __HAVE_ARCH_STRCPY
 extern char *strcpy(char *dest, const char *src);
 
-#define __HAVE_ARCH_STRNCPY
-extern char *strncpy(char *dest, const char *src, size_t count);
-
 #define __HAVE_ARCH_STRCAT
 extern char *strcat(char *dest, const char *src);
 
diff --git a/arch/x86/lib/string_32.c b/arch/x86/lib/string_32.c
index f87ec24fa5790..a9480d73c4f08 100644
--- a/arch/x86/lib/string_32.c
+++ b/arch/x86/lib/string_32.c
@@ -30,25 +30,6 @@ char *strcpy(char *dest, const char *src)
 EXPORT_SYMBOL(strcpy);
 #endif
 
-#ifdef __HAVE_ARCH_STRNCPY
-char *strncpy(char *dest, const char *src, size_t count)
-{
-	int d0, d1, d2, d3;
-	asm volatile("1:\tdecl %2\n\t"
-		"js 2f\n\t"
-		"lodsb\n\t"
-		"stosb\n\t"
-		"testb %%al,%%al\n\t"
-		"jne 1b\n\t"
-		"rep stosb\n"
-		"2:"
-		: "=&S" (d0), "=&D" (d1), "=&c" (d2), "=&a" (d3)
-		: "0" (src), "1" (dest), "2" (count) : "memory");
-	return dest;
-}
-EXPORT_SYMBOL(strncpy);
-#endif
-
 #ifdef __HAVE_ARCH_STRCAT
 char *strcat(char *dest, const char *src)
 {