linux-kernel - [PATCH 1/2] string: move __compiletime

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Message-ID: <20260205100517.292858-1-xieyuanbin1@huawei.com>
Date: Thu, 5 Feb 2026 18:05:16 +0800
From: Xie Yuanbin <xieyuanbin1@...wei.com>
To: <maddy@...ux.ibm.com>, <mpe@...erman.id.au>, <npiggin@...il.com>,
	<chleroy@...nel.org>, <kees@...nel.org>, <andy@...nel.org>
CC: <linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
	<linux-hardening@...r.kernel.org>, <lilinjie8@...wei.com>,
	<liaohua4@...wei.com>, <xieyuanbin1@...wei.com>
Subject: [PATCH 1/2] string: move __compiletime_strlen() to string.h

Move __compiletime_strlen() to string.h, so that others can use.

Signed-off-by: Xie Yuanbin <xieyuanbin1@...wei.com>
---
 include/linux/fortify-string.h | 15 ---------------
 include/linux/string.h         | 15 +++++++++++++++
 lib/tests/fortify_kunit.c      |  3 ++-
 3 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
index 171982e53c9a..c181dac26353 100644
--- a/include/linux/fortify-string.h
+++ b/include/linux/fortify-string.h
@@ -58,21 +58,6 @@ void __read_overflow2_field(size_t avail, size_t wanted) __compiletime_warning("
 void __write_overflow(void) __compiletime_error("detected write beyond size of object (1st parameter)");
 void __write_overflow_field(size_t avail, size_t wanted) __compiletime_warning("detected write beyond size of field (1st parameter); maybe use struct_group()?");
 
-#define __compiletime_strlen(p)					\
-({								\
-	char *__p = (char *)(p);				\
-	size_t __ret = SIZE_MAX;				\
-	const size_t __p_size = __member_size(p);		\
-	if (__p_size != SIZE_MAX &&				\
-	    __builtin_constant_p(*__p)) {			\
-		size_t __p_len = __p_size - 1;			\
-		if (__builtin_constant_p(__p[__p_len]) &&	\
-		    __p[__p_len] == '\0')			\
-			__ret = __builtin_strlen(__p);		\
-	}							\
-	__ret;							\
-})
-
 #if defined(__SANITIZE_ADDRESS__)
 
 #if !defined(CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX) && !defined(CONFIG_GENERIC_ENTRY)
diff --git a/include/linux/string.h b/include/linux/string.h
index 1b564c36d721..fbae7d99bb6f 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -19,6 +19,21 @@ extern void *memdup_user(const void __user *, size_t) __realloc_size(2);
 extern void *vmemdup_user(const void __user *, size_t) __realloc_size(2);
 extern void *memdup_user_nul(const void __user *, size_t);
 
+#define __compiletime_strlen(p)					\
+({								\
+	char *__p = (char *)(p);				\
+	size_t __ret = SIZE_MAX;				\
+	const size_t __p_size = __member_size(p);		\
+	if (__p_size != SIZE_MAX &&				\
+	    __builtin_constant_p(*__p)) {			\
+		size_t __p_len = __p_size - 1;			\
+		if (__builtin_constant_p(__p[__p_len]) &&	\
+		    __p[__p_len] == '\0')			\
+			__ret = __builtin_strlen(__p);		\
+	}							\
+	__ret;							\
+})
+
 /**
  * memdup_array_user - duplicate array from user space
  * @src: source address in user space
diff --git a/lib/tests/fortify_kunit.c b/lib/tests/fortify_kunit.c
index fc9c76f026d6..86181e3bd994 100644
--- a/lib/tests/fortify_kunit.c
+++ b/lib/tests/fortify_kunit.c
@@ -49,7 +49,8 @@ void fortify_add_kunit_error(int write);
 #include <linux/vmalloc.h>
 
 /* Handle being built without CONFIG_FORTIFY_SOURCE */
-#ifndef __compiletime_strlen
+#if defined(__NO_FORTIFY) || !defined(__OPTIMIZE__) || !defined(CONFIG_FORTIFY_SOURCE)
+# undef __compiletime_strlen
 # define __compiletime_strlen __builtin_strlen
 #endif
 
-- 
2.51.0