[PATCH v4 30/35] s390/string: Add KMSAN support

[Ilya Leoshkevich <iii@linux.ibm.com>]

Add KMSAN support for the s390 implementations of the string functions.
Do this similar to how it's already done for KASAN, except that the
optimized memset{16,32,64}() functions need to be disabled: it's
important for KMSAN to know that they initialized something.

The way boot code is built with regard to string functions is
problematic, since most files think it's configured with sanitizers,
but boot/string.c doesn't. This creates various problems with the
memset64() definitions, depending on whether the code is built with
sanitizers or fortify. This should probably be streamlined, but in the
meantime resolve the issues by introducing the IN_BOOT_STRING_C macro,
similar to the existing IN_ARCH_STRING_C macro.

Reviewed-by: Alexander Potapenko <glider@google.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 arch/s390/boot/string.c        | 16 ++++++++++++++++
 arch/s390/include/asm/string.h | 20 +++++++++++++++-----
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/arch/s390/boot/string.c b/arch/s390/boot/string.c
index faccb33b462c..f6b9b1df48a8 100644
--- a/arch/s390/boot/string.c
+++ b/arch/s390/boot/string.c
@@ -1,11 +1,18 @@
 // SPDX-License-Identifier: GPL-2.0
+#define IN_BOOT_STRING_C 1
 #include <linux/ctype.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #undef CONFIG_KASAN
 #undef CONFIG_KASAN_GENERIC
+#undef CONFIG_KMSAN
 #include "../lib/string.c"
 
+/*
+ * Duplicate some functions from the common lib/string.c
+ * instead of fully including it.
+ */
+
 int strncmp(const char *cs, const char *ct, size_t count)
 {
 	unsigned char c1, c2;
@@ -22,6 +29,15 @@ int strncmp(const char *cs, const char *ct, size_t count)
 	return 0;
 }
 
+void *memset64(uint64_t *s, uint64_t v, size_t count)
+{
+	uint64_t *xs = s;
+
+	while (count--)
+		*xs++ = v;
+	return s;
+}
+
 char *skip_spaces(const char *str)
 {
 	while (isspace(*str))
diff --git a/arch/s390/include/asm/string.h b/arch/s390/include/asm/string.h
index 351685de53d2..2ab868cbae6c 100644
--- a/arch/s390/include/asm/string.h
+++ b/arch/s390/include/asm/string.h
@@ -15,15 +15,12 @@
 #define __HAVE_ARCH_MEMCPY	/* gcc builtin & arch function */
 #define __HAVE_ARCH_MEMMOVE	/* gcc builtin & arch function */
 #define __HAVE_ARCH_MEMSET	/* gcc builtin & arch function */
-#define __HAVE_ARCH_MEMSET16	/* arch function */
-#define __HAVE_ARCH_MEMSET32	/* arch function */
-#define __HAVE_ARCH_MEMSET64	/* arch function */
 
 void *memcpy(void *dest, const void *src, size_t n);
 void *memset(void *s, int c, size_t n);
 void *memmove(void *dest, const void *src, size_t n);
 
-#ifndef CONFIG_KASAN
+#if !defined(CONFIG_KASAN) && !defined(CONFIG_KMSAN)
 #define __HAVE_ARCH_MEMCHR	/* inline & arch function */
 #define __HAVE_ARCH_MEMCMP	/* arch function */
 #define __HAVE_ARCH_MEMSCAN	/* inline & arch function */
@@ -36,6 +33,9 @@ void *memmove(void *dest, const void *src, size_t n);
 #define __HAVE_ARCH_STRNCPY	/* arch function */
 #define __HAVE_ARCH_STRNLEN	/* inline & arch function */
 #define __HAVE_ARCH_STRSTR	/* arch function */
+#define __HAVE_ARCH_MEMSET16	/* arch function */
+#define __HAVE_ARCH_MEMSET32	/* arch function */
+#define __HAVE_ARCH_MEMSET64	/* arch function */
 
 /* Prototypes for non-inlined arch strings functions. */
 int memcmp(const void *s1, const void *s2, size_t n);
@@ -44,7 +44,7 @@ size_t strlcat(char *dest, const char *src, size_t n);
 char *strncat(char *dest, const char *src, size_t n);
 char *strncpy(char *dest, const char *src, size_t n);
 char *strstr(const char *s1, const char *s2);
-#endif /* !CONFIG_KASAN */
+#endif /* !defined(CONFIG_KASAN) && !defined(CONFIG_KMSAN) */
 
 #undef __HAVE_ARCH_STRCHR
 #undef __HAVE_ARCH_STRNCHR
@@ -74,20 +74,30 @@ void *__memset16(uint16_t *s, uint16_t v, size_t count);
 void *__memset32(uint32_t *s, uint32_t v, size_t count);
 void *__memset64(uint64_t *s, uint64_t v, size_t count);
 
+#ifdef __HAVE_ARCH_MEMSET16
 static inline void *memset16(uint16_t *s, uint16_t v, size_t count)
 {
 	return __memset16(s, v, count * sizeof(v));
 }
+#endif
 
+#ifdef __HAVE_ARCH_MEMSET32
 static inline void *memset32(uint32_t *s, uint32_t v, size_t count)
 {
 	return __memset32(s, v, count * sizeof(v));
 }
+#endif
 
+#ifdef __HAVE_ARCH_MEMSET64
+#ifdef IN_BOOT_STRING_C
+void *memset64(uint64_t *s, uint64_t v, size_t count);
+#else
 static inline void *memset64(uint64_t *s, uint64_t v, size_t count)
 {
 	return __memset64(s, v, count * sizeof(v));
 }
+#endif
+#endif
 
 #if !defined(IN_ARCH_STRING_C) && (!defined(CONFIG_FORTIFY_SOURCE) || defined(__NO_FORTIFY))
 
-- 
2.45.1