s390/lib: add missing memory barriers to string inline assemblies

We have a couple of inline assemblies like memchr() and strlen() that
read from memory, but tell the compiler only they need the addresses
of the strings they access.
This allows the compiler to omit the initialization of such strings
and therefore generate broken code. Add the missing memory barrier to
all string related inline assemblies to fix this potential issue. It
looks like the compiler currently does not generate broken code due to
these bugs.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/string.h

@@ -62,7 +62,7 @@ static inline void *memchr(const void * s, int c, size_t n)
 		"	jl	1f\n"
 		"	la	%0,0\n"
 		"1:"
-		: "+a" (ret), "+&a" (s) : "d" (r0) : "cc");
+		: "+a" (ret), "+&a" (s) : "d" (r0) : "cc", "memory");
 	return (void *) ret;
 }
 
@@ -74,7 +74,7 @@ static inline void *memscan(void *s, int c, size_t n)
 	asm volatile(
 		"0:	srst	%0,%1\n"
 		"	jo	0b\n"
-		: "+a" (ret), "+&a" (s) : "d" (r0) : "cc");
+		: "+a" (ret), "+&a" (s) : "d" (r0) : "cc", "memory");
 	return (void *) ret;
 }
 
@@ -115,7 +115,7 @@ static inline size_t strlen(const char *s)
 	asm volatile(
 		"0:	srst	%0,%1\n"
 		"	jo	0b"
-		: "+d" (r0), "+a" (tmp) :  : "cc");
+		: "+d" (r0), "+a" (tmp) :  : "cc", "memory");
 	return r0 - (unsigned long) s;
 }
 
@@ -128,7 +128,7 @@ static inline size_t strnlen(const char * s, size_t n)
 	asm volatile(
 		"0:	srst	%0,%1\n"
 		"	jo	0b"
-		: "+a" (end), "+a" (tmp) : "d" (r0)  : "cc");
+		: "+a" (end), "+a" (tmp) : "d" (r0)  : "cc", "memory");
 	return end - s;
 }
 #else /* IN_ARCH_STRING_C */

arch/s390/lib/string.c

@@ -20,7 +20,7 @@ static inline char *__strend(const char *s)
 
 	asm volatile ("0: srst  %0,%1\n"
 		      "   jo    0b"
-		      : "+d" (r0), "+a" (s) :  : "cc" );
+		      : "+d" (r0), "+a" (s) :  : "cc", "memory");
 	return (char *) r0;
 }
 
@@ -31,7 +31,7 @@ static inline char *__strnend(const char *s, size_t n)
 
 	asm volatile ("0: srst  %0,%1\n"
 		      "   jo    0b"
-		      : "+d" (p), "+a" (s) : "d" (r0) : "cc" );
+		      : "+d" (p), "+a" (s) : "d" (r0) : "cc", "memory");
 	return (char *) p;
 }
 
@@ -213,7 +213,7 @@ int strcmp(const char *cs, const char *ct)
 		      "   sr   %0,%1\n"
 		      "1:"
 		      : "+d" (ret), "+d" (r0), "+a" (cs), "+a" (ct)
-		      : : "cc" );
+		      : : "cc", "memory");
 	return ret;
 }
 EXPORT_SYMBOL(strcmp);
@@ -250,7 +250,7 @@ static inline int clcle(const char *s1, unsigned long l1,
 		      "   ipm   %0\n"
 		      "   srl   %0,28"
 		      : "=&d" (cc), "+a" (r2), "+a" (r3),
-			"+a" (r4), "+a" (r5) : : "cc");
+			"+a" (r4), "+a" (r5) : : "cc", "memory");
 	return cc;
 }
 
@@ -298,7 +298,7 @@ void *memchr(const void *s, int c, size_t n)
 		      "   jl	1f\n"
 		      "   la    %0,0\n"
 		      "1:"
-		      : "+a" (ret), "+&a" (s) : "d" (r0) : "cc" );
+		      : "+a" (ret), "+&a" (s) : "d" (r0) : "cc", "memory");
 	return (void *) ret;
 }
 EXPORT_SYMBOL(memchr);
@@ -336,7 +336,7 @@ void *memscan(void *s, int c, size_t n)
 
 	asm volatile ("0: srst  %0,%1\n"
 		      "   jo    0b\n"
-		      : "+a" (ret), "+&a" (s) : "d" (r0) : "cc" );
+		      : "+a" (ret), "+&a" (s) : "d" (r0) : "cc", "memory");
 	return (void *) ret;
 }
 EXPORT_SYMBOL(memscan);