s390/cmpxchg: use unsigned long values instead of void pointers

gcc and clang warn about incompatible pointer types due to the recent
cmpxchg changes:

drivers/gpu/drm/drm_lock.c:75:10: error: passing 'typeof (lock)' (aka 'volatile unsigned int *') to parameter of type 'void *' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
                   prev = cmpxchg(lock, old, new);
                          ^~~~~~~~~~~~~~~~~~~~~~~
   include/asm-generic/atomic-instrumented.h:1685:2: note: expanded from macro 'cmpxchg'
           arch_cmpxchg(__ai_ptr, __VA_ARGS__); \
           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To avoid this simply cast pointers to unsigned long and use them
instead of void pointers. This allows to stay with functions, instead
of using complex defines and having to deal with all their potential
side effects.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: d2b1f6d ("s390/cmpxchg: get rid of gcc atomic builtins")
Link: https://lore.kernel.org/linux-s390/202104130131.sMmSqpb5-lkp@intel.com/
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Author: hcahca

arch/s390/include/asm/cmpxchg.h

@@ -14,39 +14,37 @@
 
 void __xchg_called_with_bad_pointer(void);
 
-static inline unsigned long __xchg(unsigned long x, void *ptr, int size)
+static inline unsigned long __xchg(unsigned long x, unsigned long address, int size)
 {
-	unsigned long addr, old;
+	unsigned long old;
 	int shift;
 
 	switch (size) {
 	case 1:
-		addr = (unsigned long) ptr;
-		shift = (3 ^ (addr & 3)) << 3;
-		addr ^= addr & 3;
+		shift = (3 ^ (address & 3)) << 3;
+		address ^= address & 3;
 		asm volatile(
 			"       l       %0,%1\n"
 			"0:     lr      0,%0\n"
 			"       nr      0,%3\n"
 			"       or      0,%2\n"
 			"       cs      %0,0,%1\n"
 			"       jl      0b\n"
-			: "=&d" (old), "+Q" (*(int *) addr)
+			: "=&d" (old), "+Q" (*(int *) address)
 			: "d" ((x & 0xff) << shift), "d" (~(0xff << shift))
 			: "memory", "cc", "0");
 		return old >> shift;
 	case 2:
-		addr = (unsigned long) ptr;
-		shift = (2 ^ (addr & 2)) << 3;
-		addr ^= addr & 2;
+		shift = (2 ^ (address & 2)) << 3;
+		address ^= address & 2;
 		asm volatile(
 			"       l       %0,%1\n"
 			"0:     lr      0,%0\n"
 			"       nr      0,%3\n"
 			"       or      0,%2\n"
 			"       cs      %0,0,%1\n"
 			"       jl      0b\n"
-			: "=&d" (old), "+Q" (*(int *) addr)
+			: "=&d" (old), "+Q" (*(int *) address)
 			: "d" ((x & 0xffff) << shift), "d" (~(0xffff << shift))
 			: "memory", "cc", "0");
 		return old >> shift;
@@ -55,7 +53,7 @@ static inline unsigned long __xchg(unsigned long x, void *ptr, int size)
 			"       l       %0,%1\n"
 			"0:     cs      %0,%2,%1\n"
 			"       jl      0b\n"
-			: "=&d" (old), "+Q" (*(int *) ptr)
+			: "=&d" (old), "+Q" (*(int *) address)
 			: "d" (x)
 			: "memory", "cc");
 		return old;
@@ -64,7 +62,7 @@ static inline unsigned long __xchg(unsigned long x, void *ptr, int size)
 			"       lg      %0,%1\n"
 			"0:     csg     %0,%2,%1\n"
 			"       jl      0b\n"
-			: "=&d" (old), "+S" (*(long *) ptr)
+			: "=&d" (old), "+S" (*(long *) address)
 			: "d" (x)
 			: "memory", "cc");
 		return old;
@@ -78,23 +76,23 @@ static inline unsigned long __xchg(unsigned long x, void *ptr, int size)
 	__typeof__(*(ptr)) __ret;					\
 									\
 	__ret = (__typeof__(*(ptr)))					\
-		__xchg((unsigned long)(x), (void *)(ptr), sizeof(*(ptr))); \
+		__xchg((unsigned long)(x), (unsigned long)(ptr),	\
+		       sizeof(*(ptr)));					\
 	__ret;								\
 })
 
 void __cmpxchg_called_with_bad_pointer(void);
 
-static inline unsigned long __cmpxchg(void *ptr, unsigned long old,
+static inline unsigned long __cmpxchg(unsigned long address, unsigned long old,
 				      unsigned long new, int size)
 {
-	unsigned long addr, prev, tmp;
+	unsigned long prev, tmp;
 	int shift;
 
 	switch (size) {
 	case 1:
-		addr = (unsigned long) ptr;
-		shift = (3 ^ (addr & 3)) << 3;
-		addr ^= addr & 3;
+		shift = (3 ^ (address & 3)) << 3;
+		address ^= address & 3;
 		asm volatile(
 			"       l       %0,%2\n"
 			"0:     nr      %0,%5\n"
@@ -107,16 +105,15 @@ static inline unsigned long __cmpxchg(void *ptr, unsigned long old,
 			"       nr      %1,%5\n"
 			"       jnz     0b\n"
 			"1:"
-			: "=&d" (prev), "=&d" (tmp), "+Q" (*(int *) addr)
+			: "=&d" (prev), "=&d" (tmp), "+Q" (*(int *) address)
 			: "d" ((old & 0xff) << shift),
 			  "d" ((new & 0xff) << shift),
 			  "d" (~(0xff << shift))
 			: "memory", "cc");
 		return prev >> shift;
 	case 2:
-		addr = (unsigned long) ptr;
-		shift = (2 ^ (addr & 2)) << 3;
-		addr ^= addr & 2;
+		shift = (2 ^ (address & 2)) << 3;
+		address ^= address & 2;
 		asm volatile(
 			"       l       %0,%2\n"
 			"0:     nr      %0,%5\n"
@@ -129,7 +126,7 @@ static inline unsigned long __cmpxchg(void *ptr, unsigned long old,
 			"       nr      %1,%5\n"
 			"       jnz     0b\n"
 			"1:"
-			: "=&d" (prev), "=&d" (tmp), "+Q" (*(int *) addr)
+			: "=&d" (prev), "=&d" (tmp), "+Q" (*(int *) address)
 			: "d" ((old & 0xffff) << shift),
 			  "d" ((new & 0xffff) << shift),
 			  "d" (~(0xffff << shift))
@@ -138,14 +135,14 @@ static inline unsigned long __cmpxchg(void *ptr, unsigned long old,
 	case 4:
 		asm volatile(
 			"       cs      %0,%3,%1\n"
-			: "=&d" (prev), "+Q" (*(int *) ptr)
+			: "=&d" (prev), "+Q" (*(int *) address)
 			: "0" (old), "d" (new)
 			: "memory", "cc");
 		return prev;
 	case 8:
 		asm volatile(
 			"       csg     %0,%3,%1\n"
-			: "=&d" (prev), "+S" (*(long *) ptr)
+			: "=&d" (prev), "+S" (*(long *) address)
 			: "0" (old), "d" (new)
 			: "memory", "cc");
 		return prev;
@@ -159,7 +156,7 @@ static inline unsigned long __cmpxchg(void *ptr, unsigned long old,
 	__typeof__(*(ptr)) __ret;					\
 									\
 	__ret = (__typeof__(*(ptr)))					\
-		__cmpxchg((ptr), (unsigned long)(o),			\
+		__cmpxchg((unsigned long)(ptr), (unsigned long)(o),	\
 			  (unsigned long)(n), sizeof(*(ptr)));		\
 	__ret;								\
 })