[ARM] Fix byte order macros for Thumb

The byte order functions are visible to userspace.  Unfortunately,
__arch_swab32() contains an assembly instruction which is invalid when
compiling for Thumb.  This reverts to the C version when compiling for
Thumb.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 6 insertions, 4 deletions

diff --git a/include/asm-arm/byteorder.h b/include/asm-arm/byteorder.h
index 17eaf8bdf092..e6f7fcdc73b0 100644
--- a/include/asm-arm/byteorder.h
+++ b/include/asm-arm/byteorder.h
@@ -22,16 +22,18 @@ static inline __attribute_const__ __u32 ___arch__swab32(__u32 x)
 {
         __u32 t;
 
-        if (__builtin_constant_p(x)) {
-                t = x ^ ((x << 16) | (x >> 16)); /* eor r1,r0,r0,ror #16 */
-        } else {
+#ifndef __thumb__
+        if (!__builtin_constant_p(x)) {
                 /*
                  * The compiler needs a bit of a hint here to always do the
                  * right thing and not screw it up to different degrees
                  * depending on the gcc version.
                  */
                 asm ("eor\t%0, %1, %1, ror #16" : "=r" (t) : "r" (x));
-        }
+        } else
+#endif
+                t = x ^ ((x << 16) | (x >> 16)); /* eor r1,r0,r0,ror #16 */
+
         x = (x << 24) | (x >> 8);               /* mov r0,r0,ror #8      */
         t &= ~0x00FF0000;                       /* bic r1,r1,#0x00FF0000 */
         x ^= (t >> 8);                          /* eor r0,r0,r1,lsr #8   */