As noted (and fixed) a couple of times in the past, "=@cc<cond>" outputs
and clobbering of "cc" don't work well together. The compiler appears to
mean to reject such, but doesn't - in its upstream form - quite manage
to yet for "cc". Furthermore two similar macros don't clobber "cc", and
clobbering "cc" is pointless in asm()-s for x86 anyway - the compiler
always assumes status flags to be clobbered there.
Fixes: 989b5db215a2 ("x86/uaccess: Implement macros for CMPXCHG on user addresses")
Signed-off-by: Jan Beulich <[email protected]>
---
The change I continue to carry locally actually allows specifying that
"cc" is _not_ clobbered; it only happens to improve detection of bad
situations like the one here.
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -439,7 +439,7 @@ do { \
[ptr] "+m" (*_ptr), \
[old] "+a" (__old) \
: [new] ltype (__new) \
- : "memory", "cc"); \
+ : "memory"); \
if (unlikely(__err)) \
goto label; \
if (unlikely(!success)) \