From: David Laight
Sent: 16 December 2022 13:30
From: Leizhen (ThunderTown)
Sent: 16 December 2022 12:02
..
Moving the m68k version inside lib/string.c makes the test pass, too.
So it must be related to the function being inline, and gcc making
(incorrect) assumptions...
Yes, it's the compiler's fault. I just replied David Laight:
I added 'volatile' to prevent compiler optimizations, and it's OK now.
diff --git a/arch/m68k/include/asm/string.h b/arch/m68k/include/asm/string.h
index f759d944c449940..3db81e5a783c72a 100644
--- a/arch/m68k/include/asm/string.h
+++ b/arch/m68k/include/asm/string.h
@@ -42,9 +42,9 @@ static inline char *strncpy(char *dest, const char *src, size_t n)
#define __HAVE_ARCH_STRCMP
static inline int strcmp(const char *cs, const char *ct)
{
- char res;
+ signed char res;
- asm ("\n"
+ asm volatile ("\n"
"1: move.b (%0)+,%2\n" /* get *cs */
" cmp.b (%1)+,%2\n" /* compare a byte */
" jne 2f\n" /* not equal, break out */
Adding 'volatile' there shouldn't make any real difference.
I'd double-check the asm constraints for the two pointers.
They are modified by the asm, but the caller's variables
must not be changed.
I think that means they need to be normal 'input' parameters
and the result must be in different register (early clobber?).
Currently the pointers are "+r" - which I think means they
are input-output and any caller-supplied variable is
likely to get changed.
Definitely badly broken.
'cs' and 'ct' should be input parameters.
'res' needs to be an early-clobber output parameter "=&r".
Since it is actually a 'static inline' (not just a #define)
then letting cs/ct be changed probably doesn't matter.
But the lack of 'early clobber' will cause grief.
David
-
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