On Sat, Jan 29, 2005 at 05:54:44PM +0100, Imre Kaloz wrote:
> The following patch changes inline for __xchg to __always_inline in
> include/asm-mips/system.h, following the changes in git. Without this
> change linking the kernel fails.
>
> Signed-off-by: Imre Kaloz <kaloz@xxxxxxxxxxx>
> Signed-off-by: Felix Fietkau <nbd@xxxxxxxxxxx>
Imre just pointed me at this antique patch again saying it was still needed.
Back then I ditched it because I couldn't see what the problem it was
trying to fix was - but after a little brainstorming it got obvious.
Now I don't like __always_inline which forces the optimizer to do things
which may not really be what we want, for example when building with -Os
so I found a different fix using BUILD_BUG_ON(). Patch below.
Cheers,
Ralf
From: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
MIPS: Fix build error if __xchg() is not getting inlined.
If __xchg() is not getting inlined the outline version of the function
will have a reference to __xchg_called_with_bad_pointer() which does not
exist remaining. Fixed by using BUILD_BUG_ON() xchg() to check for
allowable operand sizes.
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
diff --git a/arch/mips/include/asm/system.h b/arch/mips/include/asm/system.h
index fcf5f98..587a48a 100644
--- a/arch/mips/include/asm/system.h
+++ b/arch/mips/include/asm/system.h
@@ -193,10 +193,6 @@ extern __u64 __xchg_u64_unsupported_on_32bit_kernels(volatile __u64 * m, __u64 v
#define __xchg_u64 __xchg_u64_unsupported_on_32bit_kernels
#endif
-/* This function doesn't exist, so you'll get a linker error
- if something tries to do an invalid xchg(). */
-extern void __xchg_called_with_bad_pointer(void);
-
static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int size)
{
switch (size) {
@@ -205,11 +201,17 @@ static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int siz
case 8:
return __xchg_u64(ptr, x);
}
- __xchg_called_with_bad_pointer();
+
return x;
}
-#define xchg(ptr, x) ((__typeof__(*(ptr)))__xchg((unsigned long)(x), (ptr), sizeof(*(ptr))))
+#define xchg(ptr, x) \
+({ \
+ BUILD_BUG_ON(sizeof(*(ptr)) & ~0xc); \
+ \
+ ((__typeof__(*(ptr))) \
+ __xchg((unsigned long)(x), (ptr), sizeof(*(ptr)))); \
+})
extern void set_handler(unsigned long offset, void *addr, unsigned long len);
extern void set_uncached_handler(unsigned long offset, void *addr, unsigned long len);
