https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95692
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |INVALID
Status|WAITING |RESOLVED
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Doing this fixes the issue:
int
intercept_munmap(void *start, size_t length)
{
unsigned long toc_save;
asm volatile ("std 2, %0" : "=m" (toc_save) :: "memory");
asm volatile ("nop; nop; nop; nop; nop" ::: "memory");;
volatile MyFunction_t fn;
fn = foo;
fn();
int result = syscall(
91
, start, length);
asm volatile ("ld 2, %0" : : "m" (toc_save) : "memory");;
return result;
}
That is you need to also mark the asm as clobbering memory. Otherwise the asm
can be moved.
As mentioned in the manual volatile can still move inline-asm around with
volatile:
https://gcc.gnu.org/onlinedocs/gcc-14.2.0/gcc/Extended-Asm.html#Volatile-1 :
```
Note that the compiler can move even volatile asm instructions relative to
other code, including across jump instructions. For example, on many targets
there is a system register that controls the rounding mode of floating-point
operations. Setting it with a volatile asm statement, as in the following
PowerPC example, does not work reliably.
```
