Hi,
As a followup, here is our simplified test case:
ras.s ======================
.global ras
ras:
movq $80, %r8
ras2:
pushq %rax
pushq %rcx
pushq %rdx
pushq %r9
pushq %r10
decq %r8
jz ras3
call ras2
ras3:
popq %r10
popq %r9
popq %rdx
popq %rcx
popq %rax
ret
main.c ======================
main(argc, argv)
int argc;
char *argv[];
{
for(;;)
ras();
}
compile main.c and ras.s (gcc main.c ras.s) and run ./a.out; you may
quickly see %rsp updated incorrectly, which will likely manifest as a
segmentation fault. The fault is fairly sensitive to stack alignment,
so you may need to run it a few times to hit it; simply cancel the run
and try again.
This errata affects all AMD K10 CPUs; Families 10h and 12h. It does
not affect family 15h (Bulldozer).
There is a workaround -- setting bit 0 of MSR 0xc0011029. DragonFly
just got a patch to do so, expect other systems to follow suit soon.
Thanks!
-- vs;
http://ops101.org/4k/
