On 12/09, Oleg Nesterov wrote:
>
> Cai, Ananth, thank you.
>
> So. I think we can forget about the possible kernel problems (and
> in any case we can rule out utrace).
>
> The test-case just wrong and should be fixed. The tracee can't execute
> the function descriptor in data section, that is why it gets SIGSEGV.
>
> > while the '.func_name' is the text address.
>
> tried to change the code to
>
> REGS_ACCESS (regs, nip) = (unsigned long) .raise_sigusr2
>
> but gcc doesn't like this ;)
>
> > (See
> > handle_rt_signal64 in arch/powerpc/kernel/signal_64.c and
> > kprobe_lookup_name in arch/powerpc/include/asm/kprobes.h.
>
> Thanks... looking at handle_rt_signal64(), looks like we should
> also set regs->gpr[2] = funct_desc_ptr->toc if we change regs->nip
>
>
> I hope someone who understand powerpc could fix the test-case ;)
Yes, I verified the patch below fixes step-jump-cont.c on
ibm-js20-02.lab.bos.redhat.com.
Oleg.
--- step-jump-cont.c~ 2009-12-09 12:17:04.367733643 -0500
+++ step-jump-cont.c 2009-12-09 13:12:50.708535770 -0500
@@ -153,12 +153,19 @@ raise_sigusr2 (void)
assert (0);
}
+typedef struct {
+ unsigned long entry;
+ unsigned long toc;
+ unsigned long env;
+} func_descr_t;
+
int main (void)
{
long l;
int status;
pid_t pid;
REGS_TYPE (regs);
+ func_descr_t *fp;
setbuf (stdout, NULL);
atexit (cleanup);
@@ -214,7 +221,12 @@ int main (void)
#elif defined __x86_64__
REGS_ACCESS (regs, rip) = (unsigned long) raise_sigusr2;
#elif defined __powerpc__
- REGS_ACCESS (regs, nip) = (unsigned long) raise_sigusr2;
+
+ fp = (void*)raise_sigusr2;
+
+ REGS_ACCESS(regs, nip) = fp->entry;
+ REGS_ACCESS(regs, gpr[2]) = fp->toc;
+
#else
# error "Check outer #ifdef"
#endif
