Re: [Linux-ia64] ptrace behavior accessing ar.lc and ar.ec

David Mosberger
2002-01-25T16:30:10Z

> Hi folks,
> I'm using the ptrace interface to create a
> "architectural" processor state tracing tool. When I
> access AR.LC and AR.EC, I *usually* get the expected
> result, but every once and a while it returns a bogus
> result.

> Is there a known bug, or am I using ptrace
> incorrectly?

Not a known bug.

> Here's how its used:
> lc = ptrace (PTRACE_PEEKUSER, state->pid, PT_AR_LC,
> 0);

> The tracing program observes some sort of behavior
> like:

> mov.i ar.lc = r61 (I'm pretty sure r61 is 6), and
> ptrace returns 0
> sxt4 r22=r60 ptrace returns -1
> ..... "
> (swp kernel code) "
> ..... "
> br.ctop.sptk.few .b9 ptrace returns -1, br taken
> (p17) st8 [r15]=r34 ptrace returns 5

Do you have a self-contained and small test program that reproduces
the problem? That would make it easier to investigate the problem.

--david