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

Weihaw Chuang
2002-01-25T09:28:25Z

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?

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

Many thanks,
-Wei

==************************************************************

Weihaw Chuang
wchuang@cs.ucsd.edu

************************************************************

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