Hi Mike,
(Roland may be able to help out here.)
On Wed, Mar 18, 2009 at 4:46 PM, Mike Frysinger <vapier@xxxxxxxxxx> wrote:
> the ptrace(2) page doesnt say anything about the data field (ignored or
> otherwise). it seems to be ignored, but i didnt trace the kernel
> exhaustively. the examples found via google shows that it's ignored. strace
> usage seems odd (it passes in an irrelevant pointer), which would indicate
> it's ignored as well ...
It's true that this looks like a defect in the man page. But I'm not
sure what the fix is.
In the kernel source file kernel/ptrace.c, function ptrace_resume() we
have the line
child->exit_code = data;
which seems to be executed by the PRACE_SYSCALL code path. That
implies that data is treated as a signal number (like PTRACE_CONT).
That seems consistent with the following in the strace.c source file
of strace(1):
if (ptrace(PTRACE_SYSCALL, pid, (char *) 1,
WSTOPSIG(status)) < 0) {
perror("trace: ptrace(PTRACE_SYSCALL, ...)");
cleanup();
return -1;
}
Did I misunderstand something? Your thoughts?
Cheers,
Michael
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