On Thu, 20 Mar 2008 01:05:40 +0100, Roland McGrath wrote:
...
> AFAIK no other machine has an unprivileged instruction that can enable its
> hardware single-step flag. So e.g. powerpc's MSR_SE is not truly part of
> the actual user CPU state. However, powerpc does let you set MSR_SE by
> returning from a signal handler with modified sigcontext. If that is
> really ever used, then we should make powerpc hide MSR_SE when it's forced
> by user_enable_single_step as x86 does. If not, then I'm inclined just to
> clean it up so MSR_SE is never seen by userland and setting it is ignored.
Currently step-jump-cont-strict does not support anything besides i386/x86_64.
http://sources.redhat.com/cgi-bin/cvsweb.cgi/~checkout~/tests/ptrace-tests/tests/step-jump-cont-strict.c?cvsroot=systemtap
I expect sigcontext setting MSR_SE should be tested to have no effect.
But what should happen if I do PTRACE_POKEUSER (MSR_SE = 1)?
(1) Should it get cleared on the next PTRACE_CONT or PTRACE_SINGLESTEP?
or
(2) Should PTRACE_CONT start behaving the same way as PTRACE_SINGLESTEP until
someone does PTRACE_POKEUSER (MSR_SE = 0)?
Regards,
Jan
