Messages in this thread Patch in this message | | | Date | Mon, 4 Jan 2010 19:14:12 +0100 | From | Oleg Nesterov <> | Subject | Re: s390 && user_enable_single_step() (Was: odd utrace testing results on s390x) |
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On 01/04, Martin Schwidefsky wrote: > > On Mon, 4 Jan 2010 16:52:25 +0100 > Oleg Nesterov <oleg@redhat.com> wrote: > > > We have some strange problems with utrace on s390, and so far this _looks_ > > like a s390 problem. > > > > Looks like, on any CPU user_enable_single_step() does not "work" until at > > least one thread with per_info.single_step = 1 does the context switch. > > The PER control registers only get reloaded on task switch. Can you test > if this patch fixes your problem? > > -- > Subject: [PATCH] fix loading of PER control registers for utrace. > > From: Martin Schwidefsky <schwidefsky@de.ibm.com> > > If the current task enables / disables PER tracing for itself the > PER control registers need to be loaded in FixPerRegisters. > > Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> > --- > arch/s390/kernel/ptrace.c | 3 +++ > 1 file changed, 3 insertions(+) > > --- a/arch/s390/kernel/ptrace.c > +++ b/arch/s390/kernel/ptrace.c > @@ -98,6 +98,9 @@ FixPerRegisters(struct task_struct *task > per_info->control_regs.bits.storage_alt_space_ctl = 1; > else > per_info->control_regs.bits.storage_alt_space_ctl = 0; > + > + if (task == current) > + __ctl_load(per_info->control_regs.words, 9, 11); > }
Yes it does fix the problem! Thanks a lot Martin.
However. Could you please look at 6580807da14c423f0d0a708108e6df6ebc8bc83d ? I am worried, perhaps this commit is not enough for s390. OK, do_single_step() tracehook_consider_fatal_signal(), this means the forked thread will not be killed by SIGTRAP if it is not auto-attached, but still this may be wrong.
IOW. I think this problem is minor and probably can be ignored, but if I remove tracehook_consider_fatal_signal() check from do_single_step(),
--- a/arch/s390/kernel/traps.c +++ b/arch/s390/kernel/traps.c @@ -382,8 +382,7 @@ void __kprobes do_single_step(struct pt_ SIGTRAP) == NOTIFY_STOP){ return; } - if (tracehook_consider_fatal_signal(current, SIGTRAP)) - force_sig(SIGTRAP, current); + force_sig(SIGTRAP, current); } static void default_trap_handler(struct pt_regs * regs, long interruption_code) ------------------------------------------------------------------- then the test-case from 6580807da14c423f0d0a708108e6df6ebc8bc83d fails. This probably means that copy_process()->user_disable_single_step() is not enough to clear the "this task wants single-stepping" copied from parent.
Thanks!
Oleg.
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