Messages in this thread | | | Date | Tue, 5 Jan 2010 10:26:06 +0100 | From | Martin Schwidefsky <> | Subject | Re: s390 && user_enable_single_step() (Was: odd utrace testing results on s390x) |
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On Mon, 4 Jan 2010 19:14:12 +0100 Oleg Nesterov <oleg@redhat.com> wrote:
> On 01/04, Martin Schwidefsky wrote: > > 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.
Ok, I will add that patch to the git390 queue.
> 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.
user_disable_single_step() does not remove the TIF_SINGLE_STEP bit from the forked task. Perhaps we should just clear the bit in the function.
-- blue skies, Martin.
"Reality continues to ruin my life." - Calvin.
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