[PATCH] arm64:ftrace: add save_stack_trace_regs()

[Pratyush Anand]

On Thu, Sep 1, 2016 at 5:09 PM, Will Deacon <will.deacon at arm.com> wrote:
> On Thu, Sep 01, 2016 at 04:57:30PM +0530, Pratyush Anand wrote:
>> On Fri, Jul 31, 2015 at 2:51 PM, Pratyush Anand <panand at redhat.com> wrote:
>> > Implement save_stack_trace_regs, so that stacktrace of a kprobe events can be
>> > obtained.
>> >
>> > Signed-off-by: Pratyush Anand <panand at redhat.com>
>> > ---
>> > Function will be useful only after having ARM64 kprobes upstreamed.
>> > However, since there is no dependency in applying the patch, so it may be
>> > upstreamed independently (if there is no other review comment).
>>
>>
>> Since kprobe is already in mainline now. So any comment for this patch?
>> It still applies cleanly to the latest upstream.

Humm..it just applies cleanly, but does not even compile with latest
kernel. I will rebase, retest and will resend then.

~Pratyush

>
> It would be nice if David or Akashi could review/test it.
>
> Will
>
>> > I see following stack trace for kfree with this patch in one of the case.
>> >
>> > echo stacktrace > /sys/kernel/debug/tracing/trace_options
>> > echo "p kfree" >> /sys/kernel/debug/tracing/kprobe_events
>> > echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable
>> > more /sys/kernel/debug/tracing/trace
>> >             bash-3868  [001] d...  2863.068271: p_kfree_0: (kfree+0x0/0x194)
>> >             bash-3868  [001] d...  2863.068276: <stack trace>
>> >  => kfree
>> >  => syscall_trace_exit
>> >  => __sys_trace_return_skipped
>> >
>> >  arch/arm64/kernel/stacktrace.c | 18 ++++++++++++++++++
>> >  1 file changed, 18 insertions(+)
>> >
>> > diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
>> > index 407991bf79f5..c7fa0431ef3e 100644
>> > --- a/arch/arm64/kernel/stacktrace.c
>> > +++ b/arch/arm64/kernel/stacktrace.c
>> > @@ -97,6 +97,24 @@ static int save_trace(struct stackframe *frame, void *d)
>> >         return trace->nr_entries >= trace->max_entries;
>> >  }
>> >
>> > +void save_stack_trace_regs(struct pt_regs *regs, struct stack_trace *trace)
>> > +{
>> > +       struct stack_trace_data data;
>> > +       struct stackframe frame;
>> > +
>> > +       data.trace = trace;
>> > +       data.skip = trace->skip;
>> > +       data.no_sched_functions = 0;
>> > +
>> > +       frame.fp = regs->regs[29];
>> > +       frame.sp = regs->sp;
>> > +       frame.pc = regs->pc;
>> > +
>> > +       walk_stackframe(&frame, save_trace, &data);
>> > +       if (trace->nr_entries < trace->max_entries)
>> > +               trace->entries[trace->nr_entries++] = ULONG_MAX;
>> > +}
>> > +
>> >  void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
>> >  {
>> >         struct stack_trace_data data;
>> > --
>> > 2.4.3
>> >
>> >
>> > _______________________________________________
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>> > linux-arm-kernel at lists.infradead.org
>> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>>