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SubjectRe: [PATCH -tip ] [BUGFIX]tracing/kprobes: Fix kprobe-tracer to support stack trace
(2011/05/26 11:07), Steven Rostedt wrote:
> On Thu, 2011-05-12 at 19:22 +0900, Masami Hiramatsu wrote:
>> Fix to support kernel stack trace correctly on kprobe-tracer.
>> Since the execution path of kprobe-based dynamic events is different
>> from other tracepoint-based events, normal ftrace_trace_stack() doesn't
>> work correctly. To fix that, this introduces ftrace_trace_stack_regs()
>> which traces stack via pt_regs instead of current stack register.
>>
>
> Hi Masami,
>
> I'm working to get a "fix" patch set push out, and I included this
> patch. But when I ran it on my arch test (compiling on other archs),
> this patch broke the following:
>
> arm, blackfin, powerpc, s390.
>
> (Note, due to other bugs, UML and mips does not build to test)

Oh... I see. Perhaps, we can refer the systemtap backtrace
implementation for some of them. As far as I know, it supports
arm, ppc, and s390.

>
> The problem is that these archs do not implement a:
>
> save_stack_trace_regs() function.
>
> I'm stripping this patch out of my next pull request, and it may need to
> wait till 2.6.41/2.8.1/3.1.

OK, thanks for the test!

>
> -- Steve
>
>> e.g.
>>
>> # echo p schedule > /sys/kernel/debug/tracing/kprobe_events
>> # echo 1 > /sys/kernel/debug/tracing/options/stacktrace
>> # echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable
>> # head -n 20 /sys/kernel/debug/tracing/trace
>> # tracer: nop
>> #
>> # TASK-PID CPU# TIMESTAMP FUNCTION
>> # | | | | |
>> sshd-1549 [001] 857.326335: p_schedule_0: (schedule+0x0/0x900)
>> sshd-1549 [001] 857.326337: <stack trace>
>> => schedule_hrtimeout_range
>> => poll_schedule_timeout
>> => do_select
>> => core_sys_select
>> => sys_select
>> => system_call_fastpath
>> tee-1751 [000] 857.326394: p_schedule_0: (schedule+0x0/0x900)
>> tee-1751 [000] 857.326395: <stack trace>
>> => do_group_exit
>> => sys_exit_group
>> => system_call_fastpath
>> <idle>-0 [001] 857.326406: p_schedule_0: (schedule+0x0/0x900)
>> <idle>-0 [001] 857.326407: <stack trace>
>> => start_secondary
>>
>> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
>> Cc: Steven Rostedt <rostedt@goodmis.org>
>> Cc: Frederic Weisbecker <fweisbec@gmail.com>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
>> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
>> Cc: linux-kernel@vger.kernel.org
>> ---
>> include/linux/ftrace_event.h | 4 ++++
>> kernel/trace/trace.c | 35 ++++++++++++++++++++++++++++++-----
>> kernel/trace/trace.h | 9 +++++++++
>> kernel/trace/trace_kprobe.c | 6 ++++--
>> 4 files changed, 47 insertions(+), 7 deletions(-)
>>
>> diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
>> index b5a550a..bca2499 100644
>> --- a/include/linux/ftrace_event.h
>> +++ b/include/linux/ftrace_event.h
>> @@ -117,6 +117,10 @@ void trace_current_buffer_unlock_commit(struct ring_buffer *buffer,
>> void trace_nowake_buffer_unlock_commit(struct ring_buffer *buffer,
>> struct ring_buffer_event *event,
>> unsigned long flags, int pc);
>> +void trace_nowake_buffer_unlock_commit_regs(struct ring_buffer *buffer,
>> + struct ring_buffer_event *event,
>> + unsigned long flags, int pc,
>> + struct pt_regs *regs);
>> void trace_current_buffer_discard_commit(struct ring_buffer *buffer,
>> struct ring_buffer_event *event);
>>
>> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
>> index ee9c921..bf12209 100644
>> --- a/kernel/trace/trace.c
>> +++ b/kernel/trace/trace.c
>> @@ -1191,6 +1191,18 @@ void trace_nowake_buffer_unlock_commit(struct ring_buffer *buffer,
>> }
>> EXPORT_SYMBOL_GPL(trace_nowake_buffer_unlock_commit);
>>
>> +void trace_nowake_buffer_unlock_commit_regs(struct ring_buffer *buffer,
>> + struct ring_buffer_event *event,
>> + unsigned long flags, int pc,
>> + struct pt_regs *regs)
>> +{
>> + ring_buffer_unlock_commit(buffer, event);
>> +
>> + ftrace_trace_stack_regs(buffer, flags, 0, pc, regs);
>> + ftrace_trace_userstack(buffer, flags, pc);
>> +}
>> +EXPORT_SYMBOL_GPL(trace_nowake_buffer_unlock_commit_regs);
>> +
>> void trace_current_buffer_discard_commit(struct ring_buffer *buffer,
>> struct ring_buffer_event *event)
>> {
>> @@ -1236,7 +1248,7 @@ ftrace(struct trace_array *tr, struct trace_array_cpu *data,
>> #ifdef CONFIG_STACKTRACE
>> static void __ftrace_trace_stack(struct ring_buffer *buffer,
>> unsigned long flags,
>> - int skip, int pc)
>> + int skip, int pc, struct pt_regs *regs)
>> {
>> struct ftrace_event_call *call = &event_kernel_stack;
>> struct ring_buffer_event *event;
>> @@ -1255,24 +1267,36 @@ static void __ftrace_trace_stack(struct ring_buffer *buffer,
>> trace.skip = skip;
>> trace.entries = entry->caller;
>>
>> - save_stack_trace(&trace);
>> + if (regs)
>> + save_stack_trace_regs(&trace, regs);
>> + else
>> + save_stack_trace(&trace);
>> if (!filter_check_discard(call, entry, buffer, event))
>> ring_buffer_unlock_commit(buffer, event);
>> }
>>
>> +void ftrace_trace_stack_regs(struct ring_buffer *buffer, unsigned long flags,
>> + int skip, int pc, struct pt_regs *regs)
>> +{
>> + if (!(trace_flags & TRACE_ITER_STACKTRACE))
>> + return;
>> +
>> + __ftrace_trace_stack(buffer, flags, skip, pc, regs);
>> +}
>> +
>> void ftrace_trace_stack(struct ring_buffer *buffer, unsigned long flags,
>> int skip, int pc)
>> {
>> if (!(trace_flags & TRACE_ITER_STACKTRACE))
>> return;
>>
>> - __ftrace_trace_stack(buffer, flags, skip, pc);
>> + __ftrace_trace_stack(buffer, flags, skip, pc, NULL);
>> }
>>
>> void __trace_stack(struct trace_array *tr, unsigned long flags, int skip,
>> int pc)
>> {
>> - __ftrace_trace_stack(tr->buffer, flags, skip, pc);
>> + __ftrace_trace_stack(tr->buffer, flags, skip, pc, NULL);
>> }
>>
>> /**
>> @@ -1288,7 +1312,8 @@ void trace_dump_stack(void)
>> local_save_flags(flags);
>>
>> /* skipping 3 traces, seems to get us at the caller of this function */
>> - __ftrace_trace_stack(global_trace.buffer, flags, 3, preempt_count());
>> + __ftrace_trace_stack(global_trace.buffer, flags, 3, preempt_count(),
>> + NULL);
>> }
>>
>> static DEFINE_PER_CPU(int, user_stack_count);
>> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
>> index 5e9dfc6..cbce5e4 100644
>> --- a/kernel/trace/trace.h
>> +++ b/kernel/trace/trace.h
>> @@ -389,6 +389,9 @@ void update_max_tr_single(struct trace_array *tr,
>> void ftrace_trace_stack(struct ring_buffer *buffer, unsigned long flags,
>> int skip, int pc);
>>
>> +void ftrace_trace_stack_regs(struct ring_buffer *buffer, unsigned long flags,
>> + int skip, int pc, struct pt_regs *regs);
>> +
>> void ftrace_trace_userstack(struct ring_buffer *buffer, unsigned long flags,
>> int pc);
>>
>> @@ -400,6 +403,12 @@ static inline void ftrace_trace_stack(struct ring_buffer *buffer,
>> {
>> }
>>
>> +static inline void ftrace_trace_stack_regs(struct ring_buffer *buffer,
>> + unsigned long flags, int skip,
>> + int pc, struct pt_regs *regs)
>> +{
>> +}
>> +
>> static inline void ftrace_trace_userstack(struct ring_buffer *buffer,
>> unsigned long flags, int pc)
>> {
>> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
>> index f925c45..7053ef3 100644
>> --- a/kernel/trace/trace_kprobe.c
>> +++ b/kernel/trace/trace_kprobe.c
>> @@ -1397,7 +1397,8 @@ static __kprobes void kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
>> store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize);
>>
>> if (!filter_current_check_discard(buffer, call, entry, event))
>> - trace_nowake_buffer_unlock_commit(buffer, event, irq_flags, pc);
>> + trace_nowake_buffer_unlock_commit_regs(buffer, event,
>> + irq_flags, pc, regs);
>> }
>>
>> /* Kretprobe handler */
>> @@ -1429,7 +1430,8 @@ static __kprobes void kretprobe_trace_func(struct kretprobe_instance *ri,
>> store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize);
>>
>> if (!filter_current_check_discard(buffer, call, entry, event))
>> - trace_nowake_buffer_unlock_commit(buffer, event, irq_flags, pc);
>> + trace_nowake_buffer_unlock_commit_regs(buffer, event,
>> + irq_flags, pc, regs);
>> }
>>
>> /* Event entry printers */
>
>



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