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Date: Wed, 25 May 2011 22:07:02 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Ingo Molnar <mingo@...e.hu>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Frederic Weisbecker <fweisbec@...il.com>,
linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
yrl.pp-manager.tt@...achi.com, Russell King <rmk@....linux.org.uk>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Mike Frysinger <vapier@...too.org>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH -tip ] [BUGFIX]tracing/kprobes: Fix kprobe-tracer to
support stack trace
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)
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.
-- 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@...achi.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: linux-kernel@...r.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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