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Subject[PATCH -tip ] [BUGFIX]tracing/kprobes: Fix kprobe-tracer to support stack trace
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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.

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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