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Commit 955b61e5 authored by Jason Wessel's avatar Jason Wessel
Browse files

ftrace,kdb: Extend kdb to be able to dump the ftrace buffer 



Add in a helper function to allow the kdb shell to dump the ftrace
buffer.

Modify trace.c to expose the capability to iterate over the ftrace
buffer in a read only capacity.

Signed-off-by: default avatarJason Wessel <jason.wessel@windriver.com>
Acked-by: default avatarSteven Rostedt <rostedt@goodmis.org>
CC: Frederic Weisbecker <fweisbec@gmail.com>
parent 3f0a55e3

kernel/trace/Makefile

+3 −0
Original line number Diff line number Diff line
@@ -57,5 +57,8 @@ obj-$(CONFIG_EVENT_TRACING) += trace_events_filter.o 
obj-$(CONFIG_KPROBE_EVENT) += trace_kprobe.o

obj-$(CONFIG_KSYM_TRACER) += trace_ksym.o

obj-$(CONFIG_EVENT_TRACING) += power-traces.o

ifeq ($(CONFIG_TRACING),y)

obj-$(CONFIG_KGDB_KDB) += trace_kdb.o

endif



libftrace-y := ftrace.o

kernel/trace/trace.c

+22 −21
Original line number Diff line number Diff line
@@ -101,10 +101,7 @@ static inline void ftrace_enable_cpu(void) 
	preempt_enable();

}



static cpumask_var_t __read_mostly	tracing_buffer_mask;



#define for_each_tracing_cpu(cpu)	\

	for_each_cpu(cpu, tracing_buffer_mask)

cpumask_var_t __read_mostly	tracing_buffer_mask;



/*

 * ftrace_dump_on_oops - variable to dump ftrace buffer on oops
@@ -1539,11 +1536,6 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args) 
}

EXPORT_SYMBOL_GPL(trace_vprintk);



enum trace_file_type {

	TRACE_FILE_LAT_FMT	= 1,

	TRACE_FILE_ANNOTATE	= 2,

};



static void trace_iterator_increment(struct trace_iterator *iter)

{

	/* Don't allow ftrace to trace into the ring buffers */
@@ -1641,7 +1633,7 @@ struct trace_entry *trace_find_next_entry(struct trace_iterator *iter, 
}



/* Find the next real entry, and increment the iterator to the next entry */

static void *find_next_entry_inc(struct trace_iterator *iter)

void *trace_find_next_entry_inc(struct trace_iterator *iter)

{

	iter->ent = __find_next_entry(iter, &iter->cpu,

				      &iter->lost_events, &iter->ts);
@@ -1676,19 +1668,19 @@ static void *s_next(struct seq_file *m, void *v, loff_t *pos) 
		return NULL;



	if (iter->idx < 0)

		ent = find_next_entry_inc(iter);

		ent = trace_find_next_entry_inc(iter);

	else

		ent = iter;



	while (ent && iter->idx < i)

		ent = find_next_entry_inc(iter);

		ent = trace_find_next_entry_inc(iter);



	iter->pos = *pos;



	return ent;

}



static void tracing_iter_reset(struct trace_iterator *iter, int cpu)

void tracing_iter_reset(struct trace_iterator *iter, int cpu)

{

	struct trace_array *tr = iter->tr;

	struct ring_buffer_event *event;
@@ -2049,7 +2041,7 @@ int trace_empty(struct trace_iterator *iter) 
}



/*  Called with trace_event_read_lock() held. */

static enum print_line_t print_trace_line(struct trace_iterator *iter)

enum print_line_t print_trace_line(struct trace_iterator *iter)

{

	enum print_line_t ret;
@@ -3211,7 +3203,7 @@ tracing_read_pipe(struct file *filp, char __user *ubuf, 


	trace_event_read_lock();

	trace_access_lock(iter->cpu_file);

	while (find_next_entry_inc(iter) != NULL) {

	while (trace_find_next_entry_inc(iter) != NULL) {

		enum print_line_t ret;

		int len = iter->seq.len;
@@ -3294,7 +3286,7 @@ tracing_fill_pipe_page(size_t rem, struct trace_iterator *iter) 
		if (ret != TRACE_TYPE_NO_CONSUME)

			trace_consume(iter);

		rem -= count;

		if (!find_next_entry_inc(iter))	{

		if (!trace_find_next_entry_inc(iter))	{

			rem = 0;

			iter->ent = NULL;

			break;
@@ -3350,7 +3342,7 @@ static ssize_t tracing_splice_read_pipe(struct file *filp, 
	if (ret <= 0)

		goto out_err;



	if (!iter->ent && !find_next_entry_inc(iter)) {

	if (!iter->ent && !trace_find_next_entry_inc(iter)) {

		ret = -EFAULT;

		goto out_err;

	}
@@ -4414,7 +4406,7 @@ static struct notifier_block trace_die_notifier = { 
 */

#define KERN_TRACE		KERN_EMERG



static void

void

trace_printk_seq(struct trace_seq *s)

{

	/* Probably should print a warning here. */
@@ -4429,6 +4421,13 @@ trace_printk_seq(struct trace_seq *s) 
	trace_seq_init(s);

}



void trace_init_global_iter(struct trace_iterator *iter)

{

	iter->tr = &global_trace;

	iter->trace = current_trace;

	iter->cpu_file = TRACE_PIPE_ALL_CPU;

}



static void

__ftrace_dump(bool disable_tracing, enum ftrace_dump_mode oops_dump_mode)

{
@@ -4454,8 +4453,10 @@ __ftrace_dump(bool disable_tracing, enum ftrace_dump_mode oops_dump_mode) 
	if (disable_tracing)

		ftrace_kill();



	trace_init_global_iter(&iter);



	for_each_tracing_cpu(cpu) {

		atomic_inc(&global_trace.data[cpu]->disabled);

		atomic_inc(&iter.tr->data[cpu]->disabled);

	}



	old_userobj = trace_flags & TRACE_ITER_SYM_USEROBJ;
@@ -4504,7 +4505,7 @@ __ftrace_dump(bool disable_tracing, enum ftrace_dump_mode oops_dump_mode) 
		iter.iter_flags |= TRACE_FILE_LAT_FMT;

		iter.pos = -1;



		if (find_next_entry_inc(&iter) != NULL) {

		if (trace_find_next_entry_inc(&iter) != NULL) {

			int ret;



			ret = print_trace_line(&iter);
@@ -4526,7 +4527,7 @@ __ftrace_dump(bool disable_tracing, enum ftrace_dump_mode oops_dump_mode) 
		trace_flags |= old_userobj;



		for_each_tracing_cpu(cpu) {

			atomic_dec(&global_trace.data[cpu]->disabled);

			atomic_dec(&iter.tr->data[cpu]->disabled);

		}

		tracing_on();

	}

kernel/trace/trace.h

+19 −0
Original line number Diff line number Diff line
@@ -338,6 +338,14 @@ struct trace_entry *tracing_get_trace_entry(struct trace_array *tr, 
struct trace_entry *trace_find_next_entry(struct trace_iterator *iter,

					  int *ent_cpu, u64 *ent_ts);



int trace_empty(struct trace_iterator *iter);



void *trace_find_next_entry_inc(struct trace_iterator *iter);



void trace_init_global_iter(struct trace_iterator *iter);



void tracing_iter_reset(struct trace_iterator *iter, int cpu);



void default_wait_pipe(struct trace_iterator *iter);

void poll_wait_pipe(struct trace_iterator *iter);
@@ -380,6 +388,15 @@ void tracing_start_sched_switch_record(void); 
int register_tracer(struct tracer *type);

void unregister_tracer(struct tracer *type);

int is_tracing_stopped(void);

enum trace_file_type {

	TRACE_FILE_LAT_FMT	= 1,

	TRACE_FILE_ANNOTATE	= 2,

};



extern cpumask_var_t __read_mostly tracing_buffer_mask;



#define for_each_tracing_cpu(cpu)	\

	for_each_cpu(cpu, tracing_buffer_mask)



extern int process_new_ksym_entry(char *ksymname, int op, unsigned long addr);
@@ -471,6 +488,8 @@ trace_array_vprintk(struct trace_array *tr, 
		    unsigned long ip, const char *fmt, va_list args);

int trace_array_printk(struct trace_array *tr,

		       unsigned long ip, const char *fmt, ...);

void trace_printk_seq(struct trace_seq *s);

enum print_line_t print_trace_line(struct trace_iterator *iter);



extern unsigned long trace_flags;

kernel/trace/trace_kdb.c

0 → 100644
+119 −0
Original line number Diff line number Diff line 
/*

 * kdb helper for dumping the ftrace buffer

 *

 * Copyright (C) 2010 Jason Wessel <jason.wessel@windriver.com>

 *

 * ftrace_dump_buf based on ftrace_dump:

 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>

 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>

 *

 */

#include <linux/init.h>

#include <linux/kgdb.h>

#include <linux/kdb.h>

#include <linux/ftrace.h>



#include "../debug/kdb/kdb_private.h"

#include "trace.h"

#include "trace_output.h"



static void ftrace_dump_buf(int skip_lines)

{

	/* use static because iter can be a bit big for the stack */

	static struct trace_iterator iter;

	unsigned int old_userobj;

	int cnt = 0, cpu;



	trace_init_global_iter(&iter);



	for_each_tracing_cpu(cpu) {

		atomic_inc(&iter.tr->data[cpu]->disabled);

	}



	old_userobj = trace_flags;



	/* don't look at user memory in panic mode */

	trace_flags &= ~TRACE_ITER_SYM_USEROBJ;



	kdb_printf("Dumping ftrace buffer:\n");



	/* reset all but tr, trace, and overruns */

	memset(&iter.seq, 0,

		   sizeof(struct trace_iterator) -

		   offsetof(struct trace_iterator, seq));

	iter.iter_flags |= TRACE_FILE_LAT_FMT;

	iter.pos = -1;



	for_each_tracing_cpu(cpu) {

		iter.buffer_iter[cpu] =

			ring_buffer_read_prepare(iter.tr->buffer, cpu);

		ring_buffer_read_start(iter.buffer_iter[cpu]);

		tracing_iter_reset(&iter, cpu);

	}



	if (!trace_empty(&iter))

		trace_find_next_entry_inc(&iter);

	while (!trace_empty(&iter)) {

		if (!cnt)

			kdb_printf("---------------------------------\n");

		cnt++;



		if (trace_find_next_entry_inc(&iter) != NULL && !skip_lines)

			print_trace_line(&iter);

		if (!skip_lines)

			trace_printk_seq(&iter.seq);

		else

			skip_lines--;

		if (KDB_FLAG(CMD_INTERRUPT))

			goto out;

	}



	if (!cnt)

		kdb_printf("   (ftrace buffer empty)\n");

	else

		kdb_printf("---------------------------------\n");



out:

	trace_flags = old_userobj;



	for_each_tracing_cpu(cpu) {

		atomic_dec(&iter.tr->data[cpu]->disabled);

	}



	for_each_tracing_cpu(cpu)

		if (iter.buffer_iter[cpu])

			ring_buffer_read_finish(iter.buffer_iter[cpu]);

}



/*

 * kdb_ftdump - Dump the ftrace log buffer

 */

static int kdb_ftdump(int argc, const char **argv)

{

	int skip_lines = 0;

	char *cp;



	if (argc > 1)

		return KDB_ARGCOUNT;



	if (argc) {

		skip_lines = simple_strtol(argv[1], &cp, 0);

		if (*cp)

			skip_lines = 0;

	}



	kdb_trap_printk++;

	ftrace_dump_buf(skip_lines);

	kdb_trap_printk--;



	return 0;

}



static __init int kdb_ftrace_register(void)

{

	kdb_register_repeat("ftdump", kdb_ftdump, "", "Dump ftrace log",

			    0, KDB_REPEAT_NONE);

	return 0;

}



late_initcall(kdb_ftrace_register);