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: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
CC: Frederic Weisbecker <fweisbec@gmail.com>

diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index ffb1a5b..4215530 100644 (file)
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -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

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 086d363..d6736b9 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -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 @@ waitagain:
 
        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();
        }

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 2cd9639..0605fc0 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -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;
 

diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
new file mode 100644 (file)
index 0000000..44cbda2
--- /dev/null
+++ b/kernel/trace/trace_kdb.c
@@ -0,0 +1,119 @@
+/*
+ * 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);