kernel/trace/trace_kdb.c

   1 /*
   2  * kdb helper for dumping the ftrace buffer
   3  *
   4  * Copyright (C) 2010 Jason Wessel <jason.wessel@windriver.com>
   5  *
   6  * ftrace_dump_buf based on ftrace_dump:
   7  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   8  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
   9  *
  10  */
  11 #include <linux/init.h>
  12 #include <linux/kgdb.h>
  13 #include <linux/kdb.h>
  14 #include <linux/ftrace.h>
  15
  16 #include "../debug/kdb/kdb_private.h"
  17 #include "trace.h"
  18 #include "trace_output.h"
  19
  20 static void ftrace_dump_buf(int skip_lines)
  21 {
  22         /* use static because iter can be a bit big for the stack */
  23         static struct trace_iterator iter;
  24         unsigned int old_userobj;
  25         int cnt = 0, cpu;
  26
  27         trace_init_global_iter(&iter);
  28
  29         for_each_tracing_cpu(cpu) {
  30                 atomic_inc(&iter.tr->data[cpu]->disabled);
  31         }
  32
  33         old_userobj = trace_flags;
  34
  35         /* don't look at user memory in panic mode */
  36         trace_flags &= ~TRACE_ITER_SYM_USEROBJ;
  37
  38         kdb_printf("Dumping ftrace buffer:\n");
  39
  40         /* reset all but tr, trace, and overruns */
  41         memset(&iter.seq, 0,
  42                    sizeof(struct trace_iterator) -
  43                    offsetof(struct trace_iterator, seq));
  44         iter.iter_flags |= TRACE_FILE_LAT_FMT;
  45         iter.pos = -1;
  46
  47         for_each_tracing_cpu(cpu) {
  48                 iter.buffer_iter[cpu] =
  49                         ring_buffer_read_prepare(iter.tr->buffer, cpu);
  50                 ring_buffer_read_start(iter.buffer_iter[cpu]);
  51                 tracing_iter_reset(&iter, cpu);
  52         }
  53
  54         if (!trace_empty(&iter))
  55                 trace_find_next_entry_inc(&iter);
  56         while (!trace_empty(&iter)) {
  57                 if (!cnt)
  58                         kdb_printf("---------------------------------\n");
  59                 cnt++;
  60
  61                 if (trace_find_next_entry_inc(&iter) != NULL && !skip_lines)
  62                         print_trace_line(&iter);
  63                 if (!skip_lines)
  64                         trace_printk_seq(&iter.seq);
  65                 else
  66                         skip_lines--;
  67                 if (KDB_FLAG(CMD_INTERRUPT))
  68                         goto out;
  69         }
  70
  71         if (!cnt)
  72                 kdb_printf("   (ftrace buffer empty)\n");
  73         else
  74                 kdb_printf("---------------------------------\n");
  75
  76 out:
  77         trace_flags = old_userobj;
  78
  79         for_each_tracing_cpu(cpu) {
  80                 atomic_dec(&iter.tr->data[cpu]->disabled);
  81         }
  82
  83         for_each_tracing_cpu(cpu)
  84                 if (iter.buffer_iter[cpu])
  85                         ring_buffer_read_finish(iter.buffer_iter[cpu]);
  86 }
  87
  88 /*
  89  * kdb_ftdump - Dump the ftrace log buffer
  90  */
  91 static int kdb_ftdump(int argc, const char **argv)
  92 {
  93         int skip_lines = 0;
  94         char *cp;
  95
  96         if (argc > 1)
  97                 return KDB_ARGCOUNT;
  98
  99         if (argc) {
 100                 skip_lines = simple_strtol(argv[1], &cp, 0);
 101                 if (*cp)
 102                         skip_lines = 0;
 103         }
 104
 105         kdb_trap_printk++;
 106         ftrace_dump_buf(skip_lines);
 107         kdb_trap_printk--;
 108
 109         return 0;
 110 }
 111
 112 static __init int kdb_ftrace_register(void)
 113 {
 114         kdb_register_repeat("ftdump", kdb_ftdump, "", "Dump ftrace log",
 115                             0, KDB_REPEAT_NONE);
 116         return 0;
 117 }
 118
 119 late_initcall(kdb_ftrace_register);