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 "trace.h"
  17 #include "trace_output.h"
  18
  19 static void ftrace_dump_buf(int skip_lines, long cpu_file)
  20 {
  21         /* use static because iter can be a bit big for the stack */
  22         static struct trace_iterator iter;
  23         unsigned int old_userobj;
  24         int cnt = 0, cpu;
  25
  26         trace_init_global_iter(&iter);
  27
  28         for_each_tracing_cpu(cpu) {
  29                 atomic_inc(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
  30         }
  31
  32         old_userobj = trace_flags;
  33
  34         /* don't look at user memory in panic mode */
  35         trace_flags &= ~TRACE_ITER_SYM_USEROBJ;
  36
  37         kdb_printf("Dumping ftrace buffer:\n");
  38
  39         /* reset all but tr, trace, and overruns */
  40         memset(&iter.seq, 0,
  41                    sizeof(struct trace_iterator) -
  42                    offsetof(struct trace_iterator, seq));
  43         iter.iter_flags |= TRACE_FILE_LAT_FMT;
  44         iter.pos = -1;
  45
  46         if (cpu_file == RING_BUFFER_ALL_CPUS) {
  47                 for_each_tracing_cpu(cpu) {
  48                         iter.buffer_iter[cpu] =
  49                         ring_buffer_read_prepare(iter.trace_buffer->buffer, cpu);
  50                         ring_buffer_read_start(iter.buffer_iter[cpu]);
  51                         tracing_iter_reset(&iter, cpu);
  52                 }
  53         } else {
  54                 iter.cpu_file = cpu_file;
  55                 iter.buffer_iter[cpu_file] =
  56                         ring_buffer_read_prepare(iter.trace_buffer->buffer, cpu_file);
  57                 ring_buffer_read_start(iter.buffer_iter[cpu_file]);
  58                 tracing_iter_reset(&iter, cpu_file);
  59         }
  60         if (!trace_empty(&iter))
  61                 trace_find_next_entry_inc(&iter);
  62         while (!trace_empty(&iter)) {
  63                 if (!cnt)
  64                         kdb_printf("---------------------------------\n");
  65                 cnt++;
  66
  67                 if (trace_find_next_entry_inc(&iter) != NULL && !skip_lines)
  68                         print_trace_line(&iter);
  69                 if (!skip_lines)
  70                         trace_printk_seq(&iter.seq);
  71                 else
  72                         skip_lines--;
  73                 if (KDB_FLAG(CMD_INTERRUPT))
  74                         goto out;
  75         }
  76
  77         if (!cnt)
  78                 kdb_printf("   (ftrace buffer empty)\n");
  79         else
  80                 kdb_printf("---------------------------------\n");
  81
  82 out:
  83         trace_flags = old_userobj;
  84
  85         for_each_tracing_cpu(cpu) {
  86                 atomic_dec(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
  87         }
  88
  89         for_each_tracing_cpu(cpu)
  90                 if (iter.buffer_iter[cpu])
  91                         ring_buffer_read_finish(iter.buffer_iter[cpu]);
  92 }
  93
  94 /*
  95  * kdb_ftdump - Dump the ftrace log buffer
  96  */
  97 static int kdb_ftdump(int argc, const char **argv)
  98 {
  99         int skip_lines = 0;
 100         long cpu_file;
 101         char *cp;
 102
 103         if (argc > 2)
 104                 return KDB_ARGCOUNT;
 105
 106         if (argc) {
 107                 skip_lines = simple_strtol(argv[1], &cp, 0);
 108                 if (*cp)
 109                         skip_lines = 0;
 110         }
 111
 112         if (argc == 2) {
 113                 cpu_file = simple_strtol(argv[2], &cp, 0);
 114                 if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
 115                     !cpu_online(cpu_file))
 116                         return KDB_BADINT;
 117         } else {
 118                 cpu_file = RING_BUFFER_ALL_CPUS;
 119         }
 120
 121         kdb_trap_printk++;
 122         ftrace_dump_buf(skip_lines, cpu_file);
 123         kdb_trap_printk--;
 124
 125         return 0;
 126 }
 127
 128 static __init int kdb_ftrace_register(void)
 129 {
 130         kdb_register_repeat("ftdump", kdb_ftdump, "[skip_#lines] [cpu]",
 131                             "Dump ftrace log", 0, KDB_REPEAT_NONE);
 132         return 0;
 133 }
 134
 135 late_initcall(kdb_ftrace_register);