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         static struct ring_buffer_iter *buffer_iter[CONFIG_NR_CPUS];
  24         unsigned int old_userobj;
  25         int cnt = 0, cpu;
  26
  27         trace_init_global_iter(&iter);
  28         iter.buffer_iter = buffer_iter;
  29
  30         for_each_tracing_cpu(cpu) {
  31                 atomic_inc(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
  32         }
  33
  34         old_userobj = trace_flags;
  35
  36         /* don't look at user memory in panic mode */
  37         trace_flags &= ~TRACE_ITER_SYM_USEROBJ;
  38
  39         kdb_printf("Dumping ftrace buffer:\n");
  40
  41         /* reset all but tr, trace, and overruns */
  42         memset(&iter.seq, 0,
  43                    sizeof(struct trace_iterator) -
  44                    offsetof(struct trace_iterator, seq));
  45         iter.iter_flags |= TRACE_FILE_LAT_FMT;
  46         iter.pos = -1;
  47
  48         if (cpu_file == RING_BUFFER_ALL_CPUS) {
  49                 for_each_tracing_cpu(cpu) {
  50                         iter.buffer_iter[cpu] =
  51                         ring_buffer_read_prepare(iter.trace_buffer->buffer, cpu);
  52                         ring_buffer_read_start(iter.buffer_iter[cpu]);
  53                         tracing_iter_reset(&iter, cpu);
  54                 }
  55         } else {
  56                 iter.cpu_file = cpu_file;
  57                 iter.buffer_iter[cpu_file] =
  58                         ring_buffer_read_prepare(iter.trace_buffer->buffer, cpu_file);
  59                 ring_buffer_read_start(iter.buffer_iter[cpu_file]);
  60                 tracing_iter_reset(&iter, cpu_file);
  61         }
  62
  63         while (trace_find_next_entry_inc(&iter)) {
  64                 if (!cnt)
  65                         kdb_printf("---------------------------------\n");
  66                 cnt++;
  67
  68                 if (!skip_lines) {
  69                         print_trace_line(&iter);
  70                         trace_printk_seq(&iter.seq);
  71                 } else {
  72                         skip_lines--;
  73                 }
  74
  75                 if (KDB_FLAG(CMD_INTERRUPT))
  76                         goto out;
  77         }
  78
  79         if (!cnt)
  80                 kdb_printf("   (ftrace buffer empty)\n");
  81         else
  82                 kdb_printf("---------------------------------\n");
  83
  84 out:
  85         trace_flags = old_userobj;
  86
  87         for_each_tracing_cpu(cpu) {
  88                 atomic_dec(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
  89         }
  90
  91         for_each_tracing_cpu(cpu) {
  92                 if (iter.buffer_iter[cpu]) {
  93                         ring_buffer_read_finish(iter.buffer_iter[cpu]);
  94                         iter.buffer_iter[cpu] = NULL;
  95                 }
  96         }
  97 }
  98
  99 /*
 100  * kdb_ftdump - Dump the ftrace log buffer
 101  */
 102 static int kdb_ftdump(int argc, const char **argv)
 103 {
 104         int skip_lines = 0;
 105         long cpu_file;
 106         char *cp;
 107
 108         if (argc > 2)
 109                 return KDB_ARGCOUNT;
 110
 111         if (argc) {
 112                 skip_lines = simple_strtol(argv[1], &cp, 0);
 113                 if (*cp)
 114                         skip_lines = 0;
 115         }
 116
 117         if (argc == 2) {
 118                 cpu_file = simple_strtol(argv[2], &cp, 0);
 119                 if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
 120                     !cpu_online(cpu_file))
 121                         return KDB_BADINT;
 122         } else {
 123                 cpu_file = RING_BUFFER_ALL_CPUS;
 124         }
 125
 126         kdb_trap_printk++;
 127         ftrace_dump_buf(skip_lines, cpu_file);
 128         kdb_trap_printk--;
 129
 130         return 0;
 131 }
 132
 133 static __init int kdb_ftrace_register(void)
 134 {
 135         kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]",
 136                             "Dump ftrace log", 0, KDB_ENABLE_ALWAYS_SAFE);
 137         return 0;
 138 }
 139
 140 late_initcall(kdb_ftrace_register);