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         struct trace_array *tr;
  25         unsigned int old_userobj;
  26         int cnt = 0, cpu;
  27
  28         trace_init_global_iter(&iter);
  29         iter.buffer_iter = buffer_iter;
  30         tr = iter.tr;
  31
  32         for_each_tracing_cpu(cpu) {
  33                 atomic_inc(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
  34         }
  35
  36         old_userobj = tr->trace_flags;
  37
  38         /* don't look at user memory in panic mode */
  39         tr->trace_flags &= ~TRACE_ITER_SYM_USEROBJ;
  40
  41         kdb_printf("Dumping ftrace buffer:\n");
  42
  43         /* reset all but tr, trace, and overruns */
  44         memset(&iter.seq, 0,
  45                    sizeof(struct trace_iterator) -
  46                    offsetof(struct trace_iterator, seq));
  47         iter.iter_flags |= TRACE_FILE_LAT_FMT;
  48         iter.pos = -1;
  49
  50         if (cpu_file == RING_BUFFER_ALL_CPUS) {
  51                 for_each_tracing_cpu(cpu) {
  52                         iter.buffer_iter[cpu] =
  53                         ring_buffer_read_prepare(iter.trace_buffer->buffer, cpu);
  54                         ring_buffer_read_start(iter.buffer_iter[cpu]);
  55                         tracing_iter_reset(&iter, cpu);
  56                 }
  57         } else {
  58                 iter.cpu_file = cpu_file;
  59                 iter.buffer_iter[cpu_file] =
  60                         ring_buffer_read_prepare(iter.trace_buffer->buffer, cpu_file);
  61                 ring_buffer_read_start(iter.buffer_iter[cpu_file]);
  62                 tracing_iter_reset(&iter, cpu_file);
  63         }
  64
  65         while (trace_find_next_entry_inc(&iter)) {
  66                 if (!cnt)
  67                         kdb_printf("---------------------------------\n");
  68                 cnt++;
  69
  70                 if (!skip_lines) {
  71                         print_trace_line(&iter);
  72                         trace_printk_seq(&iter.seq);
  73                 } else {
  74                         skip_lines--;
  75                 }
  76
  77                 if (KDB_FLAG(CMD_INTERRUPT))
  78                         goto out;
  79         }
  80
  81         if (!cnt)
  82                 kdb_printf("   (ftrace buffer empty)\n");
  83         else
  84                 kdb_printf("---------------------------------\n");
  85
  86 out:
  87         tr->trace_flags = old_userobj;
  88
  89         for_each_tracing_cpu(cpu) {
  90                 atomic_dec(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
  91         }
  92
  93         for_each_tracing_cpu(cpu) {
  94                 if (iter.buffer_iter[cpu]) {
  95                         ring_buffer_read_finish(iter.buffer_iter[cpu]);
  96                         iter.buffer_iter[cpu] = NULL;
  97                 }
  98         }
  99 }
 100
 101 /*
 102  * kdb_ftdump - Dump the ftrace log buffer
 103  */
 104 static int kdb_ftdump(int argc, const char **argv)
 105 {
 106         int skip_lines = 0;
 107         long cpu_file;
 108         char *cp;
 109
 110         if (argc > 2)
 111                 return KDB_ARGCOUNT;
 112
 113         if (argc) {
 114                 skip_lines = simple_strtol(argv[1], &cp, 0);
 115                 if (*cp)
 116                         skip_lines = 0;
 117         }
 118
 119         if (argc == 2) {
 120                 cpu_file = simple_strtol(argv[2], &cp, 0);
 121                 if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
 122                     !cpu_online(cpu_file))
 123                         return KDB_BADINT;
 124         } else {
 125                 cpu_file = RING_BUFFER_ALL_CPUS;
 126         }
 127
 128         kdb_trap_printk++;
 129         ftrace_dump_buf(skip_lines, cpu_file);
 130         kdb_trap_printk--;
 131
 132         return 0;
 133 }
 134
 135 static __init int kdb_ftrace_register(void)
 136 {
 137         kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]",
 138                             "Dump ftrace log", 0, KDB_ENABLE_ALWAYS_SAFE);
 139         return 0;
 140 }
 141
 142 late_initcall(kdb_ftrace_register);