LXR linux/kernel/trace/trace

   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
  19static 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
  86out:
  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 */
 104static 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
 135static __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
 142late_initcall(kdb_ftrace_register);
 143