kernel/trace/trace_kdb.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * kdb helper for dumping the ftrace buffer
   4  *
   5  * Copyright (C) 2010 Jason Wessel <jason.wessel@windriver.com>
   6  *
   7  * ftrace_dump_buf based on ftrace_dump:
   8  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   9  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
  10  *
  11  */
  12 #include <linux/init.h>
  13 #include <linux/kgdb.h>
  14 #include <linux/kdb.h>
  15 #include <linux/ftrace.h>
  16
  17 #include "trace.h"
  18 #include "trace_output.h"
  19
  20 static struct trace_iterator iter;
  21 static struct ring_buffer_iter *buffer_iter[CONFIG_NR_CPUS];
  22
  23 static void ftrace_dump_buf(int skip_entries, long cpu_file)
  24 {
  25         struct trace_array *tr;
  26         unsigned int old_userobj;
  27         int cnt = 0, cpu;
  28
  29         tr = iter.tr;
  30
  31         old_userobj = tr->trace_flags;
  32
  33         /* don't look at user memory in panic mode */
  34         tr->trace_flags &= ~TRACE_ITER_SYM_USEROBJ;
  35
  36         kdb_printf("Dumping ftrace buffer:\n");
  37         if (skip_entries)
  38                 kdb_printf("(skipping %d entries)\n", skip_entries);
  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         if (cpu_file == RING_BUFFER_ALL_CPUS) {
  48                 for_each_tracing_cpu(cpu) {
  49                         iter.buffer_iter[cpu] =
  50                         ring_buffer_read_prepare(iter.trace_buffer->buffer,
  51                                                  cpu, GFP_ATOMIC);
  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,
  59                                                  cpu_file, GFP_ATOMIC);
  60                 ring_buffer_read_start(iter.buffer_iter[cpu_file]);
  61                 tracing_iter_reset(&iter, cpu_file);
  62         }
  63
  64         while (trace_find_next_entry_inc(&iter)) {
  65                 if (!cnt)
  66                         kdb_printf("---------------------------------\n");
  67                 cnt++;
  68
  69                 if (!skip_entries) {
  70                         print_trace_line(&iter);
  71                         trace_printk_seq(&iter.seq);
  72                 } else {
  73                         skip_entries--;
  74                 }
  75
  76                 if (KDB_FLAG(CMD_INTERRUPT))
  77                         goto out;
  78         }
  79
  80         if (!cnt)
  81                 kdb_printf("   (ftrace buffer empty)\n");
  82         else
  83                 kdb_printf("---------------------------------\n");
  84
  85 out:
  86         tr->trace_flags = old_userobj;
  87
  88         for_each_tracing_cpu(cpu) {
  89                 if (iter.buffer_iter[cpu]) {
  90                         ring_buffer_read_finish(iter.buffer_iter[cpu]);
  91                         iter.buffer_iter[cpu] = NULL;
  92                 }
  93         }
  94 }
  95
  96 /*
  97  * kdb_ftdump - Dump the ftrace log buffer
  98  */
  99 static int kdb_ftdump(int argc, const char **argv)
 100 {
 101         int skip_entries = 0;
 102         long cpu_file;
 103         char *cp;
 104         int cnt;
 105         int cpu;
 106
 107         if (argc > 2)
 108                 return KDB_ARGCOUNT;
 109
 110         if (argc) {
 111                 skip_entries = simple_strtol(argv[1], &cp, 0);
 112                 if (*cp)
 113                         skip_entries = 0;
 114         }
 115
 116         if (argc == 2) {
 117                 cpu_file = simple_strtol(argv[2], &cp, 0);
 118                 if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
 119                     !cpu_online(cpu_file))
 120                         return KDB_BADINT;
 121         } else {
 122                 cpu_file = RING_BUFFER_ALL_CPUS;
 123         }
 124
 125         kdb_trap_printk++;
 126
 127         trace_init_global_iter(&iter);
 128         iter.buffer_iter = buffer_iter;
 129
 130         for_each_tracing_cpu(cpu) {
 131                 atomic_inc(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
 132         }
 133
 134         /* A negative skip_entries means skip all but the last entries */
 135         if (skip_entries < 0) {
 136                 if (cpu_file == RING_BUFFER_ALL_CPUS)
 137                         cnt = trace_total_entries(NULL);
 138                 else
 139                         cnt = trace_total_entries_cpu(NULL, cpu_file);
 140                 skip_entries = max(cnt + skip_entries, 0);
 141         }
 142
 143         ftrace_dump_buf(skip_entries, cpu_file);
 144
 145         for_each_tracing_cpu(cpu) {
 146                 atomic_dec(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
 147         }
 148
 149         kdb_trap_printk--;
 150
 151         return 0;
 152 }
 153
 154 static __init int kdb_ftrace_register(void)
 155 {
 156         kdb_register_flags("ftdump", kdb_ftdump, "[skip_#entries] [cpu]",
 157                             "Dump ftrace log; -skip dumps last #entries", 0,
 158                             KDB_ENABLE_ALWAYS_SAFE);
 159         return 0;
 160 }
 161
 162 late_initcall(kdb_ftrace_register);