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         trace_iterator_reset(&iter);
  41         iter.iter_flags |= TRACE_FILE_LAT_FMT;
  42
  43         if (cpu_file == RING_BUFFER_ALL_CPUS) {
  44                 for_each_tracing_cpu(cpu) {
  45                         iter.buffer_iter[cpu] =
  46                         ring_buffer_read_prepare(iter.trace_buffer->buffer,
  47                                                  cpu, GFP_ATOMIC);
  48                         ring_buffer_read_start(iter.buffer_iter[cpu]);
  49                         tracing_iter_reset(&iter, cpu);
  50                 }
  51         } else {
  52                 iter.cpu_file = cpu_file;
  53                 iter.buffer_iter[cpu_file] =
  54                         ring_buffer_read_prepare(iter.trace_buffer->buffer,
  55                                                  cpu_file, GFP_ATOMIC);
  56                 ring_buffer_read_start(iter.buffer_iter[cpu_file]);
  57                 tracing_iter_reset(&iter, cpu_file);
  58         }
  59
  60         while (trace_find_next_entry_inc(&iter)) {
  61                 if (!cnt)
  62                         kdb_printf("---------------------------------\n");
  63                 cnt++;
  64
  65                 if (!skip_entries) {
  66                         print_trace_line(&iter);
  67                         trace_printk_seq(&iter.seq);
  68                 } else {
  69                         skip_entries--;
  70                 }
  71
  72                 if (KDB_FLAG(CMD_INTERRUPT))
  73                         goto out;
  74         }
  75
  76         if (!cnt)
  77                 kdb_printf("   (ftrace buffer empty)\n");
  78         else
  79                 kdb_printf("---------------------------------\n");
  80
  81 out:
  82         tr->trace_flags = old_userobj;
  83
  84         for_each_tracing_cpu(cpu) {
  85                 if (iter.buffer_iter[cpu]) {
  86                         ring_buffer_read_finish(iter.buffer_iter[cpu]);
  87                         iter.buffer_iter[cpu] = NULL;
  88                 }
  89         }
  90 }
  91
  92 /*
  93  * kdb_ftdump - Dump the ftrace log buffer
  94  */
  95 static int kdb_ftdump(int argc, const char **argv)
  96 {
  97         int skip_entries = 0;
  98         long cpu_file;
  99         char *cp;
 100         int cnt;
 101         int cpu;
 102
 103         if (argc > 2)
 104                 return KDB_ARGCOUNT;
 105
 106         if (argc) {
 107                 skip_entries = simple_strtol(argv[1], &cp, 0);
 108                 if (*cp)
 109                         skip_entries = 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
 123         trace_init_global_iter(&iter);
 124         iter.buffer_iter = buffer_iter;
 125
 126         for_each_tracing_cpu(cpu) {
 127                 atomic_inc(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
 128         }
 129
 130         /* A negative skip_entries means skip all but the last entries */
 131         if (skip_entries < 0) {
 132                 if (cpu_file == RING_BUFFER_ALL_CPUS)
 133                         cnt = trace_total_entries(NULL);
 134                 else
 135                         cnt = trace_total_entries_cpu(NULL, cpu_file);
 136                 skip_entries = max(cnt + skip_entries, 0);
 137         }
 138
 139         ftrace_dump_buf(skip_entries, cpu_file);
 140
 141         for_each_tracing_cpu(cpu) {
 142                 atomic_dec(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
 143         }
 144
 145         kdb_trap_printk--;
 146
 147         return 0;
 148 }
 149
 150 static __init int kdb_ftrace_register(void)
 151 {
 152         kdb_register_flags("ftdump", kdb_ftdump, "[skip_#entries] [cpu]",
 153                             "Dump ftrace log; -skip dumps last #entries", 0,
 154                             KDB_ENABLE_ALWAYS_SAFE);
 155         return 0;
 156 }
 157
 158 late_initcall(kdb_ftrace_register);