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 void ftrace_dump_buf(int skip_lines, long cpu_file)
  21 {
  22         /* use static because iter can be a bit big for the stack */
  23         static struct trace_iterator iter;
  24         static struct ring_buffer_iter *buffer_iter[CONFIG_NR_CPUS];
  25         struct trace_array *tr;
  26         unsigned int old_userobj;
  27         int cnt = 0, cpu;
  28
  29         trace_init_global_iter(&iter);
  30         iter.buffer_iter = buffer_iter;
  31         tr = iter.tr;
  32
  33         for_each_tracing_cpu(cpu) {
  34                 atomic_inc(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
  35         }
  36
  37         old_userobj = tr->trace_flags;
  38
  39         /* don't look at user memory in panic mode */
  40         tr->trace_flags &= ~TRACE_ITER_SYM_USEROBJ;
  41
  42         kdb_printf("Dumping ftrace buffer:\n");
  43
  44         /* reset all but tr, trace, and overruns */
  45         memset(&iter.seq, 0,
  46                    sizeof(struct trace_iterator) -
  47                    offsetof(struct trace_iterator, seq));
  48         iter.iter_flags |= TRACE_FILE_LAT_FMT;
  49         iter.pos = -1;
  50
  51         if (cpu_file == RING_BUFFER_ALL_CPUS) {
  52                 for_each_tracing_cpu(cpu) {
  53                         iter.buffer_iter[cpu] =
  54                         ring_buffer_read_prepare(iter.trace_buffer->buffer,
  55                                                  cpu, GFP_ATOMIC);
  56                         ring_buffer_read_start(iter.buffer_iter[cpu]);
  57                         tracing_iter_reset(&iter, cpu);
  58                 }
  59         } else {
  60                 iter.cpu_file = cpu_file;
  61                 iter.buffer_iter[cpu_file] =
  62                         ring_buffer_read_prepare(iter.trace_buffer->buffer,
  63                                                  cpu_file, GFP_ATOMIC);
  64                 ring_buffer_read_start(iter.buffer_iter[cpu_file]);
  65                 tracing_iter_reset(&iter, cpu_file);
  66         }
  67
  68         while (trace_find_next_entry_inc(&iter)) {
  69                 if (!cnt)
  70                         kdb_printf("---------------------------------\n");
  71                 cnt++;
  72
  73                 if (!skip_lines) {
  74                         print_trace_line(&iter);
  75                         trace_printk_seq(&iter.seq);
  76                 } else {
  77                         skip_lines--;
  78                 }
  79
  80                 if (KDB_FLAG(CMD_INTERRUPT))
  81                         goto out;
  82         }
  83
  84         if (!cnt)
  85                 kdb_printf("   (ftrace buffer empty)\n");
  86         else
  87                 kdb_printf("---------------------------------\n");
  88
  89 out:
  90         tr->trace_flags = old_userobj;
  91
  92         for_each_tracing_cpu(cpu) {
  93                 atomic_dec(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
  94         }
  95
  96         for_each_tracing_cpu(cpu) {
  97                 if (iter.buffer_iter[cpu]) {
  98                         ring_buffer_read_finish(iter.buffer_iter[cpu]);
  99                         iter.buffer_iter[cpu] = NULL;
 100                 }
 101         }
 102 }
 103
 104 /*
 105  * kdb_ftdump - Dump the ftrace log buffer
 106  */
 107 static int kdb_ftdump(int argc, const char **argv)
 108 {
 109         int skip_lines = 0;
 110         long cpu_file;
 111         char *cp;
 112
 113         if (argc > 2)
 114                 return KDB_ARGCOUNT;
 115
 116         if (argc) {
 117                 skip_lines = simple_strtol(argv[1], &cp, 0);
 118                 if (*cp)
 119                         skip_lines = 0;
 120         }
 121
 122         if (argc == 2) {
 123                 cpu_file = simple_strtol(argv[2], &cp, 0);
 124                 if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
 125                     !cpu_online(cpu_file))
 126                         return KDB_BADINT;
 127         } else {
 128                 cpu_file = RING_BUFFER_ALL_CPUS;
 129         }
 130
 131         kdb_trap_printk++;
 132         ftrace_dump_buf(skip_lines, cpu_file);
 133         kdb_trap_printk--;
 134
 135         return 0;
 136 }
 137
 138 static __init int kdb_ftrace_register(void)
 139 {
 140         kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]",
 141                             "Dump ftrace log", 0, KDB_ENABLE_ALWAYS_SAFE);
 142         return 0;
 143 }
 144
 145 late_initcall(kdb_ftrace_register);