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         trace_iterator_reset(&iter);
  45         iter.iter_flags |= TRACE_FILE_LAT_FMT;
  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_lines) {
  70                         print_trace_line(&iter);
  71                         trace_printk_seq(&iter.seq);
  72                 } else {
  73                         skip_lines--;
  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                 atomic_dec(&per_cpu_ptr(iter.trace_buffer->data, cpu)->disabled);
  90         }
  91
  92         for_each_tracing_cpu(cpu) {
  93                 if (iter.buffer_iter[cpu]) {
  94                         ring_buffer_read_finish(iter.buffer_iter[cpu]);
  95                         iter.buffer_iter[cpu] = NULL;
  96                 }
  97         }
  98 }
  99
 100 /*
 101  * kdb_ftdump - Dump the ftrace log buffer
 102  */
 103 static int kdb_ftdump(int argc, const char **argv)
 104 {
 105         int skip_lines = 0;
 106         long cpu_file;
 107         char *cp;
 108
 109         if (argc > 2)
 110                 return KDB_ARGCOUNT;
 111
 112         if (argc) {
 113                 skip_lines = simple_strtol(argv[1], &cp, 0);
 114                 if (*cp)
 115                         skip_lines = 0;
 116         }
 117
 118         if (argc == 2) {
 119                 cpu_file = simple_strtol(argv[2], &cp, 0);
 120                 if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
 121                     !cpu_online(cpu_file))
 122                         return KDB_BADINT;
 123         } else {
 124                 cpu_file = RING_BUFFER_ALL_CPUS;
 125         }
 126
 127         kdb_trap_printk++;
 128         ftrace_dump_buf(skip_lines, cpu_file);
 129         kdb_trap_printk--;
 130
 131         return 0;
 132 }
 133
 134 static __init int kdb_ftrace_register(void)
 135 {
 136         kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]",
 137                             "Dump ftrace log", 0, KDB_ENABLE_ALWAYS_SAFE);
 138         return 0;
 139 }
 140
 141 late_initcall(kdb_ftrace_register);