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_start(iter.array_buffer->buffer, 47 cpu, GFP_ATOMIC); 48 tracing_iter_reset(&iter, cpu); 49 } 50 } else { 51 iter.cpu_file = cpu_file; 52 iter.buffer_iter[cpu_file] = 53 ring_buffer_read_start(iter.array_buffer->buffer, 54 cpu_file, GFP_ATOMIC); 55 tracing_iter_reset(&iter, cpu_file); 56 } 57 58 while (trace_find_next_entry_inc(&iter)) { 59 if (!cnt) 60 kdb_printf("---------------------------------\n"); 61 cnt++; 62 63 if (!skip_entries) { 64 print_trace_line(&iter); 65 trace_printk_seq(&iter.seq); 66 } else { 67 skip_entries--; 68 } 69 70 if (KDB_FLAG(CMD_INTERRUPT)) 71 goto out; 72 } 73 74 if (!cnt) 75 kdb_printf(" (ftrace buffer empty)\n"); 76 else 77 kdb_printf("---------------------------------\n"); 78 79 out: 80 tr->trace_flags = old_userobj; 81 82 for_each_tracing_cpu(cpu) { 83 if (iter.buffer_iter[cpu]) { 84 ring_buffer_read_finish(iter.buffer_iter[cpu]); 85 iter.buffer_iter[cpu] = NULL; 86 } 87 } 88 } 89 90 /* 91 * kdb_ftdump - Dump the ftrace log buffer 92 */ 93 static int kdb_ftdump(int argc, const char **argv) 94 { 95 int skip_entries = 0; 96 long cpu_file; 97 int err; 98 int cnt; 99 100 if (argc > 2) 101 return KDB_ARGCOUNT; 102 103 if (argc && kstrtoint(argv[1], 0, &skip_entries)) 104 return KDB_BADINT; 105 106 if (argc == 2) { 107 err = kstrtol(argv[2], 0, &cpu_file); 108 if (err || cpu_file >= NR_CPUS || cpu_file < 0 || 109 !cpu_online(cpu_file)) 110 return KDB_BADINT; 111 } else { 112 cpu_file = RING_BUFFER_ALL_CPUS; 113 } 114 115 kdb_trap_printk++; 116 117 trace_init_global_iter(&iter); 118 iter.buffer_iter = buffer_iter; 119 120 tracer_tracing_disable(iter.tr); 121 122 /* A negative skip_entries means skip all but the last entries */ 123 if (skip_entries < 0) { 124 if (cpu_file == RING_BUFFER_ALL_CPUS) 125 cnt = trace_total_entries(NULL); 126 else 127 cnt = trace_total_entries_cpu(NULL, cpu_file); 128 skip_entries = max(cnt + skip_entries, 0); 129 } 130 131 ftrace_dump_buf(skip_entries, cpu_file); 132 133 tracer_tracing_enable(iter.tr); 134 135 kdb_trap_printk--; 136 137 return 0; 138 } 139 140 static kdbtab_t ftdump_cmd = { 141 .name = "ftdump", 142 .func = kdb_ftdump, 143 .usage = "[skip_#entries] [cpu]", 144 .help = "Dump ftrace log; -skip dumps last #entries", 145 .flags = KDB_ENABLE_ALWAYS_SAFE, 146 }; 147 148 static __init int kdb_ftrace_register(void) 149 { 150 kdb_register(&ftdump_cmd); 151 return 0; 152 } 153 154 late_initcall(kdb_ftrace_register); 155