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
ftrace_dump_buf(int skip_entries,long cpu_file)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 */
kdb_ftdump(int argc,const char ** argv)93 static int kdb_ftdump(int argc, const char **argv)
94 {
95 int skip_entries = 0;
96 long cpu_file;
97 char *cp;
98 int cnt;
99 int cpu;
100
101 if (argc > 2)
102 return KDB_ARGCOUNT;
103
104 if (argc) {
105 skip_entries = simple_strtol(argv[1], &cp, 0);
106 if (*cp)
107 skip_entries = 0;
108 }
109
110 if (argc == 2) {
111 cpu_file = simple_strtol(argv[2], &cp, 0);
112 if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
113 !cpu_online(cpu_file))
114 return KDB_BADINT;
115 } else {
116 cpu_file = RING_BUFFER_ALL_CPUS;
117 }
118
119 kdb_trap_printk++;
120
121 trace_init_global_iter(&iter);
122 iter.buffer_iter = buffer_iter;
123
124 for_each_tracing_cpu(cpu) {
125 atomic_inc(&per_cpu_ptr(iter.array_buffer->data, cpu)->disabled);
126 }
127
128 /* A negative skip_entries means skip all but the last entries */
129 if (skip_entries < 0) {
130 if (cpu_file == RING_BUFFER_ALL_CPUS)
131 cnt = trace_total_entries(NULL);
132 else
133 cnt = trace_total_entries_cpu(NULL, cpu_file);
134 skip_entries = max(cnt + skip_entries, 0);
135 }
136
137 ftrace_dump_buf(skip_entries, cpu_file);
138
139 for_each_tracing_cpu(cpu) {
140 atomic_dec(&per_cpu_ptr(iter.array_buffer->data, cpu)->disabled);
141 }
142
143 kdb_trap_printk--;
144
145 return 0;
146 }
147
148 static kdbtab_t ftdump_cmd = {
149 .name = "ftdump",
150 .func = kdb_ftdump,
151 .usage = "[skip_#entries] [cpu]",
152 .help = "Dump ftrace log; -skip dumps last #entries",
153 .flags = KDB_ENABLE_ALWAYS_SAFE,
154 };
155
kdb_ftrace_register(void)156 static __init int kdb_ftrace_register(void)
157 {
158 kdb_register(&ftdump_cmd);
159 return 0;
160 }
161
162 late_initcall(kdb_ftrace_register);
163