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