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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * kdb helper for dumping the ftrace buffer
4 *
5 * Copyright (C) 2010 Jason Wessel <[email protected]>
6 *
7 * ftrace_dump_buf based on ftrace_dump:
8 * Copyright (C) 2007-2008 Steven Rostedt <[email protected]>
9 * Copyright (C) 2008 Ingo Molnar <[email protected]>
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
20static struct trace_iterator iter;
21static struct ring_buffer_iter *buffer_iter[CONFIG_NR_CPUS];
22
23static 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
79out:
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 */
93static 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
140static 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
148static __init int kdb_ftrace_register(void)
149{
150 kdb_register(&ftdump_cmd);
151 return 0;
152}
153
154late_initcall(kdb_ftrace_register);