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
 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);