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 	char *cp;
100 	int cnt;
101 	int cpu;
102 
103 	if (argc > 2)
104 		return KDB_ARGCOUNT;
105 
106 	if (argc) {
107 		skip_entries = simple_strtol(argv[1], &cp, 0);
108 		if (*cp)
109 			skip_entries = 0;
110 	}
111 
112 	if (argc == 2) {
113 		cpu_file = simple_strtol(argv[2], &cp, 0);
114 		if (*cp || cpu_file >= NR_CPUS || cpu_file < 0 ||
115 		    !cpu_online(cpu_file))
116 			return KDB_BADINT;
117 	} else {
118 		cpu_file = RING_BUFFER_ALL_CPUS;
119 	}
120 
121 	kdb_trap_printk++;
122 
123 	trace_init_global_iter(&iter);
124 	iter.buffer_iter = buffer_iter;
125 
126 	for_each_tracing_cpu(cpu) {
127 		atomic_inc(&per_cpu_ptr(iter.array_buffer->data, cpu)->disabled);
128 	}
129 
130 	/* A negative skip_entries means skip all but the last entries */
131 	if (skip_entries < 0) {
132 		if (cpu_file == RING_BUFFER_ALL_CPUS)
133 			cnt = trace_total_entries(NULL);
134 		else
135 			cnt = trace_total_entries_cpu(NULL, cpu_file);
136 		skip_entries = max(cnt + skip_entries, 0);
137 	}
138 
139 	ftrace_dump_buf(skip_entries, cpu_file);
140 
141 	for_each_tracing_cpu(cpu) {
142 		atomic_dec(&per_cpu_ptr(iter.array_buffer->data, cpu)->disabled);
143 	}
144 
145 	kdb_trap_printk--;
146 
147 	return 0;
148 }
149 
150 static kdbtab_t ftdump_cmd = {
151 	.name = "ftdump",
152 	.func = kdb_ftdump,
153 	.usage = "[skip_#entries] [cpu]",
154 	.help = "Dump ftrace log; -skip dumps last #entries",
155 	.flags = KDB_ENABLE_ALWAYS_SAFE,
156 };
157 
kdb_ftrace_register(void)158 static __init int kdb_ftrace_register(void)
159 {
160 	kdb_register(&ftdump_cmd);
161 	return 0;
162 }
163 
164 late_initcall(kdb_ftrace_register);
165