1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * trace binary printk
4 *
5 * Copyright (C) 2008 Lai Jiangshan <laijs@cn.fujitsu.com>
6 *
7 */
8 #include <linux/seq_file.h>
9 #include <linux/security.h>
10 #include <linux/uaccess.h>
11 #include <linux/kernel.h>
12 #include <linux/ftrace.h>
13 #include <linux/string.h>
14 #include <linux/module.h>
15 #include <linux/mutex.h>
16 #include <linux/ctype.h>
17 #include <linux/list.h>
18 #include <linux/slab.h>
19
20 #include "trace.h"
21
22 #ifdef CONFIG_MODULES
23
24 /*
25 * modules trace_printk()'s formats are autosaved in struct trace_bprintk_fmt
26 * which are queued on trace_bprintk_fmt_list.
27 */
28 static LIST_HEAD(trace_bprintk_fmt_list);
29
30 /* serialize accesses to trace_bprintk_fmt_list */
31 static DEFINE_MUTEX(btrace_mutex);
32
33 struct trace_bprintk_fmt {
34 struct list_head list;
35 const char *fmt;
36 };
37
38 static inline struct trace_bprintk_fmt *lookup_format(const char *fmt)
39 {
40 struct trace_bprintk_fmt *pos;
41
42 if (!fmt)
43 return ERR_PTR(-EINVAL);
44
45 list_for_each_entry(pos, &trace_bprintk_fmt_list, list) {
46 if (!strcmp(pos->fmt, fmt))
47 return pos;
48 }
49 return NULL;
50 }
51
52 static
53 void hold_module_trace_bprintk_format(const char **start, const char **end)
54 {
55 const char **iter;
56 char *fmt;
57
58 /* allocate the trace_printk per cpu buffers */
59 if (start != end)
60 trace_printk_init_buffers();
61
62 mutex_lock(&btrace_mutex);
63 for (iter = start; iter < end; iter++) {
64 struct trace_bprintk_fmt *tb_fmt = lookup_format(*iter);
65 if (tb_fmt) {
66 if (!IS_ERR(tb_fmt))
67 *iter = tb_fmt->fmt;
68 continue;
69 }
70
71 fmt = NULL;
72 tb_fmt = kmalloc(sizeof(*tb_fmt), GFP_KERNEL);
73 if (tb_fmt) {
74 fmt = kmalloc(strlen(*iter) + 1, GFP_KERNEL);
75 if (fmt) {
76 list_add_tail(&tb_fmt->list, &trace_bprintk_fmt_list);
77 strcpy(fmt, *iter);
78 tb_fmt->fmt = fmt;
79 } else
80 kfree(tb_fmt);
81 }
82 *iter = fmt;
83
84 }
85 mutex_unlock(&btrace_mutex);
86 }
87
88 static int module_trace_bprintk_format_notify(struct notifier_block *self,
89 unsigned long val, void *data)
90 {
91 struct module *mod = data;
92 if (mod->num_trace_bprintk_fmt) {
93 const char **start = mod->trace_bprintk_fmt_start;
94 const char **end = start + mod->num_trace_bprintk_fmt;
95
96 if (val == MODULE_STATE_COMING)
97 hold_module_trace_bprintk_format(start, end);
98 }
99 return NOTIFY_OK;
100 }
101
102 /*
103 * The debugfs/tracing/printk_formats file maps the addresses with
104 * the ASCII formats that are used in the bprintk events in the
105 * buffer. For userspace tools to be able to decode the events from
106 * the buffer, they need to be able to map the address with the format.
107 *
108 * The addresses of the bprintk formats are in their own section
109 * __trace_printk_fmt. But for modules we copy them into a link list.
110 * The code to print the formats and their addresses passes around the
111 * address of the fmt string. If the fmt address passed into the seq
112 * functions is within the kernel core __trace_printk_fmt section, then
113 * it simply uses the next pointer in the list.
114 *
115 * When the fmt pointer is outside the kernel core __trace_printk_fmt
116 * section, then we need to read the link list pointers. The trick is
117 * we pass the address of the string to the seq function just like
118 * we do for the kernel core formats. To get back the structure that
119 * holds the format, we simply use container_of() and then go to the
120 * next format in the list.
121 */
122 static const char **
123 find_next_mod_format(int start_index, void *v, const char **fmt, loff_t *pos)
124 {
125 struct trace_bprintk_fmt *mod_fmt;
126
127 if (list_empty(&trace_bprintk_fmt_list))
128 return NULL;
129
130 /*
131 * v will point to the address of the fmt record from t_next
132 * v will be NULL from t_start.
133 * If this is the first pointer or called from start
134 * then we need to walk the list.
135 */
136 if (!v || start_index == *pos) {
137 struct trace_bprintk_fmt *p;
138
139 /* search the module list */
140 list_for_each_entry(p, &trace_bprintk_fmt_list, list) {
141 if (start_index == *pos)
142 return &p->fmt;
143 start_index++;
144 }
145 /* pos > index */
146 return NULL;
147 }
148
149 /*
150 * v points to the address of the fmt field in the mod list
151 * structure that holds the module print format.
152 */
153 mod_fmt = container_of(v, typeof(*mod_fmt), fmt);
154 if (mod_fmt->list.next == &trace_bprintk_fmt_list)
155 return NULL;
156
157 mod_fmt = container_of(mod_fmt->list.next, typeof(*mod_fmt), list);
158
159 return &mod_fmt->fmt;
160 }
161
162 static void format_mod_start(void)
163 {
164 mutex_lock(&btrace_mutex);
165 }
166
167 static void format_mod_stop(void)
168 {
169 mutex_unlock(&btrace_mutex);
170 }
171
172 #else /* !CONFIG_MODULES */
173 __init static int
174 module_trace_bprintk_format_notify(struct notifier_block *self,
175 unsigned long val, void *data)
176 {
177 return NOTIFY_OK;
178 }
179 static inline const char **
180 find_next_mod_format(int start_index, void *v, const char **fmt, loff_t *pos)
181 {
182 return NULL;
183 }
184 static inline void format_mod_start(void) { }
185 static inline void format_mod_stop(void) { }
186 #endif /* CONFIG_MODULES */
187
188 static bool __read_mostly trace_printk_enabled = true;
189
190 void trace_printk_control(bool enabled)
191 {
192 trace_printk_enabled = enabled;
193 }
194
195 __initdata_or_module static
196 struct notifier_block module_trace_bprintk_format_nb = {
197 .notifier_call = module_trace_bprintk_format_notify,
198 };
199
200 int __trace_bprintk(unsigned long ip, const char *fmt, ...)
201 {
202 int ret;
203 va_list ap;
204
205 if (unlikely(!fmt))
206 return 0;
207
208 if (!trace_printk_enabled)
209 return 0;
210
211 va_start(ap, fmt);
212 ret = trace_vbprintk(ip, fmt, ap);
213 va_end(ap);
214 return ret;
215 }
216 EXPORT_SYMBOL_GPL(__trace_bprintk);
217
218 int __ftrace_vbprintk(unsigned long ip, const char *fmt, va_list ap)
219 {
220 if (unlikely(!fmt))
221 return 0;
222
223 if (!trace_printk_enabled)
224 return 0;
225
226 return trace_vbprintk(ip, fmt, ap);
227 }
228 EXPORT_SYMBOL_GPL(__ftrace_vbprintk);
229
230 int __trace_printk(unsigned long ip, const char *fmt, ...)
231 {
232 int ret;
233 va_list ap;
234
235 if (!trace_printk_enabled)
236 return 0;
237
238 va_start(ap, fmt);
239 ret = trace_vprintk(ip, fmt, ap);
240 va_end(ap);
241 return ret;
242 }
243 EXPORT_SYMBOL_GPL(__trace_printk);
244
245 int __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap)
246 {
247 if (!trace_printk_enabled)
248 return 0;
249
250 return trace_vprintk(ip, fmt, ap);
251 }
252 EXPORT_SYMBOL_GPL(__ftrace_vprintk);
253
254 bool trace_is_tracepoint_string(const char *str)
255 {
256 const char **ptr = __start___tracepoint_str;
257
258 for (ptr = __start___tracepoint_str; ptr < __stop___tracepoint_str; ptr++) {
259 if (str == *ptr)
260 return true;
261 }
262 return false;
263 }
264
265 static const char **find_next(void *v, loff_t *pos)
266 {
267 const char **fmt = v;
268 int start_index;
269 int last_index;
270
271 start_index = __stop___trace_bprintk_fmt - __start___trace_bprintk_fmt;
272
273 if (*pos < start_index)
274 return __start___trace_bprintk_fmt + *pos;
275
276 /*
277 * The __tracepoint_str section is treated the same as the
278 * __trace_printk_fmt section. The difference is that the
279 * __trace_printk_fmt section should only be used by trace_printk()
280 * in a debugging environment, as if anything exists in that section
281 * the trace_prink() helper buffers are allocated, which would just
282 * waste space in a production environment.
283 *
284 * The __tracepoint_str sections on the other hand are used by
285 * tracepoints which need to map pointers to their strings to
286 * the ASCII text for userspace.
287 */
288 last_index = start_index;
289 start_index = __stop___tracepoint_str - __start___tracepoint_str;
290
291 if (*pos < last_index + start_index)
292 return __start___tracepoint_str + (*pos - last_index);
293
294 start_index += last_index;
295 return find_next_mod_format(start_index, v, fmt, pos);
296 }
297
298 static void *
299 t_start(struct seq_file *m, loff_t *pos)
300 {
301 format_mod_start();
302 return find_next(NULL, pos);
303 }
304
305 static void *t_next(struct seq_file *m, void * v, loff_t *pos)
306 {
307 (*pos)++;
308 return find_next(v, pos);
309 }
310
311 static int t_show(struct seq_file *m, void *v)
312 {
313 const char **fmt = v;
314 const char *str = *fmt;
315 int i;
316
317 if (!*fmt)
318 return 0;
319
320 seq_printf(m, "0x%lx : \"", *(unsigned long *)fmt);
321
322 /*
323 * Tabs and new lines need to be converted.
324 */
325 for (i = 0; str[i]; i++) {
326 switch (str[i]) {
327 case '\n':
328 seq_puts(m, "\\n");
329 break;
330 case '\t':
331 seq_puts(m, "\\t");
332 break;
333 case '\\':
334 seq_putc(m, '\\');
335 break;
336 case '"':
337 seq_puts(m, "\\\"");
338 break;
339 default:
340 seq_putc(m, str[i]);
341 }
342 }
343 seq_puts(m, "\"\n");
344
345 return 0;
346 }
347
348 static void t_stop(struct seq_file *m, void *p)
349 {
350 format_mod_stop();
351 }
352
353 static const struct seq_operations show_format_seq_ops = {
354 .start = t_start,
355 .next = t_next,
356 .show = t_show,
357 .stop = t_stop,
358 };
359
360 static int
361 ftrace_formats_open(struct inode *inode, struct file *file)
362 {
363 int ret;
364
365 ret = security_locked_down(LOCKDOWN_TRACEFS);
366 if (ret)
367 return ret;
368
369 return seq_open(file, &show_format_seq_ops);
370 }
371
372 static const struct file_operations ftrace_formats_fops = {
373 .open = ftrace_formats_open,
374 .read = seq_read,
375 .llseek = seq_lseek,
376 .release = seq_release,
377 };
378
379 static __init int init_trace_printk_function_export(void)
380 {
381 int ret;
382
383 ret = tracing_init_dentry();
384 if (ret)
385 return 0;
386
387 trace_create_file("printk_formats", TRACE_MODE_READ, NULL,
388 NULL, &ftrace_formats_fops);
389
390 return 0;
391 }
392
393 fs_initcall(init_trace_printk_function_export);
394
395 static __init int init_trace_printk(void)
396 {
397 return register_module_notifier(&module_trace_bprintk_format_nb);
398 }
399
400 early_initcall(init_trace_printk);
401
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