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(error: -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(fmt: *iter); |
65 | if (tb_fmt) { |
66 | if (!IS_ERR(ptr: tb_fmt)) |
67 | *iter = tb_fmt->fmt; |
68 | continue; |
69 | } |
70 | |
71 | fmt = NULL; |
72 | tb_fmt = kmalloc(size: sizeof(*tb_fmt), GFP_KERNEL); |
73 | if (tb_fmt) { |
74 | fmt = kmalloc(strlen(*iter) + 1, GFP_KERNEL); |
75 | if (fmt) { |
76 | list_add_tail(new: &tb_fmt->list, head: &trace_bprintk_fmt_list); |
77 | strcpy(p: fmt, q: *iter); |
78 | tb_fmt->fmt = fmt; |
79 | } else |
80 | kfree(objp: tb_fmt); |
81 | } |
82 | *iter = fmt; |
83 | |
84 | } |
85 | mutex_unlock(lock: &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(head: &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(lock: &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, args: 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, args: 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, args: 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, args: 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, fmt: "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, s: "\\n" ); |
329 | break; |
330 | case '\t': |
331 | seq_puts(m, s: "\\t" ); |
332 | break; |
333 | case '\\': |
334 | seq_putc(m, c: '\\'); |
335 | break; |
336 | case '"': |
337 | seq_puts(m, s: "\\\"" ); |
338 | break; |
339 | default: |
340 | seq_putc(m, c: str[i]); |
341 | } |
342 | } |
343 | seq_puts(m, s: "\"\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(what: 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(name: "printk_formats" , TRACE_MODE_READ, NULL, |
388 | NULL, fops: &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(nb: &module_trace_bprintk_format_nb); |
398 | } |
399 | |
400 | early_initcall(init_trace_printk); |
401 | |