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2fa2d39a FG |
1 | /* |
2 | * lttng-context-callstack.c | |
3 | * | |
4 | * LTTng callstack event context. | |
5 | * | |
6 | * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
7 | * Copyright (C) 2014 Francis Giraldeau <francis.giraldeau@gmail.com> | |
8 | * | |
9 | * This library is free software; you can redistribute it and/or | |
10 | * modify it under the terms of the GNU Lesser General Public | |
11 | * License as published by the Free Software Foundation; only | |
12 | * version 2.1 of the License. | |
13 | * | |
14 | * This library is distributed in the hope that it will be useful, | |
15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
17 | * Lesser General Public License for more details. | |
18 | * | |
19 | * You should have received a copy of the GNU Lesser General Public | |
20 | * License along with this library; if not, write to the Free Software | |
21 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
22 | * | |
23 | * The callstack context can be added to any kernel | |
24 | * event. It records either the kernel or the userspace callstack, up to a | |
25 | * max depth. The context is a CTF sequence, such that it uses only the space | |
26 | * required for the number of callstack entries. | |
27 | * | |
28 | * It allocates callstack buffers per-CPU up to 4 interrupt nesting. This | |
29 | * nesting limit is the same as defined in the ring buffer. It therefore uses a | |
30 | * fixed amount of memory, proportional to the number of CPUs: | |
31 | * | |
32 | * size = cpus * nest * depth * sizeof(unsigned long) | |
33 | * | |
34 | * Which is about 800 bytes per-CPUs on 64-bit host and a depth of 25. The | |
35 | * allocation is done at the initialization to avoid memory allocation | |
36 | * overhead while tracing, using a shallow stack. | |
37 | * | |
38 | * The kernel callstack is recovered using save_stack_trace(), and the | |
39 | * userspace callstack uses save_stack_trace_user(). They rely on frame | |
40 | * pointers. These are usually available for the kernel, but the compiler | |
41 | * option -fomit-frame-pointer frequently used in popular Linux distributions | |
42 | * may cause the userspace callstack to be unreliable, and is a known | |
43 | * limitation of this approach. If frame pointers are not available, it | |
44 | * produces no error, but the callstack will be empty. We still provide the | |
45 | * feature, because it works well for runtime environments having frame | |
46 | * pointers. In the future, unwind support and/or last branch record may | |
47 | * provide a solution to this problem. | |
48 | * | |
49 | * The symbol name resolution is left to the trace reader. | |
50 | */ | |
51 | ||
52 | #include <linux/module.h> | |
53 | #include <linux/slab.h> | |
54 | #include <linux/sched.h> | |
55 | #include <linux/utsname.h> | |
56 | #include <linux/stacktrace.h> | |
57 | #include <linux/spinlock.h> | |
58 | #include "lttng-events.h" | |
59 | #include "wrapper/ringbuffer/backend.h" | |
60 | #include "wrapper/ringbuffer/frontend.h" | |
61 | #include "wrapper/vmalloc.h" | |
62 | #include "lttng-tracer.h" | |
63 | ||
64cc198b MD |
64 | #define MAX_ENTRIES 25 |
65 | ||
66 | struct lttng_cs_nesting { | |
67 | struct stack_trace stack_trace; | |
68 | unsigned long entries[MAX_ENTRIES]; | |
69 | }; | |
2fa2d39a FG |
70 | |
71 | struct lttng_cs { | |
64cc198b | 72 | struct lttng_cs_nesting level[RING_BUFFER_MAX_NESTING]; |
2fa2d39a FG |
73 | }; |
74 | ||
75 | struct field_data { | |
2fa2d39a | 76 | struct lttng_cs __percpu *cs_percpu; |
64cc198b | 77 | int mode; |
2fa2d39a FG |
78 | }; |
79 | ||
80 | struct lttng_cs_type { | |
81 | const char *name; | |
82 | const char *save_func_name; | |
83 | void (*save_func)(struct stack_trace *trace); | |
84 | }; | |
85 | ||
86 | enum lttng_cs_ctx_modes { | |
87 | CALLSTACK_KERNEL = 0, | |
88 | CALLSTACK_USER = 1, | |
89 | }; | |
90 | ||
91 | static struct lttng_cs_type cs_types[] = { | |
92 | { | |
64cc198b MD |
93 | .name = "callstack_kernel", |
94 | .save_func_name = "save_stack_trace", | |
95 | .save_func = NULL, | |
2fa2d39a FG |
96 | }, |
97 | { | |
64cc198b MD |
98 | .name = "callstack_user", |
99 | .save_func_name = "save_stack_trace_user", | |
100 | .save_func = NULL, | |
2fa2d39a FG |
101 | }, |
102 | }; | |
103 | ||
104 | static | |
105 | int init_type(int mode) | |
106 | { | |
107 | unsigned long func; | |
108 | ||
109 | if (cs_types[mode].save_func) | |
110 | return 0; | |
111 | func = kallsyms_lookup_funcptr(cs_types[mode].save_func_name); | |
112 | if (!func) { | |
113 | printk(KERN_WARNING "LTTng: symbol lookup failed: %s\n", | |
114 | cs_types[mode].save_func_name); | |
115 | return -EINVAL; | |
116 | } | |
117 | cs_types[mode].save_func = (void *) func; | |
118 | return 0; | |
119 | } | |
120 | ||
121 | static | |
122 | struct stack_trace *stack_trace_context(struct lttng_ctx_field *field, | |
123 | struct lib_ring_buffer_ctx *ctx) | |
124 | { | |
125 | int nesting; | |
126 | struct lttng_cs *cs; | |
3c1a57e8 | 127 | struct field_data *fdata = field->priv; |
2fa2d39a FG |
128 | |
129 | /* | |
130 | * get_cpu() is not required, preemption is already | |
131 | * disabled while event is written. | |
132 | * | |
133 | * max nesting is checked in lib_ring_buffer_get_cpu(). | |
134 | * Check it again as a safety net. | |
135 | */ | |
136 | cs = per_cpu_ptr(fdata->cs_percpu, ctx->cpu); | |
137 | nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1; | |
138 | if (nesting >= RING_BUFFER_MAX_NESTING) { | |
139 | return NULL; | |
140 | } | |
64cc198b | 141 | return &cs->level[nesting].stack_trace; |
2fa2d39a FG |
142 | } |
143 | ||
144 | /* | |
145 | * In order to reserve the correct size, the callstack is computed. The | |
146 | * resulting callstack is saved to be accessed in the record step. | |
147 | */ | |
148 | static | |
149 | size_t lttng_callstack_get_size(size_t offset, struct lttng_ctx_field *field, | |
150 | struct lib_ring_buffer_ctx *ctx, | |
151 | struct lttng_channel *chan) | |
152 | { | |
153 | size_t size = 0; | |
154 | struct stack_trace *trace; | |
3c1a57e8 | 155 | struct field_data *fdata = field->priv; |
2fa2d39a FG |
156 | |
157 | /* do not write data if no space is available */ | |
158 | trace = stack_trace_context(field, ctx); | |
60d51de0 MD |
159 | if (unlikely(!trace)) { |
160 | size += lib_ring_buffer_align(offset, lttng_alignof(unsigned int)); | |
161 | size += sizeof(unsigned int); | |
162 | size += lib_ring_buffer_align(offset, lttng_alignof(unsigned long)); | |
163 | return size; | |
164 | } | |
2fa2d39a FG |
165 | |
166 | /* reset stack trace, no need to clear memory */ | |
167 | trace->nr_entries = 0; | |
168 | ||
169 | /* do the real work and reserve space */ | |
170 | cs_types[fdata->mode].save_func(trace); | |
ea15538d MD |
171 | /* |
172 | * Remove final ULONG_MAX delimiter. If we cannot find it, add | |
173 | * our own marker to show that the stack is incomplete. This is | |
174 | * more compact for a trace. | |
175 | */ | |
176 | if (trace->nr_entries > 0 | |
177 | && trace->entries[trace->nr_entries - 1] == ULONG_MAX) { | |
178 | trace->nr_entries--; | |
179 | } | |
2fa2d39a FG |
180 | size += lib_ring_buffer_align(offset, lttng_alignof(unsigned int)); |
181 | size += sizeof(unsigned int); | |
182 | size += lib_ring_buffer_align(offset, lttng_alignof(unsigned long)); | |
183 | size += sizeof(unsigned long) * trace->nr_entries; | |
ea15538d MD |
184 | /* Add our own ULONG_MAX delimiter to show incomplete stack. */ |
185 | if (trace->nr_entries == trace->max_entries) | |
186 | size += sizeof(unsigned long); | |
2fa2d39a FG |
187 | return size; |
188 | } | |
189 | ||
190 | static | |
191 | void lttng_callstack_record(struct lttng_ctx_field *field, | |
64cc198b MD |
192 | struct lib_ring_buffer_ctx *ctx, |
193 | struct lttng_channel *chan) | |
2fa2d39a FG |
194 | { |
195 | struct stack_trace *trace = stack_trace_context(field, ctx); | |
ea15538d | 196 | unsigned int nr_seq_entries; |
2fa2d39a | 197 | |
60d51de0 MD |
198 | if (unlikely(!trace)) { |
199 | nr_seq_entries = 0; | |
200 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int)); | |
201 | chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int)); | |
202 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long)); | |
2fa2d39a | 203 | return; |
60d51de0 | 204 | } |
2fa2d39a | 205 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int)); |
ea15538d MD |
206 | nr_seq_entries = trace->nr_entries; |
207 | if (trace->nr_entries == trace->max_entries) | |
208 | nr_seq_entries++; | |
209 | chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int)); | |
2fa2d39a FG |
210 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long)); |
211 | chan->ops->event_write(ctx, trace->entries, | |
212 | sizeof(unsigned long) * trace->nr_entries); | |
ea15538d MD |
213 | /* Add our own ULONG_MAX delimiter to show incomplete stack. */ |
214 | if (trace->nr_entries == trace->max_entries) { | |
215 | unsigned long delim = ULONG_MAX; | |
216 | ||
217 | chan->ops->event_write(ctx, &delim, sizeof(unsigned long)); | |
218 | } | |
2fa2d39a FG |
219 | } |
220 | ||
221 | static | |
222 | void field_data_free(struct field_data *fdata) | |
223 | { | |
2fa2d39a FG |
224 | if (!fdata) |
225 | return; | |
2fa2d39a FG |
226 | free_percpu(fdata->cs_percpu); |
227 | kfree(fdata); | |
228 | } | |
229 | ||
230 | static | |
64cc198b | 231 | struct field_data __percpu *field_data_create(int type) |
2fa2d39a FG |
232 | { |
233 | int cpu, i; | |
2fa2d39a | 234 | struct lttng_cs __percpu *cs_set; |
64cc198b | 235 | struct field_data *fdata; |
2fa2d39a | 236 | |
64cc198b | 237 | fdata = kzalloc(sizeof(*fdata), GFP_KERNEL); |
2fa2d39a FG |
238 | if (!fdata) |
239 | return NULL; | |
240 | cs_set = alloc_percpu(struct lttng_cs); | |
241 | if (!cs_set) | |
242 | goto error_alloc; | |
243 | ||
244 | fdata->cs_percpu = cs_set; | |
245 | for_each_possible_cpu(cpu) { | |
64cc198b MD |
246 | struct lttng_cs *cs; |
247 | ||
2fa2d39a FG |
248 | cs = per_cpu_ptr(cs_set, cpu); |
249 | for (i = 0; i < RING_BUFFER_MAX_NESTING; i++) { | |
64cc198b MD |
250 | struct lttng_cs_nesting *level; |
251 | ||
252 | level = &cs->level[i]; | |
253 | level->stack_trace.entries = level->entries; | |
254 | level->stack_trace.max_entries = MAX_ENTRIES; | |
2fa2d39a FG |
255 | } |
256 | } | |
257 | fdata->mode = type; | |
258 | return fdata; | |
259 | ||
260 | error_alloc: | |
261 | field_data_free(fdata); | |
262 | return NULL; | |
263 | } | |
264 | ||
265 | static | |
266 | void lttng_callstack_destroy(struct lttng_ctx_field *field) | |
267 | { | |
3c1a57e8 | 268 | struct field_data *fdata = field->priv; |
2fa2d39a FG |
269 | |
270 | field_data_free(fdata); | |
271 | } | |
272 | ||
273 | static | |
274 | int __lttng_add_callstack_generic(struct lttng_ctx **ctx, int mode) | |
275 | { | |
276 | const char *ctx_name = cs_types[mode].name; | |
277 | struct lttng_ctx_field *field; | |
278 | struct field_data *fdata; | |
279 | int ret; | |
280 | ||
281 | ret = init_type(mode); | |
282 | if (ret) | |
283 | return ret; | |
284 | field = lttng_append_context(ctx); | |
285 | if (!field) | |
286 | return -ENOMEM; | |
287 | if (lttng_find_context(*ctx, ctx_name)) { | |
2fa2d39a FG |
288 | ret = -EEXIST; |
289 | goto error_find; | |
290 | } | |
64cc198b | 291 | fdata = field_data_create(mode); |
2fa2d39a FG |
292 | if (!fdata) { |
293 | ret = -ENOMEM; | |
294 | goto error_create; | |
295 | } | |
296 | ||
297 | field->event_field.name = ctx_name; | |
298 | field->event_field.type.atype = atype_sequence; | |
299 | field->event_field.type.u.sequence.elem_type.atype = atype_integer; | |
300 | field->event_field.type.u.sequence.elem_type.u.basic.integer.size = sizeof(unsigned long) * CHAR_BIT; | |
301 | field->event_field.type.u.sequence.elem_type.u.basic.integer.alignment = lttng_alignof(long) * CHAR_BIT; | |
302 | field->event_field.type.u.sequence.elem_type.u.basic.integer.signedness = lttng_is_signed_type(unsigned long); | |
303 | field->event_field.type.u.sequence.elem_type.u.basic.integer.reverse_byte_order = 0; | |
304 | field->event_field.type.u.sequence.elem_type.u.basic.integer.base = 16; | |
305 | field->event_field.type.u.sequence.elem_type.u.basic.integer.encoding = lttng_encode_none; | |
306 | ||
307 | field->event_field.type.u.sequence.length_type.atype = atype_integer; | |
308 | field->event_field.type.u.sequence.length_type.u.basic.integer.size = sizeof(unsigned int) * CHAR_BIT; | |
309 | field->event_field.type.u.sequence.length_type.u.basic.integer.alignment = lttng_alignof(unsigned int) * CHAR_BIT; | |
310 | field->event_field.type.u.sequence.length_type.u.basic.integer.signedness = lttng_is_signed_type(unsigned int); | |
311 | field->event_field.type.u.sequence.length_type.u.basic.integer.reverse_byte_order = 0; | |
312 | field->event_field.type.u.sequence.length_type.u.basic.integer.base = 10; | |
313 | field->event_field.type.u.sequence.length_type.u.basic.integer.encoding = lttng_encode_none; | |
314 | ||
315 | field->get_size_arg = lttng_callstack_get_size; | |
316 | field->record = lttng_callstack_record; | |
3c1a57e8 | 317 | field->priv = fdata; |
2fa2d39a FG |
318 | field->destroy = lttng_callstack_destroy; |
319 | wrapper_vmalloc_sync_all(); | |
2fa2d39a FG |
320 | return 0; |
321 | ||
322 | error_create: | |
323 | field_data_free(fdata); | |
324 | error_find: | |
325 | lttng_remove_context_field(ctx, field); | |
326 | return ret; | |
327 | } | |
328 | ||
329 | /** | |
330 | * lttng_add_callstack_to_ctx - add callstack event context | |
331 | * | |
332 | * @ctx: the lttng_ctx pointer to initialize | |
333 | * @type: the context type | |
334 | * | |
335 | * Supported callstack type supported: | |
336 | * LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL | |
337 | * Records the callstack of the kernel | |
338 | * LTTNG_KERNEL_CONTEXT_CALLSTACK_USER | |
339 | * Records the callstack of the userspace program (from the kernel) | |
340 | * | |
341 | * Return 0 for success, or error code. | |
342 | */ | |
343 | int lttng_add_callstack_to_ctx(struct lttng_ctx **ctx, int type) | |
344 | { | |
345 | switch (type) { | |
346 | case LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL: | |
347 | return __lttng_add_callstack_generic(ctx, CALLSTACK_KERNEL); | |
348 | case LTTNG_KERNEL_CONTEXT_CALLSTACK_USER: | |
349 | return __lttng_add_callstack_generic(ctx, CALLSTACK_USER); | |
350 | default: | |
351 | return -EINVAL; | |
352 | } | |
353 | } | |
354 | EXPORT_SYMBOL_GPL(lttng_add_callstack_to_ctx); | |
355 | ||
356 | MODULE_LICENSE("GPL and additional rights"); | |
357 | MODULE_AUTHOR("Francis Giraldeau"); | |
358 | MODULE_DESCRIPTION("Linux Trace Toolkit Callstack Support"); |