Commit | Line | Data |
---|---|---|
b7cdc182 | 1 | /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only) |
b29c6286 MD |
2 | * |
3 | * lttng-context-callstack-stackwalk-impl.h | |
4 | * | |
5 | * LTTng callstack event context, stackwalk implementation. Targets | |
6 | * kernels and architectures using the stacktrace common infrastructure | |
7 | * introduced in the upstream Linux kernel by commit 214d8ca6ee | |
8 | * "stacktrace: Provide common infrastructure" (merged in Linux 5.2, | |
9 | * then gradually introduced within architectures). | |
10 | * | |
11 | * Copyright (C) 2014-2019 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
12 | * Copyright (C) 2014 Francis Giraldeau <francis.giraldeau@gmail.com> | |
13 | */ | |
14 | ||
15 | #define MAX_ENTRIES 128 | |
16 | ||
17 | enum lttng_cs_ctx_modes { | |
18 | CALLSTACK_KERNEL = 0, | |
19 | CALLSTACK_USER = 1, | |
20 | NR_CALLSTACK_MODES, | |
21 | }; | |
22 | ||
23 | struct lttng_stack_trace { | |
24 | unsigned long entries[MAX_ENTRIES]; | |
25 | unsigned int nr_entries; | |
26 | }; | |
27 | ||
28 | struct lttng_cs { | |
29 | struct lttng_stack_trace stack_trace[RING_BUFFER_MAX_NESTING]; | |
30 | }; | |
31 | ||
32 | struct field_data { | |
33 | struct lttng_cs __percpu *cs_percpu; | |
34 | enum lttng_cs_ctx_modes mode; | |
35 | }; | |
36 | ||
37 | static | |
38 | unsigned int (*save_func_kernel)(unsigned long *store, unsigned int size, | |
39 | unsigned int skipnr); | |
40 | static | |
41 | unsigned int (*save_func_user)(unsigned long *store, unsigned int size); | |
42 | ||
43 | static | |
44 | const char *lttng_cs_ctx_mode_name(enum lttng_cs_ctx_modes mode) | |
45 | { | |
46 | switch (mode) { | |
47 | case CALLSTACK_KERNEL: | |
48 | return "callstack_kernel"; | |
49 | case CALLSTACK_USER: | |
50 | return "callstack_user"; | |
51 | default: | |
52 | return NULL; | |
53 | } | |
54 | } | |
55 | ||
ceabb767 MD |
56 | static |
57 | const char *lttng_cs_ctx_mode_length_name(enum lttng_cs_ctx_modes mode) | |
58 | { | |
59 | switch (mode) { | |
60 | case CALLSTACK_KERNEL: | |
61 | return "_callstack_kernel_length"; | |
62 | case CALLSTACK_USER: | |
63 | return "_callstack_user_length"; | |
64 | default: | |
65 | return NULL; | |
66 | } | |
67 | } | |
68 | ||
b29c6286 MD |
69 | static |
70 | int init_type_callstack_kernel(void) | |
71 | { | |
72 | unsigned long func; | |
73 | const char *func_name = "stack_trace_save"; | |
74 | ||
75 | if (save_func_kernel) | |
76 | return 0; | |
77 | func = kallsyms_lookup_funcptr(func_name); | |
78 | if (!func) { | |
79 | printk(KERN_WARNING "LTTng: symbol lookup failed: %s\n", | |
80 | func_name); | |
81 | return -EINVAL; | |
82 | } | |
83 | save_func_kernel = (void *) func; | |
84 | return 0; | |
85 | } | |
86 | ||
87 | static | |
88 | int init_type_callstack_user(void) | |
89 | { | |
90 | unsigned long func; | |
91 | const char *func_name = "stack_trace_save_user"; | |
92 | ||
93 | if (save_func_user) | |
94 | return 0; | |
95 | func = kallsyms_lookup_funcptr(func_name); | |
96 | if (!func) { | |
97 | printk(KERN_WARNING "LTTng: symbol lookup failed: %s\n", | |
98 | func_name); | |
99 | return -EINVAL; | |
100 | } | |
101 | save_func_user = (void *) func; | |
102 | return 0; | |
103 | } | |
104 | ||
105 | static | |
106 | int init_type(enum lttng_cs_ctx_modes mode) | |
107 | { | |
108 | switch (mode) { | |
109 | case CALLSTACK_KERNEL: | |
110 | return init_type_callstack_kernel(); | |
111 | case CALLSTACK_USER: | |
112 | return init_type_callstack_user(); | |
113 | default: | |
114 | return -EINVAL; | |
115 | } | |
116 | } | |
117 | ||
118 | static | |
119 | void lttng_cs_set_init(struct lttng_cs __percpu *cs_set) | |
120 | { | |
121 | } | |
122 | ||
123 | /* Keep track of nesting inside userspace callstack context code */ | |
124 | DEFINE_PER_CPU(int, callstack_user_nesting); | |
125 | ||
126 | static | |
127 | struct lttng_stack_trace *stack_trace_context(struct lttng_ctx_field *field, | |
128 | struct lib_ring_buffer_ctx *ctx) | |
129 | { | |
130 | int buffer_nesting, cs_user_nesting; | |
131 | struct lttng_cs *cs; | |
132 | struct field_data *fdata = field->priv; | |
133 | ||
134 | /* | |
135 | * Do not gather the userspace callstack context when the event was | |
136 | * triggered by the userspace callstack context saving mechanism. | |
137 | */ | |
138 | cs_user_nesting = per_cpu(callstack_user_nesting, ctx->cpu); | |
139 | ||
140 | if (fdata->mode == CALLSTACK_USER && cs_user_nesting >= 1) | |
141 | return NULL; | |
142 | ||
143 | /* | |
144 | * get_cpu() is not required, preemption is already | |
145 | * disabled while event is written. | |
146 | * | |
147 | * max nesting is checked in lib_ring_buffer_get_cpu(). | |
148 | * Check it again as a safety net. | |
149 | */ | |
150 | cs = per_cpu_ptr(fdata->cs_percpu, ctx->cpu); | |
151 | buffer_nesting = per_cpu(lib_ring_buffer_nesting, ctx->cpu) - 1; | |
152 | if (buffer_nesting >= RING_BUFFER_MAX_NESTING) | |
153 | return NULL; | |
154 | ||
155 | return &cs->stack_trace[buffer_nesting]; | |
156 | } | |
157 | ||
ceabb767 MD |
158 | static |
159 | size_t lttng_callstack_length_get_size(size_t offset, struct lttng_ctx_field *field, | |
160 | struct lib_ring_buffer_ctx *ctx, | |
161 | struct lttng_channel *chan) | |
162 | { | |
163 | size_t orig_offset = offset; | |
164 | ||
165 | offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned int)); | |
166 | offset += sizeof(unsigned int); | |
167 | return offset - orig_offset; | |
168 | } | |
169 | ||
b29c6286 MD |
170 | /* |
171 | * In order to reserve the correct size, the callstack is computed. The | |
172 | * resulting callstack is saved to be accessed in the record step. | |
173 | */ | |
174 | static | |
ceabb767 MD |
175 | size_t lttng_callstack_sequence_get_size(size_t offset, struct lttng_ctx_field *field, |
176 | struct lib_ring_buffer_ctx *ctx, | |
177 | struct lttng_channel *chan) | |
b29c6286 MD |
178 | { |
179 | struct lttng_stack_trace *trace; | |
180 | struct field_data *fdata = field->priv; | |
181 | size_t orig_offset = offset; | |
182 | ||
183 | /* do not write data if no space is available */ | |
184 | trace = stack_trace_context(field, ctx); | |
185 | if (unlikely(!trace)) { | |
b29c6286 MD |
186 | offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned long)); |
187 | return offset - orig_offset; | |
188 | } | |
189 | ||
190 | /* reset stack trace, no need to clear memory */ | |
191 | trace->nr_entries = 0; | |
192 | ||
193 | switch (fdata->mode) { | |
194 | case CALLSTACK_KERNEL: | |
195 | /* do the real work and reserve space */ | |
196 | trace->nr_entries = save_func_kernel(trace->entries, | |
197 | MAX_ENTRIES, 0); | |
198 | break; | |
199 | case CALLSTACK_USER: | |
200 | ++per_cpu(callstack_user_nesting, ctx->cpu); | |
201 | /* do the real work and reserve space */ | |
202 | trace->nr_entries = save_func_user(trace->entries, | |
203 | MAX_ENTRIES); | |
204 | per_cpu(callstack_user_nesting, ctx->cpu)--; | |
205 | break; | |
206 | default: | |
207 | WARN_ON_ONCE(1); | |
208 | } | |
209 | ||
210 | /* | |
211 | * If the array is filled, add our own marker to show that the | |
212 | * stack is incomplete. | |
213 | */ | |
b29c6286 MD |
214 | offset += lib_ring_buffer_align(offset, lttng_alignof(unsigned long)); |
215 | offset += sizeof(unsigned long) * trace->nr_entries; | |
216 | /* Add our own ULONG_MAX delimiter to show incomplete stack. */ | |
217 | if (trace->nr_entries == MAX_ENTRIES) | |
218 | offset += sizeof(unsigned long); | |
219 | return offset - orig_offset; | |
220 | } | |
221 | ||
222 | static | |
ceabb767 | 223 | void lttng_callstack_length_record(struct lttng_ctx_field *field, |
b29c6286 MD |
224 | struct lib_ring_buffer_ctx *ctx, |
225 | struct lttng_channel *chan) | |
226 | { | |
227 | struct lttng_stack_trace *trace = stack_trace_context(field, ctx); | |
228 | unsigned int nr_seq_entries; | |
229 | ||
ceabb767 | 230 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned int)); |
b29c6286 MD |
231 | if (unlikely(!trace)) { |
232 | nr_seq_entries = 0; | |
ceabb767 MD |
233 | } else { |
234 | nr_seq_entries = trace->nr_entries; | |
235 | if (trace->nr_entries == MAX_ENTRIES) | |
236 | nr_seq_entries++; | |
237 | } | |
238 | chan->ops->event_write(ctx, &nr_seq_entries, sizeof(unsigned int)); | |
239 | } | |
240 | ||
241 | static | |
242 | void lttng_callstack_sequence_record(struct lttng_ctx_field *field, | |
243 | struct lib_ring_buffer_ctx *ctx, | |
244 | struct lttng_channel *chan) | |
245 | { | |
246 | struct lttng_stack_trace *trace = stack_trace_context(field, ctx); | |
247 | unsigned int nr_seq_entries; | |
248 | ||
249 | lib_ring_buffer_align_ctx(ctx, lttng_alignof(unsigned long)); | |
250 | if (unlikely(!trace)) { | |
b29c6286 MD |
251 | return; |
252 | } | |
b29c6286 MD |
253 | nr_seq_entries = trace->nr_entries; |
254 | if (trace->nr_entries == MAX_ENTRIES) | |
255 | nr_seq_entries++; | |
b29c6286 MD |
256 | chan->ops->event_write(ctx, trace->entries, |
257 | sizeof(unsigned long) * trace->nr_entries); | |
258 | /* Add our own ULONG_MAX delimiter to show incomplete stack. */ | |
259 | if (trace->nr_entries == MAX_ENTRIES) { | |
260 | unsigned long delim = ULONG_MAX; | |
261 | ||
262 | chan->ops->event_write(ctx, &delim, sizeof(unsigned long)); | |
263 | } | |
264 | } |