| 1 | /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only) |
| 2 | * |
| 3 | * lttng-context-callstack.c |
| 4 | * |
| 5 | * LTTng callstack event context. |
| 6 | * |
| 7 | * Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 8 | * Copyright (C) 2014 Francis Giraldeau <francis.giraldeau@gmail.com> |
| 9 | * |
| 10 | * The callstack context can be added to any kernel event. It records |
| 11 | * either the kernel or the userspace callstack, up to a max depth. The |
| 12 | * context is a CTF sequence, such that it uses only the space required |
| 13 | * for the number of callstack entries. |
| 14 | * |
| 15 | * It allocates callstack buffers per-CPU up to 4 interrupt nesting. |
| 16 | * This nesting limit is the same as defined in the ring buffer. It |
| 17 | * therefore uses a fixed amount of memory, proportional to the number |
| 18 | * of CPUs: |
| 19 | * |
| 20 | * size = cpus * nest * depth * sizeof(unsigned long) |
| 21 | * |
| 22 | * Which is 4096 bytes per CPU on 64-bit host and a depth of 128. |
| 23 | * The allocation is done at the initialization to avoid memory |
| 24 | * allocation overhead while tracing, using a shallow stack. |
| 25 | * |
| 26 | * The kernel callstack is recovered using save_stack_trace(), and the |
| 27 | * userspace callstack uses save_stack_trace_user(). They rely on frame |
| 28 | * pointers. These are usually available for the kernel, but the |
| 29 | * compiler option -fomit-frame-pointer frequently used in popular Linux |
| 30 | * distributions may cause the userspace callstack to be unreliable, and |
| 31 | * is a known limitation of this approach. If frame pointers are not |
| 32 | * available, it produces no error, but the callstack will be empty. We |
| 33 | * still provide the feature, because it works well for runtime |
| 34 | * environments having frame pointers. In the future, unwind support |
| 35 | * and/or last branch record may provide a solution to this problem. |
| 36 | * |
| 37 | * The symbol name resolution is left to the trace reader. |
| 38 | */ |
| 39 | |
| 40 | #include <linux/module.h> |
| 41 | #include <linux/slab.h> |
| 42 | #include <linux/sched.h> |
| 43 | #include <linux/utsname.h> |
| 44 | #include <linux/stacktrace.h> |
| 45 | #include <linux/spinlock.h> |
| 46 | #include <ringbuffer/backend.h> |
| 47 | #include <ringbuffer/frontend.h> |
| 48 | #include <lttng/events.h> |
| 49 | #include <lttng/events-internal.h> |
| 50 | #include <lttng/tracer.h> |
| 51 | #include <lttng/endian.h> |
| 52 | #include "wrapper/vmalloc.h" |
| 53 | |
| 54 | #ifdef CONFIG_ARCH_STACKWALK |
| 55 | #include "lttng-context-callstack-stackwalk-impl.h" |
| 56 | #else |
| 57 | #include "lttng-context-callstack-legacy-impl.h" |
| 58 | #endif |
| 59 | |
| 60 | #define NR_FIELDS 2 |
| 61 | |
| 62 | static |
| 63 | void field_data_free(struct field_data *fdata) |
| 64 | { |
| 65 | if (!fdata) |
| 66 | return; |
| 67 | free_percpu(fdata->cs_percpu); |
| 68 | kfree(fdata); |
| 69 | } |
| 70 | |
| 71 | static |
| 72 | struct field_data __percpu *field_data_create(enum lttng_cs_ctx_modes mode) |
| 73 | { |
| 74 | struct lttng_cs __percpu *cs_set; |
| 75 | struct field_data *fdata; |
| 76 | |
| 77 | fdata = kzalloc(sizeof(*fdata), GFP_KERNEL); |
| 78 | if (!fdata) |
| 79 | return NULL; |
| 80 | cs_set = alloc_percpu(struct lttng_cs); |
| 81 | if (!cs_set) |
| 82 | goto error_alloc; |
| 83 | lttng_cs_set_init(cs_set); |
| 84 | fdata->cs_percpu = cs_set; |
| 85 | fdata->mode = mode; |
| 86 | return fdata; |
| 87 | |
| 88 | error_alloc: |
| 89 | field_data_free(fdata); |
| 90 | return NULL; |
| 91 | } |
| 92 | |
| 93 | static |
| 94 | void lttng_callstack_sequence_destroy(void *priv) |
| 95 | { |
| 96 | struct field_data *fdata = priv; |
| 97 | |
| 98 | field_data_free(fdata); |
| 99 | } |
| 100 | |
| 101 | static const struct lttng_kernel_event_field *event_fields_kernel[NR_FIELDS] = { |
| 102 | lttng_kernel_static_event_field("_callstack_kernel_length", |
| 103 | lttng_kernel_static_type_integer_from_type(unsigned int, __BYTE_ORDER, 10), |
| 104 | false, false, false), |
| 105 | lttng_kernel_static_event_field("callstack_kernel", |
| 106 | lttng_kernel_static_type_sequence(NULL, |
| 107 | lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16), |
| 108 | 0, none), |
| 109 | false, false, false), |
| 110 | }; |
| 111 | |
| 112 | static const struct lttng_kernel_event_field *event_fields_user[NR_FIELDS] = { |
| 113 | lttng_kernel_static_event_field("_callstack_user_length", |
| 114 | lttng_kernel_static_type_integer_from_type(unsigned int, __BYTE_ORDER, 10), |
| 115 | false, false, false), |
| 116 | lttng_kernel_static_event_field("callstack_user", |
| 117 | lttng_kernel_static_type_sequence(NULL, |
| 118 | lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16), |
| 119 | 0, none), |
| 120 | false, false, false), |
| 121 | }; |
| 122 | |
| 123 | const struct lttng_kernel_event_field **lttng_cs_event_fields(enum lttng_cs_ctx_modes mode) |
| 124 | { |
| 125 | switch (mode) { |
| 126 | case CALLSTACK_KERNEL: |
| 127 | return event_fields_kernel; |
| 128 | case CALLSTACK_USER: |
| 129 | return event_fields_user; |
| 130 | default: |
| 131 | return NULL; |
| 132 | } |
| 133 | } |
| 134 | |
| 135 | static |
| 136 | int __lttng_add_callstack_generic(struct lttng_kernel_ctx **ctx, |
| 137 | enum lttng_cs_ctx_modes mode) |
| 138 | { |
| 139 | const struct lttng_kernel_event_field **event_fields; |
| 140 | struct lttng_kernel_ctx_field ctx_field; |
| 141 | struct field_data *fdata; |
| 142 | int ret, i; |
| 143 | |
| 144 | ret = init_type(mode); |
| 145 | if (ret) |
| 146 | return ret; |
| 147 | event_fields = lttng_cs_event_fields(mode); |
| 148 | if (!event_fields) { |
| 149 | return -EINVAL; |
| 150 | } |
| 151 | for (i = 0; i < NR_FIELDS; i++) { |
| 152 | if (lttng_kernel_find_context(*ctx, event_fields[i]->name)) |
| 153 | return -EEXIST; |
| 154 | } |
| 155 | fdata = field_data_create(mode); |
| 156 | if (!fdata) { |
| 157 | ret = -ENOMEM; |
| 158 | goto error_create; |
| 159 | } |
| 160 | memset(&ctx_field, 0, sizeof(ctx_field)); |
| 161 | ctx_field.event_field = event_fields[0]; |
| 162 | ctx_field.get_size = lttng_callstack_length_get_size; |
| 163 | ctx_field.record = lttng_callstack_length_record; |
| 164 | ctx_field.priv = fdata; |
| 165 | ret = lttng_kernel_context_append(ctx, &ctx_field); |
| 166 | if (ret) { |
| 167 | ret = -ENOMEM; |
| 168 | goto error_append0; |
| 169 | } |
| 170 | |
| 171 | memset(&ctx_field, 0, sizeof(ctx_field)); |
| 172 | ctx_field.event_field = event_fields[1]; |
| 173 | ctx_field.get_size = lttng_callstack_sequence_get_size; |
| 174 | ctx_field.record = lttng_callstack_sequence_record; |
| 175 | ctx_field.destroy = lttng_callstack_sequence_destroy; |
| 176 | ctx_field.priv = fdata; |
| 177 | ret = lttng_kernel_context_append(ctx, &ctx_field); |
| 178 | if (ret) { |
| 179 | ret = -ENOMEM; |
| 180 | goto error_append1; |
| 181 | } |
| 182 | return 0; |
| 183 | |
| 184 | error_append1: |
| 185 | lttng_kernel_context_remove_last(ctx); |
| 186 | error_append0: |
| 187 | field_data_free(fdata); |
| 188 | error_create: |
| 189 | return ret; |
| 190 | } |
| 191 | |
| 192 | /** |
| 193 | * lttng_add_callstack_to_ctx - add callstack event context |
| 194 | * |
| 195 | * @ctx: the lttng_ctx pointer to initialize |
| 196 | * @type: the context type |
| 197 | * |
| 198 | * Supported callstack type supported: |
| 199 | * LTTNG_KERNEL_CONTEXT_CALLSTACK_KERNEL |
| 200 | * Records the callstack of the kernel |
| 201 | * LTTNG_KERNEL_CONTEXT_CALLSTACK_USER |
| 202 | * Records the callstack of the userspace program (from the kernel) |
| 203 | * |
| 204 | * Return 0 for success, or error code. |
| 205 | */ |
| 206 | int lttng_add_callstack_to_ctx(struct lttng_kernel_ctx **ctx, int type) |
| 207 | { |
| 208 | switch (type) { |
| 209 | case LTTNG_KERNEL_ABI_CONTEXT_CALLSTACK_KERNEL: |
| 210 | return __lttng_add_callstack_generic(ctx, CALLSTACK_KERNEL); |
| 211 | #ifdef CONFIG_X86 |
| 212 | case LTTNG_KERNEL_ABI_CONTEXT_CALLSTACK_USER: |
| 213 | return __lttng_add_callstack_generic(ctx, CALLSTACK_USER); |
| 214 | #endif |
| 215 | default: |
| 216 | return -EINVAL; |
| 217 | } |
| 218 | } |
| 219 | EXPORT_SYMBOL_GPL(lttng_add_callstack_to_ctx); |