| 1 | /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only) |
| 2 | * |
| 3 | * probes/lttng-kretprobes.c |
| 4 | * |
| 5 | * LTTng kretprobes integration module. |
| 6 | * |
| 7 | * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 8 | */ |
| 9 | |
| 10 | #include <linux/module.h> |
| 11 | #include <wrapper/kprobes.h> |
| 12 | #include <linux/slab.h> |
| 13 | #include <linux/kref.h> |
| 14 | #include <lttng/events.h> |
| 15 | #include <lttng/events-internal.h> |
| 16 | #include <ringbuffer/frontend_types.h> |
| 17 | #include <wrapper/vmalloc.h> |
| 18 | #include <wrapper/irqflags.h> |
| 19 | #include <lttng/tracer.h> |
| 20 | #include <blacklist/kprobes.h> |
| 21 | |
| 22 | enum lttng_kretprobe_type { |
| 23 | EVENT_ENTRY = 0, |
| 24 | EVENT_EXIT = 1, |
| 25 | }; |
| 26 | |
| 27 | struct lttng_krp { |
| 28 | struct kretprobe krp; |
| 29 | struct lttng_kernel_event_common *event[2]; /* ENTRY and EXIT */ |
| 30 | struct kref kref_register; |
| 31 | struct kref kref_alloc; |
| 32 | }; |
| 33 | |
| 34 | static |
| 35 | int _lttng_kretprobes_handler(struct kretprobe_instance *krpi, |
| 36 | struct pt_regs *regs, |
| 37 | enum lttng_kretprobe_type type) |
| 38 | { |
| 39 | struct lttng_krp *lttng_krp = |
| 40 | container_of(lttng_get_kretprobe(krpi), struct lttng_krp, krp); |
| 41 | struct lttng_kernel_event_common *event = lttng_krp->event[type]; |
| 42 | struct lttng_kernel_probe_ctx lttng_probe_ctx = { |
| 43 | .event = event, |
| 44 | .interruptible = !lttng_regs_irqs_disabled(regs), |
| 45 | }; |
| 46 | struct { |
| 47 | unsigned long ip; |
| 48 | unsigned long parent_ip; |
| 49 | } payload; |
| 50 | |
| 51 | switch (event->type) { |
| 52 | case LTTNG_KERNEL_EVENT_TYPE_RECORDER: |
| 53 | { |
| 54 | struct lttng_kernel_event_recorder *event_recorder = |
| 55 | container_of(event, struct lttng_kernel_event_recorder, parent); |
| 56 | struct lttng_kernel_channel_buffer *chan = event_recorder->chan; |
| 57 | |
| 58 | if (unlikely(!LTTNG_READ_ONCE(chan->parent.session->active))) |
| 59 | return 0; |
| 60 | if (unlikely(!LTTNG_READ_ONCE(chan->parent.enabled))) |
| 61 | return 0; |
| 62 | break; |
| 63 | } |
| 64 | case LTTNG_KERNEL_EVENT_TYPE_NOTIFIER: /* Fall-through. */ |
| 65 | default: |
| 66 | WARN_ON_ONCE(1); |
| 67 | } |
| 68 | |
| 69 | if (unlikely(!LTTNG_READ_ONCE(event->enabled))) |
| 70 | return 0; |
| 71 | |
| 72 | switch (event->type) { |
| 73 | case LTTNG_KERNEL_EVENT_TYPE_RECORDER: |
| 74 | { |
| 75 | struct lttng_kernel_event_recorder *event_recorder = |
| 76 | container_of(event, struct lttng_kernel_event_recorder, parent); |
| 77 | struct lttng_kernel_channel_buffer *chan = event_recorder->chan; |
| 78 | struct lttng_kernel_ring_buffer_ctx ctx; |
| 79 | int ret; |
| 80 | |
| 81 | payload.ip = (unsigned long) lttng_get_kretprobe(krpi)->kp.addr; |
| 82 | payload.parent_ip = (unsigned long) krpi->ret_addr; |
| 83 | |
| 84 | lib_ring_buffer_ctx_init(&ctx, event_recorder, sizeof(payload), |
| 85 | lttng_alignof(payload), <tng_probe_ctx); |
| 86 | ret = chan->ops->event_reserve(&ctx); |
| 87 | if (ret < 0) |
| 88 | return 0; |
| 89 | lib_ring_buffer_align_ctx(&ctx, lttng_alignof(payload)); |
| 90 | chan->ops->event_write(&ctx, &payload, sizeof(payload)); |
| 91 | chan->ops->event_commit(&ctx); |
| 92 | break; |
| 93 | } |
| 94 | case LTTNG_KERNEL_EVENT_TYPE_NOTIFIER: /* Fall-through. */ |
| 95 | default: |
| 96 | WARN_ON_ONCE(1); |
| 97 | } |
| 98 | return 0; |
| 99 | } |
| 100 | |
| 101 | static |
| 102 | int lttng_kretprobes_handler_entry(struct kretprobe_instance *krpi, |
| 103 | struct pt_regs *regs) |
| 104 | { |
| 105 | return _lttng_kretprobes_handler(krpi, regs, EVENT_ENTRY); |
| 106 | } |
| 107 | |
| 108 | static |
| 109 | int lttng_kretprobes_handler_exit(struct kretprobe_instance *krpi, |
| 110 | struct pt_regs *regs) |
| 111 | { |
| 112 | return _lttng_kretprobes_handler(krpi, regs, EVENT_EXIT); |
| 113 | } |
| 114 | |
| 115 | static const struct lttng_kernel_event_field *event_fields[] = { |
| 116 | lttng_kernel_static_event_field("ip", |
| 117 | lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16), |
| 118 | false, false, false), |
| 119 | lttng_kernel_static_event_field("parent_ip", |
| 120 | lttng_kernel_static_type_integer_from_type(unsigned long, __BYTE_ORDER, 16), |
| 121 | false, false, false), |
| 122 | }; |
| 123 | |
| 124 | static const struct lttng_kernel_tracepoint_class tp_class = { |
| 125 | .nr_fields = ARRAY_SIZE(event_fields), |
| 126 | .fields = event_fields, |
| 127 | }; |
| 128 | |
| 129 | /* |
| 130 | * Create event description |
| 131 | */ |
| 132 | static |
| 133 | int lttng_create_kprobe_event(const char *name, struct lttng_kernel_event_recorder *event_recorder, |
| 134 | enum lttng_kretprobe_type type) |
| 135 | { |
| 136 | struct lttng_kernel_event_desc *desc; |
| 137 | char *alloc_name; |
| 138 | size_t name_len; |
| 139 | const char *suffix = NULL; |
| 140 | int ret; |
| 141 | |
| 142 | desc = kzalloc(sizeof(*desc), GFP_KERNEL); |
| 143 | if (!desc) |
| 144 | return -ENOMEM; |
| 145 | name_len = strlen(name); |
| 146 | switch (type) { |
| 147 | case EVENT_ENTRY: |
| 148 | suffix = "_entry"; |
| 149 | break; |
| 150 | case EVENT_EXIT: |
| 151 | suffix = "_exit"; |
| 152 | break; |
| 153 | } |
| 154 | name_len += strlen(suffix); |
| 155 | alloc_name = kmalloc(name_len + 1, GFP_KERNEL); |
| 156 | if (!alloc_name) { |
| 157 | ret = -ENOMEM; |
| 158 | goto error_str; |
| 159 | } |
| 160 | strcpy(alloc_name, name); |
| 161 | strcat(alloc_name, suffix); |
| 162 | desc->event_name = alloc_name; |
| 163 | desc->tp_class = &tp_class; |
| 164 | desc->owner = THIS_MODULE; |
| 165 | event_recorder->priv->parent.desc = desc; |
| 166 | |
| 167 | return 0; |
| 168 | |
| 169 | error_str: |
| 170 | kfree(desc); |
| 171 | return ret; |
| 172 | } |
| 173 | |
| 174 | int lttng_kretprobes_register(const char *name, |
| 175 | const char *symbol_name, |
| 176 | uint64_t offset, |
| 177 | uint64_t addr, |
| 178 | struct lttng_kernel_event_recorder *event_recorder_entry, |
| 179 | struct lttng_kernel_event_recorder *event_recorder_exit) |
| 180 | { |
| 181 | int ret; |
| 182 | struct lttng_krp *lttng_krp; |
| 183 | |
| 184 | /* Kprobes expects a NULL symbol name if unused */ |
| 185 | if (symbol_name[0] == '\0') |
| 186 | symbol_name = NULL; |
| 187 | |
| 188 | ret = lttng_create_kprobe_event(name, event_recorder_entry, EVENT_ENTRY); |
| 189 | if (ret) |
| 190 | goto error; |
| 191 | ret = lttng_create_kprobe_event(name, event_recorder_exit, EVENT_EXIT); |
| 192 | if (ret) |
| 193 | goto event_exit_error; |
| 194 | lttng_krp = kzalloc(sizeof(*lttng_krp), GFP_KERNEL); |
| 195 | if (!lttng_krp) |
| 196 | goto krp_error; |
| 197 | lttng_krp->krp.entry_handler = lttng_kretprobes_handler_entry; |
| 198 | lttng_krp->krp.handler = lttng_kretprobes_handler_exit; |
| 199 | if (symbol_name) { |
| 200 | char *alloc_symbol; |
| 201 | |
| 202 | alloc_symbol = kstrdup(symbol_name, GFP_KERNEL); |
| 203 | if (!alloc_symbol) { |
| 204 | ret = -ENOMEM; |
| 205 | goto name_error; |
| 206 | } |
| 207 | lttng_krp->krp.kp.symbol_name = |
| 208 | alloc_symbol; |
| 209 | event_recorder_entry->priv->parent.u.kretprobe.symbol_name = |
| 210 | alloc_symbol; |
| 211 | event_recorder_exit->priv->parent.u.kretprobe.symbol_name = |
| 212 | alloc_symbol; |
| 213 | } |
| 214 | lttng_krp->krp.kp.offset = offset; |
| 215 | lttng_krp->krp.kp.addr = (void *) (unsigned long) addr; |
| 216 | |
| 217 | /* Allow probe handler to find event structures */ |
| 218 | lttng_krp->event[EVENT_ENTRY] = &event_recorder_entry->parent; |
| 219 | lttng_krp->event[EVENT_EXIT] = &event_recorder_exit->parent; |
| 220 | event_recorder_entry->priv->parent.u.kretprobe.lttng_krp = lttng_krp; |
| 221 | event_recorder_exit->priv->parent.u.kretprobe.lttng_krp = lttng_krp; |
| 222 | |
| 223 | /* |
| 224 | * Both events must be unregistered before the kretprobe is |
| 225 | * unregistered. Same for memory allocation. |
| 226 | */ |
| 227 | kref_init(<tng_krp->kref_alloc); |
| 228 | kref_get(<tng_krp->kref_alloc); /* inc refcount to 2, no overflow. */ |
| 229 | kref_init(<tng_krp->kref_register); |
| 230 | kref_get(<tng_krp->kref_register); /* inc refcount to 2, no overflow. */ |
| 231 | |
| 232 | /* |
| 233 | * Ensure the memory we just allocated don't trigger page faults. |
| 234 | * Well.. kprobes itself puts the page fault handler on the blacklist, |
| 235 | * but we can never be too careful. |
| 236 | */ |
| 237 | wrapper_vmalloc_sync_mappings(); |
| 238 | |
| 239 | ret = register_kretprobe(<tng_krp->krp); |
| 240 | if (ret) |
| 241 | goto register_error; |
| 242 | return 0; |
| 243 | |
| 244 | register_error: |
| 245 | kfree(lttng_krp->krp.kp.symbol_name); |
| 246 | name_error: |
| 247 | kfree(lttng_krp); |
| 248 | krp_error: |
| 249 | kfree(event_recorder_exit->priv->parent.desc->event_name); |
| 250 | kfree(event_recorder_exit->priv->parent.desc); |
| 251 | event_exit_error: |
| 252 | kfree(event_recorder_entry->priv->parent.desc->event_name); |
| 253 | kfree(event_recorder_entry->priv->parent.desc); |
| 254 | error: |
| 255 | return ret; |
| 256 | } |
| 257 | EXPORT_SYMBOL_GPL(lttng_kretprobes_register); |
| 258 | |
| 259 | static |
| 260 | void _lttng_kretprobes_unregister_release(struct kref *kref) |
| 261 | { |
| 262 | struct lttng_krp *lttng_krp = |
| 263 | container_of(kref, struct lttng_krp, kref_register); |
| 264 | unregister_kretprobe(<tng_krp->krp); |
| 265 | } |
| 266 | |
| 267 | void lttng_kretprobes_unregister(struct lttng_kernel_event_recorder *event_recorder) |
| 268 | { |
| 269 | kref_put(&event_recorder->priv->parent.u.kretprobe.lttng_krp->kref_register, |
| 270 | _lttng_kretprobes_unregister_release); |
| 271 | } |
| 272 | EXPORT_SYMBOL_GPL(lttng_kretprobes_unregister); |
| 273 | |
| 274 | static |
| 275 | void _lttng_kretprobes_release(struct kref *kref) |
| 276 | { |
| 277 | struct lttng_krp *lttng_krp = |
| 278 | container_of(kref, struct lttng_krp, kref_alloc); |
| 279 | kfree(lttng_krp->krp.kp.symbol_name); |
| 280 | } |
| 281 | |
| 282 | void lttng_kretprobes_destroy_private(struct lttng_kernel_event_recorder *event_recorder) |
| 283 | { |
| 284 | kfree(event_recorder->priv->parent.desc->event_name); |
| 285 | kfree(event_recorder->priv->parent.desc); |
| 286 | kref_put(&event_recorder->priv->parent.u.kretprobe.lttng_krp->kref_alloc, |
| 287 | _lttng_kretprobes_release); |
| 288 | } |
| 289 | EXPORT_SYMBOL_GPL(lttng_kretprobes_destroy_private); |
| 290 | |
| 291 | int lttng_kretprobes_event_enable_state(struct lttng_kernel_event_common *event, |
| 292 | int enable) |
| 293 | { |
| 294 | struct lttng_kernel_event_common *event_exit; |
| 295 | struct lttng_krp *lttng_krp; |
| 296 | |
| 297 | if (event->priv->instrumentation != LTTNG_KERNEL_ABI_KRETPROBE) { |
| 298 | return -EINVAL; |
| 299 | } |
| 300 | if (event->enabled == enable) { |
| 301 | return -EBUSY; |
| 302 | } |
| 303 | lttng_krp = event->priv->u.kretprobe.lttng_krp; |
| 304 | event_exit = lttng_krp->event[EVENT_EXIT]; |
| 305 | WRITE_ONCE(event->enabled, enable); |
| 306 | WRITE_ONCE(event_exit->enabled, enable); |
| 307 | return 0; |
| 308 | } |
| 309 | EXPORT_SYMBOL_GPL(lttng_kretprobes_event_enable_state); |
| 310 | |
| 311 | MODULE_LICENSE("GPL and additional rights"); |
| 312 | MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>"); |
| 313 | MODULE_DESCRIPTION("LTTng kretprobes probes"); |
| 314 | MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "." |
| 315 | __stringify(LTTNG_MODULES_MINOR_VERSION) "." |
| 316 | __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION) |
| 317 | LTTNG_MODULES_EXTRAVERSION); |