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