probes/lttng-kretprobes.c

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