probes/lttng-uprobes.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only)
   2  *
   3  * probes/lttng-uprobes.c
   4  *
   5  * LTTng uprobes integration module.
   6  *
   7  * Copyright (C) 2013 Yannick Brosseau <yannick.brosseau@gmail.com>
   8  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   9  *
  10  */
  11
  12 #include <linux/fdtable.h>
  13 #include <linux/list.h>
  14 #include <linux/module.h>
  15 #include <linux/namei.h>
  16 #include <linux/slab.h>
  17 #include <linux/uaccess.h>
  18 #include <linux/uprobes.h>
  19 #include <lttng/lttng-events.h>
  20 #include <lttng/lttng-tracer.h>
  21 #include <wrapper/irqflags.h>
  22 #include <ringbuffer/frontend_types.h>
  23
  24 static
  25 int lttng_uprobes_handler_pre(struct uprobe_consumer *uc, struct pt_regs *regs)
  26 {
  27         struct lttng_uprobe_handler *uprobe_handler =
  28                 container_of(uc, struct lttng_uprobe_handler, up_consumer);
  29         struct lttng_event *event = uprobe_handler->event;
  30         struct lttng_probe_ctx lttng_probe_ctx = {
  31                 .event = event,
  32                 .interruptible = !lttng_regs_irqs_disabled(regs),
  33         };
  34         struct lttng_channel *chan = event->chan;
  35         struct lib_ring_buffer_ctx ctx;
  36         int ret;
  37
  38         struct {
  39                 unsigned long ip;
  40         } payload;
  41
  42         if (unlikely(!READ_ONCE(chan->session->active)))
  43                 return 0;
  44         if (unlikely(!READ_ONCE(chan->enabled)))
  45                 return 0;
  46         if (unlikely(!READ_ONCE(event->enabled)))
  47                 return 0;
  48
  49         lib_ring_buffer_ctx_init(&ctx, chan->chan, &lttng_probe_ctx,
  50                 sizeof(payload), lttng_alignof(payload), -1);
  51
  52         ret = chan->ops->event_reserve(&ctx, event->id);
  53         if (ret < 0)
  54                 return 0;
  55
  56         /* Event payload. */
  57         payload.ip = (unsigned long)instruction_pointer(regs);
  58
  59         lib_ring_buffer_align_ctx(&ctx, lttng_alignof(payload));
  60         chan->ops->event_write(&ctx, &payload, sizeof(payload));
  61         chan->ops->event_commit(&ctx);
  62         return 0;
  63 }
  64
  65 /*
  66  * Create event description.
  67  */
  68 static
  69 int lttng_create_uprobe_event(const char *name, struct lttng_event *event)
  70 {
  71         struct lttng_event_desc *desc;
  72         struct lttng_event_field *fields;
  73         int ret;
  74
  75         desc = kzalloc(sizeof(*event->desc), GFP_KERNEL);
  76         if (!desc)
  77                 return -ENOMEM;
  78         desc->name = kstrdup(name, GFP_KERNEL);
  79         if (!desc->name) {
  80                 ret = -ENOMEM;
  81                 goto error_str;
  82         }
  83
  84         desc->nr_fields = 1;
  85         desc->fields = fields =
  86                 kzalloc(1 * sizeof(struct lttng_event_field), GFP_KERNEL);
  87
  88         if (!desc->fields) {
  89                 ret = -ENOMEM;
  90                 goto error_fields;
  91         }
  92         fields[0].name = "ip";
  93         fields[0].type.atype = atype_integer;
  94         fields[0].type.u.integer.size = sizeof(unsigned long) * CHAR_BIT;
  95         fields[0].type.u.integer.alignment = lttng_alignof(unsigned long) * CHAR_BIT;
  96         fields[0].type.u.integer.signedness = lttng_is_signed_type(unsigned long);
  97         fields[0].type.u.integer.reverse_byte_order = 0;
  98         fields[0].type.u.integer.base = 16;
  99         fields[0].type.u.integer.encoding = lttng_encode_none;
 100
 101         desc->owner = THIS_MODULE;
 102         event->desc = desc;
 103
 104         return 0;
 105
 106 error_fields:
 107         kfree(desc->name);
 108 error_str:
 109         kfree(desc);
 110         return ret;
 111 }
 112
 113 /*
 114  * Returns the inode struct from the current task and an fd. The inode is
 115  * grabbed by this function and must be put once we are done with it using
 116  * iput().
 117  */
 118 static struct inode *get_inode_from_fd(int fd)
 119 {
 120         struct file *file;
 121         struct inode *inode;
 122
 123         rcu_read_lock();
 124         /*
 125          * Returns the file backing the given fd. Needs to be done inside an RCU
 126          * critical section.
 127          */
 128         file = fcheck(fd);
 129         if (file == NULL) {
 130                 printk(KERN_WARNING "Cannot access file backing the fd(%d)\n", fd);
 131                 inode = NULL;
 132                 goto error;
 133         }
 134
 135         /* Grab a reference on the inode. */
 136         inode = igrab(file->f_path.dentry->d_inode);
 137         if (inode == NULL)
 138                 printk(KERN_WARNING "Cannot grab a reference on the inode.\n");
 139 error:
 140         rcu_read_unlock();
 141         return inode;
 142 }
 143
 144 int lttng_uprobes_add_callsite(struct lttng_event *event,
 145         struct lttng_kernel_event_callsite __user *callsite)
 146 {
 147         int ret = 0;
 148         struct lttng_uprobe_handler *uprobe_handler;
 149
 150         if (!event) {
 151                 ret = -EINVAL;
 152                 goto end;
 153         }
 154
 155         uprobe_handler = kzalloc(sizeof(struct lttng_uprobe_handler), GFP_KERNEL);
 156         if (!uprobe_handler) {
 157                 printk(KERN_WARNING "Error allocating uprobe_uprobe_handlers");
 158                 ret = -ENOMEM;
 159                 goto end;
 160         }
 161
 162         uprobe_handler->event = event;
 163         uprobe_handler->up_consumer.handler = lttng_uprobes_handler_pre;
 164
 165         ret = copy_from_user(&uprobe_handler->offset, &callsite->u.uprobe.offset, sizeof(uint64_t));
 166         if (ret) {
 167                 goto register_error;
 168         }
 169
 170         ret = uprobe_register(event->u.uprobe.inode,
 171                               uprobe_handler->offset, &uprobe_handler->up_consumer);
 172         if (ret) {
 173                 printk(KERN_WARNING "Error registering probe on inode %lu "
 174                        "and offset 0x%llx\n", event->u.uprobe.inode->i_ino,
 175                        uprobe_handler->offset);
 176                 ret = -1;
 177                 goto register_error;
 178         }
 179
 180         list_add(&uprobe_handler->node, &event->u.uprobe.head);
 181
 182         return ret;
 183
 184 register_error:
 185         kfree(uprobe_handler);
 186 end:
 187         return ret;
 188 }
 189 EXPORT_SYMBOL_GPL(lttng_uprobes_add_callsite);
 190
 191 int lttng_uprobes_register(const char *name, int fd, struct lttng_event *event)
 192 {
 193         int ret = 0;
 194         struct inode *inode;
 195
 196         ret = lttng_create_uprobe_event(name, event);
 197         if (ret)
 198                 goto error;
 199
 200         inode = get_inode_from_fd(fd);
 201         if (!inode) {
 202                 printk(KERN_WARNING "Cannot get inode from fd\n");
 203                 ret = -EBADF;
 204                 goto inode_error;
 205         }
 206         event->u.uprobe.inode = inode;
 207         INIT_LIST_HEAD(&event->u.uprobe.head);
 208
 209         return 0;
 210
 211 inode_error:
 212         kfree(event->desc->name);
 213         kfree(event->desc);
 214 error:
 215         return ret;
 216 }
 217 EXPORT_SYMBOL_GPL(lttng_uprobes_register);
 218
 219 void lttng_uprobes_unregister(struct lttng_event *event)
 220 {
 221         struct lttng_uprobe_handler *iter, *tmp;
 222
 223         /*
 224          * Iterate over the list of handler, remove each handler from the list
 225          * and free the struct.
 226          */
 227         list_for_each_entry_safe(iter, tmp, &event->u.uprobe.head, node) {
 228                 uprobe_unregister(event->u.uprobe.inode, iter->offset,
 229                                   &iter->up_consumer);
 230                 list_del(&iter->node);
 231                 kfree(iter);
 232         }
 233 }
 234 EXPORT_SYMBOL_GPL(lttng_uprobes_unregister);
 235
 236 void lttng_uprobes_destroy_private(struct lttng_event *event)
 237 {
 238         iput(event->u.uprobe.inode);
 239         kfree(event->desc->name);
 240         kfree(event->desc);
 241 }
 242 EXPORT_SYMBOL_GPL(lttng_uprobes_destroy_private);
 243
 244 MODULE_LICENSE("GPL and additional rights");
 245 MODULE_AUTHOR("Yannick Brosseau");
 246 MODULE_DESCRIPTION("Linux Trace Toolkit Uprobes Support");