src/bin/lttng-sessiond/lttng-syscall.c

   1 /*
   2  * Copyright (C) 2014 David Goulet <dgoulet@efficios.com>
   3  *
   4  * SPDX-License-Identifier: GPL-2.0-only
   5  *
   6  */
   7
   8 #define _LGPL_SOURCE
   9 #include <stdbool.h>
  10
  11 #include <common/common.h>
  12 #include <common/kernel-ctl/kernel-ctl.h>
  13
  14 #include "lttng-sessiond.h"
  15 #include "kernel.h"
  16 #include "lttng-syscall.h"
  17 #include "utils.h"
  18
  19 /* Global syscall table. */
  20 struct syscall *syscall_table;
  21
  22 /* Number of entry in the syscall table. */
  23 static size_t syscall_table_nb_entry;
  24
  25 /*
  26  * Populate the system call table using the kernel tracer.
  27  *
  28  * Return 0 on success and the syscall table is allocated. On error, a negative
  29  * value is returned.
  30  */
  31 int syscall_init_table(int tracer_fd)
  32 {
  33         int ret, fd, err;
  34         size_t nbmem;
  35         FILE *fp;
  36         /* Syscall data from the kernel. */
  37         size_t index = 0;
  38         bool at_least_one_syscall = false;
  39         uint32_t bitness;
  40         char name[SYSCALL_NAME_LEN];
  41
  42 #if (SYSCALL_NAME_LEN == 255)
  43 #define SYSCALL_NAME_LEN_SCANF_IS_A_BROKEN_API  "254"
  44 #endif
  45
  46         DBG3("Syscall init system call table");
  47
  48         fd = kernctl_syscall_list(tracer_fd);
  49         if (fd < 0) {
  50                 ret = fd;
  51                 PERROR("kernelctl syscall list");
  52                 goto error_ioctl;
  53         }
  54
  55         fp = fdopen(fd, "r");
  56         if (!fp) {
  57                 ret = -errno;
  58                 PERROR("syscall list fdopen");
  59                 goto error_fp;
  60         }
  61
  62         nbmem = SYSCALL_TABLE_INIT_SIZE;
  63         syscall_table = zmalloc(sizeof(struct syscall) * nbmem);
  64         if (!syscall_table) {
  65                 ret = -errno;
  66                 PERROR("syscall list zmalloc");
  67                 goto error;
  68         }
  69
  70         while (fscanf(fp,
  71                                 "syscall { index = %zu; \
  72                                 name = %" SYSCALL_NAME_LEN_SCANF_IS_A_BROKEN_API "[^;]; \
  73                                 bitness = %u; };\n",
  74                                 &index, name, &bitness) == 3) {
  75                 at_least_one_syscall = true;
  76                 if (index >= nbmem) {
  77                         struct syscall *new_list;
  78                         size_t new_nbmem;
  79
  80                         /* Double memory size. */
  81                         new_nbmem = max(index + 1, nbmem << 1);
  82                         if (new_nbmem > (SIZE_MAX / sizeof(*new_list))) {
  83                                 /* Overflow, stop everything, something went really wrong. */
  84                                 ERR("Syscall listing memory size overflow. Stopping");
  85                                 free(syscall_table);
  86                                 syscall_table = NULL;
  87                                 ret = -EINVAL;
  88                                 goto error;
  89                         }
  90
  91                         DBG("Reallocating syscall table from %zu to %zu entries", nbmem,
  92                                         new_nbmem);
  93                         new_list = realloc(syscall_table, new_nbmem * sizeof(*new_list));
  94                         if (!new_list) {
  95                                 ret = -errno;
  96                                 PERROR("syscall list realloc");
  97                                 goto error;
  98                         }
  99
 100                         /* Zero out the new memory. */
 101                         memset(new_list + nbmem, 0,
 102                                         (new_nbmem - nbmem) * sizeof(*new_list));
 103                         nbmem = new_nbmem;
 104                         syscall_table = new_list;
 105                 }
 106                 syscall_table[index].index = index;
 107                 syscall_table[index].bitness = bitness;
 108                 if (lttng_strncpy(syscall_table[index].name, name,
 109                                 sizeof(syscall_table[index].name))) {
 110                         ret = -EINVAL;
 111                         free(syscall_table);
 112                         syscall_table = NULL;
 113                         goto error;
 114                 }
 115                 /*
 116                 DBG("Syscall name '%s' at index %" PRIu32 " of bitness %u",
 117                                 syscall_table[index].name,
 118                                 syscall_table[index].index,
 119                                 syscall_table[index].bitness);
 120                 */
 121         }
 122
 123         /* Index starts at 0. */
 124         if (at_least_one_syscall) {
 125                 syscall_table_nb_entry = index + 1;
 126         }
 127
 128         ret = 0;
 129
 130 error:
 131         err = fclose(fp);
 132         if (err) {
 133                 PERROR("syscall list fclose");
 134         }
 135         return ret;
 136
 137 error_fp:
 138         err = close(fd);
 139         if (err) {
 140                 PERROR("syscall list close");
 141         }
 142
 143 error_ioctl:
 144         return ret;
 145 }
 146
 147 /*
 148  * Helper function for the list syscalls command that empty the temporary
 149  * syscall hashtable used to track duplicate between 32 and 64 bit arch.
 150  *
 151  * This empty the hash table and destroys it after. After this, the pointer is
 152  * unsuable. RCU read side lock MUST be acquired before calling this.
 153  */
 154 static void destroy_syscall_ht(struct lttng_ht *ht)
 155 {
 156         struct lttng_ht_iter iter;
 157         struct syscall *ksyscall;
 158
 159         DBG3("Destroying syscall hash table.");
 160
 161         if (!ht) {
 162                 return;
 163         }
 164
 165         cds_lfht_for_each_entry(ht->ht, &iter.iter, ksyscall, node.node) {
 166                 int ret;
 167
 168                 ret = lttng_ht_del(ht, &iter);
 169                 assert(!ret);
 170                 free(ksyscall);
 171         }
 172         ht_cleanup_push(ht);
 173 }
 174
 175 /*
 176  * Allocate the given hashtable pointer.
 177  *
 178  * Return 0 on success else a negative LTTNG error value.
 179  */
 180 static int init_syscall_ht(struct lttng_ht **ht)
 181 {
 182         int ret;
 183
 184         *ht = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
 185         if (!*ht) {
 186                 ret = -LTTNG_ERR_NOMEM;
 187         } else {
 188                 ret = 0;
 189         }
 190
 191         return ret;
 192 }
 193
 194 /*
 195  * Lookup a syscall in the given hash table by name.
 196  *
 197  * Return syscall object if found or else NULL.
 198  */
 199 static struct syscall *lookup_syscall(struct lttng_ht *ht, const char *name)
 200 {
 201         struct lttng_ht_node_str *node;
 202         struct lttng_ht_iter iter;
 203         struct syscall *ksyscall = NULL;
 204
 205         assert(ht);
 206         assert(name);
 207
 208         lttng_ht_lookup(ht, (void *) name, &iter);
 209         node = lttng_ht_iter_get_node_str(&iter);
 210         if (node) {
 211                 ksyscall = caa_container_of(node, struct syscall, node);
 212         }
 213
 214         return ksyscall;
 215 }
 216
 217 /*
 218  * Using the given syscall object in the events array with the bitness of the
 219  * syscall at index in the syscall table.
 220  */
 221 static void update_event_syscall_bitness(struct lttng_event *events,
 222                 unsigned int index, unsigned int syscall_index)
 223 {
 224         assert(events);
 225
 226         if (syscall_table[index].bitness == 32) {
 227                 events[syscall_index].flags |= LTTNG_EVENT_FLAG_SYSCALL_32;
 228         } else {
 229                 events[syscall_index].flags |= LTTNG_EVENT_FLAG_SYSCALL_64;
 230         }
 231 }
 232
 233 /*
 234  * Allocate and initialize syscall object and add it to the given hashtable.
 235  *
 236  * Return 0 on success else -LTTNG_ERR_NOMEM.
 237  */
 238 static int add_syscall_to_ht(struct lttng_ht *ht, unsigned int index,
 239                 unsigned int syscall_index)
 240 {
 241         int ret;
 242         struct syscall *ksyscall;
 243
 244         assert(ht);
 245
 246         ksyscall = zmalloc(sizeof(*ksyscall));
 247         if (!ksyscall) {
 248                 ret = -LTTNG_ERR_NOMEM;
 249                 goto error;
 250         }
 251
 252         strncpy(ksyscall->name, syscall_table[index].name,
 253                         sizeof(ksyscall->name));
 254         ksyscall->bitness = syscall_table[index].bitness;
 255         ksyscall->index = syscall_index;
 256         lttng_ht_node_init_str(&ksyscall->node, ksyscall->name);
 257         lttng_ht_add_unique_str(ht, &ksyscall->node);
 258         ret = 0;
 259
 260 error:
 261         return ret;
 262 }
 263
 264 /*
 265  * List syscalls present in the kernel syscall global array, allocate and
 266  * populate the events structure with them. Skip the empty syscall name.
 267  *
 268  * Return the number of entries in the array else a negative value.
 269  */
 270 ssize_t syscall_table_list(struct lttng_event **_events)
 271 {
 272         int i, index = 0;
 273         ssize_t ret;
 274         struct lttng_event *events;
 275         /* Hash table used to filter duplicate out. */
 276         struct lttng_ht *syscalls_ht = NULL;
 277
 278         assert(_events);
 279
 280         DBG("Syscall table listing.");
 281
 282         rcu_read_lock();
 283
 284         /*
 285          * Allocate at least the number of total syscall we have even if some of
 286          * them might not be valid. The count below will make sure to return the
 287          * right size of the events array.
 288          */
 289         events = zmalloc(syscall_table_nb_entry * sizeof(*events));
 290         if (!events) {
 291                 PERROR("syscall table list zmalloc");
 292                 ret = -LTTNG_ERR_NOMEM;
 293                 goto error;
 294         }
 295
 296         ret = init_syscall_ht(&syscalls_ht);
 297         if (ret < 0) {
 298                 goto error;
 299         }
 300
 301         for (i = 0; i < syscall_table_nb_entry; i++) {
 302                 struct syscall *ksyscall;
 303
 304                 /* Skip empty syscalls. */
 305                 if (*syscall_table[i].name == '\0') {
 306                         continue;
 307                 }
 308
 309                 ksyscall = lookup_syscall(syscalls_ht, syscall_table[i].name);
 310                 if (ksyscall) {
 311                         update_event_syscall_bitness(events, i, ksyscall->index);
 312                         continue;
 313                 }
 314
 315                 ret = add_syscall_to_ht(syscalls_ht, i, index);
 316                 if (ret < 0) {
 317                         goto error;
 318                 }
 319
 320                 /* Copy the event information in the event's array. */
 321                 strncpy(events[index].name, syscall_table[i].name,
 322                                 sizeof(events[index].name));
 323                 update_event_syscall_bitness(events, i, index);
 324                 events[index].type = LTTNG_EVENT_SYSCALL;
 325                 /* This makes the command line not print the enabled/disabled field. */
 326                 events[index].enabled = -1;
 327                 index++;
 328         }
 329
 330         destroy_syscall_ht(syscalls_ht);
 331         *_events = events;
 332         rcu_read_unlock();
 333         return index;
 334
 335 error:
 336         destroy_syscall_ht(syscalls_ht);
 337         free(events);
 338         rcu_read_unlock();
 339         return ret;
 340 }