src/journal/journald-kmsg.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <fcntl.h>
   4 #include <sys/epoll.h>
   5 #include <sys/mman.h>
   6 #include <sys/socket.h>
   7 #include <unistd.h>
   8
   9 #include "libudev.h"
  10 #include "sd-messages.h"
  11
  12 #include "alloc-util.h"
  13 #include "escape.h"
  14 #include "fd-util.h"
  15 #include "format-util.h"
  16 #include "io-util.h"
  17 #include "journald-kmsg.h"
  18 #include "journald-server.h"
  19 #include "journald-syslog.h"
  20 #include "parse-util.h"
  21 #include "process-util.h"
  22 #include "stdio-util.h"
  23 #include "string-util.h"
  24
  25 void server_forward_kmsg(
  26         Server *s,
  27         int priority,
  28         const char *identifier,
  29         const char *message,
  30         const struct ucred *ucred) {
  31
  32         _cleanup_free_ char *ident_buf = NULL;
  33         struct iovec iovec[5];
  34         char header_priority[DECIMAL_STR_MAX(priority) + 3],
  35              header_pid[STRLEN("[]: ") + DECIMAL_STR_MAX(pid_t) + 1];
  36         int n = 0;
  37
  38         assert(s);
  39         assert(priority >= 0);
  40         assert(priority <= 999);
  41         assert(message);
  42
  43         if (_unlikely_(LOG_PRI(priority) > s->max_level_kmsg))
  44                 return;
  45
  46         if (_unlikely_(s->dev_kmsg_fd < 0))
  47                 return;
  48
  49         /* Never allow messages with kernel facility to be written to
  50          * kmsg, regardless where the data comes from. */
  51         priority = syslog_fixup_facility(priority);
  52
  53         /* First: priority field */
  54         xsprintf(header_priority, "<%i>", priority);
  55         iovec[n++] = IOVEC_MAKE_STRING(header_priority);
  56
  57         /* Second: identifier and PID */
  58         if (ucred) {
  59                 if (!identifier) {
  60                         get_process_comm(ucred->pid, &ident_buf);
  61                         identifier = ident_buf;
  62                 }
  63
  64                 xsprintf(header_pid, "["PID_FMT"]: ", ucred->pid);
  65
  66                 if (identifier)
  67                         iovec[n++] = IOVEC_MAKE_STRING(identifier);
  68
  69                 iovec[n++] = IOVEC_MAKE_STRING(header_pid);
  70         } else if (identifier) {
  71                 iovec[n++] = IOVEC_MAKE_STRING(identifier);
  72                 iovec[n++] = IOVEC_MAKE_STRING(": ");
  73         }
  74
  75         /* Fourth: message */
  76         iovec[n++] = IOVEC_MAKE_STRING(message);
  77         iovec[n++] = IOVEC_MAKE_STRING("\n");
  78
  79         if (writev(s->dev_kmsg_fd, iovec, n) < 0)
  80                 log_debug_errno(errno, "Failed to write to /dev/kmsg for logging: %m");
  81 }
  82
  83 static bool is_us(const char *identifier, const char *pid) {
  84         pid_t pid_num;
  85
  86         if (!identifier || !pid)
  87                 return false;
  88
  89         if (parse_pid(pid, &pid_num) < 0)
  90                 return false;
  91
  92         return pid_num == getpid_cached() &&
  93                streq(identifier, program_invocation_short_name);
  94 }
  95
  96 static void dev_kmsg_record(Server *s, char *p, size_t l) {
  97
  98         _cleanup_free_ char *message = NULL, *syslog_priority = NULL, *syslog_pid = NULL, *syslog_facility = NULL, *syslog_identifier = NULL, *source_time = NULL, *identifier = NULL, *pid = NULL;
  99         struct iovec iovec[N_IOVEC_META_FIELDS + 7 + N_IOVEC_KERNEL_FIELDS + 2 + N_IOVEC_UDEV_FIELDS];
 100         char *kernel_device = NULL;
 101         unsigned long long usec;
 102         size_t n = 0, z = 0, j;
 103         int priority, r;
 104         char *e, *f, *k;
 105         uint64_t serial;
 106         size_t pl;
 107
 108         assert(s);
 109         assert(p);
 110
 111         if (l <= 0)
 112                 return;
 113
 114         e = memchr(p, ',', l);
 115         if (!e)
 116                 return;
 117         *e = 0;
 118
 119         r = safe_atoi(p, &priority);
 120         if (r < 0 || priority < 0 || priority > 999)
 121                 return;
 122
 123         if (s->forward_to_kmsg && LOG_FAC(priority) != LOG_KERN)
 124                 return;
 125
 126         l -= (e - p) + 1;
 127         p = e + 1;
 128         e = memchr(p, ',', l);
 129         if (!e)
 130                 return;
 131         *e = 0;
 132
 133         r = safe_atou64(p, &serial);
 134         if (r < 0)
 135                 return;
 136
 137         if (s->kernel_seqnum) {
 138                 /* We already read this one? */
 139                 if (serial < *s->kernel_seqnum)
 140                         return;
 141
 142                 /* Did we lose any? */
 143                 if (serial > *s->kernel_seqnum)
 144                         server_driver_message(s, 0,
 145                                               "MESSAGE_ID=" SD_MESSAGE_JOURNAL_MISSED_STR,
 146                                               LOG_MESSAGE("Missed %"PRIu64" kernel messages",
 147                                                           serial - *s->kernel_seqnum),
 148                                               NULL);
 149
 150                 /* Make sure we never read this one again. Note that
 151                  * we always store the next message serial we expect
 152                  * here, simply because this makes handling the first
 153                  * message with serial 0 easy. */
 154                 *s->kernel_seqnum = serial + 1;
 155         }
 156
 157         l -= (e - p) + 1;
 158         p = e + 1;
 159         f = memchr(p, ';', l);
 160         if (!f)
 161                 return;
 162         /* Kernel 3.6 has the flags field, kernel 3.5 lacks that */
 163         e = memchr(p, ',', l);
 164         if (!e || f < e)
 165                 e = f;
 166         *e = 0;
 167
 168         r = safe_atollu(p, &usec);
 169         if (r < 0)
 170                 return;
 171
 172         l -= (f - p) + 1;
 173         p = f + 1;
 174         e = memchr(p, '\n', l);
 175         if (!e)
 176                 return;
 177         *e = 0;
 178
 179         pl = e - p;
 180         l -= (e - p) + 1;
 181         k = e + 1;
 182
 183         for (j = 0; l > 0 && j < N_IOVEC_KERNEL_FIELDS; j++) {
 184                 char *m;
 185                 /* Metadata fields attached */
 186
 187                 if (*k != ' ')
 188                         break;
 189
 190                 k++, l--;
 191
 192                 e = memchr(k, '\n', l);
 193                 if (!e)
 194                         return;
 195
 196                 *e = 0;
 197
 198                 if (cunescape_length_with_prefix(k, e - k, "_KERNEL_", UNESCAPE_RELAX, &m) < 0)
 199                         break;
 200
 201                 if (startswith(m, "_KERNEL_DEVICE="))
 202                         kernel_device = m + 15;
 203
 204                 iovec[n++] = IOVEC_MAKE_STRING(m);
 205                 z++;
 206
 207                 l -= (e - k) + 1;
 208                 k = e + 1;
 209         }
 210
 211         if (kernel_device) {
 212                 struct udev_device *ud;
 213
 214                 ud = udev_device_new_from_device_id(s->udev, kernel_device);
 215                 if (ud) {
 216                         const char *g;
 217                         struct udev_list_entry *ll;
 218                         char *b;
 219
 220                         g = udev_device_get_devnode(ud);
 221                         if (g) {
 222                                 b = strappend("_UDEV_DEVNODE=", g);
 223                                 if (b) {
 224                                         iovec[n++] = IOVEC_MAKE_STRING(b);
 225                                         z++;
 226                                 }
 227                         }
 228
 229                         g = udev_device_get_sysname(ud);
 230                         if (g) {
 231                                 b = strappend("_UDEV_SYSNAME=", g);
 232                                 if (b) {
 233                                         iovec[n++] = IOVEC_MAKE_STRING(b);
 234                                         z++;
 235                                 }
 236                         }
 237
 238                         j = 0;
 239                         ll = udev_device_get_devlinks_list_entry(ud);
 240                         udev_list_entry_foreach(ll, ll) {
 241
 242                                 if (j > N_IOVEC_UDEV_FIELDS)
 243                                         break;
 244
 245                                 g = udev_list_entry_get_name(ll);
 246                                 if (g) {
 247                                         b = strappend("_UDEV_DEVLINK=", g);
 248                                         if (b) {
 249                                                 iovec[n++] = IOVEC_MAKE_STRING(b);
 250                                                 z++;
 251                                         }
 252                                 }
 253
 254                                 j++;
 255                         }
 256
 257                         udev_device_unref(ud);
 258                 }
 259         }
 260
 261         if (asprintf(&source_time, "_SOURCE_MONOTONIC_TIMESTAMP=%llu", usec) >= 0)
 262                 iovec[n++] = IOVEC_MAKE_STRING(source_time);
 263
 264         iovec[n++] = IOVEC_MAKE_STRING("_TRANSPORT=kernel");
 265
 266         if (asprintf(&syslog_priority, "PRIORITY=%i", priority & LOG_PRIMASK) >= 0)
 267                 iovec[n++] = IOVEC_MAKE_STRING(syslog_priority);
 268
 269         if (asprintf(&syslog_facility, "SYSLOG_FACILITY=%i", LOG_FAC(priority)) >= 0)
 270                 iovec[n++] = IOVEC_MAKE_STRING(syslog_facility);
 271
 272         if (LOG_FAC(priority) == LOG_KERN)
 273                 iovec[n++] = IOVEC_MAKE_STRING("SYSLOG_IDENTIFIER=kernel");
 274         else {
 275                 pl -= syslog_parse_identifier((const char**) &p, &identifier, &pid);
 276
 277                 /* Avoid any messages we generated ourselves via
 278                  * log_info() and friends. */
 279                 if (is_us(identifier, pid))
 280                         goto finish;
 281
 282                 if (identifier) {
 283                         syslog_identifier = strappend("SYSLOG_IDENTIFIER=", identifier);
 284                         if (syslog_identifier)
 285                                 iovec[n++] = IOVEC_MAKE_STRING(syslog_identifier);
 286                 }
 287
 288                 if (pid) {
 289                         syslog_pid = strappend("SYSLOG_PID=", pid);
 290                         if (syslog_pid)
 291                                 iovec[n++] = IOVEC_MAKE_STRING(syslog_pid);
 292                 }
 293         }
 294
 295         if (cunescape_length_with_prefix(p, pl, "MESSAGE=", UNESCAPE_RELAX, &message) >= 0)
 296                 iovec[n++] = IOVEC_MAKE_STRING(message);
 297
 298         server_dispatch_message(s, iovec, n, ELEMENTSOF(iovec), NULL, NULL, priority, 0);
 299
 300 finish:
 301         for (j = 0; j < z; j++)
 302                 free(iovec[j].iov_base);
 303 }
 304
 305 static int server_read_dev_kmsg(Server *s) {
 306         char buffer[8192+1]; /* the kernel-side limit per record is 8K currently */
 307         ssize_t l;
 308
 309         assert(s);
 310         assert(s->dev_kmsg_fd >= 0);
 311
 312         l = read(s->dev_kmsg_fd, buffer, sizeof(buffer) - 1);
 313         if (l == 0)
 314                 return 0;
 315         if (l < 0) {
 316                 /* Old kernels who don't allow reading from /dev/kmsg
 317                  * return EINVAL when we try. So handle this cleanly,
 318                  * but don' try to ever read from it again. */
 319                 if (errno == EINVAL) {
 320                         s->dev_kmsg_event_source = sd_event_source_unref(s->dev_kmsg_event_source);
 321                         return 0;
 322                 }
 323
 324                 if (IN_SET(errno, EAGAIN, EINTR, EPIPE))
 325                         return 0;
 326
 327                 return log_error_errno(errno, "Failed to read from kernel: %m");
 328         }
 329
 330         dev_kmsg_record(s, buffer, l);
 331         return 1;
 332 }
 333
 334 int server_flush_dev_kmsg(Server *s) {
 335         int r;
 336
 337         assert(s);
 338
 339         if (s->dev_kmsg_fd < 0)
 340                 return 0;
 341
 342         if (!s->dev_kmsg_readable)
 343                 return 0;
 344
 345         log_debug("Flushing /dev/kmsg...");
 346
 347         for (;;) {
 348                 r = server_read_dev_kmsg(s);
 349                 if (r < 0)
 350                         return r;
 351
 352                 if (r == 0)
 353                         break;
 354         }
 355
 356         return 0;
 357 }
 358
 359 static int dispatch_dev_kmsg(sd_event_source *es, int fd, uint32_t revents, void *userdata) {
 360         Server *s = userdata;
 361
 362         assert(es);
 363         assert(fd == s->dev_kmsg_fd);
 364         assert(s);
 365
 366         if (revents & EPOLLERR)
 367                 log_warning("/dev/kmsg buffer overrun, some messages lost.");
 368
 369         if (!(revents & EPOLLIN))
 370                 log_error("Got invalid event from epoll for /dev/kmsg: %"PRIx32, revents);
 371
 372         return server_read_dev_kmsg(s);
 373 }
 374
 375 int server_open_dev_kmsg(Server *s) {
 376         mode_t mode;
 377         int r;
 378
 379         assert(s);
 380
 381         if (s->read_kmsg)
 382                 mode = O_RDWR|O_CLOEXEC|O_NONBLOCK|O_NOCTTY;
 383         else
 384                 mode = O_WRONLY|O_CLOEXEC|O_NONBLOCK|O_NOCTTY;
 385
 386         s->dev_kmsg_fd = open("/dev/kmsg", mode);
 387         if (s->dev_kmsg_fd < 0) {
 388                 log_full(errno == ENOENT ? LOG_DEBUG : LOG_WARNING,
 389                          "Failed to open /dev/kmsg, ignoring: %m");
 390                 return 0;
 391         }
 392
 393         if (!s->read_kmsg)
 394                 return 0;
 395
 396         r = sd_event_add_io(s->event, &s->dev_kmsg_event_source, s->dev_kmsg_fd, EPOLLIN, dispatch_dev_kmsg, s);
 397         if (r < 0) {
 398
 399                 /* This will fail with EPERM on older kernels where
 400                  * /dev/kmsg is not readable. */
 401                 if (r == -EPERM) {
 402                         r = 0;
 403                         goto fail;
 404                 }
 405
 406                 log_error_errno(r, "Failed to add /dev/kmsg fd to event loop: %m");
 407                 goto fail;
 408         }
 409
 410         r = sd_event_source_set_priority(s->dev_kmsg_event_source, SD_EVENT_PRIORITY_IMPORTANT+10);
 411         if (r < 0) {
 412                 log_error_errno(r, "Failed to adjust priority of kmsg event source: %m");
 413                 goto fail;
 414         }
 415
 416         s->dev_kmsg_readable = true;
 417
 418         return 0;
 419
 420 fail:
 421         s->dev_kmsg_event_source = sd_event_source_unref(s->dev_kmsg_event_source);
 422         s->dev_kmsg_fd = safe_close(s->dev_kmsg_fd);
 423
 424         return r;
 425 }
 426
 427 int server_open_kernel_seqnum(Server *s) {
 428         _cleanup_close_ int fd;
 429         uint64_t *p;
 430         int r;
 431
 432         assert(s);
 433
 434         /* We store the seqnum we last read in an mmaped file. That
 435          * way we can just use it like a variable, but it is
 436          * persistent and automatically flushed at reboot. */
 437
 438         fd = open("/run/systemd/journal/kernel-seqnum", O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW, 0644);
 439         if (fd < 0) {
 440                 log_error_errno(errno, "Failed to open /run/systemd/journal/kernel-seqnum, ignoring: %m");
 441                 return 0;
 442         }
 443
 444         r = posix_fallocate(fd, 0, sizeof(uint64_t));
 445         if (r != 0) {
 446                 log_error_errno(r, "Failed to allocate sequential number file, ignoring: %m");
 447                 return 0;
 448         }
 449
 450         p = mmap(NULL, sizeof(uint64_t), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
 451         if (p == MAP_FAILED) {
 452                 log_error_errno(errno, "Failed to map sequential number file, ignoring: %m");
 453                 return 0;
 454         }
 455
 456         s->kernel_seqnum = p;
 457
 458         return 0;
 459 }