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