src/journal/journald-console.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright 2011 Lennart Poettering
   6
   7   systemd is free software; you can redistribute it and/or modify it
   8   under the terms of the GNU Lesser General Public License as published by
   9   the Free Software Foundation; either version 2.1 of the License, or
  10   (at your option) any later version.
  11
  12   systemd is distributed in the hope that it will be useful, but
  13   WITHOUT ANY WARRANTY; without even the implied warranty of
  14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15   Lesser General Public License for more details.
  16
  17   You should have received a copy of the GNU Lesser General Public License
  18   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  19 ***/
  20
  21 #include <fcntl.h>
  22 #include <sys/socket.h>
  23 #include <time.h>
  24
  25 #include "alloc-util.h"
  26 #include "fd-util.h"
  27 #include "fileio.h"
  28 #include "format-util.h"
  29 #include "io-util.h"
  30 #include "journald-console.h"
  31 #include "journald-server.h"
  32 #include "parse-util.h"
  33 #include "process-util.h"
  34 #include "stdio-util.h"
  35 #include "terminal-util.h"
  36
  37 static bool prefix_timestamp(void) {
  38
  39         static int cached_printk_time = -1;
  40
  41         if (_unlikely_(cached_printk_time < 0)) {
  42                 _cleanup_free_ char *p = NULL;
  43
  44                 cached_printk_time =
  45                         read_one_line_file("/sys/module/printk/parameters/time", &p) >= 0
  46                         && parse_boolean(p) > 0;
  47         }
  48
  49         return cached_printk_time;
  50 }
  51
  52 void server_forward_console(
  53                 Server *s,
  54                 int priority,
  55                 const char *identifier,
  56                 const char *message,
  57                 const struct ucred *ucred) {
  58
  59         struct iovec iovec[5];
  60         struct timespec ts;
  61         char tbuf[sizeof("[] ")-1 + DECIMAL_STR_MAX(ts.tv_sec) + DECIMAL_STR_MAX(ts.tv_nsec)-3 + 1];
  62         char header_pid[sizeof("[]: ")-1 + DECIMAL_STR_MAX(pid_t)];
  63         _cleanup_free_ char *ident_buf = NULL;
  64         _cleanup_close_ int fd = -1;
  65         const char *tty;
  66         int n = 0;
  67
  68         assert(s);
  69         assert(message);
  70
  71         if (LOG_PRI(priority) > s->max_level_console)
  72                 return;
  73
  74         /* First: timestamp */
  75         if (prefix_timestamp()) {
  76                 assert_se(clock_gettime(CLOCK_MONOTONIC, &ts) == 0);
  77                 xsprintf(tbuf, "[%5"PRI_TIME".%06"PRI_NSEC"] ",
  78                          ts.tv_sec,
  79                          (nsec_t)ts.tv_nsec / 1000);
  80
  81                 iovec[n++] = IOVEC_MAKE_STRING(tbuf);
  82         }
  83
  84         /* Second: identifier and PID */
  85         if (ucred) {
  86                 if (!identifier) {
  87                         get_process_comm(ucred->pid, &ident_buf);
  88                         identifier = ident_buf;
  89                 }
  90
  91                 xsprintf(header_pid, "["PID_FMT"]: ", ucred->pid);
  92
  93                 if (identifier)
  94                         iovec[n++] = IOVEC_MAKE_STRING(identifier);
  95
  96                 iovec[n++] = IOVEC_MAKE_STRING(header_pid);
  97         } else if (identifier) {
  98                 iovec[n++] = IOVEC_MAKE_STRING(identifier);
  99                 iovec[n++] = IOVEC_MAKE_STRING(": ");
 100         }
 101
 102         /* Fourth: message */
 103         iovec[n++] = IOVEC_MAKE_STRING(message);
 104         iovec[n++] = IOVEC_MAKE_STRING("\n");
 105
 106         tty = s->tty_path ?: "/dev/console";
 107
 108         /* Before you ask: yes, on purpose we open/close the console for each log line we write individually. This is a
 109          * good strategy to avoid journald getting killed by the kernel's SAK concept (it doesn't fix this entirely,
 110          * but minimizes the time window the kernel might end up killing journald due to SAK). It also makes things
 111          * easier for us so that we don't have to recover from hangups and suchlike triggered on the console. */
 112
 113         fd = open_terminal(tty, O_WRONLY|O_NOCTTY|O_CLOEXEC);
 114         if (fd < 0) {
 115                 log_debug_errno(fd, "Failed to open %s for logging: %m", tty);
 116                 return;
 117         }
 118
 119         if (writev(fd, iovec, n) < 0)
 120                 log_debug_errno(errno, "Failed to write to %s for logging: %m", tty);
 121 }