src/system-update-generator/system-update-generator.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <unistd.h>
   5
   6 #include "fs-util.h"
   7 #include "generator.h"
   8 #include "log.h"
   9 #include "proc-cmdline.h"
  10 #include "special.h"
  11 #include "string-util.h"
  12 #include "util.h"
  13
  14 /*
  15  * Implements the logic described in systemd.offline-updates(7).
  16  */
  17
  18 static const char *arg_dest = NULL;
  19
  20 static int generate_symlink(void) {
  21         const char *p = NULL;
  22
  23         if (laccess("/system-update", F_OK) < 0) {
  24                 if (errno == ENOENT)
  25                         return 0;
  26
  27                 log_error_errno(errno, "Failed to check for system update: %m");
  28                 return -EINVAL;
  29         }
  30
  31         p = strjoina(arg_dest, "/" SPECIAL_DEFAULT_TARGET);
  32         if (symlink(SYSTEM_DATA_UNIT_PATH "/system-update.target", p) < 0)
  33                 return log_error_errno(errno, "Failed to create symlink %s: %m", p);
  34
  35         return 1;
  36 }
  37
  38 static int parse_proc_cmdline_item(const char *key, const char *value, void *data) {
  39         assert(key);
  40
  41         /* Check if a run level is specified on the kernel command line. The
  42          * command line has higher priority than any on-disk configuration, so
  43          * it'll make any symlink we create moot.
  44          */
  45
  46         if (streq(key, "systemd.unit") && !proc_cmdline_value_missing(key, value))
  47                 log_warning("Offline system update overridden by kernel command line systemd.unit= setting");
  48         else if (!value && runlevel_to_target(key))
  49                 log_warning("Offline system update overridden by runlevel \"%s\" on the kernel command line", key);
  50
  51         return 0;
  52 }
  53
  54 static int run(const char *dest, const char *dest_early, const char *dest_late) {
  55         int r;
  56
  57         assert_se(arg_dest = dest_early);
  58
  59         r = generate_symlink();
  60         if (r <= 0)
  61                 return r;
  62
  63         /* We parse the command line only to emit warnings. */
  64         r = proc_cmdline_parse(parse_proc_cmdline_item, NULL, 0);
  65         if (r < 0)
  66                 log_warning_errno(r, "Failed to parse kernel command line, ignoring: %m");
  67
  68         return 0;
  69 }
  70
  71 DEFINE_MAIN_GENERATOR_FUNCTION(run);