1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
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 "unit-file.h"
13 #include "util.h"
14
15 /*
16 * Implements the logic described in systemd.offline-updates(7).
17 */
18
19 static const char *arg_dest = NULL;
20
generate_symlink(void)21 static int generate_symlink(void) {
22 const char *p = NULL;
23
24 if (laccess("/system-update", F_OK) < 0) {
25 if (errno == ENOENT)
26 return 0;
27
28 log_error_errno(errno, "Failed to check for system update: %m");
29 return -EINVAL;
30 }
31
32 p = strjoina(arg_dest, "/" SPECIAL_DEFAULT_TARGET);
33 if (symlink(SYSTEM_DATA_UNIT_DIR "/system-update.target", p) < 0)
34 return log_error_errno(errno, "Failed to create symlink %s: %m", p);
35
36 return 1;
37 }
38
parse_proc_cmdline_item(const char * key,const char * value,void * data)39 static int parse_proc_cmdline_item(const char *key, const char *value, void *data) {
40 assert(key);
41
42 /* Check if a run level is specified on the kernel command line. The
43 * command line has higher priority than any on-disk configuration, so
44 * it'll make any symlink we create moot.
45 */
46
47 if (streq(key, "systemd.unit") && !proc_cmdline_value_missing(key, value))
48 log_warning("Offline system update overridden by kernel command line systemd.unit= setting");
49 else if (!value && runlevel_to_target(key))
50 log_warning("Offline system update overridden by runlevel \"%s\" on the kernel command line", key);
51
52 return 0;
53 }
54
run(const char * dest,const char * dest_early,const char * dest_late)55 static int run(const char *dest, const char *dest_early, const char *dest_late) {
56 int r;
57
58 assert_se(arg_dest = dest_early);
59
60 r = generate_symlink();
61 if (r <= 0)
62 return r;
63
64 /* We parse the command line only to emit warnings. */
65 r = proc_cmdline_parse(parse_proc_cmdline_item, NULL, 0);
66 if (r < 0)
67 log_warning_errno(r, "Failed to parse kernel command line, ignoring: %m");
68
69 return 0;
70 }
71
72 DEFINE_MAIN_GENERATOR_FUNCTION(run);
73