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-rw-r--r--src/system-update-generator/system-update-generator.c72
1 files changed, 72 insertions, 0 deletions
diff --git a/src/system-update-generator/system-update-generator.c b/src/system-update-generator/system-update-generator.c
new file mode 100644
index 0000000..fc5aaa9
--- /dev/null
+++ b/src/system-update-generator/system-update-generator.c
@@ -0,0 +1,72 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <unistd.h>
+
+#include "fs-util.h"
+#include "generator.h"
+#include "log.h"
+#include "proc-cmdline.h"
+#include "special.h"
+#include "string-util.h"
+#include "unit-file.h"
+#include "util.h"
+
+/*
+ * Implements the logic described in systemd.offline-updates(7).
+ */
+
+static const char *arg_dest = NULL;
+
+static int generate_symlink(void) {
+ const char *p = NULL;
+
+ if (laccess("/system-update", F_OK) < 0) {
+ if (errno == ENOENT)
+ return 0;
+
+ log_error_errno(errno, "Failed to check for system update: %m");
+ return -EINVAL;
+ }
+
+ p = strjoina(arg_dest, "/" SPECIAL_DEFAULT_TARGET);
+ if (symlink(SYSTEM_DATA_UNIT_DIR "/system-update.target", p) < 0)
+ return log_error_errno(errno, "Failed to create symlink %s: %m", p);
+
+ return 1;
+}
+
+static int parse_proc_cmdline_item(const char *key, const char *value, void *data) {
+ assert(key);
+
+ /* Check if a run level is specified on the kernel command line. The
+ * command line has higher priority than any on-disk configuration, so
+ * it'll make any symlink we create moot.
+ */
+
+ if (streq(key, "systemd.unit") && !proc_cmdline_value_missing(key, value))
+ log_warning("Offline system update overridden by kernel command line systemd.unit= setting");
+ else if (!value && runlevel_to_target(key))
+ log_warning("Offline system update overridden by runlevel \"%s\" on the kernel command line", key);
+
+ return 0;
+}
+
+static int run(const char *dest, const char *dest_early, const char *dest_late) {
+ int r;
+
+ assert_se(arg_dest = dest_early);
+
+ r = generate_symlink();
+ if (r <= 0)
+ return r;
+
+ /* We parse the command line only to emit warnings. */
+ r = proc_cmdline_parse(parse_proc_cmdline_item, NULL, 0);
+ if (r < 0)
+ log_warning_errno(r, "Failed to parse kernel command line, ignoring: %m");
+
+ return 0;
+}
+
+DEFINE_MAIN_GENERATOR_FUNCTION(run);