add "systemd-bless-boot-generator"

This generator automatically pulls in "systemd-bless-boot.service" if
a boot with boot counting is detected.

meson.build

@@ -1805,6 +1805,14 @@ if conf.get('ENABLE_EFI') == 1 and conf.get('HAVE_BLKID') == 1
                    install_rpath : rootlibexecdir,
                    install : true,
                    install_dir : rootlibexecdir)
+
+        executable('systemd-bless-boot-generator',
+                   'src/boot/bless-boot-generator.c',
+                   include_directories : includes,
+                   link_with : [libshared],
+                   install_rpath : rootlibexecdir,
+                   install : true,
+                   install_dir : systemgeneratordir)
 endif
 
 exe = executable('systemd-socket-activate', 'src/activate/activate.c',

src/boot/bless-boot-generator.c

@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <errno.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "efivars.h"
+#include "log.h"
+#include "mkdir.h"
+#include "special.h"
+#include "string-util.h"
+#include "util.h"
+#include "virt.h"
+
+/* This generator pulls systemd-bless-boot.service into the initial transaction if the "LoaderBootCountPath" EFI
+ * variable is set, i.e. the system boots up with boot counting in effect, which means we should mark the boot as
+ * "good" if we manage to boot up far enough. */
+
+static const char *arg_dest = "/tmp";
+
+int main(int argc, char *argv[]) {
+        const char *p;
+
+        log_set_prohibit_ipc(true);
+        log_set_target(LOG_TARGET_AUTO);
+        log_parse_environment();
+        log_open();
+
+        umask(0022);
+
+        if (argc > 1 && argc != 4) {
+                log_error("This program takes three or no arguments.");
+                return EXIT_FAILURE;
+        }
+
+        if (argc > 1)
+                arg_dest = argv[2];
+
+        if (in_initrd() > 0) {
+                log_debug("Skipping generator, running in the initrd.");
+                return EXIT_SUCCESS;
+        }
+
+        if (detect_container() > 0) {
+                log_debug("Skipping generator, running in a container.");
+                return EXIT_SUCCESS;
+        }
+
+        if (!is_efi_boot()) {
+                log_debug("Skipping generator, not an EFI boot.");
+                return EXIT_SUCCESS;
+        }
+
+        if (access("/sys/firmware/efi/efivars/LoaderBootCountPath-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f", F_OK) < 0) {
+
+                if (errno == ENOENT) {
+                        log_debug_errno(errno, "Skipping generator, not booted with boot counting in effect.");
+                        return EXIT_SUCCESS;
+                }
+
+                log_error_errno(errno, "Failed to check if LoaderBootCountPath EFI variable exists: %m");
+                return EXIT_FAILURE;
+        }
+
+        /* We pull this in from basic.target so that it ends up in all "regular" boot ups, but not in rescue.target or
+         * even emergency.target. */
+        p = strjoina(arg_dest, "/" SPECIAL_BASIC_TARGET ".wants/systemd-bless-boot.service");
+        (void) mkdir_parents(p, 0755);
+        if (symlink(SYSTEM_DATA_UNIT_PATH "/systemd-bless-boot.service", p) < 0) {
+                log_error_errno(errno, "Failed to create symlink '%s': %m", p);
+                return EXIT_FAILURE;
+        }
+
+        return EXIT_SUCCESS;
+}