binfmt,tmpfiles,modules-load,sysctl: rework the various early-boot services that work on .d/ directories

This unifies much of the logic behind them:

- All four will now ofllow the rule that the earlier file and earlier
  assignment in the .d/ directories wins. Before, sysctl was the only
  outlier, where the later setting always won.

- All four now support getopt() and --help on the command line.

- All four can now handle specification of configuration file names on
  the command line to apply. The tools will automatically find them, and
  apply them. Previously only tmpfiles could do that. This is useful for
  %post scripts in RPMs and suchlike.

- This fixes various error path issues in conf_files_list()

src/binfmt/binfmt.c

@@ -26,6 +26,7 @@
 #include <stdio.h>
 #include <limits.h>
 #include <stdarg.h>
+#include <getopt.h>
 
 #include "log.h"
 #include "hashmap.h"
@@ -33,28 +34,34 @@
 #include "util.h"
 #include "conf-files.h"
 
+static const char conf_file_dirs[] =
+        "/etc/binfmt.d\0"
+        "/run/binfmt.d\0"
+        "/usr/local/lib/binfmt.d\0"
+        "/usr/lib/binfmt.d\0"
+#ifdef HAVE_SPLIT_USR
+        "/lib/binfmt.d\0"
+#endif
+        ;
+
 static int delete_rule(const char *rule) {
-        char *x, *fn = NULL, *e;
-        int r;
+        _cleanup_free_ char *x = NULL, *fn = NULL;
+        char *e;
 
         assert(rule[0]);
 
-        if (!(x = strdup(rule)))
+        x = strdup(rule);
+        if (!x)
                 return log_oom();
 
         e = strchrnul(x+1, x[0]);
         *e = 0;
 
-        asprintf(&fn, "/proc/sys/fs/binfmt_misc/%s", x+1);
-        free(x);
-
+        fn = strappend("/proc/sys/fs/binfmt_misc/", x+1);
         if (!fn)
                 return log_oom();
 
-        r = write_one_line_file(fn, "-1");
-        free(fn);
-
-        return r;
+        return write_one_line_file(fn, "-1");
 }
 
 static int apply_rule(const char *rule) {
@@ -62,7 +69,8 @@ static int apply_rule(const char *rule) {
 
         delete_rule(rule);
 
-        if ((r = write_one_line_file("/proc/sys/fs/binfmt_misc/register", rule)) < 0) {
+        r = write_one_line_file("/proc/sys/fs/binfmt_misc/register", rule);
+        if (r < 0) {
                 log_error("Failed to add binary format: %s", strerror(-r));
                 return r;
         }
@@ -71,21 +79,22 @@ static int apply_rule(const char *rule) {
 }
 
 static int apply_file(const char *path, bool ignore_enoent) {
-        FILE *f;
-        int r = 0;
+        _cleanup_fclose_ FILE *f = NULL;
+        int r;
 
         assert(path);
 
-        if (!(f = fopen(path, "re"))) {
-                if (ignore_enoent && errno == ENOENT)
+        r = search_and_fopen_nulstr(path, "re", conf_file_dirs, &f);
+        if (r < 0) {
+                if (ignore_enoent && r == -ENOENT)
                         return 0;
 
-                log_error("Failed to open file '%s', ignoring: %m", path);
-                return -errno;
+                log_error("Failed to open file '%s', ignoring: %s", path, strerror(-r));
+                return r;
         }
 
         log_debug("apply: %s\n", path);
-        while (!feof(f)) {
+        for (;;) {
                 char l[LINE_MAX], *p;
                 int k;
 
@@ -94,30 +103,71 @@ static int apply_file(const char *path, bool ignore_enoent) {
                                 break;
 
                         log_error("Failed to read file '%s', ignoring: %m", path);
-                        r = -errno;
-                        goto finish;
+                        return -errno;
                 }
 
                 p = strstrip(l);
-
                 if (!*p)
                         continue;
-
                 if (strchr(COMMENTS, *p))
                         continue;
 
-                if ((k = apply_rule(p)) < 0 && r == 0)
+                k = apply_rule(p);
+                if (k < 0 && r == 0)
                         r = k;
         }
 
-finish:
-        fclose(f);
-
         return r;
 }
 
+static int help(void) {
+
+        printf("%s [OPTIONS...] [CONFIGURATION FILE...]\n\n"
+               "Registers binary formats.\n\n"
+               "  -h --help             Show this help\n",
+               program_invocation_short_name);
+
+        return 0;
+}
+
+static int parse_argv(int argc, char *argv[]) {
+
+        static const struct option options[] = {
+                { "help",      no_argument,       NULL, 'h'           },
+                { NULL,        0,                 NULL, 0             }
+        };
+
+        int c;
+
+        assert(argc >= 0);
+        assert(argv);
+
+        while ((c = getopt_long(argc, argv, "h", options, NULL)) >= 0) {
+
+                switch (c) {
+
+                case 'h':
+                        help();
+                        return 0;
+
+                case '?':
+                        return -EINVAL;
+
+                default:
+                        log_error("Unknown option code %c", c);
+                        return -EINVAL;
+                }
+        }
+
+        return 1;
+}
+
 int main(int argc, char *argv[]) {
-        int r = 0;
+        int r, k;
+
+        r = parse_argv(argc, argv);
+        if (r <= 0)
+                return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
 
         log_set_target(LOG_TARGET_AUTO);
         log_parse_environment();
@@ -125,28 +175,21 @@ int main(int argc, char *argv[]) {
 
         umask(0022);
 
-        if (argc > 1) {
+        r = 0;
+
+        if (argc > optind) {
                 int i;
 
-                for (i = 1; i < argc; i++) {
-                        int k;
-
+                for (i = optind; i < argc; i++) {
                         k = apply_file(argv[i], false);
                         if (k < 0 && r == 0)
                                 r = k;
                 }
         } else {
-                char **files, **f;
+                _cleanup_strv_free_ char **files = NULL;
+                char **f;
 
-                r = conf_files_list(&files, ".conf", NULL,
-                                    "/etc/binfmt.d",
-                                    "/run/binfmt.d",
-                                    "/usr/local/lib/binfmt.d",
-                                    "/usr/lib/binfmt.d",
-#ifdef HAVE_SPLIT_USR
-                                    "/lib/binfmt.d",
-#endif
-                                    NULL);
+                r = conf_files_list_nulstr(&files, ".conf", NULL, conf_file_dirs);
                 if (r < 0) {
                         log_error("Failed to enumerate binfmt.d files: %s", strerror(-r));
                         goto finish;
@@ -156,15 +199,12 @@ int main(int argc, char *argv[]) {
                 write_one_line_file("/proc/sys/fs/binfmt_misc/status", "-1");
 
                 STRV_FOREACH(f, files) {
-                        int k;
-
                         k = apply_file(*f, true);
                         if (k < 0 && r == 0)
                                 r = k;
                 }
-
-                strv_free(files);
         }
+
 finish:
         return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
 }