binfmt: add binfmt tool to set up binfmt_misc at boot

src/binfmt.c

@@ -0,0 +1,187 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <stdlib.h>
+#include <stdbool.h>
+#include <errno.h>
+#include <string.h>
+#include <stdio.h>
+#include <limits.h>
+
+#include "log.h"
+#include "util.h"
+
+static int delete_rule(const char *rule) {
+        char *x, *fn, *e;
+        int r;
+
+        assert(rule[0]);
+
+        if (!(x = strdup(rule)))
+                return -ENOMEM;
+
+        e = strchrnul(x+1, x[0]);
+        *e = 0;
+
+        asprintf(&fn, "/proc/sys/fs/binfmt_misc/%s", x+1);
+        free(x);
+
+        if (!fn)
+                return -ENOMEM;
+
+        r = write_one_line_file(fn, "-1");
+        free(fn);
+
+        return r;
+}
+
+static int apply_rule(const char *rule) {
+        int r;
+
+        delete_rule(rule);
+
+        if ((r = write_one_line_file("/proc/sys/fs/binfmt_misc/register", rule)) < 0) {
+                log_error("Failed to add binary format: %s", strerror(-r));
+                return r;
+        }
+
+        return 0;
+}
+
+static int apply_file(const char *path, bool ignore_enoent) {
+        FILE *f;
+        int r = 0;
+
+        assert(path);
+
+        if (!(f = fopen(path, "re"))) {
+                if (ignore_enoent && errno == ENOENT)
+                        return 0;
+
+                log_error("Failed to open file '%s', ignoring: %m", path);
+                return -errno;
+        }
+
+        while (!feof(f)) {
+                char l[LINE_MAX], *p;
+                int k;
+
+                if (!fgets(l, sizeof(l), f)) {
+                        if (feof(f))
+                                break;
+
+                        log_error("Failed to read file '%s', ignoring: %m", path);
+                        r = -errno;
+                        goto finish;
+                }
+
+                p = strstrip(l);
+
+                if (!*p)
+                        continue;
+
+                if (strchr(COMMENTS, *p))
+                        continue;
+
+                if ((k = apply_rule(p)) < 0 && r == 0)
+                        r = k;
+        }
+
+finish:
+        fclose(f);
+
+        return r;
+}
+
+static int scandir_filter(const struct dirent *d) {
+        assert(d);
+
+        if (ignore_file(d->d_name))
+                return 0;
+
+        if (d->d_type != DT_REG &&
+            d->d_type != DT_LNK &&
+            d->d_type != DT_UNKNOWN)
+                return 0;
+
+        return endswith(d->d_name, ".conf");
+}
+
+static int apply_tree(const char *path) {
+        struct dirent **de = NULL;
+        int n, i, r = 0;
+
+        if ((n = scandir(path, &de, scandir_filter, alphasort)) < 0) {
+
+                if (errno == ENOENT)
+                        return 0;
+
+                log_error("Failed to enumerate %s files: %m", path);
+                return -errno;
+        }
+
+        for (i = 0; i < n; i++) {
+                char *fn;
+                int k;
+
+                k = asprintf(&fn, "%s/%s", path, de[i]->d_name);
+                free(de[i]);
+
+                if (k < 0) {
+                        log_error("Failed to allocate file name.");
+
+                        if (r == 0)
+                                r = -ENOMEM;
+                        continue;
+                }
+
+                if ((k = apply_file(fn, true)) < 0 && r == 0)
+                        r = k;
+        }
+
+        free(de);
+
+        return r;
+}
+
+int main(int argc, char *argv[]) {
+        int r = 0;
+
+        if (argc > 2) {
+                log_error("This program expects one or no arguments.");
+                return EXIT_FAILURE;
+        }
+
+        log_set_target(LOG_TARGET_AUTO);
+        log_parse_environment();
+        log_open();
+
+        if (argc > 1)
+                r = apply_file(argv[1], false);
+        else {
+                /* Flush out all rules */
+                write_one_line_file("/proc/sys/fs/binfmt_misc/status", "-1");
+
+                r = apply_tree("/etc/binfmt.d");
+        }
+
+        return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
+}

src/util.c

@@ -513,7 +513,16 @@ int write_one_line_file(const char *fn, const char *line) {
         if (!endswith(line, "\n"))
                 fputc('\n', f);
 
-        r = 0;
+        fflush(f);
+
+        if (ferror(f)) {
+                if (errno != 0)
+                        r = -errno;
+                else
+                        r = -EIO;
+        } else
+                r = 0;
+
 finish:
         fclose(f);
         return r;