src/binfmt/binfmt.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <errno.h>
   4 #include <getopt.h>
   5 #include <limits.h>
   6 #include <stdbool.h>
   7 #include <stdio.h>
   8 #include <stdlib.h>
   9 #include <sys/stat.h>
  10 #include <sys/types.h>
  11
  12 #include "alloc-util.h"
  13 #include "binfmt-util.h"
  14 #include "build.h"
  15 #include "conf-files.h"
  16 #include "constants.h"
  17 #include "fd-util.h"
  18 #include "fileio.h"
  19 #include "log.h"
  20 #include "main-func.h"
  21 #include "pager.h"
  22 #include "path-util.h"
  23 #include "pretty-print.h"
  24 #include "string-util.h"
  25 #include "strv.h"
  26
  27 static CatFlags arg_cat_flags = CAT_CONFIG_OFF;
  28 static PagerFlags arg_pager_flags = 0;
  29 static bool arg_unregister = false;
  30
  31 static int delete_rule(const char *rulename) {
  32         const char *fn = strjoina("/proc/sys/fs/binfmt_misc/", rulename);
  33         return write_string_file(fn, "-1", WRITE_STRING_FILE_DISABLE_BUFFER);
  34 }
  35
  36 static int apply_rule(const char *filename, unsigned line, const char *rule) {
  37         assert(filename);
  38         assert(line > 0);
  39         assert(rule);
  40         assert(rule[0]);
  41
  42         _cleanup_free_ char *rulename = NULL;
  43         int r;
  44
  45         rulename = strdupcspn(rule + 1, CHAR_TO_STR(rule[0]));
  46         if (!rulename)
  47                 return log_oom();
  48
  49         if (!filename_is_valid(rulename) ||
  50             STR_IN_SET(rulename, "register", "status"))
  51                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
  52                                        "%s:%u: Rule name '%s' is not valid, refusing.",
  53                                        filename, line, rulename);
  54         r = delete_rule(rulename);
  55         if (r < 0 && r != -ENOENT)
  56                 log_warning_errno(r, "%s:%u: Failed to delete rule '%s', ignoring: %m",
  57                                   filename, line, rulename);
  58         if (r >= 0)
  59                 log_debug("%s:%u: Rule '%s' deleted.", filename, line, rulename);
  60
  61         r = write_string_file("/proc/sys/fs/binfmt_misc/register", rule, WRITE_STRING_FILE_DISABLE_BUFFER);
  62         if (r < 0)
  63                 return log_error_errno(r, "%s:%u: Failed to add binary format '%s': %m",
  64                                        filename, line, rulename);
  65
  66         log_debug("%s:%u: Binary format '%s' registered.", filename, line, rulename);
  67         return 0;
  68 }
  69
  70 static int apply_file(const char *filename, bool ignore_enoent) {
  71         _cleanup_fclose_ FILE *f = NULL;
  72         _cleanup_free_ char *pp = NULL;
  73         int r;
  74
  75         assert(filename);
  76
  77         r = search_and_fopen(filename, "re", NULL, (const char**) CONF_PATHS_STRV("binfmt.d"), &f, &pp);
  78         if (r < 0) {
  79                 if (ignore_enoent && r == -ENOENT)
  80                         return 0;
  81
  82                 return log_error_errno(r, "Failed to open file '%s': %m", filename);
  83         }
  84
  85         log_debug("Applying %s%s", pp, special_glyph(SPECIAL_GLYPH_ELLIPSIS));
  86         for (unsigned line = 1;; line++) {
  87                 _cleanup_free_ char *text = NULL;
  88                 int k;
  89
  90                 k = read_stripped_line(f, LONG_LINE_MAX, &text);
  91                 if (k < 0)
  92                         return log_error_errno(k, "Failed to read file '%s': %m", pp);
  93                 if (k == 0)
  94                         break;
  95
  96                 if (isempty(text))
  97                         continue;
  98                 if (strchr(COMMENTS, text[0]))
  99                         continue;
 100
 101                 RET_GATHER(r, apply_rule(filename, line, text));
 102         }
 103
 104         return r;
 105 }
 106
 107 static int cat_config(char **files) {
 108         pager_open(arg_pager_flags);
 109
 110         return cat_files(NULL, files, arg_cat_flags);
 111 }
 112
 113 static int help(void) {
 114         _cleanup_free_ char *link = NULL;
 115         int r;
 116
 117         r = terminal_urlify_man("systemd-binfmt.service", "8", &link);
 118         if (r < 0)
 119                 return log_oom();
 120
 121         printf("%s [OPTIONS...] [CONFIGURATION FILE...]\n\n"
 122                "Registers binary formats with the kernel.\n\n"
 123                "  -h --help             Show this help\n"
 124                "     --version          Show package version\n"
 125                "     --cat-config       Show configuration files\n"
 126                "     --tldr             Show non-comment parts of configuration\n"
 127                "     --no-pager         Do not pipe output into a pager\n"
 128                "     --unregister       Unregister all existing entries\n"
 129                "\nSee the %s for details.\n",
 130                program_invocation_short_name,
 131                link);
 132
 133         return 0;
 134 }
 135
 136 static int parse_argv(int argc, char *argv[]) {
 137         enum {
 138                 ARG_VERSION = 0x100,
 139                 ARG_CAT_CONFIG,
 140                 ARG_TLDR,
 141                 ARG_NO_PAGER,
 142                 ARG_UNREGISTER,
 143         };
 144
 145         static const struct option options[] = {
 146                 { "help",       no_argument, NULL, 'h'            },
 147                 { "version",    no_argument, NULL, ARG_VERSION    },
 148                 { "cat-config", no_argument, NULL, ARG_CAT_CONFIG },
 149                 { "tldr",       no_argument, NULL, ARG_TLDR       },
 150                 { "no-pager",   no_argument, NULL, ARG_NO_PAGER   },
 151                 { "unregister", no_argument, NULL, ARG_UNREGISTER },
 152                 {}
 153         };
 154
 155         int c;
 156
 157         assert(argc >= 0);
 158         assert(argv);
 159
 160         while ((c = getopt_long(argc, argv, "h", options, NULL)) >= 0)
 161
 162                 switch (c) {
 163
 164                 case 'h':
 165                         return help();
 166
 167                 case ARG_VERSION:
 168                         return version();
 169
 170                 case ARG_CAT_CONFIG:
 171                         arg_cat_flags = CAT_CONFIG_ON;
 172                         break;
 173
 174                 case ARG_TLDR:
 175                         arg_cat_flags = CAT_TLDR;
 176                         break;
 177
 178                 case ARG_NO_PAGER:
 179                         arg_pager_flags |= PAGER_DISABLE;
 180                         break;
 181
 182                 case ARG_UNREGISTER:
 183                         arg_unregister = true;
 184                         break;
 185
 186                 case '?':
 187                         return -EINVAL;
 188
 189                 default:
 190                         assert_not_reached();
 191                 }
 192
 193         if ((arg_unregister || arg_cat_flags != CAT_CONFIG_OFF) && argc > optind)
 194                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
 195                                        "Positional arguments are not allowed with --cat-config/--tldr or --unregister.");
 196
 197         return 1;
 198 }
 199
 200 static int binfmt_mounted_warn(void) {
 201         int r;
 202
 203         r = binfmt_mounted();
 204         if (r < 0)
 205                 return log_error_errno(r, "Failed to check if /proc/sys/fs/binfmt_misc is mounted: %m");
 206         if (r == 0)
 207                 log_debug("/proc/sys/fs/binfmt_misc is not mounted in read-write mode, skipping.");
 208
 209         return r;
 210 }
 211
 212 static int run(int argc, char *argv[]) {
 213         int r;
 214
 215         r = parse_argv(argc, argv);
 216         if (r <= 0)
 217                 return r;
 218
 219         log_setup();
 220
 221         umask(0022);
 222
 223         r = 0;
 224
 225         if (arg_unregister)
 226                 return disable_binfmt();
 227
 228         if (argc > optind) {
 229                 r = binfmt_mounted_warn();
 230                 if (r <= 0)
 231                         return r;
 232
 233                 for (int i = optind; i < argc; i++)
 234                         RET_GATHER(r, apply_file(argv[i], false));
 235
 236         } else {
 237                 _cleanup_strv_free_ char **files = NULL;
 238
 239                 r = conf_files_list_strv(&files, ".conf", NULL, 0, (const char**) CONF_PATHS_STRV("binfmt.d"));
 240                 if (r < 0)
 241                         return log_error_errno(r, "Failed to enumerate binfmt.d files: %m");
 242
 243                 if (arg_cat_flags != CAT_CONFIG_OFF)
 244                         return cat_config(files);
 245
 246                 r = binfmt_mounted_warn();
 247                 if (r <= 0)
 248                         return r;
 249
 250                 /* Flush out all rules */
 251                 r = write_string_file("/proc/sys/fs/binfmt_misc/status", "-1", WRITE_STRING_FILE_DISABLE_BUFFER);
 252                 if (r < 0)
 253                         log_warning_errno(r, "Failed to flush binfmt_misc rules, ignoring: %m");
 254                 else
 255                         log_debug("Flushed all binfmt_misc rules.");
 256
 257                 STRV_FOREACH(f, files)
 258                         RET_GATHER(r, apply_file(*f, true));
 259         }
 260
 261         return r;
 262 }
 263
 264 DEFINE_MAIN_FUNCTION(run);