udevadm verify: introduce --root option

When udevadm verify is invoked without positional arguments and loads
all rules files from the system like the udev daemon does, this option
can be used to operate on files underneath the specified root path.

man/udevadm.xml

@@ -769,6 +769,11 @@
             parsed. When set to <constant>never</constant>, names will
             never be resolved.</para>
           </listitem>
+          <term><option>--root=<replaceable>PATH</replaceable></option></term>
+          <listitem>
+            <para>When looking for udev rules files located in udev/rules.d directories,
+            operate on files underneath the specified root path <replaceable>PATH</replaceable>.</para>
+          </listitem>
         </varlistentry>
 
         <xi:include href="standard-options.xml" xpointer="help" />

shell-completion/bash/udevadm

@@ -64,7 +64,7 @@ _udevadm() {
         [MONITOR_ARG]='-s --subsystem-match -t --tag-match'
         [TEST]='-a --action -N --resolve-names'
         [TEST_BUILTIN]='-a --action'
-        [VERIFY]='-N --resolve-names'
+        [VERIFY]='-N --resolve-names --root'
         [WAIT]='-t --timeout --initialized=no --removed --settle'
         [LOCK]='-t --timeout -d --device -b --backing -p --print'
     )
@@ -254,6 +254,10 @@ _udevadm() {
                     -N|--resolve-names)
                         comps='early never'
                         ;;
+                    --root)
+                        comps=$(compgen -A directory -- "$cur" )
+                        compopt -o dirnames
+                        ;;
                     *)
                         comps=''
                         ;;

shell-completion/zsh/_udevadm

@@ -108,6 +108,7 @@ _udevadm_test-builtin(){
 _udevadm_verify(){
     _arguments \
         {-N+,--resolve-names=}'[When to resolve names.]:resolve:(early never)' \
+        '--root=[Operate on catalog hierarchy under specified directory]:directories:_directories' \
         {-h,--help}'[Print help text.]' \
         '*::files:_files'
 }

src/udev/udevadm-verify.c

@@ -10,12 +10,17 @@
 #include "conf-files.h"
 #include "constants.h"
 #include "log.h"
+#include "parse-argument.h"
 #include "pretty-print.h"
+#include "static-destruct.h"
 #include "strv.h"
 #include "udev-rules.h"
 #include "udevadm.h"
 
 static ResolveNameTiming arg_resolve_name_timing = RESOLVE_NAME_EARLY;
+static char *arg_root = NULL;
+
+STATIC_DESTRUCTOR_REGISTER(arg_root, freep);
 
 static int help(void) {
         _cleanup_free_ char *link = NULL;
@@ -30,6 +35,7 @@ static int help(void) {
                "  -h --help                            Show this help\n"
                "  -V --version                         Show package version\n"
                "  -N --resolve-names=early|never       When to resolve names\n"
+               "  --root=PATH                          Operate on an alternate filesystem root\n"
                "\nSee the %s for details.\n",
                program_invocation_short_name,
                ansi_highlight(),
@@ -40,14 +46,18 @@ static int help(void) {
 }
 
 static int parse_argv(int argc, char *argv[]) {
+        enum {
+                ARG_ROOT = 0x100,
+        };
         static const struct option options[] = {
-                { "help",          no_argument,       NULL, 'h' },
-                { "version",       no_argument,       NULL, 'V' },
-                { "resolve-names", required_argument, NULL, 'N' },
+                { "help",          no_argument,       NULL, 'h'         },
+                { "version",       no_argument,       NULL, 'V'         },
+                { "resolve-names", required_argument, NULL, 'N'         },
+                { "root",          required_argument, NULL, ARG_ROOT    },
                 {}
         };
 
-        int c;
+        int r, c;
 
         assert(argc >= 0);
         assert(argv);
@@ -71,12 +81,22 @@ static int parse_argv(int argc, char *argv[]) {
                         if (arg_resolve_name_timing == RESOLVE_NAME_NEVER)
                                 arg_resolve_name_timing = RESOLVE_NAME_LATE;
                         break;
+                case ARG_ROOT:
+                        r = parse_path_argument(optarg, /* suppress_root= */ true, &arg_root);
+                        if (r < 0)
+                                return r;
+                        break;
+
                 case '?':
                         return -EINVAL;
                 default:
                         assert_not_reached();
                 }
 
+        if (arg_root && optind < argc)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "Combination of --root= and FILEs is not supported.");
+
         return 1;
 }
 
@@ -124,9 +144,12 @@ int verify_main(int argc, char *argv[], void *userdata) {
                 const char* const* rules_dirs = STRV_MAKE_CONST(CONF_PATHS("udev/rules.d"));
                 _cleanup_strv_free_ char **files = NULL;
 
-                r = conf_files_list_strv(&files, ".rules", NULL, 0, rules_dirs);
+                r = conf_files_list_strv(&files, ".rules", arg_root, 0, rules_dirs);
                 if (r < 0)
                         return log_error_errno(r, "Failed to enumerate rules files: %m");
+                if (arg_root && strv_isempty(files))
+                        return log_error_errno(SYNTHETIC_ERRNO(ENOENT),
+                                               "No rules files found in %s", arg_root);
 
                 return verify_rules(rules, files);
         }