mdev: add environment variable match

function                                             old     new   delta
make_device                                         1998    2189    +191
clean_up_cur_rule                                     61      96     +35
dirAction                                             75      87     +12
mdev_main                                            838     849     +11
packed_usage                                       29272   29273      +1
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 5/0 up/down: 250/0)             Total: 250 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 71 insertions, 6 deletions

diff --git a/util-linux/mdev.c b/util-linux/mdev.c
index c592ef687..775e5c241 100644
--- a/util-linux/mdev.c
+++ b/util-linux/mdev.c
@@ -80,7 +80,7 @@
 //usage:        IF_FEATURE_MDEV_CONF(
 //usage:       "\n"
 //usage:       "It uses /etc/mdev.conf with lines\n"
-//usage:       "        [-]DEVNAME UID:GID PERM"
+//usage:       "        [-][ENV=regex;]...DEVNAME UID:GID PERM"
 //usage:                        IF_FEATURE_MDEV_RENAME(" [>|=PATH]|[!]")
 //usage:                        IF_FEATURE_MDEV_EXEC(" [@|$|*PROG]")
 //usage:       "\n"
@@ -233,6 +233,12 @@
 static const char keywords[] ALIGN1 = "add\0remove\0change\0";
 enum { OP_add, OP_remove };
 
+struct envmatch {
+        struct envmatch *next;
+        char *envname;
+        regex_t match;
+};
+
 struct rule {
         bool keep_matching;
         bool regex_compiled;
@@ -243,6 +249,7 @@ struct rule {
         char *ren_mov;
         IF_FEATURE_MDEV_EXEC(char *r_cmd;)
         regex_t match;
+        struct envmatch *envmatch;
 };
 
 struct globals {
@@ -288,14 +295,48 @@ static void make_default_cur_rule(void)
 
 static void clean_up_cur_rule(void)
 {
+        struct envmatch *e;
+
         free(G.cur_rule.envvar);
+        free(G.cur_rule.ren_mov);
         if (G.cur_rule.regex_compiled)
                 regfree(&G.cur_rule.match);
-        free(G.cur_rule.ren_mov);
         IF_FEATURE_MDEV_EXEC(free(G.cur_rule.r_cmd);)
+        e = G.cur_rule.envmatch;
+        while (e) {
+                free(e->envname);
+                regfree(&e->match);
+                e = e->next;
+        }
         make_default_cur_rule();
 }
 
+static char *parse_envmatch_pfx(char *val)
+{
+        struct envmatch **nextp = &G.cur_rule.envmatch;
+
+        for (;;) {
+                struct envmatch *e;
+                char *semicolon;
+                char *eq = strchr(val, '=');
+                if (!eq /* || eq == val? */)
+                        return val;
+                if (endofname(val) != eq)
+                        return val;
+                semicolon = strchr(eq, ';');
+                if (!semicolon)
+                        return val;
+                /* ENVVAR=regex;... */
+                *nextp = e = xzalloc(sizeof(*e));
+                nextp = &e->next;
+                e->envname = xstrndup(val, eq - val);
+                *semicolon = '\0';
+                xregcomp(&e->match, eq + 1, REG_EXTENDED);
+                *semicolon = ';';
+                val = semicolon + 1;
+        }
+}
+
 static void parse_next_rule(void)
 {
         /* Note: on entry, G.cur_rule is set to default */
@@ -314,6 +355,7 @@ static void parse_next_rule(void)
                 val = tokens[0];
                 G.cur_rule.keep_matching = ('-' == val[0]);
                 val += G.cur_rule.keep_matching; /* swallow leading dash */
+                val = parse_envmatch_pfx(val);
                 if (val[0] == '@') {
                         /* @major,minor[-minor2] */
                         /* (useful when name is ambiguous:
@@ -328,8 +370,10 @@ static void parse_next_rule(void)
                         if (sc == 2)
                                 G.cur_rule.min1 = G.cur_rule.min0;
                 } else {
+                        char *eq = strchr(val, '=');
                         if (val[0] == '$') {
-                                char *eq = strchr(++val, '=');
+                                /* $ENVVAR=regex ... */
+                                val++;
                                 if (!eq) {
                                         bb_error_msg("bad $envvar=regex on line %d", G.parser->lineno);
                                         goto next_rule;
@@ -423,6 +467,21 @@ static const struct rule *next_rule(void)
         return rule;
 }
 
+static int env_matches(struct envmatch *e)
+{
+        while (e) {
+                int r;
+                char *val = getenv(e->envname);
+                if (!val)
+                        return 0;
+                r = regexec(&e->match, val, /*size*/ 0, /*range[]*/ NULL, /*eflags*/ 0);
+                if (r != 0) /* no match */
+                        return 0;
+                e = e->next;
+        }
+        return 1;
+}
+
 #else
 
 # define next_rule() (&G.cur_rule)
@@ -537,6 +596,8 @@ static void make_device(char *device_name, char *path, int operation)
                 rule = next_rule();
 
 #if ENABLE_FEATURE_MDEV_CONF
+                if (!env_matches(rule->envmatch))
+                        continue;
                 if (rule->maj >= 0) {  /* @maj,min rule */
                         if (major != rule->maj)
                                 continue;
@@ -749,8 +810,10 @@ static int FAST_FUNC dirAction(const char *fileName UNUSED_PARAM,
         if (1 == depth) {
                 free(G.subsystem);
                 G.subsystem = strrchr(fileName, '/');
-                if (G.subsystem)
+                if (G.subsystem) {
                         G.subsystem = xstrdup(G.subsystem + 1);
+                        xsetenv("SUBSYSTEM", G.subsystem);
+                }
         }
 
         return (depth >= MAX_SYSFS_DEPTH ? SKIP : TRUE);
@@ -843,8 +906,8 @@ int mdev_main(int argc UNUSED_PARAM, char **argv)
         xchdir("/dev");
 
         if (argv[1] && strcmp(argv[1], "-s") == 0) {
-                /* Scan:
-                 * mdev -s
+                /*
+                 * Scan: mdev -s
                  */
                 struct stat st;
 
@@ -856,6 +919,8 @@ int mdev_main(int argc UNUSED_PARAM, char **argv)
                 G.root_major = major(st.st_dev);
                 G.root_minor = minor(st.st_dev);
 
+                putenv((char*)"ACTION=add");
+
                 /* ACTION_FOLLOWLINKS is needed since in newer kernels
                  * /sys/block/loop* (for example) are symlinks to dirs,
                  * not real directories.