init: add subsystem rules to ueventd.rc

By default ueventd creates device nodes under /dev based on the ueventd
DEVPATH.  Several subsystems have special rules which are hardcoded in
devices.c.  Moving forward these special rules should go in ueventd.rc.

Special rules have the syntax:

	subsystem <s>
		devname (uevent_devname|uevent_devpath)
		[dirname <dir>]

Devices matching SUBSYSTEM=<s> will be populated under <dir>.  dirname
is optional and defaults to /dev.  If dirname is provided, <dir> must
start with "/".

If devname is uevent_devname, ueventd will create the device node as
<dir>/DEVNAME.  DEVNAME may include intermediate subdirectories, which
ueventd will automatically create.

If devname is uevent_devpath, ueventd will use the legacy behavior of
computing DEVPATH_BASE=basepath(DEVPATH), and creating the device node
as <dir>/DEVPATH_BASE.

The new parsing code is based on init_parser.c, with small tweaks to
handle commands which don't fall under a section header.

Change-Id: I3bd1b59d7e62dfc9d289cf6ae889e237fb5bd7c5
Signed-off-by: Greg Hackmann <ghackmann@google.com>

5 files changed, 268 insertions, 33 deletions

diff --git a/init/devices.c b/init/devices.c
index 2551ca83f..f7df45340 100644
--- a/init/devices.c
+++ b/init/devices.c
@@ -44,6 +44,7 @@
 #include <cutils/uevent.h>
 
 #include "devices.h"
+#include "ueventd_parser.h"
 #include "util.h"
 #include "log.h"
 
@@ -560,48 +561,76 @@ static void handle_block_device_event(struct uevent *uevent)
             uevent->major, uevent->minor, links);
 }
 
+#define DEVPATH_LEN 96
+
+static bool assemble_devpath(char *devpath, const char *dirname,
+        const char *devname)
+{
+    int s = snprintf(devpath, DEVPATH_LEN, "%s/%s", dirname, devname);
+    if (s < 0) {
+        ERROR("failed to assemble device path (%s); ignoring event\n",
+                strerror(errno));
+        return false;
+    } else if (s >= DEVPATH_LEN) {
+        ERROR("%s/%s exceeds %u-character limit on path; ignoring event\n",
+                dirname, devname, DEVPATH_LEN);
+        return false;
+    }
+    return true;
+}
+
+static void mkdir_recursive_for_devpath(const char *devpath)
+{
+    char dir[DEVPATH_LEN];
+    char *slash;
+
+    strcpy(dir, devpath);
+    slash = strrchr(dir, '/');
+    *slash = '\0';
+    mkdir_recursive(dir, 0755);
+}
+
 static void handle_generic_device_event(struct uevent *uevent)
 {
     char *base;
     const char *name;
-    char devpath[96] = {0};
+    char devpath[DEVPATH_LEN] = {0};
     char **links = NULL;
 
     name = parse_device_name(uevent, 64);
     if (!name)
         return;
 
-    if (!strncmp(uevent->subsystem, "usb", 3)) {
+    struct ueventd_subsystem *subsystem =
+            ueventd_subsystem_find_by_name(uevent->subsystem);
+
+    if (subsystem) {
+        const char *devname;
+
+        switch (subsystem->devname_src) {
+        case DEVNAME_UEVENT_DEVNAME:
+            devname = uevent->device_name;
+            break;
+
+        case DEVNAME_UEVENT_DEVPATH:
+            devname = name;
+            break;
+
+        default:
+            ERROR("%s subsystem's devpath option is not set; ignoring event\n",
+                    uevent->subsystem);
+            return;
+        }
+
+        if (!assemble_devpath(devpath, subsystem->dirname, devname))
+            return;
+        mkdir_recursive_for_devpath(devpath);
+    } else if (!strncmp(uevent->subsystem, "usb", 3)) {
          if (!strcmp(uevent->subsystem, "usb")) {
             if (uevent->device_name) {
-                /*
-                 * create device node provided by kernel if present
-                 * see drivers/base/core.c
-                 */
-                char *p = devpath;
-                int s = snprintf(devpath, sizeof(devpath), "/dev/%s",
-                        uevent->device_name);
-                if (s < 0) {
-                    ERROR("failed to assemble device path (%s); ignoring event\n",
-                            strerror(errno));
-                    return;
-                } else if ((size_t)s >= sizeof(devpath)) {
-                    ERROR("/dev/%s exceeds %u-character limit on path; ignoring event\n",
-                            uevent->device_name, sizeof(devpath));
+                if (!assemble_devpath(devpath, "/dev", uevent->device_name))
                     return;
-                }
-
-                /* skip leading /dev/ */
-                p += 5;
-                /* build directories */
-                while (*p) {
-                    if (*p == '/') {
-                        *p = 0;
-                        make_dir(devpath, 0755);
-                        *p = '/';
-                    }
-                    p++;
-                }
+                mkdir_recursive_for_devpath(devpath);
              }
              else {
                  /* This imitates the file system that would be created
diff --git a/init/ueventd.h b/init/ueventd.h
index 9066e4780..0a454c5ab 100644
--- a/init/ueventd.h
+++ b/init/ueventd.h
@@ -17,6 +17,21 @@
 #ifndef _INIT_UEVENTD_H_
 #define _INIT_UEVENTD_H_
 
+#include <cutils/list.h>
+#include <sys/types.h>
+
+struct ueventd_subsystem {
+    struct listnode slist;
+
+    const char *name;
+    enum {
+        DEVNAME_UNKNOWN = 0,
+        DEVNAME_UEVENT_DEVNAME,
+        DEVNAME_UEVENT_DEVPATH,
+    } devname_src;
+    const char *dirname;
+};
+
 int ueventd_main(int argc, char **argv);
 
 #endif
diff --git a/init/ueventd_keywords.h b/init/ueventd_keywords.h
new file mode 100644
index 000000000..88e8f0158
--- /dev/null
+++ b/init/ueventd_keywords.h
@@ -0,0 +1,15 @@
+#ifndef KEYWORD
+#define __MAKE_KEYWORD_ENUM__
+#define KEYWORD(symbol, flags, nargs) K_##symbol,
+enum {
+    K_UNKNOWN,
+#endif
+    KEYWORD(subsystem,      SECTION,    1)
+    KEYWORD(devname,        OPTION,     1)
+    KEYWORD(dirname,        OPTION,     1)
+#ifdef __MAKE_KEYWORD_ENUM__
+    KEYWORD_COUNT,
+};
+#undef __MAKE_KEYWORD_ENUM__
+#undef KEYWORD
+#endif
diff --git a/init/ueventd_parser.c b/init/ueventd_parser.c
index 3e60df5b8..e447006e5 100644
--- a/init/ueventd_parser.c
+++ b/init/ueventd_parser.c
@@ -14,18 +14,189 @@
  * limitations under the License.
  */
 
+#include <ctype.h>
+#include <errno.h>
 #include <stdio.h>
 #include <unistd.h>
 #include <stdarg.h>
+#include <stdlib.h>
 #include <string.h>
 
+#include "ueventd.h"
 #include "ueventd_parser.h"
 #include "parser.h"
 #include "log.h"
 #include "util.h"
 
+static list_declare(subsystem_list);
+
 static void parse_line_device(struct parse_state *state, int nargs, char **args);
 
+#define SECTION 0x01
+#define OPTION  0x02
+
+#include "ueventd_keywords.h"
+
+#define KEYWORD(symbol, flags, nargs) \
+    [ K_##symbol ] = { #symbol, nargs + 1, flags, },
+
+static struct {
+    const char *name;
+    unsigned char nargs;
+    unsigned char flags;
+} keyword_info[KEYWORD_COUNT] = {
+    [ K_UNKNOWN ] = { "unknown", 0, 0 },
+#include "ueventd_keywords.h"
+};
+#undef KEYWORD
+
+#define kw_is(kw, type) (keyword_info[kw].flags & (type))
+#define kw_nargs(kw) (keyword_info[kw].nargs)
+
+static int lookup_keyword(const char *s)
+{
+    switch (*s++) {
+    case 'd':
+        if (!strcmp(s, "evname")) return K_devname;
+        if (!strcmp(s, "irname")) return K_dirname;
+        break;
+    case 's':
+        if (!strcmp(s, "ubsystem")) return K_subsystem;
+        break;
+    }
+    return K_UNKNOWN;
+}
+
+static void parse_line_no_op(struct parse_state *state __attribute__((unused)),
+        int nargs __attribute__((unused)), char **args  __attribute__((unused)))
+{
+}
+
+static int valid_name(const char *name)
+{
+    while (*name) {
+        if (!isalnum(*name) && (*name != '_') && (*name != '-')) {
+            return 0;
+        }
+        name++;
+    }
+    return 1;
+}
+
+struct ueventd_subsystem *ueventd_subsystem_find_by_name(const char *name)
+{
+    struct listnode *node;
+    struct ueventd_subsystem *s;
+
+    list_for_each(node, &subsystem_list) {
+        s = node_to_item(node, struct ueventd_subsystem, slist);
+        if (!strcmp(s->name, name)) {
+            return s;
+        }
+    }
+    return 0;
+}
+
+static void *parse_subsystem(struct parse_state *state,
+        int nargs __attribute__((unused)), char **args)
+{
+    struct ueventd_subsystem *s;
+
+    if (!valid_name(args[1])) {
+        parse_error(state, "invalid subsystem name '%s'\n", args[1]);
+        return 0;
+    }
+
+    s = ueventd_subsystem_find_by_name(args[1]);
+    if (s) {
+        parse_error(state, "ignored duplicate definition of subsystem '%s'\n",
+                args[1]);
+        return 0;
+    }
+
+    s = calloc(1, sizeof(*s));
+    if (!s) {
+        parse_error(state, "out of memory\n");
+        return 0;
+    }
+    s->name = args[1];
+    s->dirname = "/dev";
+    list_add_tail(&subsystem_list, &s->slist);
+    return s;
+}
+
+static void parse_line_subsystem(struct parse_state *state, int nargs,
+        char **args)
+{
+    struct ueventd_subsystem *s = state->context;
+    int kw;
+
+    if (nargs == 0) {
+        return;
+    }
+
+    kw = lookup_keyword(args[0]);
+    switch (kw) {
+    case K_devname:
+        if (!strcmp(args[1], "uevent_devname"))
+            s->devname_src = DEVNAME_UEVENT_DEVNAME;
+        else if (!strcmp(args[1], "uevent_devpath"))
+            s->devname_src = DEVNAME_UEVENT_DEVPATH;
+        else
+            parse_error(state, "invalid devname '%s'\n", args[1]);
+        break;
+
+    case K_dirname:
+        if (args[1][0] == '/')
+            s->dirname = args[1];
+        else
+            parse_error(state, "dirname '%s' does not start with '/'\n",
+                    args[1]);
+        break;
+
+    default:
+        parse_error(state, "invalid option '%s'\n", args[0]);
+    }
+}
+
+static void parse_new_section(struct parse_state *state, int kw,
+                       int nargs, char **args)
+{
+    printf("[ %s %s ]\n", args[0],
+           nargs > 1 ? args[1] : "");
+
+    switch(kw) {
+    case K_subsystem:
+        state->context = parse_subsystem(state, nargs, args);
+        if (state->context) {
+            state->parse_line = parse_line_subsystem;
+            return;
+        }
+        break;
+    }
+    state->parse_line = parse_line_no_op;
+}
+
+static void parse_line(struct parse_state *state, char **args, int nargs)
+{
+    int kw = lookup_keyword(args[0]);
+    int kw_nargs = kw_nargs(kw);
+
+    if (nargs < kw_nargs) {
+        parse_error(state, "%s requires %d %s\n", args[0], kw_nargs - 1,
+            kw_nargs > 2 ? "arguments" : "argument");
+        return;
+    }
+
+    if (kw_is(kw, SECTION)) {
+        parse_new_section(state, kw, nargs, args);
+    } else if (kw_is(kw, OPTION)) {
+        state->parse_line(state, nargs, args);
+    } else {
+        parse_line_device(state, nargs, args);
+    }
+}
+
 static void parse_config(const char *fn, char *s)
 {
     struct parse_state state;
@@ -36,18 +207,19 @@ static void parse_config(const char *fn, char *s)
     state.line = 1;
     state.ptr = s;
     state.nexttoken = 0;
-    state.parse_line = parse_line_device;
+    state.parse_line = parse_line_no_op;
     for (;;) {
         int token = next_token(&state);
         switch (token) {
         case T_EOF:
-            state.parse_line(&state, 0, 0);
+            parse_line(&state, args, nargs);
             return;
         case T_NEWLINE:
             if (nargs) {
-                state.parse_line(&state, nargs, args);
+                parse_line(&state, args, nargs);
                 nargs = 0;
             }
+            state.line++;
             break;
         case T_TEXT:
             if (nargs < UEVENTD_PARSER_MAXARGS) {
@@ -69,7 +241,8 @@ int ueventd_parse_config_file(const char *fn)
     return 0;
 }
 
-static void parse_line_device(struct parse_state* state, int nargs, char **args)
+static void parse_line_device(struct parse_state *state __attribute__((unused)),
+        int nargs, char **args)
 {
     set_device_permission(nargs, args);
 }
diff --git a/init/ueventd_parser.h b/init/ueventd_parser.h
index 3684285aa..907cc49de 100644
--- a/init/ueventd_parser.h
+++ b/init/ueventd_parser.h
@@ -17,9 +17,12 @@
 #ifndef _INIT_UEVENTD_PARSER_H_
 #define _INIT_UEVENTD_PARSER_H_
 
+#include "ueventd.h"
+
 #define UEVENTD_PARSER_MAXARGS 5
 
 int ueventd_parse_config_file(const char *fn);
 void set_device_permission(int nargs, char **args);
+struct ueventd_subsystem *ueventd_subsystem_find_by_name(const char *name);
 
 #endif