/* vi: set sw=4 ts=4: */
/*
 * mdev - Mini udev for busybox
 *
 * Copyright 2005 Rob Landley <rob@landley.net>
 * Copyright 2005 Frank Sorenson <frank@tuxrocks.com>
 *
 * Licensed under GPL version 2, see file LICENSE in this tarball for details.
 */
#include "libbb.h"
#include "xregex.h"

/* "mdev -s" scans /sys/class/xxx, looking for directories which have dev
 * file (it is of the form "M:m\n"). Example: /sys/class/tty/tty0/dev
 * contains "4:0\n". Directory name is taken as device name, path component
 * directly after /sys/class/ as subsystem. In this example, "tty0" and "tty".
 * Then mdev creates the /dev/device_name node.
 * If /sys/class/.../dev file does not exist, mdev still may act
 * on this device: see "@|$|*command args..." parameter in config file.
 *
 * mdev w/o parameters is called as hotplug helper. It takes device
 * and subsystem names from $DEVPATH and $SUBSYSTEM, extracts
 * maj,min from "/sys/$DEVPATH/dev" and also examines
 * $ACTION ("add"/"delete") and $FIRMWARE.
 *
 * If action is "add", mdev creates /dev/device_name similarly to mdev -s.
 * (todo: explain "delete" and $FIRMWARE)
 *
 * If /etc/mdev.conf exists, it may modify /dev/device_name's properties.
 * /etc/mdev.conf file format:
 *
 * [-][subsystem/]device  user:grp  mode  [>|=path] [@|$|*command args...]
 * [-]@maj,min[-min2]     user:grp  mode  [>|=path] [@|$|*command args...]
 * [-]$envvar=val         user:grp  mode  [>|=path] [@|$|*command args...]
 *
 * Leading minus in 1st field means "don't stop on this line", otherwise
 * search is stopped after the matching line is encountered.
 *
 * The device name or "subsystem/device" combo is matched against 1st field
 * (which is a regex), or maj,min is matched against 1st field,
 * or specified environment variable (as regex) is matched against 1st field.
 *
 * $envvar=val format is useful for loading modules for hot-plugged devices
 * which do not have driver loaded yet. In this case /sys/class/.../dev
 * does not exist, but $MODALIAS is set to needed module's name
 * (actually, an alias to it) by kernel. This rule instructs mdev
 * to load the module and exit:
 *    $MODALIAS=.* 0:0 660 @modprobe "$MODALIAS"
 * The kernel will generate another hotplug event when /sys/class/.../dev
 * file appears.
 *
 * When line matches, the device node is created, chmod'ed and chown'ed,
 * moved to path, and if >path, a symlink to moved node is created,
 * all this if /sys/class/.../dev exists.
 *    Examples:
 *    =loop/      - moves to /dev/loop
 *    >disk/sda%1 - moves to /dev/disk/sdaN, makes /dev/sdaN a symlink
 *
 * Then "command args..." is executed (via sh -c 'command args...').
 * @:execute on creation, $:on deletion, *:on both.
 * This happens regardless of /sys/class/.../dev existence.
 */

struct globals {
        int root_major, root_minor;
        char *subsystem;
} FIX_ALIASING;
#define G (*(struct globals*)&bb_common_bufsiz1)

/* Prevent infinite loops in /sys symlinks */
#define MAX_SYSFS_DEPTH 3

/* We use additional 64+ bytes in make_device() */
#define SCRATCH_SIZE 80

/* Builds an alias path.
 * This function potentionally reallocates the alias parameter.
 * Only used for ENABLE_FEATURE_MDEV_RENAME
 */
static char *build_alias(char *alias, const char *device_name)
{
        char *dest;

        /* ">bar/": rename to bar/device_name */
        /* ">bar[/]baz": rename to bar[/]baz */
        dest = strrchr(alias, '/');
        if (dest) { /* ">bar/[baz]" ? */
                *dest = '\0'; /* mkdir bar */
                bb_make_directory(alias, 0755, FILEUTILS_RECUR);
                *dest = '/';
                if (dest[1] == '\0') { /* ">bar/" => ">bar/device_name" */
                        dest = alias;
                        alias = concat_path_file(alias, device_name);
                        free(dest);
                }
        }

        return alias;
}

/* mknod in /dev based on a path like "/sys/block/hda/hda1"
 * NB1: path parameter needs to have SCRATCH_SIZE scratch bytes
 * after NUL, but we promise to not mangle (IOW: to restore if needed)
 * path string.
 * NB2: "mdev -s" may call us many times, do not leak memory/fds!
 */
static void make_device(char *path, int delete)
{
        char *device_name, *subsystem_slash_devname;
        int major, minor, type, len;
        mode_t mode;
        parser_t *parser;

        /* Try to read major/minor string.  Note that the kernel puts \n after
         * the data, so we don't need to worry about null terminating the string
         * because sscanf() will stop at the first nondigit, which \n is.
         * We also depend on path having writeable space after it.
         */
        major = -1;
        if (!delete) {
                char *dev_maj_min = path + strlen(path);

                strcpy(dev_maj_min, "/dev");
                len = open_read_close(path, dev_maj_min + 1, 64);
                *dev_maj_min = '\0';
                if (len < 1) {
                        if (!ENABLE_FEATURE_MDEV_EXEC)
                                return;
                        /* no "dev" file, but we can still run scripts
                         * based on device name */
                } else if (sscanf(++dev_maj_min, "%u:%u", &major, &minor) != 2) {
                        major = -1;
                }
        }
        /* else: for delete, -1 still deletes the node, but < -1 suppresses that */

        /* Determine device name, type, major and minor */
        device_name = (char*) bb_basename(path);
        /* http://kernel.org/doc/pending/hotplug.txt says that only
         * "/sys/block/..." is for block devices. "/sys/bus" etc is not.
         * But since 2.6.25 block devices are also in /sys/class/block.
         * We use strstr("/block/") to forestall future surprises. */
        type = S_IFCHR;
        if (strstr(path, "/block/") || (G.subsystem && strncmp(G.subsystem, "block", 5) == 0))
                type = S_IFBLK;

        /* Make path point to "subsystem/device_name" */
        subsystem_slash_devname = NULL;
        /* Check for coldplug invocations first */
        if (strncmp(path, "/sys/block/", 11) == 0) /* legacy case */
                path += sizeof("/sys/") - 1;
        else if (strncmp(path, "/sys/class/", 11) == 0)
                path += sizeof("/sys/class/") - 1;
        else {
                /* Example of a hotplug invocation:
                 * SUBSYSTEM="block"
                 * DEVPATH="/sys" + "/devices/virtual/mtd/mtd3/mtdblock3"
                 * ("/sys" is added by mdev_main)
                 * - path does not contain subsystem
                 */
                subsystem_slash_devname = concat_path_file(G.subsystem, device_name);
                path = subsystem_slash_devname;
        }

        /* If we have config file, look up user settings */
        if (ENABLE_FEATURE_MDEV_CONF)
                parser = config_open2("/etc/mdev.conf", fopen_for_read);

        do {
                int keep_matching;
                struct bb_uidgid_t ugid;
                char *tokens[4];
                char *command = NULL;
                char *alias = NULL;
                char aliaslink = aliaslink; /* for compiler */

                /* Defaults in case we won't match any line */
                ugid.uid = ugid.gid = 0;
                keep_matching = 0;
                mode = 0660;

                if (ENABLE_FEATURE_MDEV_CONF
                 && config_read(parser, tokens, 4, 3, "# \t", PARSE_NORMAL)
                ) {
                        char *val;
                        char *str_to_match;
                        regmatch_t off[1 + 9 * ENABLE_FEATURE_MDEV_RENAME_REGEXP];

                        val = tokens[0];
                        keep_matching = ('-' == val[0]);
                        val += keep_matching; /* swallow leading dash */

                        /* Match against either "subsystem/device_name"
                         * or "device_name" alone */
                        str_to_match = strchr(val, '/') ? path : device_name;

                        /* Fields: regex uid:gid mode [alias] [cmd] */

                        if (val[0] == '@') {
                                /* @major,minor[-minor2] */
                                /* (useful when name is ambiguous:
                                 * "/sys/class/usb/lp0" and
                                 * "/sys/class/printer/lp0") */
                                int cmaj, cmin0, cmin1, sc;
                                if (major < 0)
                                        continue; /* no dev, no match */
                                sc = sscanf(val, "@%u,%u-%u", &cmaj, &cmin0, &cmin1);
                                if (sc < 1
                                 || major != cmaj
                                 || (sc == 2 && minor != cmin0)
                                 || (sc == 3 && (minor < cmin0 || minor > cmin1))
                                ) {
                                        continue; /* this line doesn't match */
                                }
                                goto line_matches;
                        }
                        if (val[0] == '$') {
                                /* regex to match an environment variable */
                                char *eq = strchr(++val, '=');
                                if (!eq)
                                        continue;
                                *eq = '\0';
                                str_to_match = getenv(val);
                                if (!str_to_match)
                                        continue;
                                str_to_match -= strlen(val) + 1;
                                *eq = '=';
                        }
                        /* else: regex to match [subsystem/]device_name */

                        {
                                regex_t match;
                                int result;

                                xregcomp(&match, val, REG_EXTENDED);
                                result = regexec(&match, str_to_match, ARRAY_SIZE(off), off, 0);
                                regfree(&match);
                                //bb_error_msg("matches:");
                                //for (int i = 0; i < ARRAY_SIZE(off); i++) {
                                //      if (off[i].rm_so < 0) continue;
                                //      bb_error_msg("match %d: '%.*s'\n", i,
                                //              (int)(off[i].rm_eo - off[i].rm_so),
                                //              device_name + off[i].rm_so);
                                //}

                                /* If no match, skip rest of line */
                                /* (regexec returns whole pattern as "range" 0) */
                                if (result
                                 || off[0].rm_so
                                 || ((int)off[0].rm_eo != (int)strlen(str_to_match))
                                ) {
                                        continue; /* this line doesn't match */
                                }
                        }
 line_matches:
                        /* This line matches. Stop parsing after parsing
                         * the rest the line unless keep_matching == 1 */

                        /* 2nd field: uid:gid - device ownership */
                        if (get_uidgid(&ugid, tokens[1], 1) == 0)
                                bb_error_msg("unknown user/group %s on line %d", tokens[1], parser->lineno);

                        /* 3rd field: mode - device permissions */
                        bb_parse_mode(tokens[2], &mode);

                        val = tokens[3];
                        /* 4th field (opt): ">|=alias" or "!" to not create the node */

                        if (ENABLE_FEATURE_MDEV_RENAME && val) {
                                char *a, *s, *st;

                                a = val;
                                s = strchrnul(val, ' ');
                                st = strchrnul(val, '\t');
                                if (st < s)
                                        s = st;
                                st = (s[0] && s[1]) ? s+1 : NULL;

                                aliaslink = a[0];
                                if (aliaslink == '!' && s == a+1) {
                                        val = st;
                                        /* "!": suppress node creation/deletion */
                                        major = -2;
                                }
                                else if (aliaslink == '>' || aliaslink == '=') {
                                        val = st;
                                        s[0] = '\0';
                                        if (ENABLE_FEATURE_MDEV_RENAME_REGEXP) {
                                                char *p;
                                                unsigned i, n;

                                                /* substitute %1..9 with off[1..9], if any */
                                                n = 0;
                                                s = a;
                                                while (*s)
                                                        if (*s++ == '%')
                                                                n++;

                                                p = alias = xzalloc(strlen(a) + n * strlen(str_to_match));
                                                s = a + 1;
                                                while (*s) {
                                                        *p = *s;
                                                        if ('%' == *s) {
                                                                i = (s[1] - '0');
                                                                if (i <= 9 && off[i].rm_so >= 0) {
                                                                        n = off[i].rm_eo - off[i].rm_so;
                                                                        strncpy(p, str_to_match + off[i].rm_so, n);
                                                                        p += n - 1;
                                                                        s++;
                                                                }
                                                        }
                                                        p++;
                                                        s++;
                                                }
                                        } else {
                                                alias = xstrdup(a + 1);
                                        }
                                }
                        }

                        if (ENABLE_FEATURE_MDEV_EXEC && val) {
                                const char *s = "$@*";
                                const char *s2 = strchr(s, val[0]);

                                if (!s2) {
                                        bb_error_msg("bad line %u", parser->lineno);
                                        if (ENABLE_FEATURE_MDEV_RENAME)
                                                free(alias);
                                        continue;
                                }

                                /* Are we running this command now?
                                 * Run $cmd on delete, @cmd on create, *cmd on both
                                 */
                                if (s2 - s != delete) {
                                        /* We are here if: '*',
                                         * or: '@' and delete = 0,
                                         * or: '$' and delete = 1
                                         */
                                        command = xstrdup(val + 1);
                                }
                        }
                }

                /* End of field parsing */

                /* "Execute" the line we found */
                {
                        const char *node_name;

                        node_name = device_name;
                        if (ENABLE_FEATURE_MDEV_RENAME && alias)
                                node_name = alias = build_alias(alias, device_name);

                        if (!delete && major >= 0) {
                                if (mknod(node_name, mode | type, makedev(major, minor)) && errno != EEXIST)
                                        bb_perror_msg("can't create '%s'", node_name);
                                if (major == G.root_major && minor == G.root_minor)
                                        symlink(node_name, "root");
                                if (ENABLE_FEATURE_MDEV_CONF) {
                                        chmod(node_name, mode);
                                        chown(node_name, ugid.uid, ugid.gid);
                                }
                                if (ENABLE_FEATURE_MDEV_RENAME && alias) {
                                        if (aliaslink == '>')
                                                symlink(node_name, device_name);
                                }
                        }

                        if (ENABLE_FEATURE_MDEV_EXEC && command) {
                                /* setenv will leak memory, use putenv/unsetenv/free */
                                char *s = xasprintf("%s=%s", "MDEV", node_name);
                                char *s1 = xasprintf("%s=%s", "SUBSYSTEM", G.subsystem);
                                putenv(s);
                                putenv(s1);
                                if (system(command) == -1)
                                        bb_perror_msg("can't run '%s'", command);
                                bb_unsetenv_and_free(s1);
                                bb_unsetenv_and_free(s);
                                free(command);
                        }

                        if (delete && major >= -1) {
                                if (ENABLE_FEATURE_MDEV_RENAME && alias) {
                                        if (aliaslink == '>')
                                                unlink(device_name);
                                }
                                unlink(node_name);
                        }

                        if (ENABLE_FEATURE_MDEV_RENAME)
                                free(alias);
                }

                /* We found matching line.
                 * Stop unless it was prefixed with '-' */
                if (ENABLE_FEATURE_MDEV_CONF && !keep_matching)
                        break;

        /* end of "while line is read from /etc/mdev.conf" */
        } while (ENABLE_FEATURE_MDEV_CONF);

        if (ENABLE_FEATURE_MDEV_CONF)
                config_close(parser);
        free(subsystem_slash_devname);
}

/* File callback for /sys/ traversal */
static int FAST_FUNC fileAction(const char *fileName,
                struct stat *statbuf UNUSED_PARAM,
                void *userData,
                int depth UNUSED_PARAM)
{
        size_t len = strlen(fileName) - 4; /* can't underflow */
        char *scratch = userData;

        /* len check is for paranoid reasons */
        if (strcmp(fileName + len, "/dev") != 0 || len >= PATH_MAX)
                return FALSE;

        strcpy(scratch, fileName);
        scratch[len] = '\0';
        make_device(scratch, /*delete:*/ 0);

        return TRUE;
}

/* Directory callback for /sys/ traversal */
static int FAST_FUNC dirAction(const char *fileName UNUSED_PARAM,
                struct stat *statbuf UNUSED_PARAM,
                void *userData UNUSED_PARAM,
                int depth)
{
        /* Extract device subsystem -- the name of the directory
         * under /sys/class/ */
        if (1 == depth) {
                free(G.subsystem);
                G.subsystem = strrchr(fileName, '/');
                if (G.subsystem)
                        G.subsystem = xstrdup(G.subsystem + 1);
        }

        return (depth >= MAX_SYSFS_DEPTH ? SKIP : TRUE);
}

/* For the full gory details, see linux/Documentation/firmware_class/README
 *
 * Firmware loading works like this:
 * - kernel sets FIRMWARE env var
 * - userspace checks /lib/firmware/$FIRMWARE
 * - userspace waits for /sys/$DEVPATH/loading to appear
 * - userspace writes "1" to /sys/$DEVPATH/loading
 * - userspace copies /lib/firmware/$FIRMWARE into /sys/$DEVPATH/data
 * - userspace writes "0" (worked) or "-1" (failed) to /sys/$DEVPATH/loading
 * - kernel loads firmware into device
 */
static void load_firmware(const char *firmware, const char *sysfs_path)
{
        int cnt;
        int firmware_fd, loading_fd, data_fd;

        /* check for /lib/firmware/$FIRMWARE */
        xchdir("/lib/firmware");
        firmware_fd = xopen(firmware, O_RDONLY);

        /* in case we goto out ... */
        data_fd = -1;

        /* check for /sys/$DEVPATH/loading ... give 30 seconds to appear */
        xchdir(sysfs_path);
        for (cnt = 0; cnt < 30; ++cnt) {
                loading_fd = open("loading", O_WRONLY);
                if (loading_fd != -1)
                        goto loading;
                sleep(1);
        }
        goto out;

 loading:
        /* tell kernel we're loading by "echo 1 > /sys/$DEVPATH/loading" */
        if (full_write(loading_fd, "1", 1) != 1)
                goto out;

        /* load firmware into /sys/$DEVPATH/data */
        data_fd = open("data", O_WRONLY);
        if (data_fd == -1)
                goto out;
        cnt = bb_copyfd_eof(firmware_fd, data_fd);

        /* tell kernel result by "echo [0|-1] > /sys/$DEVPATH/loading" */
        if (cnt > 0)
                full_write(loading_fd, "0", 1);
        else
                full_write(loading_fd, "-1", 2);

 out:
        if (ENABLE_FEATURE_CLEAN_UP) {
                close(firmware_fd);
                close(loading_fd);
                close(data_fd);
        }
}

int mdev_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int mdev_main(int argc UNUSED_PARAM, char **argv)
{
        RESERVE_CONFIG_BUFFER(temp, PATH_MAX + SCRATCH_SIZE);

        /* We can be called as hotplug helper */
        /* Kernel cannot provide suitable stdio fds for us, do it ourself */
        bb_sanitize_stdio();

        /* Force the configuration file settings exactly */
        umask(0);

        xchdir("/dev");

        if (argv[1] && strcmp(argv[1], "-s") == 0) {
                /* Scan:
                 * mdev -s
                 */
                struct stat st;

                xstat("/", &st);
                G.root_major = major(st.st_dev);
                G.root_minor = minor(st.st_dev);

                /* ACTION_FOLLOWLINKS is needed since in newer kernels
                 * /sys/block/loop* (for example) are symlinks to dirs,
                 * not real directories.
                 * (kernel's CONFIG_SYSFS_DEPRECATED makes them real dirs,
                 * but we can't enforce that on users)
                 */
                if (access("/sys/class/block", F_OK) != 0) {
                        /* Scan obsolete /sys/block only if /sys/class/block
                         * doesn't exist. Otherwise we'll have dupes.
                         * Also, do not complain if it doesn't exist.
                         * Some people configure kernel to have no blockdevs.
                         */
                        recursive_action("/sys/block",
                                ACTION_RECURSE | ACTION_FOLLOWLINKS | ACTION_QUIET,
                                fileAction, dirAction, temp, 0);
                }
                recursive_action("/sys/class",
                        ACTION_RECURSE | ACTION_FOLLOWLINKS,
                        fileAction, dirAction, temp, 0);
        } else {
                char *fw;
                char *seq;
                char *action;
                char *env_path;
                static const char keywords[] ALIGN1 = "remove\0add\0";
                enum { OP_remove = 0, OP_add };
                smalluint op;

                /* Hotplug:
                 * env ACTION=... DEVPATH=... SUBSYSTEM=... [SEQNUM=...] mdev
                 * ACTION can be "add" or "remove"
                 * DEVPATH is like "/block/sda" or "/class/input/mice"
                 */
                action = getenv("ACTION");
                env_path = getenv("DEVPATH");
                G.subsystem = getenv("SUBSYSTEM");
                if (!action || !env_path /*|| !G.subsystem*/)
                        bb_show_usage();
                fw = getenv("FIRMWARE");
                op = index_in_strings(keywords, action);
                /* If it exists, does /dev/mdev.seq match $SEQNUM?
                 * If it does not match, earlier mdev is running
                 * in parallel, and we need to wait */
                seq = getenv("SEQNUM");
                if (seq) {
                        int timeout = 2000 / 32; /* 2000 msec */
                        do {
                                int seqlen;
                                char seqbuf[sizeof(int)*3 + 2];

                                seqlen = open_read_close("mdev.seq", seqbuf, sizeof(seqbuf-1));
                                if (seqlen < 0) {
                                        seq = NULL;
                                        break;
                                }
                                seqbuf[seqlen] = '\0';
                                if (seqbuf[0] == '\n' /* seed file? */
                                 || strcmp(seq, seqbuf) == 0 /* correct idx? */
                                ) {
                                        break;
                                }
                                usleep(32*1000);
                        } while (--timeout);
                }

                snprintf(temp, PATH_MAX, "/sys%s", env_path);
                if (op == OP_remove) {
                        /* Ignoring "remove firmware". It was reported
                         * to happen and to cause erroneous deletion
                         * of device nodes. */
                        if (!fw)
                                make_device(temp, /*delete:*/ 1);
                }
                else if (op == OP_add) {
                        make_device(temp, /*delete:*/ 0);
                        if (ENABLE_FEATURE_MDEV_LOAD_FIRMWARE) {
                                if (fw)
                                        load_firmware(fw, temp);
                        }
                }

                if (seq) {
                        xopen_xwrite_close("mdev.seq", utoa(xatou(seq) + 1));
                }
        }

        if (ENABLE_FEATURE_CLEAN_UP)
                RELEASE_CONFIG_BUFFER(temp);

        return EXIT_SUCCESS;
}