source: MondoRescue/branches/3.0/mindi-busybox/util-linux/mdev.c@ 2899

/* 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 GPLv2, see file LICENSE in this source tree.
 */
#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;
}