source: MondoRescue/branches/3.3/mindi-busybox/libbb/appletlib.c@ 3621

/* vi: set sw=4 ts=4: */
/*
 * Utility routines.
 *
 * Copyright (C) tons of folks.  Tracking down who wrote what
 * isn't something I'm going to worry about...  If you wrote something
 * here, please feel free to acknowledge your work.
 *
 * Based in part on code from sash, Copyright (c) 1999 by David I. Bell
 * Permission has been granted to redistribute this code under GPL.
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

/* We are trying to not use printf, this benefits the case when selected
 * applets are really simple. Example:
 *
 * $ ./busybox
 * ...
 * Currently defined functions:
 *         basename, false, true
 *
 * $ size busybox
 *    text    data     bss     dec     hex filename
 *    4473      52      72    4597    11f5 busybox
 *
 * FEATURE_INSTALLER or FEATURE_SUID will still link printf routines in. :(
 */
#include "busybox.h"

#if !(defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__NetBSD__) \
    || defined(__APPLE__) \
    )
# include <malloc.h> /* for mallopt */
#endif


/* Declare <applet>_main() */
#define PROTOTYPES
#include "applets.h"
#undef PROTOTYPES

/* Include generated applet names, pointers to <applet>_main, etc */
#include "applet_tables.h"
/* ...and if applet_tables generator says we have only one applet... */
#ifdef SINGLE_APPLET_MAIN
# undef ENABLE_FEATURE_INDIVIDUAL
# define ENABLE_FEATURE_INDIVIDUAL 1
# undef IF_FEATURE_INDIVIDUAL
# define IF_FEATURE_INDIVIDUAL(...) __VA_ARGS__
#endif

#include "usage_compressed.h"

static void run_applet_and_exit(const char *name, char **argv) NORETURN;

#if ENABLE_SHOW_USAGE && !ENABLE_FEATURE_COMPRESS_USAGE
static const char usage_messages[] ALIGN1 = UNPACKED_USAGE;
#else
# define usage_messages 0
#endif

#if ENABLE_FEATURE_COMPRESS_USAGE

static const char packed_usage[] ALIGN1 = { PACKED_USAGE };
# include "bb_archive.h"
static const char *unpack_usage_messages(void)
{
    char *outbuf = NULL;
    bunzip_data *bd;
    int i;

    i = start_bunzip(&bd,
            /* src_fd: */ -1,
            /* inbuf:  */ packed_usage,
            /* len:    */ sizeof(packed_usage));
    /* read_bunzip can longjmp to start_bunzip, and ultimately
     * end up here with i != 0 on read data errors! Not trivial */
    if (!i) {
        /* Cannot use xmalloc: will leak bd in NOFORK case! */
        outbuf = malloc_or_warn(sizeof(UNPACKED_USAGE));
        if (outbuf)
            read_bunzip(bd, outbuf, sizeof(UNPACKED_USAGE));
    }
    dealloc_bunzip(bd);
    return outbuf;
}
# define dealloc_usage_messages(s) free(s)

#else

# define unpack_usage_messages() usage_messages
# define dealloc_usage_messages(s) ((void)(s))

#endif /* FEATURE_COMPRESS_USAGE */


void FAST_FUNC bb_show_usage(void)
{
    if (ENABLE_SHOW_USAGE) {
#ifdef SINGLE_APPLET_STR
        /* Imagine that this applet is "true". Dont suck in printf! */
        const char *usage_string = unpack_usage_messages();

        if (*usage_string == '\b') {
            full_write2_str("No help available.\n\n");
        } else {
            full_write2_str("Usage: "SINGLE_APPLET_STR" ");
            full_write2_str(usage_string);
            full_write2_str("\n\n");
        }
        if (ENABLE_FEATURE_CLEAN_UP)
            dealloc_usage_messages((char*)usage_string);
#else
        const char *p;
        const char *usage_string = p = unpack_usage_messages();
        int ap = find_applet_by_name(applet_name);

        if (ap < 0) /* never happens, paranoia */
            xfunc_die();
        while (ap) {
            while (*p++) continue;
            ap--;
        }
        full_write2_str(bb_banner);
        full_write2_str(" multi-call binary.\n");
        if (*p == '\b')
            full_write2_str("\nNo help available.\n\n");
        else {
            full_write2_str("\nUsage: ");
            full_write2_str(applet_name);
            full_write2_str(" ");
            full_write2_str(p);
            full_write2_str("\n");
        }
        if (ENABLE_FEATURE_CLEAN_UP)
            dealloc_usage_messages((char*)usage_string);
#endif
    }
    xfunc_die();
}

int FAST_FUNC find_applet_by_name(const char *name)
{
    unsigned i, max;
    int j;
    const char *p;

/* The commented-out word-at-a-time code is ~40% faster, but +160 bytes.
 * "Faster" here saves ~0.5 microsecond of real time - not worth it.
 */
#if 0 /*BB_UNALIGNED_MEMACCESS_OK && BB_LITTLE_ENDIAN*/
    uint32_t n32;

    /* Handle all names < 2 chars long early */
    if (name[0] == '\0')
        return -1; /* "" is not a valid applet name */
    if (name[1] == '\0') {
        if (!ENABLE_TEST)
            return -1; /* 1-char name is not valid */
        if (name[0] != ']')
            return -1; /* 1-char name which isn't "[" is not valid */
        /* applet "[" is always applet #0: */
        return 0;
    }
#endif

    p = applet_names;
    i = 0;
#if KNOWN_APPNAME_OFFSETS <= 0
    max = NUM_APPLETS;
#else
    max = NUM_APPLETS * KNOWN_APPNAME_OFFSETS;
    for (j = ARRAY_SIZE(applet_nameofs)-1; j >= 0; j--) {
        const char *pp = applet_names + applet_nameofs[j];
        if (strcmp(name, pp) >= 0) {
            //bb_error_msg("name:'%s' >= pp:'%s'", name, pp);
            p = pp;
            i = max - NUM_APPLETS;
            break;
        }
        max -= NUM_APPLETS;
    }
    max /= (unsigned)KNOWN_APPNAME_OFFSETS;
    i /= (unsigned)KNOWN_APPNAME_OFFSETS;
    //bb_error_msg("name:'%s' starting from:'%s' i:%u max:%u", name, p, i, max);
#endif

    /* Open-coded linear search without strcmp/strlen calls for speed */

#if 0 /*BB_UNALIGNED_MEMACCESS_OK && BB_LITTLE_ENDIAN*/
    /* skip "[\0" name, it's surely not it */
    if (ENABLE_TEST && LONE_CHAR(p, '['))
        i++, p += 2;
    /* All remaining applet names in p[] are at least 2 chars long */
    /* name[] is also at least 2 chars long */

    n32 = (name[0] << 0) | (name[1] << 8) | (name[2] << 16);
    while (i < max) {
        uint32_t p32;
        char ch;

        /* Quickly check match of the first 3 bytes */
        move_from_unaligned32(p32, p);
        p += 3;
        if ((p32 & 0x00ffffff) != n32) {
            /* Most likely case: 3 first bytes do not match */
            i++;
            if ((p32 & 0x00ff0000) == '\0')
                continue; // p[2] was NUL
            p++;
            if ((p32 & 0xff000000) == '\0')
                continue; // p[3] was NUL
            /* p[0..3] aren't matching and none is NUL, check the rest */
            while (*p++ != '\0')
                continue;
            continue;
        }

        /* Unlikely branch: first 3 bytes ([0..2]) match */
        if ((p32 & 0x00ff0000) == '\0') {
            /* name is 2-byte long, it is full match */
            //bb_error_msg("found:'%s' i:%u", name, i);
            return i;
        }
        /* Check remaining bytes [3..NUL] */
        ch = (p32 >> 24);
        j = 3;
        while (ch == name[j]) {
            if (ch == '\0') {
                //bb_error_msg("found:'%s' i:%u", name, i);
                return i;
            }
            ch = *++p;
            j++;
        }
        /* Not a match. Skip it, including NUL */
        while (ch != '\0')
            ch = *++p;
        p++;
        i++;
    }
    return -1;
#else
    while (i < max) {
        char ch;
        j = 0;
        /* Do we see "name\0" in applet_names[p] position? */
        while ((ch = *p) == name[j]) {
            if (ch == '\0') {
                //bb_error_msg("found:'%s' i:%u", name, i);
                return i; /* yes */
            }
            p++;
            j++;
        }
        /* No.
         * p => 1st non-matching char in applet_names[],
         * skip to and including NUL.
         */
        while (ch != '\0')
            ch = *++p;
        p++;
        i++;
    }
    return -1;
#endif
}


void lbb_prepare(const char *applet
        IF_FEATURE_INDIVIDUAL(, char **argv))
                MAIN_EXTERNALLY_VISIBLE;
void lbb_prepare(const char *applet
        IF_FEATURE_INDIVIDUAL(, char **argv))
{
#ifdef __GLIBC__
    (*(int **)&bb_errno) = __errno_location();
    barrier();
#endif
    applet_name = applet;

    if (ENABLE_LOCALE_SUPPORT)
        setlocale(LC_ALL, "");

#if ENABLE_FEATURE_INDIVIDUAL
    /* Redundant for busybox (run_applet_and_exit covers that case)
     * but needed for "individual applet" mode */
    if (argv[1]
     && !argv[2]
     && strcmp(argv[1], "--help") == 0
     && !is_prefixed_with(applet, "busybox")
    ) {
        /* Special case. POSIX says "test --help"
         * should be no different from e.g. "test --foo".  */
        if (!ENABLE_TEST || strcmp(applet_name, "test") != 0)
            bb_show_usage();
    }
#endif
}

/* The code below can well be in applets/applets.c, as it is used only
 * for busybox binary, not "individual" binaries.
 * However, keeping it here and linking it into libbusybox.so
 * (together with remaining tiny applets/applets.o)
 * makes it possible to avoid --whole-archive at link time.
 * This makes (shared busybox) + libbusybox smaller.
 * (--gc-sections would be even better....)
 */

const char *applet_name;
#if !BB_MMU
bool re_execed;
#endif


/* If not built as a single-applet executable... */
#if !defined(SINGLE_APPLET_MAIN)

IF_FEATURE_SUID(static uid_t ruid;)  /* real uid */

# if ENABLE_FEATURE_SUID_CONFIG

static struct suid_config_t {
    /* next ptr must be first: this struct needs to be llist-compatible */
    struct suid_config_t *m_next;
    struct bb_uidgid_t m_ugid;
    int m_applet;
    mode_t m_mode;
} *suid_config;

static bool suid_cfg_readable;

/* check if u is member of group g */
static int ingroup(uid_t u, gid_t g)
{
    struct group *grp = getgrgid(g);
    if (grp) {
        char **mem;
        for (mem = grp->gr_mem; *mem; mem++) {
            struct passwd *pwd = getpwnam(*mem);
            if (pwd && (pwd->pw_uid == u))
                return 1;
        }
    }
    return 0;
}

/* libbb candidate */
static char *get_trimmed_slice(char *s, char *e)
{
    /* First, consider the value at e to be nul and back up until we
     * reach a non-space char.  Set the char after that (possibly at
     * the original e) to nul. */
    while (e-- > s) {
        if (!isspace(*e)) {
            break;
        }
    }
    e[1] = '\0';

    /* Next, advance past all leading space and return a ptr to the
     * first non-space char; possibly the terminating nul. */
    return skip_whitespace(s);
}

static void parse_config_file(void)
{
    /* Don't depend on the tools to combine strings. */
    static const char config_file[] ALIGN1 = "/etc/busybox.conf";

    struct suid_config_t *sct_head;
    int applet_no;
    FILE *f;
    const char *errmsg;
    unsigned lc;
    smallint section;
    struct stat st;

    ruid = getuid();
    if (ruid == 0) /* run by root - don't need to even read config file */
        return;

    if ((stat(config_file, &st) != 0)       /* No config file? */
     || !S_ISREG(st.st_mode)                /* Not a regular file? */
     || (st.st_uid != 0)                    /* Not owned by root? */
     || (st.st_mode & (S_IWGRP | S_IWOTH))  /* Writable by non-root? */
     || !(f = fopen_for_read(config_file))  /* Cannot open? */
    ) {
        return;
    }

    suid_cfg_readable = 1;
    sct_head = NULL;
    section = lc = 0;

    while (1) {
        char buffer[256];
        char *s;

        if (!fgets(buffer, sizeof(buffer), f)) { /* Are we done? */
            // Looks like bloat
            //if (ferror(f)) {   /* Make sure it wasn't a read error. */
            //  errmsg = "reading";
            //  goto pe_label;
            //}
            fclose(f);
            suid_config = sct_head; /* Success, so set the pointer. */
            return;
        }

        s = buffer;
        lc++;                   /* Got a (partial) line. */

        /* If a line is too long for our buffer, we consider it an error.
         * The following test does mistreat one corner case though.
         * If the final line of the file does not end with a newline and
         * yet exactly fills the buffer, it will be treated as too long
         * even though there isn't really a problem.  But it isn't really
         * worth adding code to deal with such an unlikely situation, and
         * we do err on the side of caution.  Besides, the line would be
         * too long if it did end with a newline. */
        if (!strchr(s, '\n') && !feof(f)) {
            errmsg = "line too long";
            goto pe_label;
        }

        /* Trim leading and trailing whitespace, ignoring comments, and
         * check if the resulting string is empty. */
        s = get_trimmed_slice(s, strchrnul(s, '#'));
        if (!*s) {
            continue;
        }

        /* Check for a section header. */

        if (*s == '[') {
            /* Unlike the old code, we ignore leading and trailing
             * whitespace for the section name.  We also require that
             * there are no stray characters after the closing bracket. */
            char *e = strchr(s, ']');
            if (!e   /* Missing right bracket? */
             || e[1] /* Trailing characters? */
             || !*(s = get_trimmed_slice(s+1, e)) /* Missing name? */
            ) {
                errmsg = "section header";
                goto pe_label;
            }
            /* Right now we only have one section so just check it.
             * If more sections are added in the future, please don't
             * resort to cascading ifs with multiple strcasecmp calls.
             * That kind of bloated code is all too common.  A loop
             * and a string table would be a better choice unless the
             * number of sections is very small. */
            if (strcasecmp(s, "SUID") == 0) {
                section = 1;
                continue;
            }
            section = -1;   /* Unknown section so set to skip. */
            continue;
        }

        /* Process sections. */

        if (section == 1) {     /* SUID */
            /* Since we trimmed leading and trailing space above, we're
             * now looking for strings of the form
             *    <key>[::space::]*=[::space::]*<value>
             * where both key and value could contain inner whitespace. */

            /* First get the key (an applet name in our case). */
            char *e = strchr(s, '=');
            if (e) {
                s = get_trimmed_slice(s, e);
            }
            if (!e || !*s) {    /* Missing '=' or empty key. */
                errmsg = "keyword";
                goto pe_label;
            }

            /* Ok, we have an applet name.  Process the rhs if this
             * applet is currently built in and ignore it otherwise.
             * Note: this can hide config file bugs which only pop
             * up when the busybox configuration is changed. */
            applet_no = find_applet_by_name(s);
            if (applet_no >= 0) {
                unsigned i;
                struct suid_config_t *sct;

                /* Note: We currently don't check for duplicates!
                 * The last config line for each applet will be the
                 * one used since we insert at the head of the list.
                 * I suppose this could be considered a feature. */
                sct = xzalloc(sizeof(*sct));
                sct->m_applet = applet_no;
                /*sct->m_mode = 0;*/
                sct->m_next = sct_head;
                sct_head = sct;

                /* Get the specified mode. */

                e = skip_whitespace(e+1);

                for (i = 0; i < 3; i++) {
                    /* There are 4 chars for each of user/group/other.
                     * "x-xx" instead of "x-" are to make
                     * "idx > 3" check catch invalid chars.
                     */
                    static const char mode_chars[] ALIGN1 = "Ssx-" "Ssx-" "x-xx";
                    static const unsigned short mode_mask[] ALIGN2 = {
                        S_ISUID, S_ISUID|S_IXUSR, S_IXUSR, 0, /* Ssx- */
                        S_ISGID, S_ISGID|S_IXGRP, S_IXGRP, 0, /* Ssx- */
                                                  S_IXOTH, 0  /*   x- */
                    };
                    const char *q = strchrnul(mode_chars + 4*i, *e);
                    unsigned idx = q - (mode_chars + 4*i);
                    if (idx > 3) {
                        errmsg = "mode";
                        goto pe_label;
                    }
                    sct->m_mode |= mode_mask[q - mode_chars];
                    e++;
                }

                /* Now get the user/group info. */

                s = skip_whitespace(e);
                /* Default is 0.0, else parse USER.GROUP: */
                if (*s) {
                    /* We require whitespace between mode and USER.GROUP */
                    if ((s == e) || !(e = strchr(s, '.'))) {
                        errmsg = "uid.gid";
                        goto pe_label;
                    }
                    *e = ':'; /* get_uidgid needs USER:GROUP syntax */
                    if (get_uidgid(&sct->m_ugid, s) == 0) {
                        errmsg = "unknown user/group";
                        goto pe_label;
                    }
                }
            }
            continue;
        }

        /* Unknown sections are ignored. */

        /* Encountering configuration lines prior to seeing a
         * section header is treated as an error.  This is how
         * the old code worked, but it may not be desirable.
         * We may want to simply ignore such lines in case they
         * are used in some future version of busybox. */
        if (!section) {
            errmsg = "keyword outside section";
            goto pe_label;
        }
    } /* while (1) */

 pe_label:
    fclose(f);
    bb_error_msg("parse error in %s, line %u: %s", config_file, lc, errmsg);

    /* Release any allocated memory before returning. */
    llist_free((llist_t*)sct_head, NULL);
}
# else
static inline void parse_config_file(void)
{
    IF_FEATURE_SUID(ruid = getuid();)
}
# endif /* FEATURE_SUID_CONFIG */


# if ENABLE_FEATURE_SUID
static void check_suid(int applet_no)
{
    gid_t rgid;  /* real gid */

    if (ruid == 0) /* set by parse_config_file() */
        return; /* run by root - no need to check more */
    rgid = getgid();

#  if ENABLE_FEATURE_SUID_CONFIG
    if (suid_cfg_readable) {
        uid_t uid;
        struct suid_config_t *sct;
        mode_t m;

        for (sct = suid_config; sct; sct = sct->m_next) {
            if (sct->m_applet == applet_no)
                goto found;
        }
        goto check_need_suid;
 found:
        /* Is this user allowed to run this applet? */
        m = sct->m_mode;
        if (sct->m_ugid.uid == ruid)
            /* same uid */
            m >>= 6;
        else if ((sct->m_ugid.gid == rgid) || ingroup(ruid, sct->m_ugid.gid))
            /* same group / in group */
            m >>= 3;
        if (!(m & S_IXOTH)) /* is x bit not set? */
            bb_error_msg_and_die("you have no permission to run this applet");

        /* We set effective AND saved ids. If saved-id is not set
         * like we do below, seteuid(0) can still later succeed! */

        /* Are we directed to change gid
         * (APPLET = *s* USER.GROUP or APPLET = *S* USER.GROUP)?
         */
        if (sct->m_mode & S_ISGID)
            rgid = sct->m_ugid.gid;
        /* else: we will set egid = rgid, thus dropping sgid effect */
        if (setresgid(-1, rgid, rgid))
            bb_perror_msg_and_die("setresgid");

        /* Are we directed to change uid
         * (APPLET = s** USER.GROUP or APPLET = S** USER.GROUP)?
         */
        uid = ruid;
        if (sct->m_mode & S_ISUID)
            uid = sct->m_ugid.uid;
        /* else: we will set euid = ruid, thus dropping suid effect */
        if (setresuid(-1, uid, uid))
            bb_perror_msg_and_die("setresuid");

        goto ret;
    }
#   if !ENABLE_FEATURE_SUID_CONFIG_QUIET
    {
        static bool onetime = 0;

        if (!onetime) {
            onetime = 1;
            bb_error_msg("using fallback suid method");
        }
    }
#   endif
 check_need_suid:
#  endif
    if (APPLET_SUID(applet_no) == BB_SUID_REQUIRE) {
        /* Real uid is not 0. If euid isn't 0 too, suid bit
         * is most probably not set on our executable */
        if (geteuid())
            bb_error_msg_and_die("must be suid to work properly");
    } else if (APPLET_SUID(applet_no) == BB_SUID_DROP) {
        xsetgid(rgid);  /* drop all privileges */
        xsetuid(ruid);
    }
#  if ENABLE_FEATURE_SUID_CONFIG
 ret: ;
    llist_free((llist_t*)suid_config, NULL);
#  endif
}
# else
#  define check_suid(x) ((void)0)
# endif /* FEATURE_SUID */


# if ENABLE_FEATURE_INSTALLER
static const char usr_bin [] ALIGN1 = "/usr/bin/";
static const char usr_sbin[] ALIGN1 = "/usr/sbin/";
static const char *const install_dir[] = {
    &usr_bin [8], /* "/" */
    &usr_bin [4], /* "/bin/" */
    &usr_sbin[4]  /* "/sbin/" */
#  if !ENABLE_INSTALL_NO_USR
    ,usr_bin
    ,usr_sbin
#  endif
};

/* create (sym)links for each applet */
static void install_links(const char *busybox, int use_symbolic_links,
        char *custom_install_dir)
{
    /* directory table
     * this should be consistent w/ the enum,
     * busybox.h::bb_install_loc_t, or else... */
    int (*lf)(const char *, const char *);
    char *fpc;
        const char *appname = applet_names;
    unsigned i;
    int rc;

    lf = link;
    if (use_symbolic_links)
        lf = symlink;

    for (i = 0; i < ARRAY_SIZE(applet_main); i++) {
        fpc = concat_path_file(
                custom_install_dir ? custom_install_dir : install_dir[APPLET_INSTALL_LOC(i)],
                appname);
        // debug: bb_error_msg("%slinking %s to busybox",
        //      use_symbolic_links ? "sym" : "", fpc);
        rc = lf(busybox, fpc);
        if (rc != 0 && errno != EEXIST) {
            bb_simple_perror_msg(fpc);
        }
        free(fpc);
        while (*appname++ != '\0')
            continue;
    }
}
# elif ENABLE_BUSYBOX
static void install_links(const char *busybox UNUSED_PARAM,
        int use_symbolic_links UNUSED_PARAM,
        char *custom_install_dir UNUSED_PARAM)
{
}
# endif

# if ENABLE_BUSYBOX
/* If we were called as "busybox..." */
static int busybox_main(char **argv)
{
    if (!argv[1]) {
        /* Called without arguments */
        const char *a;
        int col;
        unsigned output_width;
 help:
        output_width = 80;
        if (ENABLE_FEATURE_AUTOWIDTH) {
            /* Obtain the terminal width */
            output_width = get_terminal_width(2);
        }

        dup2(1, 2);
        full_write2_str(bb_banner); /* reuse const string */
        full_write2_str(" multi-call binary.\n"); /* reuse */
        full_write2_str(
            "BusyBox is copyrighted by many authors between 1998-2015.\n"
            "Licensed under GPLv2. See source distribution for detailed\n"
            "copyright notices.\n"
            "\n"
            "Usage: busybox [function [arguments]...]\n"
            "   or: busybox --list"IF_FEATURE_INSTALLER("[-full]")"\n"
            IF_FEATURE_INSTALLER(
            "   or: busybox --install [-s] [DIR]\n"
            )
            "   or: function [arguments]...\n"
            "\n"
            IF_NOT_FEATURE_SH_STANDALONE(
            "\tBusyBox is a multi-call binary that combines many common Unix\n"
            "\tutilities into a single executable.  Most people will create a\n"
            "\tlink to busybox for each function they wish to use and BusyBox\n"
            "\twill act like whatever it was invoked as.\n"
            )
            IF_FEATURE_SH_STANDALONE(
            "\tBusyBox is a multi-call binary that combines many common Unix\n"
            "\tutilities into a single executable.  The shell in this build\n"
            "\tis configured to run built-in utilities without $PATH search.\n"
            "\tYou don't need to install a link to busybox for each utility.\n"
            "\tTo run external program, use full path (/sbin/ip instead of ip).\n"
            )
            "\n"
            "Currently defined functions:\n"
        );
        col = 0;
        a = applet_names;
        /* prevent last comma to be in the very last pos */
        output_width--;
        while (*a) {
            int len2 = strlen(a) + 2;
            if (col >= (int)output_width - len2) {
                full_write2_str(",\n");
                col = 0;
            }
            if (col == 0) {
                col = 6;
                full_write2_str("\t");
            } else {
                full_write2_str(", ");
            }
            full_write2_str(a);
            col += len2;
            a += len2 - 1;
        }
        full_write2_str("\n\n");
        return 0;
    }

    if (is_prefixed_with(argv[1], "--list")) {
        unsigned i = 0;
        const char *a = applet_names;
        dup2(1, 2);
        while (*a) {
#  if ENABLE_FEATURE_INSTALLER
            if (argv[1][6]) /* --list-full? */
                full_write2_str(install_dir[APPLET_INSTALL_LOC(i)] + 1);
#  endif
            full_write2_str(a);
            full_write2_str("\n");
            i++;
            while (*a++ != '\0')
                continue;
        }
        return 0;
    }

    if (ENABLE_FEATURE_INSTALLER && strcmp(argv[1], "--install") == 0) {
        int use_symbolic_links;
        const char *busybox;

        busybox = xmalloc_readlink(bb_busybox_exec_path);
        if (!busybox) {
            /* bb_busybox_exec_path is usually "/proc/self/exe".
             * In chroot, readlink("/proc/self/exe") usually fails.
             * In such case, better use argv[0] as symlink target
             * if it is a full path name.
             */
            if (argv[0][0] != '/')
                bb_error_msg_and_die("'%s' is not an absolute path", argv[0]);
            busybox = argv[0];
        }
        /* busybox --install [-s] [DIR]:
         * -s: make symlinks
         * DIR: directory to install links to
         */
        use_symbolic_links = (argv[2] && strcmp(argv[2], "-s") == 0 && ++argv);
        install_links(busybox, use_symbolic_links, argv[2]);
        return 0;
    }

    if (strcmp(argv[1], "--help") == 0) {
        /* "busybox --help [<applet>]" */
        if (!argv[2])
            goto help;
        /* convert to "<applet> --help" */
        argv[0] = argv[2];
        argv[2] = NULL;
    } else {
        /* "busybox <applet> arg1 arg2 ..." */
        argv++;
    }
    /* We support "busybox /a/path/to/applet args..." too. Allows for
     * "#!/bin/busybox"-style wrappers */
    applet_name = bb_get_last_path_component_nostrip(argv[0]);
    run_applet_and_exit(applet_name, argv);
}
# endif

void FAST_FUNC run_applet_no_and_exit(int applet_no, char **argv)
{
    int argc = 1;

    while (argv[argc])
        argc++;

    /* Reinit some shared global data */
    xfunc_error_retval = EXIT_FAILURE;
    applet_name = bb_get_last_path_component_nostrip(argv[0]);

    /* Special case. POSIX says "test --help"
     * should be no different from e.g. "test --foo".
     * Thus for "test", we skip --help check.
     * "true" and "false" are also special.
     */
    if (1
#if defined APPLET_NO_test
     && applet_no != APPLET_NO_test
#endif
#if defined APPLET_NO_true
     && applet_no != APPLET_NO_true
#endif
#if defined APPLET_NO_false
     && applet_no != APPLET_NO_false
#endif
    ) {
        if (argc == 2 && strcmp(argv[1], "--help") == 0) {
            /* Make "foo --help" exit with 0: */
            xfunc_error_retval = 0;
            bb_show_usage();
        }
    }
    if (ENABLE_FEATURE_SUID)
        check_suid(applet_no);
    exit(applet_main[applet_no](argc, argv));
}

static NORETURN void run_applet_and_exit(const char *name, char **argv)
{
    int applet;

# if ENABLE_BUSYBOX
    if (is_prefixed_with(name, "busybox"))
        exit(busybox_main(argv));
# endif
    /* find_applet_by_name() search is more expensive, so goes second */
    applet = find_applet_by_name(name);
    if (applet >= 0)
        run_applet_no_and_exit(applet, argv);

    /*bb_error_msg_and_die("applet not found"); - links in printf */
    full_write2_str(applet_name);
    full_write2_str(": applet not found\n");
    /* POSIX: "If a command is not found, the exit status shall be 127" */
    exit(127);
}

#endif /* !defined(SINGLE_APPLET_MAIN) */



#if ENABLE_BUILD_LIBBUSYBOX
int lbb_main(char **argv)
#else
int main(int argc UNUSED_PARAM, char **argv)
#endif
{
#if 0
    /* TODO: find a use for a block of memory between end of .bss
     * and end of page. For example, I'm getting "_end:0x812e698 2408 bytes"
     * - more than 2k of wasted memory (in this particular build)
     * *per each running process*!
     * (If your linker does not generate "_end" name, weak attribute
     * makes &_end == NULL, end_len == 0 here.)
     */
    extern char _end[] __attribute__((weak));
    unsigned end_len = (-(int)_end) & 0xfff;
    printf("_end:%p %u bytes\n", &_end, end_len);
#endif

    /* Tweak malloc for reduced memory consumption */
#ifdef M_TRIM_THRESHOLD
    /* M_TRIM_THRESHOLD is the maximum amount of freed top-most memory
     * to keep before releasing to the OS
     * Default is way too big: 256k
     */
    mallopt(M_TRIM_THRESHOLD, 8 * 1024);
#endif
#ifdef M_MMAP_THRESHOLD
    /* M_MMAP_THRESHOLD is the request size threshold for using mmap()
     * Default is too big: 256k
     */
    mallopt(M_MMAP_THRESHOLD, 32 * 1024 - 256);
#endif

#if !BB_MMU
    /* NOMMU re-exec trick sets high-order bit in first byte of name */
    if (argv[0][0] & 0x80) {
        re_execed = 1;
        argv[0][0] &= 0x7f;
    }
#endif

#if defined(SINGLE_APPLET_MAIN)
    /* Only one applet is selected in .config */
    if (argv[1] && is_prefixed_with(argv[0], "busybox")) {
        /* "busybox <applet> <params>" should still work as expected */
        argv++;
    }
    /* applet_names in this case is just "applet\0\0" */
    lbb_prepare(applet_names IF_FEATURE_INDIVIDUAL(, argv));
    return SINGLE_APPLET_MAIN(argc, argv);
#else
    lbb_prepare("busybox" IF_FEATURE_INDIVIDUAL(, argv));

#if !ENABLE_BUSYBOX
    if (argv[1] && is_prefixed_with(bb_basename(argv[0]), "busybox"))
        argv++;
#endif
    applet_name = argv[0];
    if (applet_name[0] == '-')
        applet_name++;
    applet_name = bb_basename(applet_name);

    parse_config_file(); /* ...maybe, if FEATURE_SUID_CONFIG */

    run_applet_and_exit(applet_name, argv);
#endif
}