/* 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. :(
 */

/* Define this accessor before we #define "errno" our way */
#include <errno.h>
static inline int *get_perrno(void) { return &errno; }

#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"

#if ENABLE_FEATURE_SH_EMBEDDED_SCRIPTS
# define DEFINE_SCRIPT_DATA 1
# include "embedded_scripts.h"
#else
# define NUM_SCRIPTS 0
#endif
#if NUM_SCRIPTS > 0
# include "bb_archive.h"
static const char packed_scripts[] ALIGN1 = { PACKED_SCRIPTS };
#endif

/* "Do not compress usage text if uncompressed text is small
 *  and we don't include bunzip2 code for other reasons"
 *
 * Useful for mass one-applet rebuild (bunzip2 code is ~2.7k).
 *
 * Unlike BUNZIP2, if FEATURE_SEAMLESS_BZ2 is on, bunzip2 code is built but
 * still may be unused if none of the selected applets calls open_zipped()
 * or its friends; we test for (FEATURE_SEAMLESS_BZ2 && <APPLET>) instead.
 * For example, only if TAR and FEATURE_SEAMLESS_BZ2 are both selected,
 * then bunzip2 code will be linked in anyway, and disabling help compression
 * would be not optimal:
 */
#if UNPACKED_USAGE_LENGTH < 4*1024 \
 && !(ENABLE_FEATURE_SEAMLESS_BZ2 && ENABLE_TAR) \
 && !(ENABLE_FEATURE_SEAMLESS_BZ2 && ENABLE_MODPROBE) \
 && !(ENABLE_FEATURE_SEAMLESS_BZ2 && ENABLE_INSMOD) \
 && !(ENABLE_FEATURE_SEAMLESS_BZ2 && ENABLE_DEPMOD) \
 && !(ENABLE_FEATURE_SEAMLESS_BZ2 && ENABLE_MAN) \
 && !ENABLE_BUNZIP2 \
 && !ENABLE_BZCAT
# undef  ENABLE_FEATURE_COMPRESS_USAGE
# define ENABLE_FEATURE_COMPRESS_USAGE 0
#endif


unsigned FAST_FUNC string_array_len(char **argv)
{
        char **start = argv;

        while (*argv)
                argv++;

        return argv - start;
}


#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"
# define unpack_usage_messages() \
        unpack_bz2_data(packed_usage, sizeof(packed_usage), sizeof(UNPACKED_USAGE))
# 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 link in printf! */
                const char *usage_string = unpack_usage_messages();

                if (usage_string) {
                        if (*usage_string == '\b') {
                                full_write2_str("No help available\n");
                        } else {
                                full_write2_str("Usage: "SINGLE_APPLET_STR" ");
                                full_write2_str(usage_string);
                                full_write2_str("\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 || usage_string == NULL)
                        xfunc_die();
                while (ap) {
                        while (*p++) continue;
                        ap--;
                }
                full_write2_str(bb_banner);
                full_write2_str(" multi-call binary.\n"); /* common string */
                if (*p == '\b')
                        full_write2_str("\nNo help available\n");
                else {
                        full_write2_str("\nUsage: ");
                        full_write2_str(applet_name);
                        if (p[0]) {
                                if (p[0] != '\n')
                                        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;
        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;
#if KNOWN_APPNAME_OFFSETS <= 0
        i = 0;
#else
        i = NUM_APPLETS * (KNOWN_APPNAME_OFFSETS - 1);
        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;
                        break;
                }
                i -= NUM_APPLETS;
        }
        i /= (unsigned)KNOWN_APPNAME_OFFSETS;
        //bb_error_msg("name:'%s' starting from:'%s' i:%u", name, p, i);
#endif

        /* Open-coded linear search without strcmp/strlen calls for speed */
        while (*p) {
                /* Do we see "name\0" at current position in applet_names? */
                for (j = 0; *p == name[j]; ++j) {
                        if (*p++ == '\0') {
                                //bb_error_msg("found:'%s' i:%u", name, i);
                                return i; /* yes */
                        }
                }
                /* No. Have we gone too far, alphabetically? */
                if (*p > name[j]) {
                        //bb_error_msg("break:'%s' i:%u", name, i);
                        break;
                }
                /* No. Move to the start of the next applet name. */
                while (*p++ != '\0')
                        continue;
                i++;
        }
        return -1;
}


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 bb_cached_errno_ptr
        ASSIGN_CONST_PTR(&bb_errno, get_perrno());
#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]
         && strcmp(argv[1], "--help") == 0
         && !is_prefixed_with(applet, "busybox")
        ) {
                /* Special cases. POSIX says "test --help"
                 * should be no different from e.g. "test --foo".
                 */
                if (!(ENABLE_TEST && strcmp(applet_name, "test") == 0)
                 && !(ENABLE_TRUE && strcmp(applet_name, "true") == 0)
                 && !(ENABLE_FALSE && strcmp(applet_name, "false") == 0)
                 && !(ENABLE_ECHO && strcmp(applet_name, "echo") == 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;

/* 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 && NUM_APPLETS > 0
#  if ENABLE_FEATURE_SUID_CONFIG
/* 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;
}
#  endif

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_simple_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_simple_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_simple_perror_msg_and_die("setresuid");

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

                if (!onetime) {
                        onetime = 1;
                        bb_simple_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_simple_error_msg_and_die("must be suid to work properly");
        } else if (APPLET_SUID(applet_no) == BB_SUID_DROP) {
                /*
                 * Drop all privileges.
                 *
                 * Don't check for errors: in normal use, they are impossible,
                 * and in special cases, exiting is harmful. Example:
                 * 'unshare --user' when user's shell is also from busybox.
                 *
                 * 'unshare --user' creates a new user namespace without any
                 * uid mappings. Thus, busybox binary is setuid nobody:nogroup
                 * within the namespace, as that is the only user. However,
                 * since no uids are mapped, calls to setgid/setuid
                 * fail (even though they would do nothing).
                 */
                setgid(rgid);
                setuid(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[] ALIGN_PTR = {
        &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 || NUM_APPLETS > 0
static void run_applet_and_exit(const char *name, char **argv) NORETURN;
#endif

# if NUM_SCRIPTS > 0
static int find_script_by_name(const char *name)
{
        int i;
        int applet = find_applet_by_name(name);

        if (applet >= 0) {
                for (i = 0; i < NUM_SCRIPTS; ++i)
                        if (applet_numbers[i] == applet)
                                return i;
        }
        return -1;
}

int scripted_main(int argc UNUSED_PARAM, char **argv) MAIN_EXTERNALLY_VISIBLE;
int scripted_main(int argc UNUSED_PARAM, char **argv)
{
        int script = find_script_by_name(applet_name);
        if (script >= 0)
#  if ENABLE_SHELL_ASH
                return ash_main(-script - 1, argv);
#  elif ENABLE_SHELL_HUSH
                return hush_main(-script - 1, argv);
#  else
                return 1;
#  endif
        return 0;
}

char* FAST_FUNC
get_script_content(unsigned n)
{
        char *t = unpack_bz2_data(packed_scripts, sizeof(packed_scripts),
                                        UNPACKED_SCRIPTS_LENGTH);
        if (t) {
                while (n != 0) {
                        while (*t++ != '\0')
                                continue;
                        n--;
                }
        }
        return t;
}
# endif /* NUM_SCRIPTS > 0 */

# if ENABLE_BUSYBOX
#  if ENABLE_FEATURE_SH_STANDALONE && ENABLE_FEATURE_TAB_COMPLETION
    /*
     * Insert "busybox" into applet table as well.
     * This makes standalone shell tab-complete this name too.
     * (Otherwise having "busybox" in applet table is not necessary,
     * there is other code which routes "busyboxANY_SUFFIX" name
     * to busybox_main()).
     */
//usage:#define busybox_trivial_usage NOUSAGE_STR
//usage:#define busybox_full_usage ""
//applet:IF_BUSYBOX(IF_FEATURE_SH_STANDALONE(IF_FEATURE_TAB_COMPLETION(APPLET(busybox, BB_DIR_BIN, BB_SUID_MAYBE))))
int busybox_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
#  else
#   define busybox_main(argc,argv) busybox_main(argv)
static
#  endif
int busybox_main(int argc UNUSED_PARAM, char **argv)
{
        if (!argv[1]) {
                /* Called without arguments */
                const char *a;
                int col;
                unsigned output_width;
 help:
                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 ENABLE_FEATURE_SHOW_SCRIPT && NUM_SCRIPTS > 0
                        "   or: busybox --show SCRIPT\n"
#  endif
                        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;
                /* prevent last comma to be in the very last pos */
                output_width--;
                a = applet_names;
                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");
                return 0;
        }

#  if ENABLE_FEATURE_SHOW_SCRIPT && NUM_SCRIPTS > 0
        if (strcmp(argv[1], "--show") == 0) {
                int n;
                if (!argv[2])
                        bb_error_msg_and_die(bb_msg_requires_arg, "--show");
                n = find_script_by_name(argv[2]);
                if (n < 0)
                        bb_error_msg_and_die("script '%s' not found", argv[2]);
                full_write1_str(get_script_content(n));
                return 0;
        }
#  endif

        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]
#  if ENABLE_FEATURE_SH_STANDALONE && ENABLE_FEATURE_TAB_COMPLETION
                 || strcmp(argv[2], "busybox") == 0 /* prevent getting "No help available" */
#  endif
                )
                        goto help;
                /* convert to "<applet> --help" */
                applet_name = argv[0] = argv[2];
                argv[2] = NULL;
                if (find_applet_by_name(applet_name) >= 0) {
                        /* Make "--help foo" exit with 0: */
                        xfunc_error_retval = 0;
                        bb_show_usage();
                } /* else: unknown applet, fall through (causes "applet not found" later) */
        } 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

# if NUM_APPLETS > 0
void FAST_FUNC show_usage_if_dash_dash_help(int applet_no, char **argv)
{
        /* Special case. POSIX says "test --help"
         * should be no different from e.g. "test --foo".
         * Thus for "test", we skip --help check.
         * "true", "false", "echo" 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 defined APPLET_NO_echo
         && applet_no != APPLET_NO_echo
#  endif
#  if ENABLE_TEST1 || ENABLE_TEST2
         && argv[0][0] != '[' /* exclude [ --help ] and [[ --help ]] too */
#  endif
        ) {
                if (argv[1] && strcmp(argv[1], "--help") == 0) {
                        /* Make "foo --help [...]" exit with 0: */
                        xfunc_error_retval = 0;
                        bb_show_usage();
                }
        }
}

void FAST_FUNC run_applet_no_and_exit(int applet_no, const char *name, char **argv)
{
        int argc;

        /*
         * We do not use argv[0]: do not want to repeat massaging of
         * "-/sbin/halt" -> "halt", for example.
         */
        applet_name = name;

        show_usage_if_dash_dash_help(applet_no, argv);

        if (ENABLE_FEATURE_SUID)
                check_suid(applet_no);

        argc = string_array_len(argv);
        xfunc_error_retval = applet_main[applet_no](argc, argv);

        /* Note: applet_main() may also not return (die on a xfunc or such) */
        xfunc_die();
}
# endif /* NUM_APPLETS > 0 */

# if ENABLE_BUSYBOX || NUM_APPLETS > 0
static NORETURN void run_applet_and_exit(const char *name, char **argv)
{
#  if ENABLE_BUSYBOX
        if (is_prefixed_with(name, "busybox"))
                exit(busybox_main(/*unused:*/ 0, argv));
#  endif
#  if NUM_APPLETS > 0
        /* find_applet_by_name() search is more expensive, so goes second */
        {
                int applet = find_applet_by_name(name);
                if (applet >= 0)
                        run_applet_no_and_exit(applet, name, argv);
        }
#  endif

        /*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

#else /* defined(SINGLE_APPLET_MAIN) */

# if NUM_SCRIPTS > 0
/* if SINGLE_APPLET_MAIN, these two functions are simpler: */
int scripted_main(int argc UNUSED_PARAM, char **argv) MAIN_EXTERNALLY_VISIBLE;
int scripted_main(int argc UNUSED_PARAM, char **argv)
{
#  if ENABLE_SHELL_ASH
        int script = 0;
        return ash_main(-script - 1, argv);
#  elif ENABLE_SHELL_HUSH
        int script = 0;
        return hush_main(-script - 1, argv);
#  else
        return 1;
#  endif
}
char* FAST_FUNC
get_script_content(unsigned n UNUSED_PARAM)
{
        char *t = unpack_bz2_data(packed_scripts, sizeof(packed_scripts),
                                        UNPACKED_SCRIPTS_LENGTH);
        return t;
}
# endif /* NUM_SCRIPTS > 0 */

#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 0 /*def M_TOP_PAD*/
        /* When the program break is increased, then M_TOP_PAD bytes are added
         * to the sbrk(2) request. When the heap is trimmed because of free(3),
         * this much free space is preserved at the top of the heap.
         * glibc default seems to be way too big: 128k, but need to verify.
         */
        mallopt(M_TOP_PAD, 8 * 1024);
#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));
# if ENABLE_BUILD_LIBBUSYBOX
        return SINGLE_APPLET_MAIN(string_array_len(argv), argv);
# else
        return SINGLE_APPLET_MAIN(argc, argv);
# endif

#elif !ENABLE_BUSYBOX && NUM_APPLETS == 0

        full_write2_str(bb_basename(argv[0]));
        full_write2_str(": no applets enabled\n");
        return 127;

#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);

        /* If we are a result of execv("/proc/self/exe"), fix ugly comm of "exe" */
        if (ENABLE_FEATURE_SH_STANDALONE
         || ENABLE_FEATURE_PREFER_APPLETS
         || !BB_MMU
        ) {
                if (NUM_APPLETS > 1) {
                        /* Careful, do not trash comm of "SCRIPT.sh" -
                         * the case when started from e.g. #!/bin/ash script.
                         * (not limited to shells - #!/bin/awk scripts also exist)
                         */
                        if (re_execed_comm())
                                set_task_comm(applet_name);
                }
        }

        parse_config_file(); /* ...maybe, if FEATURE_SUID_CONFIG */
        run_applet_and_exit(applet_name, argv);

#endif
}