ash: builtin: Mark more regular built-ins
[oweals/busybox.git] / libbb / appletlib.c
index c22686e55df8b6bdc40a942b45f6a8734b89aec2..f842e73cc28d6a8b8d05bc48f620dd6f3d0bdda4 100644 (file)
@@ -11,7 +11,6 @@
  *
  * 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:
  *
 #include "busybox.h"
 
 #if !(defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__NetBSD__) \
-        || defined(__APPLE__) \
+    || defined(__APPLE__) \
     )
 # include <malloc.h> /* for mallopt */
 #endif
 
-
 /* Declare <applet>_main() */
 #define PROTOTYPES
 #include "applets.h"
 
 #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;
@@ -63,27 +107,8 @@ static const char usage_messages[] ALIGN1 = UNPACKED_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 unpack_usage_messages() \
+       unpack_bz2_data(packed_usage, sizeof(packed_usage), sizeof(UNPACKED_USAGE))
 # define dealloc_usage_messages(s) free(s)
 
 #else
@@ -98,39 +123,44 @@ 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! */
+               /* Imagine that this applet is "true". Dont link 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 (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);
                }
-               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 */
+               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");
+               full_write2_str(" multi-call binary.\n"); /* common string */
                if (*p == '\b')
-                       full_write2_str("\nNo help available.\n\n");
+                       full_write2_str("\nNo help available\n");
                else {
                        full_write2_str("\nUsage: ");
                        full_write2_str(applet_name);
-                       full_write2_str(" ");
-                       full_write2_str(p);
-                       full_write2_str("\n\n");
+                       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);
@@ -139,32 +169,127 @@ void FAST_FUNC bb_show_usage(void)
        xfunc_die();
 }
 
-#if NUM_APPLETS > 8
-static int applet_name_compare(const void *name, const void *idx)
-{
-       int i = (int)(ptrdiff_t)idx - 1;
-       return strcmp(name, APPLET_NAME(i));
-}
-#endif
 int FAST_FUNC find_applet_by_name(const char *name)
 {
-#if NUM_APPLETS > 8
-       /* Do a binary search to find the applet entry given the name. */
+       unsigned i, max;
+       int j;
        const char *p;
-       p = bsearch(name, (void*)(ptrdiff_t)1, ARRAY_SIZE(applet_main), 1, applet_name_compare);
-       /*
-        * if (!p) return -1;
-        * ^^^^^^^^^^^^^^^^^^ the code below will do this if p == NULL :)
-        */
-       return (int)(ptrdiff_t)p - 1;
+
+/* 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
-       /* A version which does not pull in bsearch */
-       int i = 0;
-       const char *p = applet_names;
-       while (i < NUM_APPLETS) {
-               if (strcmp(name, p) == 0)
+       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;
-               p += strlen(p) + 1;
+               }
+               /* 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;
@@ -179,13 +304,12 @@ void lbb_prepare(const char *applet
                IF_FEATURE_INDIVIDUAL(, char **argv))
 {
 #ifdef __GLIBC__
-       (*(int **)&bb_errno) = __errno_location();
+       (*(int **)not_const_pp(&bb_errno)) = __errno_location();
        barrier();
 #endif
        applet_name = applet;
 
-       /* Set locale for everybody except 'init' */
-       if (ENABLE_LOCALE_SUPPORT && getpid() != 1)
+       if (ENABLE_LOCALE_SUPPORT)
                setlocale(LC_ALL, "");
 
 #if ENABLE_FEATURE_INDIVIDUAL
@@ -194,7 +318,7 @@ void lbb_prepare(const char *applet
        if (argv[1]
         && !argv[2]
         && strcmp(argv[1], "--help") == 0
-        && strncmp(applet, "busybox", 7) != 0
+        && !is_prefixed_with(applet, "busybox")
        ) {
                /* Special case. POSIX says "test --help"
                 * should be no different from e.g. "test --foo".  */
@@ -236,21 +360,6 @@ static struct suid_config_t {
 
 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)
 {
@@ -438,7 +547,7 @@ static void parse_config_file(void)
                                                goto pe_label;
                                        }
                                        *e = ':'; /* get_uidgid needs USER:GROUP syntax */
-                                       if (get_uidgid(&sct->m_ugid, s, /*allow_numeric:*/ 1) == 0) {
+                                       if (get_uidgid(&sct->m_ugid, s) == 0) {
                                                errmsg = "unknown user/group";
                                                goto pe_label;
                                        }
@@ -458,7 +567,6 @@ static void parse_config_file(void)
                        errmsg = "keyword outside section";
                        goto pe_label;
                }
-
        } /* while (1) */
 
  pe_label:
@@ -476,7 +584,24 @@ static inline void parse_config_file(void)
 # endif /* FEATURE_SUID_CONFIG */
 
 
-# if ENABLE_FEATURE_SUID
+# 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 */
@@ -506,7 +631,7 @@ static void check_suid(int applet_no)
                        /* 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");
+                       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! */
@@ -518,7 +643,7 @@ static void check_suid(int applet_no)
                        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");
+                       bb_simple_perror_msg_and_die("setresgid");
 
                /* Are we directed to change uid
                 * (APPLET = s** USER.GROUP or APPLET = S** USER.GROUP)?
@@ -528,7 +653,7 @@ static void check_suid(int applet_no)
                        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");
+                       bb_simple_perror_msg_and_die("setresuid");
 
                goto ret;
        }
@@ -538,7 +663,7 @@ static void check_suid(int applet_no)
 
                if (!onetime) {
                        onetime = 1;
-                       bb_error_msg("using fallback suid method");
+                       bb_simple_error_msg("using fallback suid method");
                }
        }
 #   endif
@@ -548,10 +673,23 @@ static void check_suid(int applet_no)
                /* 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");
+                       bb_simple_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);
+               /*
+                * 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: ;
@@ -585,6 +723,7 @@ static void install_links(const char *busybox, int use_symbolic_links,
         * 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;
 
@@ -595,7 +734,7 @@ static void install_links(const char *busybox, int use_symbolic_links,
        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)],
-                               APPLET_NAME(i));
+                               appname);
                // debug: bb_error_msg("%slinking %s to busybox",
                //              use_symbolic_links ? "sym" : "", fpc);
                rc = lf(busybox, fpc);
@@ -603,14 +742,83 @@ static void install_links(const char *busybox, int use_symbolic_links,
                        bb_simple_perror_msg(fpc);
                }
                free(fpc);
+               while (*appname++ != '\0')
+                       continue;
        }
 }
-# else
-#  define install_links(x,y,z) ((void)0)
+# 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 we were called as "busybox..." */
-static int busybox_main(char **argv)
+static void run_applet_and_exit(const char *name, char **argv) NORETURN;
+
+# 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_ASH || ENABLE_SH_IS_ASH || ENABLE_BASH_IS_ASH
+               exit(ash_main(-script - 1, argv));
+#elif ENABLE_HUSH || ENABLE_SH_IS_HUSH || ENABLE_BASH_IS_HUSH
+               exit(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 */
@@ -618,38 +826,46 @@ static int busybox_main(char **argv)
                int col;
                unsigned output_width;
  help:
-               output_width = 80;
-               if (ENABLE_FEATURE_AUTOWIDTH) {
-                       /* Obtain the terminal width */
-                       get_terminal_width_height(0, &output_width, NULL);
-               }
+               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 1998-2012.\n"
+                       "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;
-               a = applet_names;
                /* 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) {
@@ -666,23 +882,37 @@ static int busybox_main(char **argv)
                        col += len2;
                        a += len2 - 1;
                }
-               full_write2_str("\n\n");
+               full_write2_str("\n");
                return 0;
        }
 
-       if (strncmp(argv[1], "--list", 6) == 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 ENABLE_FEATURE_INSTALLER
                        if (argv[1][6]) /* --list-full? */
                                full_write2_str(install_dir[APPLET_INSTALL_LOC(i)] + 1);
-# endif
+#  endif
                        full_write2_str(a);
                        full_write2_str("\n");
                        i++;
-                       a += strlen(a) + 1;
+                       while (*a++ != '\0')
+                               continue;
                }
                return 0;
        }
@@ -726,58 +956,96 @@ static int busybox_main(char **argv)
         * "#!/bin/busybox"-style wrappers */
        applet_name = bb_get_last_path_component_nostrip(argv[0]);
        run_applet_and_exit(applet_name, argv);
-
-       /*bb_error_msg_and_die("applet not found"); - sucks in printf */
-       full_write2_str(applet_name);
-       full_write2_str(": applet not found\n");
-       xfunc_die();
 }
+# endif
 
-void FAST_FUNC run_applet_no_and_exit(int applet_no, char **argv)
+# if NUM_APPLETS > 0
+void FAST_FUNC run_applet_no_and_exit(int applet_no, const char *name, char **argv)
 {
-       int argc = 1;
+       int argc = string_array_len(argv);
 
-       while (argv[argc])
-               argc++;
-
-       /* Reinit some shared global data */
-       xfunc_error_retval = EXIT_FAILURE;
+       /*
+        * We do not use argv[0]: do not want to repeat massaging of
+        * "-/sbin/halt" -> "halt", for example.
+        */
+       applet_name = name;
 
-       applet_name = APPLET_NAME(applet_no);
-       if (argc == 2 && strcmp(argv[1], "--help") == 0) {
-               /* Special case. POSIX says "test --help"
-                * should be no different from e.g. "test --foo".  */
-//TODO: just compare applet_no with APPLET_NO_test
-               if (!ENABLE_TEST || strcmp(applet_name, "test") != 0) {
-                       /* If you want "foo --help" to return 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));
+       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 */
 
-void FAST_FUNC run_applet_and_exit(const char *name, char **argv)
+# if ENABLE_BUSYBOX || NUM_APPLETS > 0
+static NORETURN void run_applet_and_exit(const char *name, char **argv)
 {
-       int applet = find_applet_by_name(name);
-       if (applet >= 0)
-               run_applet_no_and_exit(applet, argv);
-       if (strncmp(name, "busybox", 7) == 0)
-               exit(busybox_main(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
 
 #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
@@ -792,6 +1060,14 @@ int main(int argc UNUSED_PARAM, char **argv)
         */
        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 */
@@ -802,29 +1078,49 @@ int main(int argc UNUSED_PARAM, char **argv)
 #endif
 
 #if defined(SINGLE_APPLET_MAIN)
+
        /* Only one applet is selected in .config */
-       if (argv[1] && strncmp(argv[0], "busybox", 7) == 0) {
+       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");
+       exit(127);
+
 #else
-       lbb_prepare("busybox" IF_FEATURE_INDIVIDUAL(, argv));
 
+       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 */
+       /* 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)
+                       set_task_comm(applet_name);
+       }
 
+       parse_config_file(); /* ...maybe, if FEATURE_SUID_CONFIG */
        run_applet_and_exit(applet_name, argv);
 
-       /*bb_error_msg_and_die("applet not found"); - sucks in printf */
-       full_write2_str(applet_name);
-       full_write2_str(": applet not found\n");
-       xfunc_die();
 #endif
 }