ash: allow shell scripts to be embedded in the binary

To assist in the deployment of shell scripts it may be convenient
to embed them in the BusyBox binary.

'Embed scripts in the binary' takes any files in the directory
'embed', concatenates them with null separators, compresses them
and embeds them in the binary.

When scripts are embedded in the binary, scripts can be run as
'busybox SCRIPT [ARGS]' or by usual (sym)link mechanism.

embed/nologin is provided as an example.

function                                             old     new   delta
packed_scripts                                         -     123    +123
unpack_scripts                                         -      87     +87
ash_main                                            1103    1171     +68
run_applet_and_exit                                   78     128     +50
get_script_content                                     -      32     +32
script_names                                           -      10     +10
expmeta                                              663     659      -4
------------------------------------------------------------------------------
(add/remove: 4/0 grow/shrink: 2/1 up/down: 370/-4)            Total: 366 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 82 insertions, 1 deletions

diff --git a/libbb/appletlib.c b/libbb/appletlib.c
index 319bcc263..08720082e 100644
--- a/libbb/appletlib.c
+++ b/libbb/appletlib.c
@@ -50,6 +50,16 @@
 
 #include "usage_compressed.h"
 
+#if ENABLE_ASH_EMBEDDED_SCRIPTS
+# define DEFINE_script_names 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"
@@ -953,7 +963,71 @@ void FAST_FUNC run_applet_no_and_exit(int applet_no, const char *name, char **ar
 }
 # endif /* NUM_APPLETS > 0 */
 
-# if ENABLE_BUSYBOX || NUM_APPLETS > 0
+# if NUM_SCRIPTS > 0
+static char *
+unpack_scripts(void)
+{
+	char *outbuf = NULL;
+	bunzip_data *bd;
+	int i;
+	jmp_buf jmpbuf;
+
+	/* Setup for I/O error handling via longjmp */
+	i = setjmp(jmpbuf);
+	if (i == 0) {
+		i = start_bunzip(&jmpbuf,
+			&bd,
+			/* src_fd: */ -1,
+			/* inbuf:  */ packed_scripts,
+			/* len:    */ sizeof(packed_scripts)
+		);
+	}
+	/* read_bunzip can longjmp and end up here with i != 0
+	 * on read data errors! Not trivial */
+	if (i == 0) {
+		outbuf = xmalloc(UNPACKED_SCRIPTS_LENGTH);
+		read_bunzip(bd, outbuf, UNPACKED_SCRIPTS_LENGTH);
+	}
+	dealloc_bunzip(bd);
+	return outbuf;
+}
+
+/*
+ * In standalone shell mode we sometimes want the index of the script
+ * and sometimes the index offset by NUM_APPLETS.
+ */
+static int
+find_script_by_name(const char *arg)
+{
+	const char *s = script_names;
+	int i = 0;
+
+	while (*s) {
+		if (strcmp(arg, s) == 0)
+			return i;
+		i++;
+		while (*s++ != '\0')
+			continue;
+	}
+	return -1;
+}
+
+char* FAST_FUNC
+get_script_content(unsigned n)
+{
+	char *t = unpack_scripts();
+	if (t) {
+		while (n != 0) {
+			while (*t++ != '\0')
+				continue;
+			n--;
+		}
+	}
+	return t;
+}
+# endif /* NUM_SCRIPTS > 0 */
+
+# if ENABLE_BUSYBOX || NUM_APPLETS > 0 || NUM_SCRIPTS > 0
 static NORETURN void run_applet_and_exit(const char *name, char **argv)
 {
 #  if ENABLE_BUSYBOX
@@ -968,6 +1042,13 @@ static NORETURN void run_applet_and_exit(const char *name, char **argv)
 			run_applet_no_and_exit(applet, name, argv);
 	}
 #  endif
+#  if NUM_SCRIPTS > 0
+	{
+		int script = find_script_by_name(name);
+		if (script >= 0)
+			exit(ash_main(-script - 1, argv));
+	}
+#  endif
 
 	/*bb_error_msg_and_die("applet not found"); - links in printf */
 	full_write2_str(applet_name);