[PATCH 1/2] Allow BusyBox to be built without a list of applet names

Tito farmatito at tiscali.it
Sat Apr 30 05:29:09 UTC 2016



On 04/29/2016 09:05 PM, ..mg.. wrote:
> On Fri, Apr 29, 2016 at 08:54:55PM +0200, Tito wrote:
>>
>>
>> On 04/29/2016 02:47 PM, Ron Yorston wrote:
>>> Use a hash of the command name to determine which applet to execute.
>>> Invalid names will also match.
>>
>> Hi,
>> what exactly means:
>> "Invalid names will also match" ?
>
>
> The lookup hash isn't collision-free: more than one input string
> points to the same applet.  Normally invalid applet names might
> cause an unexpected one to run

And this should be a GoodThing (TM) ?

Ciao,
Tito

> HTH
> -mg
>
>
>
>>
>> Ciao,
>> Tito
>>
>>
>>>
>>> Without applet names the following features don't work:
>>>
>>>   - busybox --list
>>>   - busybox --install
>>>   - tab completion for applets in standalone shell mode
>>>   - in standalone shell mode the help builtin doesn't list applets
>>>
>>> Compared with the current default configuration, not storing applet
>>> names gives:
>>>
>>> function                                             old     new   delta
>>> applet_hash                                            -     734    +734
>>> usr_bin                                               10       -     -10
>>> usr_sbin                                              11       -     -11
>>> applet_nameofs                                        14       -     -14
>>> install_dir                                           20       -     -20
>>> find_applet_by_name                                  112      69     -43
>>> applet_install_loc                                   184       -    -184
>>> run_applet_and_exit                                  675     192    -483
>>> applet_names                                        2536       -   -2536
>>> ------------------------------------------------------------------------------
>>> (add/remove: 1/6 grow/shrink: 0/2 up/down: 734/-3301)       Total: -2567 bytes
>>>     text	   data	    bss	    dec	    hex	filename
>>>   764230	   2059	   1636	 767925	  bb7b5	busybox_old
>>>   761520	   2059	   1636	 765215	  bad1f	busybox_unstripped
>>>
>>> Signed-off-by: Ron Yorston <rmy at pobox.com>
>>> ---
>>>   Config.in               |  9 +++++++++
>>>   applets/applet_tables.c | 46 ++++++++++++++++++++++++++++++++++++++++++++--
>>>   libbb/appletlib.c       | 33 ++++++++++++++++++++++++++++++++-
>>>   libbb/lineedit.c        |  2 +-
>>>   shell/ash.c             |  2 +-
>>>   5 files changed, 87 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/Config.in b/Config.in
>>> index 0a0b5d7..49ee333 100644
>>> --- a/Config.in
>>> +++ b/Config.in
>>> @@ -116,9 +116,18 @@ config FEATURE_COMPRESS_USAGE
>>>   	  and have very little memory, this might not be a win. Otherwise,
>>>   	  you probably want this.
>>>
>>> +config STORE_APPLET_NAMES
>>> +	bool "Store applet names"
>>> +	default y
>>> +	help
>>> +	  Enable BusyBox applet names to be stored in the binary.
>>> +	  Disabling this will save some space but also disables useful
>>> +	  features like the installer and listing applet names.
>>> +
>>>   config FEATURE_INSTALLER
>>>   	bool "Support --install [-s] to install applet links at runtime"
>>>   	default y
>>> +	depends on STORE_APPLET_NAMES
>>>   	help
>>>   	  Enable 'busybox --install [-s]' support. This will allow you to use
>>>   	  busybox at runtime to create hard links or symlinks for all the
>>> diff --git a/applets/applet_tables.c b/applets/applet_tables.c
>>> index 843f2ec..31ea188 100644
>>> --- a/applets/applet_tables.c
>>> +++ b/applets/applet_tables.c
>>> @@ -11,6 +11,7 @@
>>>   #include <sys/stat.h>
>>>   #include <fcntl.h>
>>>   #include <stdlib.h>
>>> +#include <stdint.h>
>>>   #include <string.h>
>>>   #include <stdio.h>
>>>   #include <unistd.h>
>>> @@ -34,6 +35,7 @@ struct bb_applet {
>>>   	/* true if instead of fork(); exec("applet"); waitpid();
>>>   	 * one can simply call applet_main(argc,argv); */
>>>   	unsigned char nofork;
>>> +	uint32_t app_hash;
>>>   };
>>>
>>>   /* Define struct bb_applet applets[] */
>>> @@ -58,9 +60,21 @@ static int str_isalnum_(const char *s)
>>>   	return 1;
>>>   }
>>>
>>> +#if !ENABLE_STORE_APPLET_NAMES
>>> +static uint32_t hash(const char *s, uint32_t mul)
>>> +{
>>> +	uint32_t h = *s++;
>>> +	while (*s)
>>> +		h = (h * mul) ^ (uint8_t)*s++;
>>> +	return (uint16_t)h & 0xffff;
>>> +}
>>> +#endif
>>> +
>>>   int main(int argc, char **argv)
>>>   {
>>>   	int i, j;
>>> +	uint32_t mul;
>>> +	int MAX_APPLET_NAME_LEN = 0;
>>>
>>>   	// In find_applet_by_name(), before linear search, narrow it down
>>>   	// by looking at N "equidistant" names. With ~350 applets:
>>> @@ -121,6 +135,8 @@ int main(int argc, char **argv)
>>>   	}
>>>
>>>   	//printf("#ifndef SKIP_definitions\n");
>>> +	mul = 0;
>>> +#if ENABLE_STORE_APPLET_NAMES
>>>   	printf("const char applet_names[] ALIGN1 = \"\"\n");
>>>   	for (i = 0; i < NUM_APPLETS; i++) {
>>>   		printf("\"%s\" \"\\0\"\n", applets[i].name);
>>> @@ -128,10 +144,36 @@ int main(int argc, char **argv)
>>>   //			MAX_APPLET_NAME_LEN = strlen(applets[i].name);
>>>   	}
>>>   	printf(";\n\n");
>>> +#else
>>> +	mul = 1;
>>> + collision:
>>> +	for (i = 0; i < NUM_APPLETS; i++) {
>>> +		int j;
>>> +		uint32_t h = hash(applets[i].name, mul);
>>> +		for (j = 0; j < i; j++) {
>>> +			if (h == applets[j].app_hash) {
>>> +				mul += 2;
>>> +				goto collision;
>>> +			}
>>> +		}
>>> +		applets[i].app_hash = h;
>>> +	}
>>> +#endif
>>> +
>>> +	printf("#define APPNAME_HASH_MUL %u\n\n", mul);
>>> +	if ( mul != 0 ) {
>>> +		printf("const uint16_t applet_hash[] ALIGN2 = {\n");
>>> +		for (i = 0; i < NUM_APPLETS; i++) {
>>> +			printf("0x%04x,\n", applets[i].app_hash);
>>> +		}
>>> +		printf("};\n\n");
>>> +	}
>>>
>>>   	for (i = 0; i < NUM_APPLETS; i++) {
>>>   		if (str_isalnum_(applets[i].name))
>>>   			printf("#define APPLET_NO_%s %d\n", applets[i].name, i);
>>> +		if (MAX_APPLET_NAME_LEN < strlen(applets[i].name))
>>> +			MAX_APPLET_NAME_LEN = strlen(applets[i].name);
>>>   	}
>>>   	printf("\n");
>>>
>>> @@ -190,8 +232,8 @@ int main(int argc, char **argv)
>>>   	printf("};\n");
>>>   #endif
>>>   	//printf("#endif /* SKIP_definitions */\n");
>>> -//	printf("\n");
>>> -//	printf("#define MAX_APPLET_NAME_LEN %u\n", MAX_APPLET_NAME_LEN);
>>> +	printf("\n");
>>> +	printf("#define MAX_APPLET_NAME_LEN %u\n", MAX_APPLET_NAME_LEN);
>>>
>>>   	if (argv[2]) {
>>>   		char line_old[80];
>>> diff --git a/libbb/appletlib.c b/libbb/appletlib.c
>>> index b682e6b..9a4f367 100644
>>> --- a/libbb/appletlib.c
>>> +++ b/libbb/appletlib.c
>>> @@ -139,6 +139,7 @@ void FAST_FUNC bb_show_usage(void)
>>>   	xfunc_die();
>>>   }
>>>
>>> +#if APPNAME_HASH_MUL == 0
>>>   int FAST_FUNC find_applet_by_name(const char *name)
>>>   {
>>>   	unsigned i, max;
>>> @@ -265,6 +266,30 @@ int FAST_FUNC find_applet_by_name(const char *name)
>>>   	return -1;
>>>   #endif
>>>   }
>>> +#else
>>> +static uint32_t hash(const char *s)
>>> +{
>>> +	uint32_t h = *s++;
>>> +	while (*s)
>>> +		h = (h * APPNAME_HASH_MUL) ^ (uint8_t)*s++;
>>> +	return (uint16_t)h & 0xffff;
>>> +}
>>> +
>>> +int FAST_FUNC find_applet_by_name(const char *name)
>>> +{
>>> +	uint32_t h = hash(name);
>>> +	int i;
>>> +
>>> +	if (strlen(name) > MAX_APPLET_NAME_LEN)
>>> +		return -1;
>>> +
>>> +	for (i=0; i<NUM_APPLETS; i++)
>>> +		if (applet_hash[i] == h)
>>> +			return i;
>>> +
>>> +	return -1;
>>> +}
>>> +#endif
>>>
>>>
>>>   void lbb_prepare(const char *applet
>>> @@ -733,7 +758,9 @@ static int busybox_main(char **argv)
>>>   			"copyright notices.\n"
>>>   			"\n"
>>>   			"Usage: busybox [function [arguments]...]\n"
>>> +			IF_STORE_APPLET_NAMES(
>>>   			"   or: busybox --list"IF_FEATURE_INSTALLER("[-full]")"\n"
>>> +			)
>>>   			IF_FEATURE_INSTALLER(
>>>   			"   or: busybox --install [-s] [DIR]\n"
>>>   			)
>>> @@ -753,8 +780,11 @@ static int busybox_main(char **argv)
>>>   			"\tTo run external program, use full path (/sbin/ip instead of ip).\n"
>>>   			)
>>>   			"\n"
>>> +			IF_STORE_APPLET_NAMES(
>>>   			"Currently defined functions:\n"
>>> +			)
>>>   		);
>>> +#if ENABLE_STORE_APPLET_NAMES
>>>   		col = 0;
>>>   		a = applet_names;
>>>   		/* prevent last comma to be in the very last pos */
>>> @@ -776,10 +806,11 @@ static int busybox_main(char **argv)
>>>   			a += len2 - 1;
>>>   		}
>>>   		full_write2_str("\n\n");
>>> +#endif
>>>   		return 0;
>>>   	}
>>>
>>> -	if (is_prefixed_with(argv[1], "--list")) {
>>> +	if (ENABLE_STORE_APPLET_NAMES && is_prefixed_with(argv[1], "--list")) {
>>>   		unsigned i = 0;
>>>   		const char *a = applet_names;
>>>   		dup2(1, 2);
>>> diff --git a/libbb/lineedit.c b/libbb/lineedit.c
>>> index 3e62f46..2c35d50 100644
>>> --- a/libbb/lineedit.c
>>> +++ b/libbb/lineedit.c
>>> @@ -775,7 +775,7 @@ static NOINLINE unsigned complete_cmd_dir_file(const char *command, int type)
>>>   	}
>>>   	pf_len = strlen(pfind);
>>>
>>> -#if ENABLE_FEATURE_SH_STANDALONE && NUM_APPLETS != 1
>>> +#if ENABLE_FEATURE_SH_STANDALONE && NUM_APPLETS != 1 && ENABLE_STORE_APPLET_NAMES
>>>   	if (type == FIND_EXE_ONLY) {
>>>   		const char *p = applet_names;
>>>
>>> diff --git a/shell/ash.c b/shell/ash.c
>>> index faa45a8..acaf95c 100644
>>> --- a/shell/ash.c
>>> +++ b/shell/ash.c
>>> @@ -12588,7 +12588,7 @@ helpcmd(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
>>>   			col = 0;
>>>   		}
>>>   	}
>>> -# if ENABLE_FEATURE_SH_STANDALONE
>>> +# if ENABLE_FEATURE_SH_STANDALONE && ENABLE_STORE_APPLET_NAMES
>>>   	{
>>>   		const char *a = applet_names;
>>>   		while (*a) {
>>>
>> _______________________________________________
>> busybox mailing list
>> busybox at busybox.net
>> http://lists.busybox.net/mailman/listinfo/busybox
> _______________________________________________
> busybox mailing list
> busybox at busybox.net
> http://lists.busybox.net/mailman/listinfo/busybox
>


More information about the busybox mailing list