u-boot/common/cmd_help.c
Wolfgang Denk 54841ab50c Make sure that argv[] argument pointers are not modified.
The hush shell dynamically allocates (and re-allocates) memory for the
argument strings in the "char *argv[]" argument vector passed to
commands.  Any code that modifies these pointers will cause serious
corruption of the malloc data structures and crash U-Boot, so make
sure the compiler can check that no such modifications are being done
by changing the code into "char * const argv[]".

This modification is the result of debugging a strange crash caused
after adding a new command, which used the following argument
processing code which has been working perfectly fine in all Unix
systems since version 6 - but not so in U-Boot:

int main (int argc, char **argv)
{
	while (--argc > 0 && **++argv == '-') {
/* ====> */	while (*++*argv) {
			switch (**argv) {
			case 'd':
				debug++;
				break;
			...
			default:
				usage ();
			}
		}
	}
	...
}

The line marked "====>" will corrupt the malloc data structures and
usually cause U-Boot to crash when the next command gets executed by
the shell.  With the modification, the compiler will prevent this with
an
	error: increment of read-only location '*argv'

N.B.: The code above can be trivially rewritten like this:

	while (--argc > 0 && **++argv == '-') {
		char *arg = *argv;
		while (*++arg) {
			switch (*arg) {
			...

Signed-off-by: Wolfgang Denk <wd@denx.de>
Acked-by: Mike Frysinger <vapier@gentoo.org>
2010-07-04 23:55:42 +02:00

50 lines
1.5 KiB
C

/*
* Copyright 2000-2009
* Wolfgang Denk, DENX Software Engineering, wd@denx.de.
*
* See file CREDITS for list of people who contributed to this
* project.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
* MA 02111-1307 USA
*/
#include <common.h>
#include <command.h>
int do_help(cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
{
return _do_help(&__u_boot_cmd_start,
&__u_boot_cmd_end - &__u_boot_cmd_start,
cmdtp, flag, argc, argv);
}
U_BOOT_CMD(
help, CONFIG_SYS_MAXARGS, 1, do_help,
"print command description/usage",
"\n"
" - print brief description of all commands\n"
"help command ...\n"
" - print detailed usage of 'command'"
);
/* This does not use the U_BOOT_CMD macro as ? can't be used in symbol names */
cmd_tbl_t __u_boot_cmd_question_mark Struct_Section = {
"?", CONFIG_SYS_MAXARGS, 1, do_help,
"alias for 'help'",
#ifdef CONFIG_SYS_LONGHELP
""
#endif /* CONFIG_SYS_LONGHELP */
};