u-boot/common/cmd_setexpr.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

96 lines
2.5 KiB
C

/*
* Copyright 2008 Freescale Semiconductor, Inc.
*
* 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
*/
/*
* This file provides a shell like 'expr' function to return.
*/
#include <common.h>
#include <config.h>
#include <command.h>
static ulong get_arg(char *s, int w)
{
ulong *p;
/*
* if the parameter starts with a '*' then assume
* it is a pointer to the value we want
*/
if (s[0] == '*') {
p = (ulong *)simple_strtoul(&s[1], NULL, 16);
switch (w) {
case 1: return((ulong)(*(uchar *)p));
case 2: return((ulong)(*(ushort *)p));
case 4:
default: return(*p);
}
} else {
return simple_strtoul(s, NULL, 16);
}
}
int do_setexpr(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
ulong a, b;
char buf[16];
int w;
/* Validate arguments */
if ((argc != 5) || (strlen(argv[3]) != 1)) {
cmd_usage(cmdtp);
return 1;
}
w = cmd_get_data_size(argv[0], 4);
a = get_arg(argv[2], w);
b = get_arg(argv[4], w);
switch (argv[3][0]) {
case '|': sprintf(buf, "%lx", (a | b)); break;
case '&': sprintf(buf, "%lx", (a & b)); break;
case '+': sprintf(buf, "%lx", (a + b)); break;
case '^': sprintf(buf, "%lx", (a ^ b)); break;
case '-': sprintf(buf, "%lx", (a - b)); break;
case '*': sprintf(buf, "%lx", (a * b)); break;
case '/': sprintf(buf, "%lx", (a / b)); break;
case '%': sprintf(buf, "%lx", (a % b)); break;
default:
printf("invalid op\n");
return 1;
}
setenv(argv[1], buf);
return 0;
}
U_BOOT_CMD(
setexpr, 5, 0, do_setexpr,
"set environment variable as the result of eval expression",
"[.b, .w, .l] name value1 <op> value2\n"
" - set environment variable 'name' to the result of the evaluated\n"
" express specified by <op>. <op> can be &, |, ^, +, -, *, /, %\n"
" size argument is only meaningful if value1 and/or value2 are memory addresses"
);