u-boot/common/cmd_strings.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

48 lines
956 B
C

/*
* cmd_strings.c - just like `strings` command
*
* Copyright (c) 2008 Analog Devices Inc.
*
* Licensed under the GPL-2 or later.
*/
#include <config.h>
#include <common.h>
#include <command.h>
static char *start_addr, *last_addr;
int do_strings(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
{
if (argc == 1) {
cmd_usage(cmdtp);
return 1;
}
if ((flag & CMD_FLAG_REPEAT) == 0) {
start_addr = (char *)simple_strtoul(argv[1], NULL, 16);
if (argc > 2)
last_addr = (char *)simple_strtoul(argv[2], NULL, 16);
else
last_addr = (char *)-1;
}
char *addr = start_addr;
do {
puts(addr);
puts("\n");
addr += strlen(addr) + 1;
} while (addr[0] && addr < last_addr);
last_addr = addr + (last_addr - start_addr);
start_addr = addr;
return 0;
}
U_BOOT_CMD(strings, 3, 1, do_strings,
"display strings",
"<addr> [byte count]\n"
" - display strings at <addr> for at least [byte count] or first double NUL"
);