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>

1 files changed, 2 insertions, 2 deletions

diff --git a/board/tqc/tqm5200/cmd_tb5200.c b/board/tqc/tqm5200/cmd_tb5200.c
index 578e716e7a..79c1b980a2 100644
--- a/board/tqc/tqm5200/cmd_tb5200.c
+++ b/board/tqc/tqm5200/cmd_tb5200.c
@@ -42,7 +42,7 @@ static void led_init(void)
 	gpt->gpt4.emsr |=  0x00000024;
 }
 
-int cmd_led(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int cmd_led(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	struct mpc5xxx_gpt_0_7 *gpt = (struct mpc5xxx_gpt_0_7 *)MPC5XXX_GPT;
 
@@ -72,7 +72,7 @@ static void sm501_backlight (unsigned int state)
 			~((1 << 26) | (1 << 27));
 }
 
-int cmd_backlight(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int cmd_backlight(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	if (strcmp (argv[1], "on") == 0) {
 		debug ("switch backlight on\n");