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>

2 files changed, 4 insertions, 4 deletions

diff --git a/board/lwmon5/kbd.c b/board/lwmon5/kbd.c
index be1a1df..0e26b89 100644
--- a/board/lwmon5/kbd.c
+++ b/board/lwmon5/kbd.c
@@ -380,7 +380,7 @@ static uchar *key_match (uchar *kbd_data)
 
 /***********************************************************************
 F* Function:     int do_kbd (cmd_tbl_t *cmdtp, int flag,
-F*                           int argc, char *argv[]) P*A*Z*
+F*                           int argc, char * const argv[]) P*A*Z*
  *
 P* Parameters:   cmd_tbl_t *cmdtp
 P*                - Pointer to our command table entry
@@ -389,7 +389,7 @@ P*                - If the CMD_FLAG_REPEAT bit is set, then this call is
 P*                  a repetition
 P*               int argc
 P*                - Argument count
-P*               char *argv[]
+P*               char * const argv[]
 P*                - Array of the actual arguments
 P*
 P* Returnvalue:  int
@@ -404,7 +404,7 @@ D* Design:       wd@denx.de
 C* Coding:       wd@denx.de
 V* Verification: dzu@denx.de
  ***********************************************************************/
-int do_kbd (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_kbd (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	uchar kbd_data[KEYBD_DATALEN];
 	char keybd_env[2 * KEYBD_DATALEN + 1];
diff --git a/board/lwmon5/lwmon5.c b/board/lwmon5/lwmon5.c
index 415e036..3948c13 100644
--- a/board/lwmon5/lwmon5.c
+++ b/board/lwmon5/lwmon5.c
@@ -304,7 +304,7 @@ void hw_watchdog_reset(void)
 	gpio_write_bit(CONFIG_SYS_GPIO_WATCHDOG, val);
 }
 
-int do_eeprom_wp(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_eeprom_wp(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	if (argc < 2) {
 		cmd_usage(cmdtp);