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, 4 insertions, 4 deletions

diff --git a/board/cm5200/fwupdate.c b/board/cm5200/fwupdate.c
index 5a27191..c1a4a19 100644
--- a/board/cm5200/fwupdate.c
+++ b/board/cm5200/fwupdate.c
@@ -35,9 +35,9 @@
 
 #include "fwupdate.h"
 
-extern int do_bootm(cmd_tbl_t *, int, int, char *[]);
+extern int do_bootm(cmd_tbl_t *, int, int, char * const []);
 extern long do_fat_read(const char *, void *, unsigned long, int);
-extern int do_fat_fsload(cmd_tbl_t *, int, int, char *[]);
+extern int do_fat_fsload(cmd_tbl_t *, int, int, char * const []);
 
 static int load_rescue_image(ulong);
 
@@ -47,7 +47,7 @@ void cm5200_fwupdate(void)
 	char *rsargs;
 	char *tmp = NULL;
 	char ka[16];
-	char *argv[3] = { "bootm", ka, NULL };
+	char * const argv[3] = { "bootm", ka, NULL };
 
 	/* Check if rescue system is disabled... */
 	if (getenv("norescue")) {
@@ -99,7 +99,7 @@ static int load_rescue_image(ulong addr)
 	char *tmp;
 	char dev[7];
 	char addr_str[16];
-	char *argv[6] = { "fatload", "usb", dev, addr_str, nxri, NULL };
+	char * const argv[6] = { "fatload", "usb", dev, addr_str, nxri, NULL };
 	block_dev_desc_t *stor_dev = NULL;
 	cmd_tbl_t *bcmd;