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, 3 insertions, 3 deletions

diff --git a/common/cmd_mmc.c b/common/cmd_mmc.c
index c67c9cf..698157f 100644
--- a/common/cmd_mmc.c
+++ b/common/cmd_mmc.c
@@ -28,7 +28,7 @@
 #ifndef CONFIG_GENERIC_MMC
 static int curr_device = -1;
 
-int do_mmc (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_mmc (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	int dev;
 
@@ -114,7 +114,7 @@ static void print_mmcinfo(struct mmc *mmc)
 	printf("Bus Width: %d-bit\n", mmc->bus_width);
 }
 
-int do_mmcinfo (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_mmcinfo (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	struct mmc *mmc;
 	int dev_num;
@@ -140,7 +140,7 @@ U_BOOT_CMD(mmcinfo, 2, 0, do_mmcinfo,
 	""
 );
 
-int do_mmcops(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_mmcops(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	int rc = 0;