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, 11 insertions, 11 deletions

diff --git a/board/digsy_mtc/cmd_mtc.c b/board/digsy_mtc/cmd_mtc.c
index ecea5b3..621980d 100644
--- a/board/digsy_mtc/cmd_mtc.c
+++ b/board/digsy_mtc/cmd_mtc.c
@@ -68,7 +68,7 @@ static void mtc_calculate_checksum(tx_msp_cmd *packet)
 		packet->cks += buff[i];
 }
 
-static int do_mtc_led(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+static int do_mtc_led(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	tx_msp_cmd pcmd;
 	rx_msp_cmd prx;
@@ -120,7 +120,7 @@ static int do_mtc_led(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
 	return err;
 }
 
-static int do_mtc_key(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+static int do_mtc_key(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	tx_msp_cmd pcmd;
 	rx_msp_cmd prx;
@@ -142,7 +142,7 @@ static int do_mtc_key(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
 	return err;
 }
 
-static int do_mtc_digout(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+static int do_mtc_digout(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	tx_msp_cmd pcmd;
 	rx_msp_cmd prx;
@@ -171,7 +171,7 @@ static int do_mtc_digout(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
 	return err;
 }
 
-static int do_mtc_digin(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+static int do_mtc_digin(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	tx_msp_cmd pcmd;
 	rx_msp_cmd prx;
@@ -205,7 +205,7 @@ static int do_mtc_digin(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
 	return err;
 }
 
-static int do_mtc_appreg(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+static int do_mtc_appreg(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	tx_msp_cmd pcmd;
 	rx_msp_cmd prx;
@@ -232,7 +232,7 @@ static int do_mtc_appreg(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
 	return err;
 }
 
-static int do_mtc_version(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+static int do_mtc_version(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	tx_msp_cmd pcmd;
 	rx_msp_cmd prx;
@@ -254,7 +254,7 @@ static int do_mtc_version(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
 	return err;
 }
 
-static int do_mtc_state(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+static int do_mtc_state(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	tx_msp_cmd pcmd;
 	rx_msp_cmd prx;
@@ -281,7 +281,7 @@ static int do_mtc_state(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
 	return err;
 }
 
-static int do_mtc_help(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[]);
+static int do_mtc_help(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]);
 
 cmd_tbl_t cmd_mtc_sub[] = {
 	U_BOOT_CMD_MKENT(led, 3, 1, do_mtc_led,
@@ -308,11 +308,11 @@ cmd_tbl_t cmd_mtc_sub[] = {
 	"[command] - get help for command\n"),
 };
 
-static int do_mtc_help(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+static int do_mtc_help(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	extern int _do_help(cmd_tbl_t *cmd_start, int cmd_items,
 			    cmd_tbl_t *cmdtp, int flag,
-			    int argc, char *argv[]);
+			    int argc, char * const argv[]);
 #ifdef CONFIG_SYS_LONGHELP
 	puts("mtc ");
 #endif
@@ -320,7 +320,7 @@ static int do_mtc_help(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
 			ARRAY_SIZE(cmd_mtc_sub), cmdtp, flag, argc, argv);
 }
 
-int cmd_mtc(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int cmd_mtc(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	cmd_tbl_t *c;
 	int err = 0;