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, 7 insertions, 7 deletions

diff --git a/board/inka4x0/inkadiag.c b/board/inka4x0/inkadiag.c
index 0a75abd..637bb5a 100644
--- a/board/inka4x0/inkadiag.c
+++ b/board/inka4x0/inkadiag.c
@@ -131,7 +131,7 @@ static void inka_digio_set_output(unsigned int state, int which)
 }
 
 static int do_inkadiag_io(cmd_tbl_t *cmdtp, int flag, int argc,
-			  char *argv[]) {
+			  char * const argv[]) {
 	unsigned int state, val;
 
 	switch (argc) {
@@ -237,7 +237,7 @@ static int ser_getc(volatile struct mpc5xxx_psc *psc)
 }
 
 static int do_inkadiag_serial(cmd_tbl_t *cmdtp, int flag, int argc,
-			      char *argv[]) {
+			      char * const argv[]) {
 	volatile struct NS16550 *uart;
 	volatile struct mpc5xxx_psc *psc;
 	unsigned int num, mode;
@@ -389,7 +389,7 @@ static void buzzer_turn_off(void)
 }
 
 static int do_inkadiag_buzzer(cmd_tbl_t *cmdtp, int flag, int argc,
-			      char *argv[]) {
+			      char * const argv[]) {
 
 	unsigned int period, freq;
 	int prev, i;
@@ -435,7 +435,7 @@ static int do_inkadiag_buzzer(cmd_tbl_t *cmdtp, int flag, int argc,
 	return 0;
 }
 
-static int do_inkadiag_help(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[]);
+static int do_inkadiag_help(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]);
 
 cmd_tbl_t cmd_inkadiag_sub[] = {
 	U_BOOT_CMD_MKENT(io, 1, 1, do_inkadiag_io, "read digital input",
@@ -450,10 +450,10 @@ cmd_tbl_t cmd_inkadiag_sub[] = {
 };
 
 static int do_inkadiag_help(cmd_tbl_t *cmdtp, int flag,
-			    int argc, char *argv[]) {
+			    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[]);
 	/* do_help prints command name - we prepend inkadiag to our subcommands! */
 #ifdef CONFIG_SYS_LONGHELP
 	puts ("inkadiag ");
@@ -463,7 +463,7 @@ static int do_inkadiag_help(cmd_tbl_t *cmdtp, int flag,
 }
 
 static int do_inkadiag(cmd_tbl_t *cmdtp, int flag, int argc,
-		       char *argv[]) {
+		       char * const argv[]) {
 	cmd_tbl_t *c;
 
 	c = find_cmd_tbl(argv[1], &cmd_inkadiag_sub[0], ARRAY_SIZE(cmd_inkadiag_sub));