commit 54841ab50c20d6fa6c9cc3eb826989da3a22d934
author Wolfgang Denk <wd@denx.de> Mon Jun 28 22:00:46 2010 +0200
committer Wolfgang Denk <wd@denx.de> Sun Jul 04 23:55:42 2010 +0200
tree 400f22f0a12ff0ae6c472bed6ac648befc1744a2
parent b218ccb5435e64ac2318bb8b6c9594ef1cc724cd

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>

board/bc3450/cmd_bc3450.c

diff --git a/board/bc3450/cmd_bc3450.c b/board/bc3450/cmd_bc3450.c
index 271ffb1..a9e4902 100644
--- a/board/bc3450/cmd_bc3450.c
+++ b/board/bc3450/cmd_bc3450.c
@@ -173,7 +173,7 @@
  * read and prints the dip switch
  * and/or external config inputs (4bits) 0...0x0F
  */
-int cmd_dip (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
+int cmd_dip (cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
 {
 	vu_long rc = 0;
 
@@ -205,7 +205,7 @@
  * buz - turns Buzzer on/off
  */
 #ifdef CONFIG_BC3450_BUZZER
-static int cmd_buz (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
+static int cmd_buz (cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
 {
 	if (argc != 2) {
 		printf ("Usage:\nspecify one argument: \"on\" or \"off\"\n");
@@ -236,7 +236,7 @@
 /*
  * fp - front panel commands
  */
-static int cmd_fp (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
+static int cmd_fp (cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
 {
 	sm501_gpio_init ();
 
@@ -491,7 +491,7 @@
 	ds1620_out (THERM_START_CONVERT, 0, 0);
 }
 
-static int cmd_temp (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
+static int cmd_temp (cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
 {
 	int i;
 	struct therm therm;
@@ -682,7 +682,7 @@
  * return 1 on CAN failure
  * return 0 if no failure
  */
-int do_can (char *argv[])
+int do_can (char * const argv[])
 {
 	int i;
 	struct mpc5xxx_mscan *can1 =
@@ -777,7 +777,7 @@
 /*
  * test - BC3450 HW test routines
  */
-int cmd_test (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
+int cmd_test (cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
 {
 #ifdef CONFIG_BC3450_CAN
 	int rcode;