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, 2 insertions, 2 deletions

diff --git a/common/lcd.c b/common/lcd.c
index 64fb1c6..93ddedf 100644
--- a/common/lcd.c
+++ b/common/lcd.c
@@ -78,7 +78,7 @@ static inline void lcd_putc_xy (ushort x, ushort y, uchar  c);
 
 static int lcd_init (void *lcdbase);
 
-static int lcd_clear (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[]);
+static int lcd_clear (cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[]);
 static void *lcd_logo (void);
 
 static int lcd_getbgcolor (void);
@@ -350,7 +350,7 @@ int drv_lcd_init (void)
 }
 
 /*----------------------------------------------------------------------*/
-static int lcd_clear (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
+static int lcd_clear (cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
 {
 #if LCD_BPP == LCD_MONOCHROME
 	/* Setting the palette */