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/board/zeus/zeus.c b/board/zeus/zeus.c
index 01273a1..e295151 100644
--- a/board/zeus/zeus.c
+++ b/board/zeus/zeus.c
@@ -44,7 +44,7 @@ extern uchar default_environment[];
 
 ulong flash_get_size(ulong base, int banknum);
 void env_crc_update(void);
-int do_reset (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[]);
+int do_reset (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]);
 
 static u32 start_time;
 
@@ -278,7 +278,7 @@ static int restore_default(void)
 	return 0;
 }
 
-int do_set_default(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_set_default(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	char *buf;
 	char *buf_save;
@@ -336,7 +336,7 @@ static inline int sw_reset_pressed(void)
 	return !(in_be32((void *)GPIO0_IR) & GPIO_VAL(CONFIG_SYS_GPIO_SW_RESET));
 }
 
-int do_chkreset(cmd_tbl_t* cmdtp, int flag, int argc, char* argv[])
+int do_chkreset(cmd_tbl_t* cmdtp, int flag, int argc, char * const argv[])
 {
 	int delta;
 	int count = 0;