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, 4 insertions, 4 deletions

diff --git a/common/cmd_load.c b/common/cmd_load.c
index d6bbb78..52ed1fa 100644
--- a/common/cmd_load.c
+++ b/common/cmd_load.c
@@ -51,7 +51,7 @@ static int do_echo = 1;
 /* -------------------------------------------------------------------- */
 
 #if defined(CONFIG_CMD_LOADS)
-int do_load_serial (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_load_serial (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	long offset = 0;
 	ulong addr;
@@ -255,7 +255,7 @@ read_record (char *buf, ulong len)
 
 #if defined(CONFIG_CMD_SAVES)
 
-int do_save_serial (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_save_serial (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	ulong offset = 0;
 	ulong size   = 0;
@@ -433,7 +433,7 @@ int  his_pad_count;  /* number of pad chars he needs */
 char his_pad_char;   /* pad chars he needs */
 char his_quote;      /* quote chars he'll use */
 
-int do_load_serial_bin (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_load_serial_bin (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	ulong offset = 0;
 	ulong addr;
@@ -1091,7 +1091,7 @@ U_BOOT_CMD(
 /* -------------------------------------------------------------------- */
 
 #if defined(CONFIG_CMD_HWFLOW)
-int do_hwflow (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_hwflow (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	extern int hwflow_onoff(int);