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_dcr.c b/common/cmd_dcr.c
index 4f23b8d..45de8cd 100644
--- a/common/cmd_dcr.c
+++ b/common/cmd_dcr.c
@@ -36,7 +36,7 @@ unsigned long set_dcr (unsigned short, unsigned long);
  * Interpreter command to retrieve an AMCC PPC 4xx Device Control Register
  * =======================================================================
  */
-int do_getdcr ( cmd_tbl_t *cmdtp, int flag, int argc, char *argv[] )
+int do_getdcr ( cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[] )
 {
 	unsigned short dcrn;	/* Device Control Register Num */
 	unsigned long value;	/* DCR's value */
@@ -63,7 +63,7 @@ int do_getdcr ( cmd_tbl_t *cmdtp, int flag, int argc, char *argv[] )
  * Interpreter command to set an AMCC PPC 4xx Device Control Register
  * ======================================================================
 */
-int do_setdcr (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
+int do_setdcr (cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
 {
 	unsigned short dcrn;	/* Device Control Register Num */
 	unsigned long value;
@@ -110,7 +110,7 @@ int do_setdcr (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
  * Device Control Register inderect addressing.
  * =======================================================================
  */
-int do_getidcr (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_getidcr (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	unsigned short adr_dcrn;	/* Device Control Register Num for Address */
 	unsigned short dat_dcrn;	/* Device Control Register Num for Data */
@@ -166,7 +166,7 @@ int do_getidcr (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
  * Device Control Register inderect addressing.
  * =======================================================================
  */
-int do_setidcr (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
+int do_setidcr (cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
 {
 	unsigned short adr_dcrn;	/* Device Control Register Num for Address */
 	unsigned short dat_dcrn;	/* Device Control Register Num for Data */