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, 5 insertions, 5 deletions

diff --git a/common/hush.c b/common/hush.c
index 9eea90f..8a74d22 100644
--- a/common/hush.c
+++ b/common/hush.c
@@ -94,7 +94,7 @@
 #include <hush.h>
 #include <command.h>        /* find_cmd */
 /*cmd_boot.c*/
-extern int do_bootd (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[]);      /* do_bootd */
+extern int do_bootd (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]);      /* do_bootd */
 #endif
 #ifndef __U_BOOT__
 #include <ctype.h>     /* isalpha, isdigit */
@@ -1024,7 +1024,7 @@ static void get_user_input(struct in_str *i)
 
 #ifdef CONFIG_BOOT_RETRY_TIME
 #  ifdef CONFIG_RESET_TO_RETRY
-	extern int do_reset (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[]);
+	extern int do_reset (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]);
 #  else
 #	error "This currently only works with CONFIG_RESET_TO_RETRY enabled"
 #  endif
@@ -1681,7 +1681,7 @@ static int run_pipe_real(struct pipe *pi)
 			} else {
 				int rcode;
 #if defined(CONFIG_CMD_BOOTD)
-	    extern int do_bootd (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[]);
+	    extern int do_bootd (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[]);
 
 				/* avoid "bootd" recursion */
 				if (cmdtp->cmd == do_bootd) {
@@ -3351,7 +3351,7 @@ static void setup_job_control(void)
 	tcsetpgrp(shell_terminal, shell_pgrp);
 }
 
-int hush_main(int argc, char **argv)
+int hush_main(int argc, char * const *argv)
 {
 	int opt;
 	FILE *input;
@@ -3588,7 +3588,7 @@ static char * make_string(char ** inp)
 }
 
 #ifdef __U_BOOT__
-int do_showvar (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
+int do_showvar (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	int i, k;
 	int rcode = 0;