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/common/cmd_mfsl.c b/common/cmd_mfsl.c
index b19ad0e6381..eeef2cddab6 100644
--- a/common/cmd_mfsl.c
+++ b/common/cmd_mfsl.c
@@ -31,7 +31,7 @@
 #include <command.h>
 #include <asm/asm.h>
 
-int do_frd (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
+int do_frd (cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
 {
 	unsigned int fslnum;
 	unsigned int num;
@@ -189,7 +189,7 @@ int do_frd (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
 	return 0;
 }
 
-int do_fwr (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
+int do_fwr (cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
 {
 	unsigned int fslnum;
 	unsigned int num;
@@ -348,7 +348,7 @@ int do_fwr (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
 
 }
 
-int do_rspr (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
+int do_rspr (cmd_tbl_t * cmdtp, int flag, int argc, char * const argv[])
 {
 	unsigned int reg = 0;
 	unsigned int val = 0;