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>

2 files changed, 3 insertions, 3 deletions

diff --git a/arch/powerpc/lib/bootm.c b/arch/powerpc/lib/bootm.c
index 6702df5..3064121 100644
--- a/arch/powerpc/lib/bootm.c
+++ b/arch/powerpc/lib/bootm.c
@@ -47,7 +47,7 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
-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[]);
 extern ulong get_effective_memsize(void);
 static ulong get_sp (void);
 static void set_clocks_in_mhz (bd_t *kbd);
@@ -297,7 +297,7 @@ static int boot_body_linux(bootm_headers_t *images)
 }
 
 __attribute__((noinline))
-int do_bootm_linux(int flag, int argc, char *argv[], bootm_headers_t *images)
+int do_bootm_linux(int flag, int argc, char * const argv[], bootm_headers_t *images)
 {
 	int	ret;
 
diff --git a/arch/powerpc/lib/kgdb.c b/arch/powerpc/lib/kgdb.c
index d3eb1f3..1ec6818 100644
--- a/arch/powerpc/lib/kgdb.c
+++ b/arch/powerpc/lib/kgdb.c
@@ -313,7 +313,7 @@ kgdb_putregs(struct pt_regs *regs, char *buf, int length)
    the debugger. */
 
 void
-kgdb_breakpoint(int argc, char *argv[])
+kgdb_breakpoint(int argc, char * const argv[])
 {
 	asm("	.globl breakinst\n\
 	     breakinst: .long 0x7d821008\n\