• Wolfgang Denk's avatar
    Make sure that argv[] argument pointers are not modified. · 54841ab5
    Wolfgang Denk authored
    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: default avatarWolfgang Denk <wd@denx.de>
    Acked-by: default avatarMike Frysinger <vapier@gentoo.org>
    54841ab5
bootm.c 4.96 KB