Function bios16

freebsd/i386/i386/bios.c:320–441

* this routine is really greedy with selectors, and uses 5: * * 32-bit code selector: to return to kernel * 16-bit code selector: for running code * data selector: for 16-bit data * util selector: extra utility selector * args selector: to handle pointers * * the util selector is set from the util16 entry in bios16_args, if a * "U" specifier is seen. * * See <machin

 * See <machine/pc/bios.h> for description of format specifiers
 */
int
bios16(struct bios_args *args, char *fmt, ...)
{
    char	*p, *stack, *stack_top;
    va_list 	ap;
    int 	flags = BIOSCODE_FLAG | BIOSDATA_FLAG;
    u_int 	i, arg_start, arg_end;
    void	*bios16_pmap_handle;
    arg_start = 0xffffffff;
    arg_end = 0;

    /*
     * Some BIOS entrypoints attempt to copy the largest-case
     * argument frame (in order to generalise handling for 
     * different entry types).  If our argument frame is 
     * smaller than this, the BIOS will reach off the top of
     * our constructed stack segment.  Pad the top of the stack
     * with some garbage to avoid this.
     */
    stack = (caddr_t)PAGE_SIZE - 32;

    va_start(ap, fmt);
    for (p = fmt; p && *p; p++) {
	switch (*p) {
	case 'p':			/* 32-bit pointer */
	    i = va_arg(ap, u_int);
	    arg_start = min(arg_start, i);
	    arg_end = max(arg_end, i);
	    flags |= BIOSARGS_FLAG;
	    stack -= 4;
	    break;

	case 'i':			/* 32-bit integer */
	    i = va_arg(ap, u_int);
	    stack -= 4;
	    break;

	case 'U':			/* 16-bit selector */
	    flags |= BIOSUTIL_FLAG;
	    /* FALLTHROUGH */
	case 'D':			/* 16-bit selector */
	case 'C':			/* 16-bit selector */
	    stack -= 2;
	    break;
	    
	case 's':			/* 16-bit integer passed as an int */
	    i = va_arg(ap, int);
	    stack -= 2;
	    break;

	default:
	    va_end(ap);
	    return (EINVAL);
	}
    }
    va_end(ap);

    if (flags & BIOSARGS_FLAG) {