core/call16.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2009-2010 Intel Corporation; author: H. Peter Anvin
   4  *
   5  *   This program is free software; you can redistribute it and/or modify
   6  *   it under the terms of the GNU General Public License as published by
   7  *   the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
   8  *   Boston MA 02110-1301, USA; either version 2 of the License, or
   9  *   (at your option) any later version; incorporated herein by reference.
  10  *
  11  * ----------------------------------------------------------------------- */
  12
  13 /*
  14  * call16.c
  15  *
  16  * Simple wrapper to call 16-bit core functions from 32-bit code
  17  */
  18
  19 #include <stddef.h>
  20 #include <stdio.h>
  21 #include "core.h"
  22
  23 __export const com32sys_t zero_regs;    /* Common all-zero register set */
  24
  25 static inline uint32_t eflags(void)
  26 {
  27     uint32_t v;
  28
  29     asm volatile("pushfl ; popl %0" : "=rm" (v));
  30     return v;
  31 }
  32
  33 __export void call16(void (*func)(void), const com32sys_t *ireg,
  34                      com32sys_t *oreg)
  35 {
  36     com32sys_t xreg = *ireg;
  37
  38     /* Enable interrupts if and only if they are enabled in the caller */
  39     xreg.eflags.l = (xreg.eflags.l & ~EFLAGS_IF) | (eflags() & EFLAGS_IF);
  40
  41     core_farcall((size_t)func, &xreg, oreg);
  42 }