Add qemu 2.4.0
[kvmfornfv.git] / qemu / roms / ipxe / src / arch / i386 / interface / syslinux / comboot_call.c
diff --git a/qemu/roms/ipxe/src/arch/i386/interface/syslinux/comboot_call.c b/qemu/roms/ipxe/src/arch/i386/interface/syslinux/comboot_call.c
new file mode 100644 (file)
index 0000000..1854501
--- /dev/null
@@ -0,0 +1,714 @@
+/*
+ * Copyright (C) 2008 Daniel Verkamp <daniel@drv.nu>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+/**
+ * @file SYSLINUX COMBOOT API
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <errno.h>
+#include <realmode.h>
+#include <biosint.h>
+#include <ipxe/console.h>
+#include <stdlib.h>
+#include <comboot.h>
+#include <bzimage.h>
+#include <pxe_call.h>
+#include <setjmp.h>
+#include <string.h>
+#include <ipxe/posix_io.h>
+#include <ipxe/process.h>
+#include <ipxe/serial.h>
+#include <ipxe/init.h>
+#include <ipxe/image.h>
+#include <ipxe/version.h>
+#include <usr/imgmgmt.h>
+#include "config/console.h"
+#include "config/serial.h"
+
+/** The "SYSLINUX" version string */
+static char __bss16_array ( syslinux_version, [32] );
+#define syslinux_version __use_data16 ( syslinux_version )
+
+/** The "SYSLINUX" copyright string */
+static char __data16_array ( syslinux_copyright, [] ) = " http://ipxe.org";
+#define syslinux_copyright __use_data16 ( syslinux_copyright )
+
+static char __data16_array ( syslinux_configuration_file, [] ) = "";
+#define syslinux_configuration_file __use_data16 ( syslinux_configuration_file )
+
+/** Feature flags */
+static uint8_t __data16 ( comboot_feature_flags ) = COMBOOT_FEATURE_IDLE_LOOP;
+#define comboot_feature_flags __use_data16 ( comboot_feature_flags )
+
+typedef union {
+       syslinux_pm_regs pm; syslinux_rm_regs rm;
+} syslinux_regs;
+
+/** Initial register values for INT 22h AX=1Ah and 1Bh */
+static syslinux_regs __text16 ( comboot_initial_regs );
+#define comboot_initial_regs __use_text16 ( comboot_initial_regs )
+
+static struct segoff __text16 ( int20_vector );
+#define int20_vector __use_text16 ( int20_vector )
+
+static struct segoff __text16 ( int21_vector );
+#define int21_vector __use_text16 ( int21_vector )
+
+static struct segoff __text16 ( int22_vector );
+#define int22_vector __use_text16 ( int22_vector )
+
+extern void int20_wrapper ( void );
+extern void int21_wrapper ( void );
+extern void int22_wrapper ( void );
+
+/* setjmp/longjmp context buffer used to return after loading an image */
+rmjmp_buf comboot_return;
+
+/* Mode flags set by INT 22h AX=0017h */
+static uint16_t comboot_graphics_mode = 0;
+
+
+/**
+ * Print a string with a particular terminator
+ */
+static void print_user_string ( unsigned int segment, unsigned int offset, char terminator ) {
+       int i = 0;
+       char c;
+       userptr_t str = real_to_user ( segment, offset );
+       for ( ; ; ) {
+               copy_from_user ( &c, str, i, 1 );
+               if ( c == terminator ) break;
+               putchar ( c );
+               i++;
+       }
+}
+
+
+/**
+ * Perform a series of memory copies from a list in low memory
+ */
+static void shuffle ( unsigned int list_segment, unsigned int list_offset, unsigned int count )
+{
+       comboot_shuffle_descriptor shuf[COMBOOT_MAX_SHUFFLE_DESCRIPTORS];
+       unsigned int i;
+
+       /* Copy shuffle descriptor list so it doesn't get overwritten */
+       copy_from_user ( shuf, real_to_user ( list_segment, list_offset ), 0,
+                        count * sizeof( comboot_shuffle_descriptor ) );
+
+       /* Do the copies */
+       for ( i = 0; i < count; i++ ) {
+               userptr_t src_u = phys_to_user ( shuf[ i ].src );
+               userptr_t dest_u = phys_to_user ( shuf[ i ].dest );
+
+               if ( shuf[ i ].src == 0xFFFFFFFF ) {
+                       /* Fill with 0 instead of copying */
+                       memset_user ( dest_u, 0, 0, shuf[ i ].len );
+               } else if ( shuf[ i ].dest == 0xFFFFFFFF ) {
+                       /* Copy new list of descriptors */
+                       count = shuf[ i ].len / sizeof( comboot_shuffle_descriptor );
+                       assert ( count <= COMBOOT_MAX_SHUFFLE_DESCRIPTORS );
+                       copy_from_user ( shuf, src_u, 0, shuf[ i ].len );
+                       i = -1;
+               } else {
+                       /* Regular copy */
+                       memmove_user ( dest_u, 0, src_u, 0, shuf[ i ].len );
+               }
+       }
+}
+
+
+/**
+ * Set default text mode
+ */
+void comboot_force_text_mode ( void ) {
+       if ( comboot_graphics_mode & COMBOOT_VIDEO_VESA ) {
+               /* Set VGA mode 3 via VESA VBE mode set */
+               __asm__ __volatile__ (
+                       REAL_CODE (
+                               "mov $0x4F02, %%ax\n\t"
+                               "mov $0x03, %%bx\n\t"
+                               "int $0x10\n\t"
+                       )
+               : : );
+       } else if ( comboot_graphics_mode & COMBOOT_VIDEO_GRAPHICS ) {
+               /* Set VGA mode 3 via standard VGA mode set */
+               __asm__ __volatile__ (
+                       REAL_CODE (
+                               "mov $0x03, %%ax\n\t"
+                               "int $0x10\n\t"
+                       )
+               : : );
+       }
+
+       comboot_graphics_mode = 0;
+}
+
+
+/**
+ * Fetch kernel and optional initrd
+ */
+static int comboot_fetch_kernel ( char *kernel_file, char *cmdline ) {
+       struct image *kernel;
+       struct image *initrd;
+       char *initrd_file;
+       int rc;
+
+       /* Find initrd= parameter, if any */
+       if ( ( initrd_file = strstr ( cmdline, "initrd=" ) ) != NULL ) {
+               char *initrd_end;
+
+               /* skip "initrd=" */
+               initrd_file += 7;
+
+               /* Find terminating space, if any, and replace with NUL */
+               initrd_end = strchr ( initrd_file, ' ' );
+               if ( initrd_end )
+                       *initrd_end = '\0';
+
+               DBG ( "COMBOOT: fetching initrd '%s'\n", initrd_file );
+
+               /* Fetch initrd */
+               if ( ( rc = imgdownload_string ( initrd_file, 0,
+                                                &initrd ) ) != 0 ) {
+                       DBG ( "COMBOOT: could not fetch initrd: %s\n",
+                             strerror ( rc ) );
+                       return rc;
+               }
+
+               /* Restore space after initrd name, if applicable */
+               if ( initrd_end )
+                       *initrd_end = ' ';
+       }
+
+       DBG ( "COMBOOT: fetching kernel '%s'\n", kernel_file );
+
+       /* Fetch kernel */
+       if ( ( rc = imgdownload_string ( kernel_file, 0, &kernel ) ) != 0 ) {
+               DBG ( "COMBOOT: could not fetch kernel: %s\n",
+                     strerror ( rc ) );
+               return rc;
+       }
+
+       /* Replace comboot image with kernel */
+       if ( ( rc = image_replace ( kernel ) ) != 0 ) {
+               DBG ( "COMBOOT: could not replace with kernel: %s\n",
+                     strerror ( rc ) );
+               return rc;
+       }
+
+       return 0;
+}
+
+
+/**
+ * Terminate program interrupt handler
+ */
+static __asmcall void int20 ( struct i386_all_regs *ix86 __unused ) {
+       rmlongjmp ( comboot_return, COMBOOT_EXIT );
+}
+
+
+/**
+ * DOS-compatible API
+ */
+static __asmcall void int21 ( struct i386_all_regs *ix86 ) {
+       ix86->flags |= CF;
+
+       switch ( ix86->regs.ah ) {
+       case 0x00:
+       case 0x4C: /* Terminate program */
+               rmlongjmp ( comboot_return, COMBOOT_EXIT );
+               break;
+
+       case 0x01: /* Get Key with Echo */
+       case 0x08: /* Get Key without Echo */
+               /* TODO: handle extended characters? */
+               ix86->regs.al = getchar( );
+
+               /* Enter */
+               if ( ix86->regs.al == 0x0A )
+                       ix86->regs.al = 0x0D;
+
+               if ( ix86->regs.ah == 0x01 )
+                       putchar ( ix86->regs.al );
+
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x02: /* Write Character */
+               putchar ( ix86->regs.dl );
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x04: /* Write Character to Serial Port */
+               serial_putc ( ix86->regs.dl );
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x09: /* Write DOS String to Console */
+               print_user_string ( ix86->segs.ds, ix86->regs.dx, '$' );
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x0B: /* Check Keyboard */
+               if ( iskey() )
+                       ix86->regs.al = 0xFF;
+               else
+                       ix86->regs.al = 0x00;
+
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x30: /* Check DOS Version */
+               /* Bottom halves all 0; top halves spell "SYSLINUX" */
+               ix86->regs.eax = 0x59530000;
+               ix86->regs.ebx = 0x4C530000;
+               ix86->regs.ecx = 0x4E490000;
+               ix86->regs.edx = 0x58550000;
+               ix86->flags &= ~CF;
+               break;
+
+       default:
+               DBG ( "COMBOOT unknown int21 function %02x\n", ix86->regs.ah );
+               break;
+       }
+}
+
+
+/**
+ * Dispatch PXE API call weakly
+ *
+ * @v ix86             Registers for PXE call
+ * @ret present                Zero if the PXE stack is present, nonzero if not
+ *
+ * A successful return only indicates that the PXE stack was available
+ * for dispatching the call; it says nothing about the success of
+ * whatever the call asked for.
+ */
+__weak int pxe_api_call_weak ( struct i386_all_regs *ix86 __unused ) {
+       return -1;
+}
+
+/**
+ * SYSLINUX API
+ */
+static __asmcall void int22 ( struct i386_all_regs *ix86 ) {
+       ix86->flags |= CF;
+
+       switch ( ix86->regs.ax ) {
+       case 0x0001: /* Get Version */
+
+               /* Number of INT 22h API functions available */
+               ix86->regs.ax = 0x001D;
+
+               /* SYSLINUX version number */
+               ix86->regs.ch = 0; /* major */
+               ix86->regs.cl = 0; /* minor */
+
+               /* SYSLINUX derivative ID */
+               ix86->regs.dl = BZI_LOADER_TYPE_IPXE;
+
+               /* SYSLINUX version */
+               snprintf ( syslinux_version, sizeof ( syslinux_version ),
+                          "\r\niPXE %s", product_version );
+
+               /* SYSLINUX version and copyright strings */
+               ix86->segs.es = rm_ds;
+               ix86->regs.si = ( ( unsigned ) __from_data16 ( syslinux_version ) );
+               ix86->regs.di = ( ( unsigned ) __from_data16 ( syslinux_copyright ) );
+
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x0002: /* Write String */
+               print_user_string ( ix86->segs.es, ix86->regs.bx, '\0' );
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x0003: /* Run command */
+               {
+                       userptr_t cmd_u = real_to_user ( ix86->segs.es, ix86->regs.bx );
+                       int len = strlen_user ( cmd_u, 0 );
+                       char cmd[len + 1];
+                       copy_from_user ( cmd, cmd_u, 0, len + 1 );
+                       DBG ( "COMBOOT: executing command '%s'\n", cmd );
+                       system ( cmd );
+                       DBG ( "COMBOOT: exiting after executing command...\n" );
+                       rmlongjmp ( comboot_return, COMBOOT_EXIT_COMMAND );
+               }
+               break;
+
+       case 0x0004: /* Run default command */
+               /* FIXME: just exit for now */
+               rmlongjmp ( comboot_return, COMBOOT_EXIT_COMMAND );
+               break;
+
+       case 0x0005: /* Force text mode */
+               comboot_force_text_mode ( );
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x0006: /* Open file */
+               {
+                       int fd;
+                       userptr_t file_u = real_to_user ( ix86->segs.es, ix86->regs.si );
+                       int len = strlen_user ( file_u, 0 );
+                       char file[len + 1];
+
+                       copy_from_user ( file, file_u, 0, len + 1 );
+
+                       if ( file[0] == '\0' ) {
+                               DBG ( "COMBOOT: attempted open with empty file name\n" );
+                               break;
+                       }
+
+                       DBG ( "COMBOOT: opening file '%s'\n", file );
+
+                       fd = open ( file );
+
+                       if ( fd < 0 ) {
+                               DBG ( "COMBOOT: error opening file %s\n", file );
+                               break;
+                       }
+
+                       /* This relies on the fact that a iPXE POSIX fd will
+                        * always fit in 16 bits.
+                        */
+#if (POSIX_FD_MAX > 65535)
+#error POSIX_FD_MAX too large
+#endif
+                       ix86->regs.si = (uint16_t) fd;
+
+                       ix86->regs.cx = COMBOOT_FILE_BLOCKSZ;
+                       ix86->regs.eax = fsize ( fd );
+                       ix86->flags &= ~CF;
+               }
+               break;
+
+       case 0x0007: /* Read file */
+               {
+                       int fd = ix86->regs.si;
+                       int len = ix86->regs.cx * COMBOOT_FILE_BLOCKSZ;
+                       int rc;
+                       fd_set fds;
+                       userptr_t buf = real_to_user ( ix86->segs.es, ix86->regs.bx );
+
+                       /* Wait for data ready to read */
+                       FD_ZERO ( &fds );
+                       FD_SET ( fd, &fds );
+
+                       select ( &fds, 1 );
+
+                       rc = read_user ( fd, buf, 0, len );
+                       if ( rc < 0 ) {
+                               DBG ( "COMBOOT: read failed\n" );
+                               ix86->regs.si = 0;
+                               break;
+                       }
+
+                       ix86->regs.ecx = rc;
+                       ix86->flags &= ~CF;
+               }
+               break;
+
+       case 0x0008: /* Close file */
+               {
+                       int fd = ix86->regs.si;
+                       close ( fd );
+                       ix86->flags &= ~CF;
+               }
+               break;
+
+       case 0x0009: /* Call PXE Stack */
+               if ( pxe_api_call_weak ( ix86 ) != 0 )
+                       ix86->flags |= CF;
+               else
+                       ix86->flags &= ~CF;
+               break;
+
+       case 0x000A: /* Get Derivative-Specific Information */
+
+               /* iPXE has its own derivative ID, so there is no defined
+                * output here; just return AL for now */
+               ix86->regs.al = BZI_LOADER_TYPE_IPXE;
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x000B: /* Get Serial Console Configuration */
+#if defined(CONSOLE_SERIAL) && !defined(COMPRESERVE)
+               ix86->regs.dx = COMCONSOLE;
+               ix86->regs.cx = 115200 / COMSPEED;
+               ix86->regs.bx = 0;
+#else
+               ix86->regs.dx = 0;
+#endif
+
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x000E: /* Get configuration file name */
+               /* FIXME: stub */
+               ix86->segs.es = rm_ds;
+               ix86->regs.bx = ( ( unsigned ) __from_data16 ( syslinux_configuration_file ) );
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x000F: /* Get IPAPPEND strings */
+               /* FIXME: stub */
+               ix86->regs.cx = 0;
+               ix86->segs.es = 0;
+               ix86->regs.bx = 0;
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x0010: /* Resolve hostname */
+               {
+                       userptr_t hostname_u = real_to_user ( ix86->segs.es, ix86->regs.bx );
+                       int len = strlen_user ( hostname_u, 0 );
+                       char hostname[len];
+                       struct in_addr addr;
+
+                       copy_from_user ( hostname, hostname_u, 0, len + 1 );
+                       
+                       /* TODO:
+                        * "If the hostname does not contain a dot (.), the
+                        * local domain name is automatically appended."
+                        */
+
+                       comboot_resolv ( hostname, &addr );
+
+                       ix86->regs.eax = addr.s_addr;
+                       ix86->flags &= ~CF;
+               }
+               break;
+
+       case 0x0011: /* Maximum number of shuffle descriptors */
+               ix86->regs.cx = COMBOOT_MAX_SHUFFLE_DESCRIPTORS;
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x0012: /* Cleanup, shuffle and boot */
+               if ( ix86->regs.cx > COMBOOT_MAX_SHUFFLE_DESCRIPTORS )
+                       break;
+
+               /* Perform final cleanup */
+               shutdown_boot();
+
+               /* Perform sequence of copies */
+               shuffle ( ix86->segs.es, ix86->regs.di, ix86->regs.cx );
+
+               /* Jump to real-mode entry point */
+               __asm__ __volatile__ (
+                       REAL_CODE ( 
+                               "pushw %0\n\t"
+                               "popw %%ds\n\t"
+                               "pushl %1\n\t"
+                               "lret\n\t"
+                       )
+                       :
+                       : "r" ( ix86->segs.ds ),
+                         "r" ( ix86->regs.ebp ),
+                         "d" ( ix86->regs.ebx ),
+                         "S" ( ix86->regs.esi ) );
+
+               assert ( 0 ); /* Execution should never reach this point */
+
+               break;
+
+       case 0x0013: /* Idle loop call */
+               step ( );
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x0015: /* Get feature flags */
+               ix86->segs.es = rm_ds;
+               ix86->regs.bx = ( ( unsigned ) __from_data16 ( &comboot_feature_flags ) );
+               ix86->regs.cx = 1; /* Number of feature flag bytes */
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x0016: /* Run kernel image */
+               {
+                       userptr_t file_u = real_to_user ( ix86->segs.ds, ix86->regs.si );
+                       userptr_t cmd_u = real_to_user ( ix86->segs.es, ix86->regs.bx );
+                       int file_len = strlen_user ( file_u, 0 );
+                       int cmd_len = strlen_user ( cmd_u, 0 );
+                       char file[file_len + 1];
+                       char cmd[cmd_len + 1];
+
+                       copy_from_user ( file, file_u, 0, file_len + 1 );
+                       copy_from_user ( cmd, cmd_u, 0, cmd_len + 1 );
+
+                       DBG ( "COMBOOT: run kernel %s %s\n", file, cmd );
+                       comboot_fetch_kernel ( file, cmd );
+                       /* Technically, we should return if we
+                        * couldn't load the kernel, but it's not safe
+                        * to do that since we have just overwritten
+                        * part of the COMBOOT program's memory space.
+                        */
+                       DBG ( "COMBOOT: exiting to run kernel...\n" );
+                       rmlongjmp ( comboot_return, COMBOOT_EXIT_RUN_KERNEL );
+               }
+               break;
+
+       case 0x0017: /* Report video mode change */
+               comboot_graphics_mode = ix86->regs.bx;
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x0018: /* Query custom font */
+               /* FIXME: stub */
+               ix86->regs.al = 0;
+               ix86->segs.es = 0;
+               ix86->regs.bx = 0;
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x001B: /* Cleanup, shuffle and boot to real mode */
+               if ( ix86->regs.cx > COMBOOT_MAX_SHUFFLE_DESCRIPTORS )
+                       break;
+
+               /* Perform final cleanup */
+               shutdown_boot();
+
+               /* Perform sequence of copies */
+               shuffle ( ix86->segs.es, ix86->regs.di, ix86->regs.cx );
+
+               /* Copy initial register values to .text16 */
+               memcpy_user ( real_to_user ( rm_cs, (unsigned) __from_text16 ( &comboot_initial_regs ) ), 0,
+                             real_to_user ( ix86->segs.ds, ix86->regs.si ), 0,
+                             sizeof(syslinux_rm_regs) );
+
+               /* Load initial register values */
+               __asm__ __volatile__ (
+                       REAL_CODE (
+                               /* Point SS:SP at the register value structure */
+                               "pushw %%cs\n\t"
+                               "popw %%ss\n\t"
+                               "movw $comboot_initial_regs, %%sp\n\t"
+
+                               /* Segment registers */
+                               "popw %%es\n\t"
+                               "popw %%ax\n\t" /* Skip CS */
+                               "popw %%ds\n\t"
+                               "popw %%ax\n\t" /* Skip SS for now */
+                               "popw %%fs\n\t"
+                               "popw %%gs\n\t"
+
+                               /* GP registers */
+                               "popl %%eax\n\t"
+                               "popl %%ecx\n\t"
+                               "popl %%edx\n\t"
+                               "popl %%ebx\n\t"
+                               "popl %%ebp\n\t" /* Skip ESP for now */
+                               "popl %%ebp\n\t"
+                               "popl %%esi\n\t"
+                               "popl %%edi\n\t"
+
+                               /* Load correct SS:ESP */
+                               "movw $(comboot_initial_regs + 6), %%sp\n\t"
+                               "popw %%ss\n\t"
+                               "movl %%cs:(comboot_initial_regs + 28), %%esp\n\t"
+
+                               "ljmp *%%cs:(comboot_initial_regs + 44)\n\t"
+                       )
+                       : : );
+
+               break;
+
+       case 0x001C: /* Get pointer to auxilliary data vector */
+               /* FIXME: stub */
+               ix86->regs.cx = 0; /* Size of the ADV */
+               ix86->flags &= ~CF;
+               break;
+
+       case 0x001D: /* Write auxilliary data vector */
+               /* FIXME: stub */
+               ix86->flags &= ~CF;
+               break;
+
+       default:
+               DBG ( "COMBOOT unknown int22 function %04x\n", ix86->regs.ax );
+               break;
+       }
+}
+
+/**
+ * Hook BIOS interrupts related to COMBOOT API (INT 20h, 21h, 22h)
+ */
+void hook_comboot_interrupts ( ) {
+
+       __asm__ __volatile__ (
+               TEXT16_CODE ( "\nint20_wrapper:\n\t"
+                             "pushl %0\n\t"
+                             "pushw %%cs\n\t"
+                             "call prot_call\n\t"
+                             "addw $4, %%sp\n\t"
+                             "call patch_cf\n\t"
+                             "iret\n\t" )
+                         : : "i" ( int20 ) );
+
+       hook_bios_interrupt ( 0x20, ( unsigned int ) int20_wrapper,
+                                     &int20_vector );
+
+       __asm__ __volatile__ (
+               TEXT16_CODE ( "\nint21_wrapper:\n\t"
+                             "pushl %0\n\t"
+                             "pushw %%cs\n\t"
+                             "call prot_call\n\t"
+                             "addw $4, %%sp\n\t"
+                             "call patch_cf\n\t"
+                             "iret\n\t" )
+                         : : "i" ( int21 ) );
+
+       hook_bios_interrupt ( 0x21, ( unsigned int ) int21_wrapper,
+                             &int21_vector );
+
+       __asm__  __volatile__ (
+               TEXT16_CODE ( "\nint22_wrapper:\n\t"
+                             "pushl %0\n\t"
+                             "pushw %%cs\n\t"
+                             "call prot_call\n\t"
+                             "addw $4, %%sp\n\t"
+                             "call patch_cf\n\t"
+                             "iret\n\t" )
+                         : : "i" ( int22) );
+
+       hook_bios_interrupt ( 0x22, ( unsigned int ) int22_wrapper,
+                             &int22_vector );
+}
+
+/**
+ * Unhook BIOS interrupts related to COMBOOT API (INT 20h, 21h, 22h)
+ */
+void unhook_comboot_interrupts ( ) {
+
+       unhook_bios_interrupt ( 0x20, ( unsigned int ) int20_wrapper,
+                               &int20_vector );
+
+       unhook_bios_interrupt ( 0x21, ( unsigned int ) int21_wrapper,
+                               &int21_vector );
+
+       unhook_bios_interrupt ( 0x22, ( unsigned int ) int22_wrapper,
+                               &int22_vector );
+}