/*
* 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 (16-bit) image format
*
*/
FILE_LICENCE ( GPL2_OR_LATER );
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <errno.h>
#include <assert.h>
#include <realmode.h>
#include <basemem.h>
#include <comboot.h>
#include <ipxe/uaccess.h>
#include <ipxe/image.h>
#include <ipxe/segment.h>
#include <ipxe/init.h>
#include <ipxe/features.h>
#include <ipxe/console.h>
FEATURE ( FEATURE_IMAGE, "COMBOOT", DHCP_EB_FEATURE_COMBOOT, 1 );
/**
* COMBOOT PSP, copied to offset 0 of code segment
*/
struct comboot_psp {
/** INT 20 instruction, executed if COMBOOT image returns with RET */
uint16_t int20;
/** Segment of first non-free paragraph of memory */
uint16_t first_non_free_para;
};
/** Offset in PSP of command line */
#define COMBOOT_PSP_CMDLINE_OFFSET 0x81
/** Maximum length of command line in PSP
* (127 bytes minus space and CR) */
#define COMBOOT_MAX_CMDLINE_LEN 125
/**
* Copy command line to PSP
*
* @v image COMBOOT image
*/
static void comboot_copy_cmdline ( struct image * image, userptr_t seg_userptr ) {
const char *cmdline = ( image->cmdline ? image->cmdline : "" );
int cmdline_len = strlen ( cmdline );
if( cmdline_len > COMBOOT_MAX_CMDLINE_LEN )
cmdline_len = COMBOOT_MAX_CMDLINE_LEN;
uint8_t len_byte = cmdline_len;
char spc = ' ', cr = '\r';
/* Copy length to byte before command line */
copy_to_user ( seg_userptr, COMBOOT_PSP_CMDLINE_OFFSET - 1,
&len_byte, 1 );
/* Command line starts with space */
copy_to_user ( seg_userptr,
COMBOOT_PSP_CMDLINE_OFFSET,
&spc, 1 );
/* Copy command line */
copy_to_user ( seg_userptr,
COMBOOT_PSP_CMDLINE_OFFSET + 1,
cmdline, cmdline_len );
/* Command line ends with CR */
copy_to_user ( seg_userptr,
COMBOOT_PSP_CMDLINE_OFFSET + cmdline_len + 1,
&cr, 1 );
}
/**
* Initialize PSP
*
* @v image COMBOOT image
* @v seg_userptr segment to initialize
*/
static void comboot_init_psp ( struct image * image, userptr_t seg_userptr ) {
struct comboot_psp psp;
/* Fill PSP */
/* INT 20h instruction, byte order reversed */
psp.int20 = 0x20CD;
/* get_fbms() returns BIOS free base memory counter, which is in
* kilobytes; x * 1024 / 16 == x * 64 == x << 6 */
psp.first_non_free_para = get_fbms() << 6;
DBGC ( image, "COMBOOT %p: first non-free paragraph = 0x%x\n",
image, psp.first_non_free_para );
/* Copy the PSP to offset 0 of segment.
* The rest of the PSP was already zeroed by
* comboot_prepare_segment. */
copy_to_user ( seg_userptr, 0, &psp, sizeof( psp ) );
/* Copy the command line to the PSP */
comboot_copy_cmdline ( image, seg_userptr );
}
/**
* Execute COMBOOT image
*
* @v image COMBOOT image
* @ret rc Return status code
*/
static int comboot_exec_loop ( struct image *image ) {
userptr_t seg_userptr = real_to_user ( COMBOOT_PSP_SEG, 0 );
int state;
state = rmsetjmp ( comboot_return );
switch ( state ) {
case 0: /* First time through; invoke COMBOOT program */
/* Initialize PSP */
comboot_init_psp ( image, seg_userptr );
/* Hook COMBOOT API interrupts */
hook_comboot_interrupts();
DBGC ( image, "executing 16-bit COMBOOT image at %4x:0100\n",
COMBOOT_PSP_SEG );
/* Unregister image, so that a "boot" command doesn't
* throw us into an execution loop. We never
* reregister ourselves; COMBOOT images expect to be
* removed on exit.
*/
unregister_image ( image );
/* Store stack segment at 0x38 and stack pointer at 0x3A
* in the PSP and jump to the image */
__asm__ __volatile__ (
REAL_CODE ( /* Save return address with segment on old stack */
"popw %%ax\n\t"
"pushw %%cs\n\t"
"pushw %%ax\n\t"
/* Set DS=ES=segment with image */
"movw %w0, %%ds\n\t"
"movw %w0, %%es\n\t"
/* Set SS:SP to new stack (end of image segment) */
"movw %w0, %%ss\n\t"
"xor %%sp, %%sp\n\t"
"pushw $0\n\t"
"pushw %w0\n\t"
"pushw $0x100\n\t"
/* Zero registers (some COM files assume GP regs are 0) */
"xorw %%ax, %%ax\n\t"
"xorw %%bx, %%bx\n\t"
"xorw %%cx, %%cx\n\t"
"xorw %%dx, %%dx\n\t"
"xorw %%si, %%si\n\t"
"xorw %%di, %%di\n\t"
"xorw %%bp, %%bp\n\t"
"lret\n\t" )
: : "r" ( COMBOOT_PSP_SEG ) : "eax" );
DBGC ( image, "COMBOOT %p: returned\n", image );
break;
case COMBOOT_EXIT:
DBGC ( image, "COMBOOT %p: exited\n", image );
break;
case COMBOOT_EXIT_RUN_KERNEL:
assert ( image->replacement );
DBGC ( image, "COMBOOT %p: exited to run kernel %s\n",
image, image->replacement->name );
break;
case COMBOOT_EXIT_COMMAND:
DBGC ( image, "COMBOOT %p: exited after executing command\n",
image );
break;
default:
assert ( 0 );
break;
}
unhook_comboot_interrupts();
comboot_force_text_mode();
return 0;
}
/**
* Check image name extension
*
* @v image COMBOOT image
* @ret rc Return status code
*/
static int comboot_identify ( struct image *image ) {
const char *ext;
ext = strrchr( image->name, '.' );
if ( ! ext ) {
DBGC ( image, "COMBOOT %p: no extension\n",
image );
return -ENOEXEC;
}
++ext;
if ( strcasecmp( ext, "cbt" ) ) {
DBGC ( image, "COMBOOT %p: unrecognized extension %s\n",
image, ext );
return -ENOEXEC;
}
return 0;
}
/**
* Load COMBOOT image into memory, preparing a segment and returning it
* @v image COMBOOT image
* @ret rc Return status code
*/
static int comboot_prepare_segment ( struct image *image )
{
userptr_t seg_userptr;
size_t filesz, memsz;
int rc;
/* Load image in segment */
seg_userptr = real_to_user ( COMBOOT_PSP_SEG, 0 );
/* Allow etra 0x100 bytes before image for PSP */
filesz = image->len + 0x100;
/* Ensure the entire 64k segment is free */
memsz = 0xFFFF;
/* Prepare, verify, and load the real-mode segment */
if ( ( rc = prep_segment ( seg_userptr, filesz, memsz ) ) != 0 ) {
DBGC ( image, "COMBOOT %p: could not prepare segment: %s\n",
image, strerror ( rc ) );
return rc;
}
/* Zero PSP */
memset_user ( seg_userptr, 0, 0, 0x100 );
/* Copy image to segment:0100 */
memcpy_user ( seg_userptr, 0x100, image->data, 0, image->len );
return 0;
}
/**
* Probe COMBOOT image
*
* @v image COMBOOT image
* @ret rc Return status code
*/
static int comboot_probe ( struct image *image ) {
int rc;
DBGC ( image, "COMBOOT %p: name '%s'\n",
image, image->name );
/* Check if this is a COMBOOT image */
if ( ( rc = comboot_identify ( image ) ) != 0 ) {
return rc;
}
return 0;
}
/**
* Execute COMBOOT image
*
* @v image COMBOOT image
* @ret rc Return status code
*/
static int comboot_exec ( struct image *image ) {
int rc;
/* Sanity check for filesize */
if( image->len >= 0xFF00 ) {
DBGC( image, "COMBOOT %p: image too large\n",
image );
return -ENOEXEC;
}
/* Prepare segment and load image */
if ( ( rc = comboot_prepare_segment ( image ) ) != 0 ) {
return rc;
}
/* Reset console */
console_reset();
return comboot_exec_loop ( image );
}
/** SYSLINUX COMBOOT (16-bit) image type */
struct image_type comboot_image_type __image_type ( PROBE_NORMAL ) = {
.name = "COMBOOT",
.probe = comboot_probe,
.exec = comboot_exec,
};
