gpxe/src/arch/i386/image/comboot.c - platform/external/syslinux - Git at Google

 /*
  * 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., 675 Mass Ave, Cambridge, MA 02139, 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 <gpxe/uaccess.h>
 #include <gpxe/image.h>
 #include <gpxe/segment.h>
 #include <gpxe/init.h>
 #include <gpxe/features.h>

 FEATURE ( FEATURE_IMAGE, "COMBOOT", DHCP_EB_FEATURE_COMBOOT, 1 );

 struct image_type comboot_image_type __image_type ( PROBE_NORMAL );

 /**
  * 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 ( 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:
 		DBGC ( image, "COMBOOT %p: exited to run kernel %p\n",
 		       image, comboot_replacement_image );
 		image->replacement = comboot_replacement_image;
 		comboot_replacement_image = NULL;
 		image_autoload ( image->replacement );
 		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, "com" ) && 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;
 }

 /**
  * Load COMBOOT image into memory
  *
  * @v image		COMBOOT image
  * @ret rc		Return status code
  */
 static int comboot_load ( 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;
 	}

 	/* This is a 16-bit COMBOOT image, valid or otherwise */
 	if ( ! image->type )
 		image->type = &comboot_image_type;

 	/* 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;
 	}

 	return 0;
 }

 /** SYSLINUX COMBOOT (16-bit) image type */
 struct image_type comboot_image_type __image_type ( PROBE_NORMAL ) = {
 	.name = "COMBOOT",
 	.load = comboot_load,
 	.exec = comboot_exec,
 };
	/*
	* 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., 675 Mass Ave, Cambridge, MA 02139, 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 <gpxe/uaccess.h>
	#include <gpxe/image.h>
	#include <gpxe/segment.h>
	#include <gpxe/init.h>
	#include <gpxe/features.h>

	FEATURE ( FEATURE_IMAGE, "COMBOOT", DHCP_EB_FEATURE_COMBOOT, 1 );

	struct image_type comboot_image_type __image_type ( PROBE_NORMAL );

	/**
	* 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 ( 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:
	DBGC ( image, "COMBOOT %p: exited to run kernel %p\n",
	image, comboot_replacement_image );
	image->replacement = comboot_replacement_image;
	comboot_replacement_image = NULL;
	image_autoload ( image->replacement );
	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, "com" ) && 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;
	}

	/**
	* Load COMBOOT image into memory
	*
	* @v image COMBOOT image
	* @ret rc Return status code
	*/
	static int comboot_load ( 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;
	}

	/* This is a 16-bit COMBOOT image, valid or otherwise */
	if ( ! image->type )
	image->type = &comboot_image_type;

	/* 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;
	}

	return 0;
	}

	/** SYSLINUX COMBOOT (16-bit) image type */
	struct image_type comboot_image_type __image_type ( PROBE_NORMAL ) = {
	.name = "COMBOOT",
	.load = comboot_load,
	.exec = comboot_exec,
	};