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/* PE Executable Multiboot Header Repair Tool */
/* This tool is release as-is to be free of use for anyone. Myself, the maker,
* am not liable for any damage or harm that may result from its use.
* This library includes a component from the multiboot header, part-verbatim.
* The license to the multiboot header file is included below.
*/
/* multiboot.h - Multiboot header file. */
/* Copyright (C) 1999,2003,2007,2008,2009 Free Software Foundation, Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL ANY
* DEVELOPER OR DISTRIBUTOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
* IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
struct multiboot_header
{
/* Must be MULTIBOOT_MAGIC - see above. */
unsigned int magic;
/* Feature flags. */
unsigned int flags;
/* The above fields plus this one must equal 0 mod 2^32. */
unsigned int checksum;
/* These are only valid if MULTIBOOT_AOUT_KLUDGE is set. */
unsigned int header_addr;
unsigned int load_addr;
unsigned int load_end_addr;
unsigned int bss_end_addr;
unsigned int entry_addr;
/* These are only valid if MULTIBOOT_VIDEO_MODE is set. */
unsigned int mode_type;
unsigned int width;
unsigned int height;
unsigned int depth;
};
#define NDEBUG
#include <stdio.h>
/* This library attempts to repair a multiboot header in a PE file
* that has become corrupted, for instance by linking too many OBJ
* files into your kernel. This causes your header to shift (even
* though it should not) and becomes unreadable. This scans for
* your header, repairs its header_addr and entry_addr values,
* and rewrites it. This application is set up as such so that it
* is easier to integrate as a post-build step in Visual C++.
*
* USAGE: PE_REWRITER file
*
* ERROR CODES:
* 1 - Could not open given file.
* 2 - No multiboot header was found.
* 3 - Invalid number of arguments
*/
const bool REWRITE_LOAD_END_ADDR = true;
const bool REWRITE_LOAD_ADDR = true;
const bool REWRITE_ENTRY_ADDR = true;
const bool REWRITE_HEADER_ADDR = true;
const unsigned int IMAGE_OFFSET = 0x00100000;
const unsigned int MB_HEADER = 0x1BADB002;
const unsigned int TEXT_OFFSET = 0x00001000;
int __cdecl main (int argc, char *argv[])
{
/* Test arguments for validity */
if (argc < 2)
{
printf("Usage: rewriter file.\n");
return 3;
}
if ((REWRITE_LOAD_END_ADDR || REWRITE_LOAD_ADDR || REWRITE_ENTRY_ADDR || REWRITE_HEADER_ADDR) == false)
{
printf("Nothing to do!\n");
return 0;
}
/* Load the file */
FILE *kernel = fopen(argv[1], "r+b");
if (kernel == NULL)
{
printf("Couldn't open Kernel File.\n");
return 1;
}
fseek(kernel, 0, SEEK_SET);
/* Stupid way of figuring out where the code actually ends.
I'm using 64-bit integers to scan in-case someone has a
64-bit variable with null values near the end of the code.
*/
unsigned int kernel_length;
if (REWRITE_LOAD_END_ADDR)
{
unsigned long long null_test;
fseek(kernel, 0, SEEK_END);
do {
if (fseek(kernel, -8, SEEK_CUR) != 0 || fread(&null_test, 8, 1, kernel) != 1 || fseek(kernel, -8, SEEK_CUR) != 0)
{
printf("This file has no multiboot header. Aborting.\n");
return 2;
}
} while (null_test == 0);
kernel_length = ftell(kernel) + 8;
fseek(kernel, 0, SEEK_SET);
}
/* Scan through the file to find the multiboot magic number.
* This is not the fastest way, but it works.
*/
unsigned int test_against;
do {
if (fread(&test_against, 4, 1, kernel) != 1 || fseek(kernel, -3, SEEK_CUR) != 0)
{
printf("This file has no multiboot header. Aborting.\n");
return 2;
}
} while (test_against != MB_HEADER);
fseek(kernel, -1, SEEK_CUR);
unsigned int header_location = ftell(kernel);
/* Now we load the header into memory */
multiboot_header header;
fread(&header, sizeof(multiboot_header), 1, kernel);
/* This is where we edit the header */
if (REWRITE_HEADER_ADDR)
header.header_addr = IMAGE_OFFSET + header_location;
if (REWRITE_ENTRY_ADDR)
header.entry_addr = IMAGE_OFFSET + header_location + sizeof(multiboot_header);
if (REWRITE_LOAD_ADDR)
header.load_addr = IMAGE_OFFSET + TEXT_OFFSET;
if (REWRITE_LOAD_END_ADDR)
header.load_end_addr = IMAGE_OFFSET + kernel_length;
/* Now we write it back where it was. */
fseek(kernel, header_location, SEEK_SET);
fwrite(&header, sizeof(multiboot_header), 1, kernel);
/* Clean up */
fclose(kernel);
return 0;
}
