From 186c2f2ff7f6f842bd5bced91d5f26dc253a08fa Mon Sep 17 00:00:00 2001 From: Vreixo Formoso Date: Sat, 18 Oct 2008 16:50:20 +0200 Subject: [PATCH] Add Thomas function needed to make isohybrid bootable images. --- Makefile.am | 1 + libisofs/eltorito.h | 23 +++- libisofs/make_isohybrid_mbr.c | 198 ++++++++++++++++++++++++++++++++++ 3 files changed, 219 insertions(+), 3 deletions(-) create mode 100644 libisofs/make_isohybrid_mbr.c diff --git a/Makefile.am b/Makefile.am index 6101ec9..34c3792 100644 --- a/Makefile.am +++ b/Makefile.am @@ -52,6 +52,7 @@ libisofs_libisofs_la_SOURCES = \ libisofs/joliet.c \ libisofs/eltorito.h \ libisofs/eltorito.c \ + libisofs/make_isohybrid_mbr.c \ libisofs/iso1999.h \ libisofs/iso1999.c \ libisofs/data_source.c diff --git a/libisofs/eltorito.h b/libisofs/eltorito.h index 3c50799..07c72a0 100644 --- a/libisofs/eltorito.h +++ b/libisofs/eltorito.h @@ -1,8 +1,8 @@ /* * Copyright (c) 2007 Vreixo Formoso - * - * This file is part of the libisofs project; you can redistribute it and/or - * modify it under the terms of the GNU General Public License version 2 as + * + * This file is part of the libisofs project; you can redistribute it and/or + * modify it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. See COPYING file for details. */ @@ -100,4 +100,21 @@ int el_torito_catalog_file_src_create(Ecma119Image *target, IsoFileSrc **src); */ int eltorito_writer_create(Ecma119Image *target); +/* + * Create a MBR for an isohybrid enabled ISOLINUX boot image. + * + * It is assumed that the caller has verified the readiness of the boot image + * by checking for 0xfb 0xc0 0x78 0x70 at bytes 0x40 to 0x43 of isolinux.bin. + * + * @param bin_lba The predicted LBA of isolinux.bin within the emerging ISO. + * @param img_blocks The predicted number of 2048 byte blocks in the ISO. + * It will get rounded up to full MBs and that many blocks + * must really be written as ISO 9660 image. + * @param mbr A buffer of at least 512 bytes to take the result which is + * to be written as the very beginning of the ISO. + * @param flag unused yet, submit 0 + * @return <0 = fatal, 0 = failed , 1 = ok , 2 = ok with size warning + */ +int make_isohybrid_mbr(int bin_lba, int *img_blocks, char *mbr, int flag); + #endif /* LIBISO_ELTORITO_H */ diff --git a/libisofs/make_isohybrid_mbr.c b/libisofs/make_isohybrid_mbr.c new file mode 100644 index 0000000..662c2f0 --- /dev/null +++ b/libisofs/make_isohybrid_mbr.c @@ -0,0 +1,198 @@ +#include +#include +#include +#include +#include +#include +#include +#include + +/* for gettimeofday() */ +#include + +/* This code stems from syslinux-3.72/utils/isohybrid, a perl script + under GPL which is Copyright 2002-2008 H. Peter Anvin. + Line numbers in comments refer to the lines of that script. + It has been analyzed and re-written in C language 2008 by Thomas Schmitt. + As soon as it is part of a libisofs test version, H. Peter Anvin will + be asked about his own copyright claims and/or license tolerance in + respect to this C code. + */ + +/* A helper function. One could replace it by one or two macros. */ +static int lsb_to_buf(char **wpt, int value, int bits, int flag) +{ + int b; + + for (b = 0; b < bits; b += 8) + *((unsigned char *) ((*wpt)++)) = (value >> b) & 0xff; + return (1); +} + +/* + * Create a MBR for an isohybrid enabled ISOLINUX boot image. + * + * It is assumed that the caller has verified the readiness of the boot image + * by checking for 0xfb 0xc0 0x78 0x70 at bytes 0x40 to 0x43 of isolinux.bin. + * + * @param bin_lba The predicted LBA of isolinux.bin within the emerging ISO. + * @param img_blocks The predicted number of 2048 byte blocks in the ISO. + * It will get rounded up to full MBs and that many blocks + * must really be written as ISO 9660 image. + * @param mbr A buffer of at least 512 bytes to take the result which is + * to be written as the very beginning of the ISO. + * @param flag unused yet, submit 0 + * @return <0 = fatal, 0 = failed , 1 = ok , 2 = ok with size warning + */ +int make_isohybrid_mbr(int bin_lba, int *img_blocks, char *mbr, int flag) +{ + /* According to H. Peter Anvin this binary code stems from + syslinux-3.72/mbr/isohdpfx.S + */ + static int mbr_code_size = 271; + static unsigned char mbr_code[271] = { 0xfa, 0x31, 0xc0, 0x8e, 0xd8, 0x8e, + 0xd0, 0xbc, 0x00, 0x7c, 0x89, 0xe6, 0x06, 0x57, 0x52, 0x8e, 0xc0, + 0xfb, 0xfc, 0xbf, 0x00, 0x06, 0xb9, 0x00, 0x01, 0xf3, 0xa5, 0xea, + 0x20, 0x06, 0x00, 0x00, 0x52, 0xb4, 0x41, 0xbb, 0xaa, 0x55, 0x31, + 0xc9, 0x30, 0xf6, 0xf9, 0xcd, 0x13, 0x72, 0x14, 0x81, 0xfb, 0x55, + 0xaa, 0x75, 0x0e, 0x83, 0xe1, 0x01, 0x74, 0x09, 0x66, 0xc7, 0x06, + 0xb4, 0x06, 0xb4, 0x42, 0xeb, 0x15, 0x5a, 0x51, 0xb4, 0x08, 0xcd, + 0x13, 0x83, 0xe1, 0x3f, 0x51, 0x0f, 0xb6, 0xc6, + + 0x40, 0x50, 0xf7, 0xe1, 0x52, 0x50, 0xbb, 0x00, 0x7c, 0xb9, 0x04, + 0x00, 0x66, 0xa1, 0xb0, 0x07, 0xe8, 0x40, 0x00, 0x72, 0x74, 0x66, + 0x40, 0x80, 0xc7, 0x02, 0xe2, 0xf4, 0x66, 0x81, 0x3e, 0x40, 0x7c, + 0xfb, 0xc0, 0x78, 0x70, 0x75, 0x07, 0xfa, 0xbc, 0xf4, 0x7b, 0xe9, + 0xc6, 0x75, 0xe8, 0x79, 0x00, 0x69, 0x73, 0x6f, 0x6c, 0x69, 0x6e, + 0x75, 0x78, 0x2e, 0x62, 0x69, 0x6e, 0x20, 0x6d, 0x69, 0x73, 0x73, + 0x69, 0x6e, 0x67, 0x20, 0x6f, 0x72, 0x20, 0x63, 0x6f, 0x72, 0x72, + 0x75, 0x70, 0x74, + + 0x2e, 0x0d, 0x0a, 0x66, 0x60, 0x66, 0x31, 0xd2, 0x66, 0x52, 0x66, + 0x50, 0x06, 0x53, 0x6a, 0x01, 0x6a, 0x10, 0x89, 0xe6, 0x66, 0xf7, + 0x36, 0xf0, 0x7b, 0xc0, 0xe4, 0x06, 0x88, 0xe1, 0x88, 0xc5, 0x92, + 0xf6, 0x36, 0xf6, 0x7b, 0x88, 0xc6, 0x08, 0xe1, 0x41, 0xb8, 0x01, + 0x02, 0x8a, 0x16, 0xfa, 0x7b, 0xcd, 0x13, 0x8d, 0x64, 0x10, 0x66, + 0x61, 0xc3, 0xe8, 0x1e, 0x00, 0x4f, 0x70, 0x65, 0x72, 0x61, 0x74, + 0x69, 0x6e, 0x67, 0x20, 0x73, 0x79, 0x73, 0x74, 0x65, 0x6d, 0x20, + 0x6c, 0x6f, 0x61, + + 0x64, 0x20, 0x65, 0x72, 0x72, 0x6f, 0x72, 0x2e, 0x0d, 0x0a, 0x5e, + 0xac, 0xb4, 0x0e, 0x8a, 0x3e, 0x62, 0x04, 0xb3, 0x07, 0xcd, 0x10, + 0x3c, 0x0a, 0x75, 0xf1, 0xcd, 0x18, 0xf4, 0xeb, 0xfd }; + + static int h = 64, s = 32; + + int i, warn_size = 0, id; + char *wpt; + off_t imgsize, cylsize, frac, padding, c, cc; + + /* For generating a weak random number */ + struct timeval tv; + struct timezone tz; + + if (bin_lba < 0 || bin_lba >= (1 << 29)) + return (0); /* 1 TB limit of signed 32 bit addressing of 512 byte blocks */ + + /* + 84: Gets size of image in bytes. + 89: + */ + imgsize = ((off_t) img_blocks) * (off_t) 2048; + + /* + 90: Computes $padding, size of padded image and number $c of + pseudo-cylinders ($h and $s are constants set in line 24). + 102: $cc is $c curbed to 1024. + */ + cylsize = h * s * 512; + frac = imgsize % cylsize; + padding = (frac > 0 ? cylsize - frac : 0); + imgsize += padding; + *img_blocks = imgsize / (off_t) 2048; + c = imgsize / cylsize; + if (c > 1024) { + warn_size = 1; + cc = 1024; + } else + cc = c; + + /* + 107: Brings the hex-encoded bytes from the file __END__ into + 113: the MBR buffer. (This function holds them in mbr_code[].) + */ + for (i = 0; i < mbr_code_size; i++) + mbr[i] = mbr_code[i]; + + /* + 118: Pads up to 432 + */ + for (i = mbr_code_size; i < 432; i++) + mbr[i] = 0; + + /* From here on use write cursor wpt */ + wpt = mbr + 432; + + /* + 120: Converts LBA of isolinux.bin to blocksize 512 and writes + to buffer. Appends 4 zero bytes. + */ + lsb_to_buf(&wpt, bin_lba * 4, 32, 0); + lsb_to_buf(&wpt, 0, 32, 0); + + /* + 121: I do not understand where $id should eventually come + from. An environment variable ? + 125: Whatever, i use some 32-bit random value with no crypto strength. + */ + gettimeofday(&tv, &tz); + id = 0xffffffff & (tv.tv_sec ^ (tv.tv_usec * 2000)); + + /* + 126: Adds 4 id bytes and 2 zero bytes. + */ + lsb_to_buf(&wpt, id, 32, 0); + lsb_to_buf(&wpt, 0, 16, 0); + + /* + 129: Composes 16 byte record from the parameters determined + 147: so far. Appends it to buffer and add 48 zero bytes. + */ + /* There are 4 "partition slots". Only the first is non-zero here. + In the perl script, the fields are set in variables and then + written to buffer. I omit the variables. + */ + /* 0x80 */ + lsb_to_buf(&wpt, 0x80, 8, 0); + /* bhead */ + lsb_to_buf(&wpt, 0, 8, 0); + /* bsect */ + lsb_to_buf(&wpt, 1, 8, 0); + /* bcyl */ + lsb_to_buf(&wpt, 0, 8, 0); + /* fstype */ + lsb_to_buf(&wpt, 0x83, 8, 0); + /* ehead */ + lsb_to_buf(&wpt, h - 1, 8, 0); + /* esect */ + lsb_to_buf(&wpt, s + (((cc - 1) & 0x300) >> 2), 8, 0); + /* ecyl */ + lsb_to_buf(&wpt, (cc - 1) & 0xff, 8, 0); + /* 0 */ + lsb_to_buf(&wpt, 0, 32, 0); + /* psize */ + lsb_to_buf(&wpt, c * h * s, 32, 0); + + /* Fill the other three slots with zeros */ + for (i = 0; i < 3 * 4; i++) + lsb_to_buf(&wpt, 0, 32, 0); + + /* + 148: Appends bytes 0x55 , 0xAA. + */ + lsb_to_buf(&wpt, 0x55, 8, 0); + lsb_to_buf(&wpt, 0xaa, 8, 0); + + return (1); +} +