#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); }