1 /* Linux kernel image support for libdwfl. 2 Copyright (C) 2009-2011 Red Hat, Inc. 3 This file is part of elfutils. 4 5 This file is free software; you can redistribute it and/or modify 6 it under the terms of either 7 8 * the GNU Lesser General Public License as published by the Free 9 Software Foundation; either version 3 of the License, or (at 10 your option) any later version 11 12 or 13 14 * the GNU General Public License as published by the Free 15 Software Foundation; either version 2 of the License, or (at 16 your option) any later version 17 18 or both in parallel, as here. 19 20 elfutils is distributed in the hope that it will be useful, but 21 WITHOUT ANY WARRANTY; without even the implied warranty of 22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 23 General Public License for more details. 24 25 You should have received copies of the GNU General Public License and 26 the GNU Lesser General Public License along with this program. If 27 not, see <http://www.gnu.org/licenses/>. */ 28 29 #include "libdwflP.h" 30 #include "system.h" 31 32 #include <unistd.h> 33 #include <endian.h> 34 35 #if BYTE_ORDER == LITTLE_ENDIAN 36 # define LE16(x) (x) 37 #else 38 # define LE16(x) bswap_16 (x) 39 #endif 40 41 /* See Documentation/x86/boot.txt in Linux kernel sources 42 for an explanation of these format details. */ 43 44 #define MAGIC1 0xaa55 45 #define MAGIC2 0x53726448 /* "HdrS" little-endian */ 46 #define MIN_VERSION 0x0208 47 48 #define H_START (H_SETUP_SECTS & -4) 49 #define H_SETUP_SECTS 0x1f1 50 #define H_MAGIC1 0x1fe 51 #define H_MAGIC2 0x202 52 #define H_VERSION 0x206 53 #define H_PAYLOAD_OFFSET 0x248 54 #define H_PAYLOAD_LENGTH 0x24c 55 #define H_END 0x250 56 #define H_READ_SIZE (H_END - H_START) 57 58 Dwfl_Error 59 internal_function 60 __libdw_image_header (int fd, off_t *start_offset, 61 void *mapped, size_t mapped_size) 62 { 63 if (likely (mapped_size > H_END)) 64 { 65 const void *header = mapped; 66 char header_buffer[H_READ_SIZE]; 67 if (header == NULL) 68 { 69 ssize_t n = pread_retry (fd, header_buffer, H_READ_SIZE, 70 *start_offset + H_START); 71 if (n < 0) 72 return DWFL_E_ERRNO; 73 if (n < H_READ_SIZE) 74 return DWFL_E_BADELF; 75 76 header = header_buffer - H_START; 77 } 78 79 if (*(uint16_t *) (header + H_MAGIC1) == LE16 (MAGIC1) 80 && *(uint32_t *) (header + H_MAGIC2) == LE32 (MAGIC2) 81 && LE16 (*(uint16_t *) (header + H_VERSION)) >= MIN_VERSION) 82 { 83 /* The magic numbers match and the version field is sufficient. 84 Extract the payload bounds. */ 85 86 uint32_t offset = LE32 (*(uint32_t *) (header + H_PAYLOAD_OFFSET)); 87 uint32_t length = LE32 (*(uint32_t *) (header + H_PAYLOAD_LENGTH)); 88 89 offset += ((*(uint8_t *) (header + H_SETUP_SECTS) ?: 4) + 1) * 512; 90 91 if (offset > H_END && offset < mapped_size 92 && mapped_size - offset >= length) 93 { 94 /* It looks kosher. Use it! */ 95 *start_offset += offset; 96 return DWFL_E_NOERROR; 97 } 98 } 99 } 100 return DWFL_E_BADELF; 101 } 102
