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 #ifdef HAVE_CONFIG_H 30 # include <config.h> 31 #endif 32 33 #include "libdwflP.h" 34 #include "system.h" 35 36 #include <unistd.h> 37 #include <endian.h> 38 39 #if BYTE_ORDER == LITTLE_ENDIAN 40 # define LE16(x) (x) 41 #else 42 # define LE16(x) bswap_16 (x) 43 #endif 44 45 /* See Documentation/x86/boot.txt in Linux kernel sources 46 for an explanation of these format details. */ 47 48 #define MAGIC1 0xaa55 49 #define MAGIC2 0x53726448 /* "HdrS" little-endian */ 50 #define MIN_VERSION 0x0208 51 52 #define H_START (H_SETUP_SECTS & -4) 53 #define H_SETUP_SECTS 0x1f1 54 #define H_MAGIC1 0x1fe 55 #define H_MAGIC2 0x202 56 #define H_VERSION 0x206 57 #define H_PAYLOAD_OFFSET 0x248 58 #define H_PAYLOAD_LENGTH 0x24c 59 #define H_END 0x250 60 #define H_READ_SIZE (H_END - H_START) 61 62 Dwfl_Error 63 internal_function 64 __libdw_image_header (int fd, off_t *start_offset, 65 void *mapped, size_t mapped_size) 66 { 67 if (likely (mapped_size > H_END)) 68 { 69 const void *header = mapped; 70 char header_buffer[H_READ_SIZE]; 71 if (header == NULL) 72 { 73 ssize_t n = pread_retry (fd, header_buffer, H_READ_SIZE, 74 *start_offset + H_START); 75 if (n < 0) 76 return DWFL_E_ERRNO; 77 if (n < H_READ_SIZE) 78 return DWFL_E_BADELF; 79 80 header = header_buffer - H_START; 81 } 82 83 if (*(uint16_t *) (header + H_MAGIC1) == LE16 (MAGIC1) 84 && *(uint32_t *) (header + H_MAGIC2) == LE32 (MAGIC2) 85 && LE16 (*(uint16_t *) (header + H_VERSION)) >= MIN_VERSION) 86 { 87 /* The magic numbers match and the version field is sufficient. 88 Extract the payload bounds. */ 89 90 uint32_t offset = LE32 (*(uint32_t *) (header + H_PAYLOAD_OFFSET)); 91 uint32_t length = LE32 (*(uint32_t *) (header + H_PAYLOAD_LENGTH)); 92 93 offset += ((*(uint8_t *) (header + H_SETUP_SECTS) ?: 4) + 1) * 512; 94 95 if (offset > H_END && offset < mapped_size 96 && mapped_size - offset >= length) 97 { 98 /* It looks kosher. Use it! */ 99 *start_offset += offset; 100 return DWFL_E_NOERROR; 101 } 102 } 103 } 104 return DWFL_E_BADELF; 105 } 106
