1/* Linux kernel image support for libdwfl. 2 Copyright (C) 2009-2011 Red Hat, Inc. 3 This file is part of Red Hat elfutils. 4 5 Red Hat elfutils is free software; you can redistribute it and/or modify 6 it under the terms of the GNU General Public License as published by the 7 Free Software Foundation; version 2 of the License. 8 9 Red Hat elfutils is distributed in the hope that it will be useful, but 10 WITHOUT ANY WARRANTY; without even the implied warranty of 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 General Public License for more details. 13 14 You should have received a copy of the GNU General Public License along 15 with Red Hat elfutils; if not, write to the Free Software Foundation, 16 Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA. 17 18 In addition, as a special exception, Red Hat, Inc. gives You the 19 additional right to link the code of Red Hat elfutils with code licensed 20 under any Open Source Initiative certified open source license 21 (http://www.opensource.org/licenses/index.php) which requires the 22 distribution of source code with any binary distribution and to 23 distribute linked combinations of the two. Non-GPL Code permitted under 24 this exception must only link to the code of Red Hat elfutils through 25 those well defined interfaces identified in the file named EXCEPTION 26 found in the source code files (the "Approved Interfaces"). The files 27 of Non-GPL Code may instantiate templates or use macros or inline 28 functions from the Approved Interfaces without causing the resulting 29 work to be covered by the GNU General Public License. Only Red Hat, 30 Inc. may make changes or additions to the list of Approved Interfaces. 31 Red Hat's grant of this exception is conditioned upon your not adding 32 any new exceptions. If you wish to add a new Approved Interface or 33 exception, please contact Red Hat. You must obey the GNU General Public 34 License in all respects for all of the Red Hat elfutils code and other 35 code used in conjunction with Red Hat elfutils except the Non-GPL Code 36 covered by this exception. If you modify this file, you may extend this 37 exception to your version of the file, but you are not obligated to do 38 so. If you do not wish to provide this exception without modification, 39 you must delete this exception statement from your version and license 40 this file solely under the GPL without exception. 41 42 Red Hat elfutils is an included package of the Open Invention Network. 43 An included package of the Open Invention Network is a package for which 44 Open Invention Network licensees cross-license their patents. No patent 45 license is granted, either expressly or impliedly, by designation as an 46 included package. Should you wish to participate in the Open Invention 47 Network licensing program, please visit www.openinventionnetwork.com 48 <http://www.openinventionnetwork.com>. */ 49 50#include "libdwflP.h" 51#include "system.h" 52 53#include <unistd.h> 54#include <endian.h> 55 56#if BYTE_ORDER == LITTLE_ENDIAN 57# define LE16(x) (x) 58#else 59# define LE16(x) bswap_16 (x) 60#endif 61 62/* See Documentation/x86/boot.txt in Linux kernel sources 63 for an explanation of these format details. */ 64 65#define MAGIC1 0xaa55 66#define MAGIC2 0x53726448 /* "HdrS" little-endian */ 67#define MIN_VERSION 0x0208 68 69#define H_START (H_SETUP_SECTS & -4) 70#define H_SETUP_SECTS 0x1f1 71#define H_MAGIC1 0x1fe 72#define H_MAGIC2 0x202 73#define H_VERSION 0x206 74#define H_PAYLOAD_OFFSET 0x248 75#define H_PAYLOAD_LENGTH 0x24c 76#define H_END 0x250 77#define H_READ_SIZE (H_END - H_START) 78 79Dwfl_Error 80internal_function 81__libdw_image_header (int fd, off64_t *start_offset, 82 void *mapped, size_t mapped_size) 83{ 84 if (likely (mapped_size > H_END)) 85 { 86 const void *header = mapped; 87 char header_buffer[H_READ_SIZE]; 88 if (header == NULL) 89 { 90 ssize_t n = pread_retry (fd, header_buffer, H_READ_SIZE, 91 *start_offset + H_START); 92 if (n < 0) 93 return DWFL_E_ERRNO; 94 if (n < H_READ_SIZE) 95 return DWFL_E_BADELF; 96 97 header = header_buffer - H_START; 98 } 99 100 if (*(uint16_t *) (header + H_MAGIC1) == LE16 (MAGIC1) 101 && *(uint32_t *) (header + H_MAGIC2) == LE32 (MAGIC2) 102 && LE16 (*(uint16_t *) (header + H_VERSION)) >= MIN_VERSION) 103 { 104 /* The magic numbers match and the version field is sufficient. 105 Extract the payload bounds. */ 106 107 uint32_t offset = LE32 (*(uint32_t *) (header + H_PAYLOAD_OFFSET)); 108 uint32_t length = LE32 (*(uint32_t *) (header + H_PAYLOAD_LENGTH)); 109 110 offset += ((*(uint8_t *) (header + H_SETUP_SECTS) ?: 4) + 1) * 512; 111 112 if (offset > H_END && offset < mapped_size 113 && mapped_size - offset >= length) 114 { 115 /* It looks kosher. Use it! */ 116 *start_offset += offset; 117 return DWFL_E_NOERROR; 118 } 119 } 120 } 121 return DWFL_E_BADELF; 122} 123