| Brian Silverman | 8649792 | 2018-02-10 19:28:39 -0500 | [diff] [blame] | 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 | } |