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
__libdw_image_header(int fd,off_t * start_offset,void * mapped,size_t mapped_size)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