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
79 Dwfl_Error
80 internal_function
__libdw_image_header(int fd,off64_t * start_offset,void * mapped,size_t mapped_size)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