1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2010 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 /* Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
28 /* All Rights Reserved */
29
30 /* Copyright (c) 1987, 1988 Microsoft Corporation */
31 /* All Rights Reserved */
32
33
34 #include <errno.h>
35 #include <libelf.h>
36 #include "decl.h"
37 #include "msg.h"
38
39 /*
40 * Routines for generating a checksum for an elf image. Typically used to create
41 * a DT_CHECKSUM entry. This checksum is intended to remain constant after
42 * operations such as strip(1)/mcs(1), thus only allocatable sections are
43 * processed, and of those, any that might be modified by these external
44 * commands are skipped.
45 */
46 #define MSW(l) (((l) >> 16) & 0x0000ffffL)
47 #define LSW(l) ((l) & 0x0000ffffL)
48
49
50 /*
51 * update and epilogue sum functions (stolen from libcmd)
52 */
53 static long
sumupd(long sum,char * cp,unsigned long cnt)54 sumupd(long sum, char *cp, unsigned long cnt)
55 {
56 if ((cp == 0) || (cnt == 0))
57 return (sum);
58
59 while (cnt--)
60 sum += *cp++ & 0x00ff;
61
62 return (sum);
63 }
64
65 static long
sumepi(long sum)66 sumepi(long sum)
67 {
68 long _sum;
69
70 _sum = LSW(sum) + MSW(sum);
71 return ((ushort_t)(LSW(_sum) + MSW(_sum)));
72 }
73
74 /*
75 * This module is compiled twice, the second time having
76 * -D_ELF64 defined. The following set of macros represent
77 * the differences between the two compilations. Be
78 * careful *not* to add any class dependent code (anything
79 * that has elf32 or elf64 in the name) to this code
80 * without hiding it behind a switchable macro like these.
81 */
82 #if defined(_ELF64)
83
84 #define elf_checksum elf64_checksum
85 #define Elf_Ehdr Elf64_Ehdr
86 #define Elf_Shdr Elf64_Shdr
87 #define getehdr elf64_getehdr
88 #define getshdr elf64_getshdr
89
90 #else /* else ELF32 */
91
92 #define elf_checksum elf32_checksum
93 #define Elf_Ehdr Elf32_Ehdr
94 #define Elf_Shdr Elf32_Shdr
95 #define getehdr elf32_getehdr
96 #define getshdr elf32_getshdr
97
98 #endif /* ELF64 */
99
100 long
elf_checksum(Elf * elf)101 elf_checksum(Elf * elf)
102 {
103 long sum = 0;
104 Elf_Ehdr * ehdr;
105 Elf_Shdr * shdr;
106 Elf_Scn * scn;
107 Elf_Data * data, * (* getdata)(Elf_Scn *, Elf_Data *);
108 size_t shnum;
109
110 if ((ehdr = getehdr(elf)) == 0)
111 return (0);
112
113 /*
114 * Determine the data information to retrieve. When called from ld()
115 * we're processing an ELF_C_IMAGE (memory) image and thus need to use
116 * elf_getdata(), as there is not yet a file image (or raw data) backing
117 * this. When called from utilities like elfdump(1) we're processing a
118 * file image and thus using the elf_rawdata() allows the same byte
119 * stream to be processed from different architectures - presently this
120 * is irrelevant, as the checksum simply sums the data bytes, their
121 * order doesn't matter. But being uncooked is slightly less overhead.
122 *
123 * If the file is writable, the raw data will not reflect any
124 * changes made in the process, so the uncooked version is only
125 * for readonly files.
126 */
127 if ((elf->ed_myflags & (EDF_MEMORY | EDF_WRITE)) != 0)
128 getdata = elf_getdata;
129 else
130 getdata = elf_rawdata;
131
132 for (shnum = 1; shnum < ehdr->e_shnum; shnum++) {
133 if ((scn = elf_getscn(elf, shnum)) == 0)
134 return (0);
135 if ((shdr = getshdr(scn)) == 0)
136 return (0);
137
138 /* Exclude strippable sections */
139 if (!(shdr->sh_flags & SHF_ALLOC))
140 continue;
141
142 /*
143 * Exclude allocable sections that can change:
144 * - The .dynsym section can contain section symbols
145 * that strip might remove.
146 * - The .dynamic section is modified by the setting of
147 * this checksum value.
148 * - The .SUNW_dof section uses ftok(3C), which returns
149 * different values, to define a key for the
150 * objects in that section.
151 */
152 if ((shdr->sh_type == SHT_DYNSYM) ||
153 (shdr->sh_type == SHT_DYNAMIC) ||
154 (shdr->sh_type == SHT_SUNW_dof))
155 continue;
156
157 data = 0;
158 while ((data = (*getdata)(scn, data)) != 0)
159 sum = sumupd(sum, data->d_buf, data->d_size);
160
161 }
162 return (sumepi(sum));
163 }
164