1 /*
2 * Copyright (C) 2009 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <errno.h>
18 #include <sys/stat.h>
19 #include <fcntl.h>
20 #include <stdio.h>
21 #include <unistd.h>
22 #include <string.h>
23 #include <strings.h>
24 #include "Retouch.h"
25 #include "applypatch/applypatch.h"
26
27 typedef struct {
28 int32_t mmap_addr;
29 char tag[4]; /* 'P', 'R', 'E', ' ' */
30 } prelink_info_t __attribute__((packed));
31
32 #define false 0
33 #define true 1
34
35 static int32_t offs_prev;
36 static uint32_t cont_prev;
37
init_compression_state(void)38 static void init_compression_state(void) {
39 offs_prev = 0;
40 cont_prev = 0;
41 }
42
43 // For details on the encoding used for relocation lists, please
44 // refer to build/tools/retouch/retouch-prepare.c. The intent is to
45 // save space by removing most of the inherent redundancy.
46
decode_bytes(uint8_t * encoded_bytes,int encoded_size,int32_t * dst_offset,uint32_t * dst_contents)47 static void decode_bytes(uint8_t *encoded_bytes, int encoded_size,
48 int32_t *dst_offset, uint32_t *dst_contents) {
49 if (encoded_size == 2) {
50 *dst_offset = offs_prev + (((encoded_bytes[0]&0x60)>>5)+1)*4;
51
52 // if the original was negative, we need to 1-pad before applying delta
53 int32_t tmp = (((encoded_bytes[0] & 0x0000001f) << 8) |
54 encoded_bytes[1]);
55 if (tmp & 0x1000) tmp = 0xffffe000 | tmp;
56 *dst_contents = cont_prev + tmp;
57 } else if (encoded_size == 3) {
58 *dst_offset = offs_prev + (((encoded_bytes[0]&0x30)>>4)+1)*4;
59
60 // if the original was negative, we need to 1-pad before applying delta
61 int32_t tmp = (((encoded_bytes[0] & 0x0000000f) << 16) |
62 (encoded_bytes[1] << 8) |
63 encoded_bytes[2]);
64 if (tmp & 0x80000) tmp = 0xfff00000 | tmp;
65 *dst_contents = cont_prev + tmp;
66 } else {
67 *dst_offset =
68 (encoded_bytes[0]<<24) |
69 (encoded_bytes[1]<<16) |
70 (encoded_bytes[2]<<8) |
71 encoded_bytes[3];
72 if (*dst_offset == 0x3fffffff) *dst_offset = -1;
73 *dst_contents =
74 (encoded_bytes[4]<<24) |
75 (encoded_bytes[5]<<16) |
76 (encoded_bytes[6]<<8) |
77 encoded_bytes[7];
78 }
79 }
80
decode_in_memory(uint8_t * encoded_bytes,int32_t * offset,uint32_t * contents)81 static uint8_t *decode_in_memory(uint8_t *encoded_bytes,
82 int32_t *offset, uint32_t *contents) {
83 int input_size, charIx;
84 uint8_t input[8];
85
86 input[0] = *(encoded_bytes++);
87 if (input[0] & 0x80)
88 input_size = 2;
89 else if (input[0] & 0x40)
90 input_size = 3;
91 else
92 input_size = 8;
93
94 // we already read one byte..
95 charIx = 1;
96 while (charIx < input_size) {
97 input[charIx++] = *(encoded_bytes++);
98 }
99
100 // depends on the decoder state!
101 decode_bytes(input, input_size, offset, contents);
102
103 offs_prev = *offset;
104 cont_prev = *contents;
105
106 return encoded_bytes;
107 }
108
retouch_mask_data(uint8_t * binary_object,int32_t binary_size,int32_t * desired_offset,int32_t * retouch_offset)109 int retouch_mask_data(uint8_t *binary_object,
110 int32_t binary_size,
111 int32_t *desired_offset,
112 int32_t *retouch_offset) {
113 retouch_info_t *r_info;
114 prelink_info_t *p_info;
115
116 int32_t target_offset = 0;
117 if (desired_offset) target_offset = *desired_offset;
118
119 int32_t p_offs = binary_size-sizeof(prelink_info_t); // prelink_info_t
120 int32_t r_offs = p_offs-sizeof(retouch_info_t); // retouch_info_t
121 int32_t b_offs; // retouch data blob
122
123 // If not retouched, we say it was a match. This might get invoked on
124 // non-retouched binaries, so that's why we need to do this.
125 if (retouch_offset != NULL) *retouch_offset = target_offset;
126 if (r_offs < 0) return (desired_offset == NULL) ?
127 RETOUCH_DATA_NOTAPPLICABLE : RETOUCH_DATA_MATCHED;
128 p_info = (prelink_info_t *)(binary_object+p_offs);
129 r_info = (retouch_info_t *)(binary_object+r_offs);
130 if (strncmp(p_info->tag, "PRE ", 4) ||
131 strncmp(r_info->tag, "RETOUCH ", 8))
132 return (desired_offset == NULL) ?
133 RETOUCH_DATA_NOTAPPLICABLE : RETOUCH_DATA_MATCHED;
134
135 b_offs = r_offs-r_info->blob_size;
136 if (b_offs < 0) {
137 printf("negative binary offset: %d = %d - %d\n",
138 b_offs, r_offs, r_info->blob_size);
139 return RETOUCH_DATA_ERROR;
140 }
141 uint8_t *b_ptr = binary_object+b_offs;
142
143 // Retouched: let's go through the work then.
144 int32_t offset_candidate = target_offset;
145 bool offset_set = false, offset_mismatch = false;
146 init_compression_state();
147 while (b_ptr < (uint8_t *)r_info) {
148 int32_t retouch_entry_offset;
149 uint32_t *retouch_entry;
150 uint32_t retouch_original_value;
151
152 b_ptr = decode_in_memory(b_ptr,
153 &retouch_entry_offset,
154 &retouch_original_value);
155 if (retouch_entry_offset < (-1) ||
156 retouch_entry_offset >= b_offs) {
157 printf("bad retouch_entry_offset: %d", retouch_entry_offset);
158 return RETOUCH_DATA_ERROR;
159 }
160
161 // "-1" means this is the value in prelink_info_t, which also gets
162 // randomized.
163 if (retouch_entry_offset == -1)
164 retouch_entry = (uint32_t *)&(p_info->mmap_addr);
165 else
166 retouch_entry = (uint32_t *)(binary_object+retouch_entry_offset);
167
168 if (desired_offset)
169 *retouch_entry = retouch_original_value + target_offset;
170
171 // Infer the randomization shift, compare to previously inferred.
172 int32_t offset_of_this_entry = (int32_t)(*retouch_entry-
173 retouch_original_value);
174 if (!offset_set) {
175 offset_candidate = offset_of_this_entry;
176 offset_set = true;
177 } else {
178 if (offset_candidate != offset_of_this_entry) {
179 offset_mismatch = true;
180 printf("offset is mismatched: %d, this entry is %d,"
181 " original 0x%x @ 0x%x",
182 offset_candidate, offset_of_this_entry,
183 retouch_original_value, retouch_entry_offset);
184 }
185 }
186 }
187 if (b_ptr > (uint8_t *)r_info) {
188 printf("b_ptr went too far: %p, while r_info is %p",
189 b_ptr, r_info);
190 return RETOUCH_DATA_ERROR;
191 }
192
193 if (offset_mismatch) return RETOUCH_DATA_MISMATCHED;
194 if (retouch_offset != NULL) *retouch_offset = offset_candidate;
195 return RETOUCH_DATA_MATCHED;
196 }
197