1 /*
2 * Copyright (C) 2023 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 "chre/platform/shared/nanoapp_loader.h"
18
19 namespace chre {
20
relocateTable(DynamicHeader * dyn,int tag)21 bool NanoappLoader::relocateTable(DynamicHeader *dyn, int tag) {
22 bool success = false;
23 if (dyn == nullptr) {
24 return false;
25 }
26
27 switch (tag) {
28 case DT_REL: {
29 if (getDynEntry(dyn, tag) == 0) {
30 LOGE("ARM Elf binaries must have DT_REL dynamic entry");
31 break;
32 }
33
34 ElfRel *reloc =
35 reinterpret_cast<ElfRel *>(mBinary + getDynEntry(dyn, DT_REL));
36 size_t relocSize = getDynEntry(dyn, DT_RELSZ);
37 size_t nRelocs = relocSize / sizeof(ElfRel);
38 LOGV("Relocation %zu entries in DT_REL table", nRelocs);
39
40 bool resolvedAllSymbols = true;
41 size_t i;
42 for (i = 0; i < nRelocs; ++i) {
43 ElfRel *curr = &reloc[i];
44 int relocType = ELFW_R_TYPE(curr->r_info);
45 ElfAddr *addr = reinterpret_cast<ElfAddr *>(mMapping + curr->r_offset);
46
47 switch (relocType) {
48 case R_ARM_RELATIVE:
49 LOGV("Resolving ARM_RELATIVE at offset %lx",
50 static_cast<long unsigned int>(curr->r_offset));
51 // TODO(b/155512914): When we move to DRAM allocations, we need to
52 // check if the above address is in a Read-Only section of memory,
53 // and give it temporary write permission if that is the case.
54 *addr += reinterpret_cast<uintptr_t>(mMapping);
55 break;
56
57 case R_ARM_ABS32: {
58 LOGV("Resolving ARM_ABS32 at offset %lx",
59 static_cast<long unsigned int>(curr->r_offset));
60 size_t posInSymbolTable = ELFW_R_SYM(curr->r_info);
61 auto *dynamicSymbolTable =
62 reinterpret_cast<ElfSym *>(mDynamicSymbolTablePtr);
63 ElfSym *sym = &dynamicSymbolTable[posInSymbolTable];
64 *addr = reinterpret_cast<uintptr_t>(mMapping + sym->st_value);
65 break;
66 }
67
68 case R_ARM_GLOB_DAT: {
69 LOGV("Resolving type ARM_GLOB_DAT at offset %lx",
70 static_cast<long unsigned int>(curr->r_offset));
71 size_t posInSymbolTable = ELFW_R_SYM(curr->r_info);
72 void *resolved = resolveData(posInSymbolTable);
73 if (resolved == nullptr) {
74 LOGV("Failed to resolve global symbol(%zu) at offset 0x%lx", i,
75 static_cast<long unsigned int>(curr->r_offset));
76 resolvedAllSymbols = false;
77 }
78 // TODO(b/155512914): When we move to DRAM allocations, we need to
79 // check if the above address is in a Read-Only section of memory,
80 // and give it temporary write permission if that is the case.
81 *addr = reinterpret_cast<ElfAddr>(resolved);
82 break;
83 }
84
85 case R_ARM_COPY:
86 LOGE("R_ARM_COPY is an invalid relocation for shared libraries");
87 break;
88 default:
89 LOGE("Invalid relocation type %u", relocType);
90 break;
91 }
92 }
93
94 if (!resolvedAllSymbols) {
95 LOGE("Unable to resolve all symbols in the binary");
96 } else {
97 success = true;
98 }
99 break;
100 }
101 case DT_RELA:
102 if (getDynEntry(dyn, tag) != 0) {
103 LOGE("ARM Elf binaries with a DT_RELA dynamic entry are unsupported");
104 } else {
105 // Not required for ARM
106 success = true;
107 }
108 break;
109 default:
110 LOGE("Unsupported table tag %d", tag);
111 }
112
113 return success;
114 }
115
resolveGot()116 bool NanoappLoader::resolveGot() {
117 ElfAddr *addr;
118 ElfRel *reloc = reinterpret_cast<ElfRel *>(
119 mMapping + getDynEntry(getDynamicHeader(), DT_JMPREL));
120 size_t relocSize = getDynEntry(getDynamicHeader(), DT_PLTRELSZ);
121 size_t nRelocs = relocSize / sizeof(ElfRel);
122 LOGV("Resolving GOT with %zu relocations", nRelocs);
123
124 bool success = true;
125
126 for (size_t i = 0; i < nRelocs; ++i) {
127 ElfRel *curr = &reloc[i];
128 int relocType = ELFW_R_TYPE(curr->r_info);
129
130 switch (relocType) {
131 case R_ARM_JUMP_SLOT: {
132 LOGV("Resolving ARM_JUMP_SLOT at offset %lx",
133 static_cast<long unsigned int>(curr->r_offset));
134 addr = reinterpret_cast<ElfAddr *>(mMapping + curr->r_offset);
135 size_t posInSymbolTable = ELFW_R_SYM(curr->r_info);
136 void *resolved = resolveData(posInSymbolTable);
137 if (resolved == nullptr) {
138 LOGE("Failed to resolve symbol(%zu) at offset 0x%x", i,
139 curr->r_offset);
140 success = false;
141 }
142 *addr = reinterpret_cast<ElfAddr>(resolved);
143 break;
144 }
145
146 default:
147 LOGE("Unsupported relocation type: %u for symbol %s", relocType,
148 getDataName(getDynamicSymbol(ELFW_R_SYM(curr->r_info))));
149 success = false;
150 }
151 }
152 return success;
153 }
154
155 } // namespace chre
156