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1 //===- Target.h -------------------------------------------------*- C++ -*-===//
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2 //
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3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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4 // See https://llvm.org/LICENSE.txt for license information.
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5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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6 //
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7 //===----------------------------------------------------------------------===//
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8
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9 #ifndef LLD_ELF_TARGET_H
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10 #define LLD_ELF_TARGET_H
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11
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236
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12 #include "Config.h"
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150
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13 #include "InputSection.h"
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14 #include "lld/Common/ErrorHandler.h"
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15 #include "llvm/Object/ELF.h"
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236
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16 #include "llvm/Support/Compiler.h"
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150
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17 #include "llvm/Support/MathExtras.h"
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18 #include <array>
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19
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20 namespace lld {
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21 std::string toString(elf::RelType type);
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22
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23 namespace elf {
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24 class Defined;
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25 class InputFile;
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26 class Symbol;
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27
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28 class TargetInfo {
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29 public:
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30 virtual uint32_t calcEFlags() const { return 0; }
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31 virtual RelExpr getRelExpr(RelType type, const Symbol &s,
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32 const uint8_t *loc) const = 0;
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33 virtual RelType getDynRel(RelType type) const { return 0; }
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34 virtual void writeGotPltHeader(uint8_t *buf) const {}
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35 virtual void writeGotHeader(uint8_t *buf) const {}
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36 virtual void writeGotPlt(uint8_t *buf, const Symbol &s) const {};
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37 virtual void writeIgotPlt(uint8_t *buf, const Symbol &s) const {}
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38 virtual int64_t getImplicitAddend(const uint8_t *buf, RelType type) const;
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39 virtual int getTlsGdRelaxSkip(RelType type) const { return 1; }
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40
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41 // If lazy binding is supported, the first entry of the PLT has code
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42 // to call the dynamic linker to resolve PLT entries the first time
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43 // they are called. This function writes that code.
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44 virtual void writePltHeader(uint8_t *buf) const {}
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45
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46 virtual void writePlt(uint8_t *buf, const Symbol &sym,
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47 uint64_t pltEntryAddr) const {}
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48 virtual void writeIplt(uint8_t *buf, const Symbol &sym,
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49 uint64_t pltEntryAddr) const {
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50 // All but PPC32 and PPC64 use the same format for .plt and .iplt entries.
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51 writePlt(buf, sym, pltEntryAddr);
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52 }
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53 virtual void writeIBTPlt(uint8_t *buf, size_t numEntries) const {}
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54 virtual void addPltHeaderSymbols(InputSection &isec) const {}
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55 virtual void addPltSymbols(InputSection &isec, uint64_t off) const {}
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56
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57 // Returns true if a relocation only uses the low bits of a value such that
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58 // all those bits are in the same page. For example, if the relocation
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59 // only uses the low 12 bits in a system with 4k pages. If this is true, the
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60 // bits will always have the same value at runtime and we don't have to emit
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61 // a dynamic relocation.
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62 virtual bool usesOnlyLowPageBits(RelType type) const;
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63
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64 // Decide whether a Thunk is needed for the relocation from File
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65 // targeting S.
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66 virtual bool needsThunk(RelExpr expr, RelType relocType,
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67 const InputFile *file, uint64_t branchAddr,
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68 const Symbol &s, int64_t a) const;
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69
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70 // On systems with range extensions we place collections of Thunks at
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71 // regular spacings that enable the majority of branches reach the Thunks.
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72 // a value of 0 means range extension thunks are not supported.
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73 virtual uint32_t getThunkSectionSpacing() const { return 0; }
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74
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75 // The function with a prologue starting at Loc was compiled with
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76 // -fsplit-stack and it calls a function compiled without. Adjust the prologue
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77 // to do the right thing. See https://gcc.gnu.org/wiki/SplitStacks.
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78 // The symbols st_other flags are needed on PowerPC64 for determining the
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79 // offset to the split-stack prologue.
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80 virtual bool adjustPrologueForCrossSplitStack(uint8_t *loc, uint8_t *end,
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81 uint8_t stOther) const;
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82
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83 // Return true if we can reach dst from src with RelType type.
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84 virtual bool inBranchRange(RelType type, uint64_t src,
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85 uint64_t dst) const;
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86
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87 virtual void relocate(uint8_t *loc, const Relocation &rel,
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88 uint64_t val) const = 0;
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89 void relocateNoSym(uint8_t *loc, RelType type, uint64_t val) const {
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90 relocate(loc, Relocation{R_NONE, type, 0, 0, nullptr}, val);
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91 }
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92 virtual void relocateAlloc(InputSectionBase &sec, uint8_t *buf) const;
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93
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94 // Do a linker relaxation pass and return true if we changed something.
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95 virtual bool relaxOnce(int pass) const { return false; }
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96
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173
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97 virtual void applyJumpInstrMod(uint8_t *loc, JumpModType type,
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98 JumpModType val) const {}
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99
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150
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100 virtual ~TargetInfo();
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101
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173
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102 // This deletes a jump insn at the end of the section if it is a fall thru to
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103 // the next section. Further, if there is a conditional jump and a direct
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104 // jump consecutively, it tries to flip the conditional jump to convert the
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105 // direct jump into a fall thru and delete it. Returns true if a jump
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106 // instruction can be deleted.
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107 virtual bool deleteFallThruJmpInsn(InputSection &is, InputFile *file,
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108 InputSection *nextIS) const {
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109 return false;
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110 }
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111
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112 unsigned defaultCommonPageSize = 4096;
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113 unsigned defaultMaxPageSize = 4096;
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114
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115 uint64_t getImageBase() const;
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116
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117 // True if _GLOBAL_OFFSET_TABLE_ is relative to .got.plt, false if .got.
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236
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118 bool gotBaseSymInGotPlt = false;
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119
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120 static constexpr RelType noneRel = 0;
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121 RelType copyRel;
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122 RelType gotRel;
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123 RelType pltRel;
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124 RelType relativeRel;
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125 RelType iRelativeRel;
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126 RelType symbolicRel;
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127 RelType tlsDescRel;
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128 RelType tlsGotRel;
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129 RelType tlsModuleIndexRel;
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130 RelType tlsOffsetRel;
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221
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131 unsigned gotEntrySize = config->wordsize;
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132 unsigned pltEntrySize;
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133 unsigned pltHeaderSize;
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134 unsigned ipltEntrySize;
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135
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136 // At least on x86_64 positions 1 and 2 are used by the first plt entry
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137 // to support lazy loading.
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138 unsigned gotPltHeaderEntriesNum = 3;
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139
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140 // On PPC ELF V2 abi, the first entry in the .got is the .TOC.
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141 unsigned gotHeaderEntriesNum = 0;
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142
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143 bool needsThunks = false;
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144
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145 // A 4-byte field corresponding to one or more trap instructions, used to pad
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146 // executable OutputSections.
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147 std::array<uint8_t, 4> trapInstr;
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148
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173
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149 // Stores the NOP instructions of different sizes for the target and is used
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150 // to pad sections that are relaxed.
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151 llvm::Optional<std::vector<std::vector<uint8_t>>> nopInstrs;
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152
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150
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153 // If a target needs to rewrite calls to __morestack to instead call
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154 // __morestack_non_split when a split-stack enabled caller calls a
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155 // non-split-stack callee this will return true. Otherwise returns false.
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156 bool needsMoreStackNonSplit = true;
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157
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221
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158 virtual RelExpr adjustTlsExpr(RelType type, RelExpr expr) const;
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159 virtual RelExpr adjustGotPcExpr(RelType type, int64_t addend,
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160 const uint8_t *loc) const;
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150
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161
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162 protected:
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163 // On FreeBSD x86_64 the first page cannot be mmaped.
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164 // On Linux this is controlled by vm.mmap_min_addr. At least on some x86_64
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165 // installs this is set to 65536, so the first 15 pages cannot be used.
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166 // Given that, the smallest value that can be used in here is 0x10000.
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167 uint64_t defaultImageBase = 0x10000;
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168 };
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169
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170 TargetInfo *getAArch64TargetInfo();
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171 TargetInfo *getAMDGPUTargetInfo();
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172 TargetInfo *getARMTargetInfo();
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173 TargetInfo *getAVRTargetInfo();
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174 TargetInfo *getHexagonTargetInfo();
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175 TargetInfo *getMSP430TargetInfo();
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176 TargetInfo *getPPC64TargetInfo();
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177 TargetInfo *getPPCTargetInfo();
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178 TargetInfo *getRISCVTargetInfo();
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179 TargetInfo *getSPARCV9TargetInfo();
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180 TargetInfo *getX86TargetInfo();
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181 TargetInfo *getX86_64TargetInfo();
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182 template <class ELFT> TargetInfo *getMipsTargetInfo();
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183
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184 struct ErrorPlace {
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185 InputSectionBase *isec;
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186 std::string loc;
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187 std::string srcLoc;
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188 };
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189
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190 // Returns input section and corresponding source string for the given location.
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191 ErrorPlace getErrorPlace(const uint8_t *loc);
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192
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193 static inline std::string getErrorLocation(const uint8_t *loc) {
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194 return getErrorPlace(loc).loc;
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195 }
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196
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197 void writePPC32GlinkSection(uint8_t *buf, size_t numEntries);
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198
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199 unsigned getPPCDFormOp(unsigned secondaryOp);
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200
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201 // In the PowerPC64 Elf V2 abi a function can have 2 entry points. The first
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202 // is a global entry point (GEP) which typically is used to initialize the TOC
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203 // pointer in general purpose register 2. The second is a local entry
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204 // point (LEP) which bypasses the TOC pointer initialization code. The
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205 // offset between GEP and LEP is encoded in a function's st_other flags.
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206 // This function will return the offset (in bytes) from the global entry-point
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207 // to the local entry-point.
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208 unsigned getPPC64GlobalEntryToLocalEntryOffset(uint8_t stOther);
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209
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221
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210 // Write a prefixed instruction, which is a 4-byte prefix followed by a 4-byte
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211 // instruction (regardless of endianness). Therefore, the prefix is always in
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212 // lower memory than the instruction.
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213 void writePrefixedInstruction(uint8_t *loc, uint64_t insn);
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214
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215 void addPPC64SaveRestore();
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216 uint64_t getPPC64TocBase();
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217 uint64_t getAArch64Page(uint64_t expr);
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236
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218 void riscvFinalizeRelax(int passes);
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219
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220 LLVM_LIBRARY_VISIBILITY extern const TargetInfo *target;
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221 TargetInfo *getTarget();
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222
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223 template <class ELFT> bool isMipsPIC(const Defined *sym);
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224
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225 void reportRangeError(uint8_t *loc, const Relocation &rel, const Twine &v,
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226 int64_t min, uint64_t max);
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221
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227 void reportRangeError(uint8_t *loc, int64_t v, int n, const Symbol &sym,
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228 const Twine &msg);
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229
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230 // Make sure that V can be represented as an N bit signed integer.
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231 inline void checkInt(uint8_t *loc, int64_t v, int n, const Relocation &rel) {
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232 if (v != llvm::SignExtend64(v, n))
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233 reportRangeError(loc, rel, Twine(v), llvm::minIntN(n), llvm::maxIntN(n));
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234 }
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235
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236 // Make sure that V can be represented as an N bit unsigned integer.
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237 inline void checkUInt(uint8_t *loc, uint64_t v, int n, const Relocation &rel) {
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238 if ((v >> n) != 0)
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239 reportRangeError(loc, rel, Twine(v), 0, llvm::maxUIntN(n));
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240 }
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241
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242 // Make sure that V can be represented as an N bit signed or unsigned integer.
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243 inline void checkIntUInt(uint8_t *loc, uint64_t v, int n,
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244 const Relocation &rel) {
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245 // For the error message we should cast V to a signed integer so that error
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246 // messages show a small negative value rather than an extremely large one
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247 if (v != (uint64_t)llvm::SignExtend64(v, n) && (v >> n) != 0)
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248 reportRangeError(loc, rel, Twine((int64_t)v), llvm::minIntN(n),
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249 llvm::maxUIntN(n));
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250 }
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251
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252 inline void checkAlignment(uint8_t *loc, uint64_t v, int n,
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253 const Relocation &rel) {
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254 if ((v & (n - 1)) != 0)
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255 error(getErrorLocation(loc) + "improper alignment for relocation " +
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256 lld::toString(rel.type) + ": 0x" + llvm::utohexstr(v) +
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257 " is not aligned to " + Twine(n) + " bytes");
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258 }
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259
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260 // Endianness-aware read/write.
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261 inline uint16_t read16(const void *p) {
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262 return llvm::support::endian::read16(p, config->endianness);
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263 }
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264
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265 inline uint32_t read32(const void *p) {
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266 return llvm::support::endian::read32(p, config->endianness);
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267 }
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268
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269 inline uint64_t read64(const void *p) {
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270 return llvm::support::endian::read64(p, config->endianness);
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271 }
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272
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273 inline void write16(void *p, uint16_t v) {
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274 llvm::support::endian::write16(p, v, config->endianness);
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275 }
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276
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277 inline void write32(void *p, uint32_t v) {
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278 llvm::support::endian::write32(p, v, config->endianness);
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279 }
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280
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281 inline void write64(void *p, uint64_t v) {
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282 llvm::support::endian::write64(p, v, config->endianness);
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283 }
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284 } // namespace elf
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285 } // namespace lld
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286
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236
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287 #ifdef __clang__
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288 #pragma clang diagnostic ignored "-Wgnu-zero-variadic-macro-arguments"
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289 #endif
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236
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290 #define invokeELFT(f, ...) \
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291 switch (config->ekind) { \
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292 case ELF32LEKind: \
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293 f<ELF32LE>(__VA_ARGS__); \
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294 break; \
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295 case ELF32BEKind: \
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296 f<ELF32BE>(__VA_ARGS__); \
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297 break; \
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298 case ELF64LEKind: \
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299 f<ELF64LE>(__VA_ARGS__); \
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300 break; \
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301 case ELF64BEKind: \
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302 f<ELF64BE>(__VA_ARGS__); \
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303 break; \
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304 default: \
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305 llvm_unreachable("unknown config->ekind"); \
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306 }
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307
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308 #endif
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