1 //===- Target.h -------------------------------------------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef LLD_ELF_TARGET_H 10 #define LLD_ELF_TARGET_H 11 12 #include "Config.h" 13 #include "InputSection.h" 14 #include "lld/Common/ErrorHandler.h" 15 #include "llvm/Object/ELF.h" 16 #include "llvm/Support/Compiler.h" 17 #include "llvm/Support/MathExtras.h" 18 #include <array> 19 20 namespace lld { 21 std::string toString(elf::RelType type); 22 23 namespace elf { 24 class Defined; 25 class InputFile; 26 class Symbol; 27 28 class TargetInfo { 29 public: 30 virtual uint32_t calcEFlags() const { return 0; } 31 virtual RelExpr getRelExpr(RelType type, const Symbol &s, 32 const uint8_t *loc) const = 0; 33 virtual RelType getDynRel(RelType type) const { return 0; } 34 virtual void writeGotPltHeader(uint8_t *buf) const {} 35 virtual void writeGotHeader(uint8_t *buf) const {} 36 virtual void writeGotPlt(uint8_t *buf, const Symbol &s) const {}; 37 virtual void writeIgotPlt(uint8_t *buf, const Symbol &s) const {} 38 virtual int64_t getImplicitAddend(const uint8_t *buf, RelType type) const; 39 virtual int getTlsGdRelaxSkip(RelType type) const { return 1; } 40 41 // If lazy binding is supported, the first entry of the PLT has code 42 // to call the dynamic linker to resolve PLT entries the first time 43 // they are called. This function writes that code. 44 virtual void writePltHeader(uint8_t *buf) const {} 45 46 virtual void writePlt(uint8_t *buf, const Symbol &sym, 47 uint64_t pltEntryAddr) const {} 48 virtual void writeIplt(uint8_t *buf, const Symbol &sym, 49 uint64_t pltEntryAddr) const { 50 // All but PPC32 and PPC64 use the same format for .plt and .iplt entries. 51 writePlt(buf, sym, pltEntryAddr); 52 } 53 virtual void writeIBTPlt(uint8_t *buf, size_t numEntries) const {} 54 virtual void addPltHeaderSymbols(InputSection &isec) const {} 55 virtual void addPltSymbols(InputSection &isec, uint64_t off) const {} 56 57 // Returns true if a relocation only uses the low bits of a value such that 58 // all those bits are in the same page. For example, if the relocation 59 // only uses the low 12 bits in a system with 4k pages. If this is true, the 60 // bits will always have the same value at runtime and we don't have to emit 61 // a dynamic relocation. 62 virtual bool usesOnlyLowPageBits(RelType type) const; 63 64 // Decide whether a Thunk is needed for the relocation from File 65 // targeting S. 66 virtual bool needsThunk(RelExpr expr, RelType relocType, 67 const InputFile *file, uint64_t branchAddr, 68 const Symbol &s, int64_t a) const; 69 70 // On systems with range extensions we place collections of Thunks at 71 // regular spacings that enable the majority of branches reach the Thunks. 72 // a value of 0 means range extension thunks are not supported. 73 virtual uint32_t getThunkSectionSpacing() const { return 0; } 74 75 // The function with a prologue starting at Loc was compiled with 76 // -fsplit-stack and it calls a function compiled without. Adjust the prologue 77 // to do the right thing. See https://gcc.gnu.org/wiki/SplitStacks. 78 // The symbols st_other flags are needed on PowerPC64 for determining the 79 // offset to the split-stack prologue. 80 virtual bool adjustPrologueForCrossSplitStack(uint8_t *loc, uint8_t *end, 81 uint8_t stOther) const; 82 83 // Return true if we can reach dst from src with RelType type. 84 virtual bool inBranchRange(RelType type, uint64_t src, 85 uint64_t dst) const; 86 87 virtual void relocate(uint8_t *loc, const Relocation &rel, 88 uint64_t val) const = 0; 89 void relocateNoSym(uint8_t *loc, RelType type, uint64_t val) const { 90 relocate(loc, Relocation{R_NONE, type, 0, 0, nullptr}, val); 91 } 92 virtual void relocateAlloc(InputSectionBase &sec, uint8_t *buf) const; 93 94 // Do a linker relaxation pass and return true if we changed something. 95 virtual bool relaxOnce(int pass) const { return false; } 96 97 virtual void applyJumpInstrMod(uint8_t *loc, JumpModType type, 98 JumpModType val) const {} 99 100 virtual ~TargetInfo(); 101 102 // This deletes a jump insn at the end of the section if it is a fall thru to 103 // the next section. Further, if there is a conditional jump and a direct 104 // jump consecutively, it tries to flip the conditional jump to convert the 105 // direct jump into a fall thru and delete it. Returns true if a jump 106 // instruction can be deleted. 107 virtual bool deleteFallThruJmpInsn(InputSection &is, InputFile *file, 108 InputSection *nextIS) const { 109 return false; 110 } 111 112 unsigned defaultCommonPageSize = 4096; 113 unsigned defaultMaxPageSize = 4096; 114 115 uint64_t getImageBase() const; 116 117 // True if _GLOBAL_OFFSET_TABLE_ is relative to .got.plt, false if .got. 118 bool gotBaseSymInGotPlt = false; 119 120 static constexpr RelType noneRel = 0; 121 RelType copyRel; 122 RelType gotRel; 123 RelType pltRel; 124 RelType relativeRel; 125 RelType iRelativeRel; 126 RelType symbolicRel; 127 RelType tlsDescRel; 128 RelType tlsGotRel; 129 RelType tlsModuleIndexRel; 130 RelType tlsOffsetRel; 131 unsigned gotEntrySize = config->wordsize; 132 unsigned pltEntrySize; 133 unsigned pltHeaderSize; 134 unsigned ipltEntrySize; 135 136 // At least on x86_64 positions 1 and 2 are used by the first plt entry 137 // to support lazy loading. 138 unsigned gotPltHeaderEntriesNum = 3; 139 140 // On PPC ELF V2 abi, the first entry in the .got is the .TOC. 141 unsigned gotHeaderEntriesNum = 0; 142 143 bool needsThunks = false; 144 145 // A 4-byte field corresponding to one or more trap instructions, used to pad 146 // executable OutputSections. 147 std::array<uint8_t, 4> trapInstr; 148 149 // Stores the NOP instructions of different sizes for the target and is used 150 // to pad sections that are relaxed. 151 std::optional<std::vector<std::vector<uint8_t>>> nopInstrs; 152 153 // If a target needs to rewrite calls to __morestack to instead call 154 // __morestack_non_split when a split-stack enabled caller calls a 155 // non-split-stack callee this will return true. Otherwise returns false. 156 bool needsMoreStackNonSplit = true; 157 158 virtual RelExpr adjustTlsExpr(RelType type, RelExpr expr) const; 159 virtual RelExpr adjustGotPcExpr(RelType type, int64_t addend, 160 const uint8_t *loc) const; 161 162 protected: 163 // On FreeBSD x86_64 the first page cannot be mmaped. 164 // On Linux this is controlled by vm.mmap_min_addr. At least on some x86_64 165 // installs this is set to 65536, so the first 15 pages cannot be used. 166 // Given that, the smallest value that can be used in here is 0x10000. 167 uint64_t defaultImageBase = 0x10000; 168 }; 169 170 TargetInfo *getAArch64TargetInfo(); 171 TargetInfo *getAMDGPUTargetInfo(); 172 TargetInfo *getARMTargetInfo(); 173 TargetInfo *getAVRTargetInfo(); 174 TargetInfo *getHexagonTargetInfo(); 175 TargetInfo *getMSP430TargetInfo(); 176 TargetInfo *getPPC64TargetInfo(); 177 TargetInfo *getPPCTargetInfo(); 178 TargetInfo *getRISCVTargetInfo(); 179 TargetInfo *getSPARCV9TargetInfo(); 180 TargetInfo *getX86TargetInfo(); 181 TargetInfo *getX86_64TargetInfo(); 182 template <class ELFT> TargetInfo *getMipsTargetInfo(); 183 184 struct ErrorPlace { 185 InputSectionBase *isec; 186 std::string loc; 187 std::string srcLoc; 188 }; 189 190 // Returns input section and corresponding source string for the given location. 191 ErrorPlace getErrorPlace(const uint8_t *loc); 192 193 static inline std::string getErrorLocation(const uint8_t *loc) { 194 return getErrorPlace(loc).loc; 195 } 196 197 void writePPC32GlinkSection(uint8_t *buf, size_t numEntries); 198 199 unsigned getPPCDFormOp(unsigned secondaryOp); 200 201 // In the PowerPC64 Elf V2 abi a function can have 2 entry points. The first 202 // is a global entry point (GEP) which typically is used to initialize the TOC 203 // pointer in general purpose register 2. The second is a local entry 204 // point (LEP) which bypasses the TOC pointer initialization code. The 205 // offset between GEP and LEP is encoded in a function's st_other flags. 206 // This function will return the offset (in bytes) from the global entry-point 207 // to the local entry-point. 208 unsigned getPPC64GlobalEntryToLocalEntryOffset(uint8_t stOther); 209 210 // Write a prefixed instruction, which is a 4-byte prefix followed by a 4-byte 211 // instruction (regardless of endianness). Therefore, the prefix is always in 212 // lower memory than the instruction. 213 void writePrefixedInstruction(uint8_t *loc, uint64_t insn); 214 215 void addPPC64SaveRestore(); 216 uint64_t getPPC64TocBase(); 217 uint64_t getAArch64Page(uint64_t expr); 218 void riscvFinalizeRelax(int passes); 219 void mergeRISCVAttributesSections(); 220 221 LLVM_LIBRARY_VISIBILITY extern const TargetInfo *target; 222 TargetInfo *getTarget(); 223 224 template <class ELFT> bool isMipsPIC(const Defined *sym); 225 226 void reportRangeError(uint8_t *loc, const Relocation &rel, const Twine &v, 227 int64_t min, uint64_t max); 228 void reportRangeError(uint8_t *loc, int64_t v, int n, const Symbol &sym, 229 const Twine &msg); 230 231 // Make sure that V can be represented as an N bit signed integer. 232 inline void checkInt(uint8_t *loc, int64_t v, int n, const Relocation &rel) { 233 if (v != llvm::SignExtend64(v, n)) 234 reportRangeError(loc, rel, Twine(v), llvm::minIntN(n), llvm::maxIntN(n)); 235 } 236 237 // Make sure that V can be represented as an N bit unsigned integer. 238 inline void checkUInt(uint8_t *loc, uint64_t v, int n, const Relocation &rel) { 239 if ((v >> n) != 0) 240 reportRangeError(loc, rel, Twine(v), 0, llvm::maxUIntN(n)); 241 } 242 243 // Make sure that V can be represented as an N bit signed or unsigned integer. 244 inline void checkIntUInt(uint8_t *loc, uint64_t v, int n, 245 const Relocation &rel) { 246 // For the error message we should cast V to a signed integer so that error 247 // messages show a small negative value rather than an extremely large one 248 if (v != (uint64_t)llvm::SignExtend64(v, n) && (v >> n) != 0) 249 reportRangeError(loc, rel, Twine((int64_t)v), llvm::minIntN(n), 250 llvm::maxUIntN(n)); 251 } 252 253 inline void checkAlignment(uint8_t *loc, uint64_t v, int n, 254 const Relocation &rel) { 255 if ((v & (n - 1)) != 0) 256 error(getErrorLocation(loc) + "improper alignment for relocation " + 257 lld::toString(rel.type) + ": 0x" + llvm::utohexstr(v) + 258 " is not aligned to " + Twine(n) + " bytes"); 259 } 260 261 // Endianness-aware read/write. 262 inline uint16_t read16(const void *p) { 263 return llvm::support::endian::read16(p, config->endianness); 264 } 265 266 inline uint32_t read32(const void *p) { 267 return llvm::support::endian::read32(p, config->endianness); 268 } 269 270 inline uint64_t read64(const void *p) { 271 return llvm::support::endian::read64(p, config->endianness); 272 } 273 274 inline void write16(void *p, uint16_t v) { 275 llvm::support::endian::write16(p, v, config->endianness); 276 } 277 278 inline void write32(void *p, uint32_t v) { 279 llvm::support::endian::write32(p, v, config->endianness); 280 } 281 282 inline void write64(void *p, uint64_t v) { 283 llvm::support::endian::write64(p, v, config->endianness); 284 } 285 } // namespace elf 286 } // namespace lld 287 288 #ifdef __clang__ 289 #pragma clang diagnostic ignored "-Wgnu-zero-variadic-macro-arguments" 290 #endif 291 #define invokeELFT(f, ...) \ 292 switch (config->ekind) { \ 293 case ELF32LEKind: \ 294 f<ELF32LE>(__VA_ARGS__); \ 295 break; \ 296 case ELF32BEKind: \ 297 f<ELF32BE>(__VA_ARGS__); \ 298 break; \ 299 case ELF64LEKind: \ 300 f<ELF64LE>(__VA_ARGS__); \ 301 break; \ 302 case ELF64BEKind: \ 303 f<ELF64BE>(__VA_ARGS__); \ 304 break; \ 305 default: \ 306 llvm_unreachable("unknown config->ekind"); \ 307 } 308 309 #endif 310