lld/ELF/Target.h

   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/ADT/StringExtras.h"
  16 #include "llvm/Object/ELF.h"
  17 #include "llvm/Object/ELFTypes.h"
  18 #include "llvm/Support/Compiler.h"
  19 #include "llvm/Support/MathExtras.h"
  20 #include <array>
  21
  22 namespace lld {
  23 std::string toString(elf::RelType type);
  24
  25 namespace elf {
  26 class Defined;
  27 class InputFile;
  28 class Symbol;
  29
  30 class TargetInfo {
  31 public:
  32   virtual uint32_t calcEFlags() const { return 0; }
  33   virtual RelExpr getRelExpr(RelType type, const Symbol &s,
  34                              const uint8_t *loc) const = 0;
  35   virtual RelType getDynRel(RelType type) const { return 0; }
  36   virtual void writeGotPltHeader(uint8_t *buf) const {}
  37   virtual void writeGotHeader(uint8_t *buf) const {}
  38   virtual void writeGotPlt(uint8_t *buf, const Symbol &s) const {};
  39   virtual void writeIgotPlt(uint8_t *buf, const Symbol &s) const {}
  40   virtual int64_t getImplicitAddend(const uint8_t *buf, RelType type) const;
  41   virtual int getTlsGdRelaxSkip(RelType type) const { return 1; }
  42
  43   // If lazy binding is supported, the first entry of the PLT has code
  44   // to call the dynamic linker to resolve PLT entries the first time
  45   // they are called. This function writes that code.
  46   virtual void writePltHeader(uint8_t *buf) const {}
  47
  48   virtual void writePlt(uint8_t *buf, const Symbol &sym,
  49                         uint64_t pltEntryAddr) const {}
  50   virtual void writeIplt(uint8_t *buf, const Symbol &sym,
  51                          uint64_t pltEntryAddr) const {
  52     // All but PPC32 and PPC64 use the same format for .plt and .iplt entries.
  53     writePlt(buf, sym, pltEntryAddr);
  54   }
  55   virtual void writeIBTPlt(uint8_t *buf, size_t numEntries) const {}
  56   virtual void addPltHeaderSymbols(InputSection &isec) const {}
  57   virtual void addPltSymbols(InputSection &isec, uint64_t off) const {}
  58
  59   // Returns true if a relocation only uses the low bits of a value such that
  60   // all those bits are in the same page. For example, if the relocation
  61   // only uses the low 12 bits in a system with 4k pages. If this is true, the
  62   // bits will always have the same value at runtime and we don't have to emit
  63   // a dynamic relocation.
  64   virtual bool usesOnlyLowPageBits(RelType type) const;
  65
  66   // Decide whether a Thunk is needed for the relocation from File
  67   // targeting S.
  68   virtual bool needsThunk(RelExpr expr, RelType relocType,
  69                           const InputFile *file, uint64_t branchAddr,
  70                           const Symbol &s, int64_t a) const;
  71
  72   // On systems with range extensions we place collections of Thunks at
  73   // regular spacings that enable the majority of branches reach the Thunks.
  74   // a value of 0 means range extension thunks are not supported.
  75   virtual uint32_t getThunkSectionSpacing() const { return 0; }
  76
  77   // The function with a prologue starting at Loc was compiled with
  78   // -fsplit-stack and it calls a function compiled without. Adjust the prologue
  79   // to do the right thing. See https://gcc.gnu.org/wiki/SplitStacks.
  80   // The symbols st_other flags are needed on PowerPC64 for determining the
  81   // offset to the split-stack prologue.
  82   virtual bool adjustPrologueForCrossSplitStack(uint8_t *loc, uint8_t *end,
  83                                                 uint8_t stOther) const;
  84
  85   // Return true if we can reach dst from src with RelType type.
  86   virtual bool inBranchRange(RelType type, uint64_t src,
  87                              uint64_t dst) const;
  88
  89   virtual void relocate(uint8_t *loc, const Relocation &rel,
  90                         uint64_t val) const = 0;
  91   void relocateNoSym(uint8_t *loc, RelType type, uint64_t val) const {
  92     relocate(loc, Relocation{R_NONE, type, 0, 0, nullptr}, val);
  93   }
  94   virtual void relocateAlloc(InputSectionBase &sec, uint8_t *buf) const;
  95
  96   // Do a linker relaxation pass and return true if we changed something.
  97   virtual bool relaxOnce(int pass) const { return false; }
  98   // Do finalize relaxation after collecting relaxation infos.
  99   virtual void finalizeRelax(int passes) const {}
 100
 101   virtual void applyJumpInstrMod(uint8_t *loc, JumpModType type,
 102                                  JumpModType val) const {}
 103
 104   virtual ~TargetInfo();
 105
 106   // This deletes a jump insn at the end of the section if it is a fall thru to
 107   // the next section.  Further, if there is a conditional jump and a direct
 108   // jump consecutively, it tries to flip the conditional jump to convert the
 109   // direct jump into a fall thru and delete it.  Returns true if a jump
 110   // instruction can be deleted.
 111   virtual bool deleteFallThruJmpInsn(InputSection &is, InputFile *file,
 112                                      InputSection *nextIS) const {
 113     return false;
 114   }
 115
 116   unsigned defaultCommonPageSize = 4096;
 117   unsigned defaultMaxPageSize = 4096;
 118
 119   uint64_t getImageBase() const;
 120
 121   // True if _GLOBAL_OFFSET_TABLE_ is relative to .got.plt, false if .got.
 122   bool gotBaseSymInGotPlt = false;
 123
 124   static constexpr RelType noneRel = 0;
 125   RelType copyRel;
 126   RelType gotRel;
 127   RelType pltRel;
 128   RelType relativeRel;
 129   RelType iRelativeRel;
 130   RelType symbolicRel;
 131   RelType tlsDescRel;
 132   RelType tlsGotRel;
 133   RelType tlsModuleIndexRel;
 134   RelType tlsOffsetRel;
 135   unsigned gotEntrySize = config->wordsize;
 136   unsigned pltEntrySize;
 137   unsigned pltHeaderSize;
 138   unsigned ipltEntrySize;
 139
 140   // At least on x86_64 positions 1 and 2 are used by the first plt entry
 141   // to support lazy loading.
 142   unsigned gotPltHeaderEntriesNum = 3;
 143
 144   // On PPC ELF V2 abi, the first entry in the .got is the .TOC.
 145   unsigned gotHeaderEntriesNum = 0;
 146
 147   // On PPC ELF V2 abi, the dynamic section needs DT_PPC64_OPT (DT_LOPROC + 3)
 148   // to be set to 0x2 if there can be multiple TOC's. Although we do not emit
 149   // multiple TOC's, there can be a mix of TOC and NOTOC addressing which
 150   // is functionally equivalent.
 151   int ppc64DynamicSectionOpt = 0;
 152
 153   bool needsThunks = false;
 154
 155   // A 4-byte field corresponding to one or more trap instructions, used to pad
 156   // executable OutputSections.
 157   std::array<uint8_t, 4> trapInstr;
 158
 159   // Stores the NOP instructions of different sizes for the target and is used
 160   // to pad sections that are relaxed.
 161   std::optional<std::vector<std::vector<uint8_t>>> nopInstrs;
 162
 163   // If a target needs to rewrite calls to __morestack to instead call
 164   // __morestack_non_split when a split-stack enabled caller calls a
 165   // non-split-stack callee this will return true. Otherwise returns false.
 166   bool needsMoreStackNonSplit = true;
 167
 168   virtual RelExpr adjustTlsExpr(RelType type, RelExpr expr) const;
 169   virtual RelExpr adjustGotPcExpr(RelType type, int64_t addend,
 170                                   const uint8_t *loc) const;
 171
 172 protected:
 173   // On FreeBSD x86_64 the first page cannot be mmaped.
 174   // On Linux this is controlled by vm.mmap_min_addr. At least on some x86_64
 175   // installs this is set to 65536, so the first 15 pages cannot be used.
 176   // Given that, the smallest value that can be used in here is 0x10000.
 177   uint64_t defaultImageBase = 0x10000;
 178 };
 179
 180 TargetInfo *getAArch64TargetInfo();
 181 TargetInfo *getAMDGPUTargetInfo();
 182 TargetInfo *getARMTargetInfo();
 183 TargetInfo *getAVRTargetInfo();
 184 TargetInfo *getHexagonTargetInfo();
 185 TargetInfo *getLoongArchTargetInfo();
 186 TargetInfo *getMSP430TargetInfo();
 187 TargetInfo *getPPC64TargetInfo();
 188 TargetInfo *getPPCTargetInfo();
 189 TargetInfo *getRISCVTargetInfo();
 190 TargetInfo *getSPARCV9TargetInfo();
 191 TargetInfo *getSystemZTargetInfo();
 192 TargetInfo *getX86TargetInfo();
 193 TargetInfo *getX86_64TargetInfo();
 194 template <class ELFT> TargetInfo *getMipsTargetInfo();
 195
 196 struct ErrorPlace {
 197   InputSectionBase *isec;
 198   std::string loc;
 199   std::string srcLoc;
 200 };
 201
 202 // Returns input section and corresponding source string for the given location.
 203 ErrorPlace getErrorPlace(const uint8_t *loc);
 204
 205 static inline std::string getErrorLocation(const uint8_t *loc) {
 206   return getErrorPlace(loc).loc;
 207 }
 208
 209 void processArmCmseSymbols();
 210
 211 void writePPC32GlinkSection(uint8_t *buf, size_t numEntries);
 212
 213 unsigned getPPCDFormOp(unsigned secondaryOp);
 214 unsigned getPPCDSFormOp(unsigned secondaryOp);
 215
 216 // In the PowerPC64 Elf V2 abi a function can have 2 entry points.  The first
 217 // is a global entry point (GEP) which typically is used to initialize the TOC
 218 // pointer in general purpose register 2.  The second is a local entry
 219 // point (LEP) which bypasses the TOC pointer initialization code. The
 220 // offset between GEP and LEP is encoded in a function's st_other flags.
 221 // This function will return the offset (in bytes) from the global entry-point
 222 // to the local entry-point.
 223 unsigned getPPC64GlobalEntryToLocalEntryOffset(uint8_t stOther);
 224
 225 // Write a prefixed instruction, which is a 4-byte prefix followed by a 4-byte
 226 // instruction (regardless of endianness). Therefore, the prefix is always in
 227 // lower memory than the instruction.
 228 void writePrefixedInstruction(uint8_t *loc, uint64_t insn);
 229
 230 void addPPC64SaveRestore();
 231 uint64_t getPPC64TocBase();
 232 uint64_t getAArch64Page(uint64_t expr);
 233 template <typename ELFT> void writeARMCmseImportLib();
 234 uint64_t getLoongArchPageDelta(uint64_t dest, uint64_t pc, RelType type);
 235 void riscvFinalizeRelax(int passes);
 236 void mergeRISCVAttributesSections();
 237 void addArmInputSectionMappingSymbols();
 238 void addArmSyntheticSectionMappingSymbol(Defined *);
 239 void sortArmMappingSymbols();
 240 void convertArmInstructionstoBE8(InputSection *sec, uint8_t *buf);
 241 void createTaggedSymbols(const SmallVector<ELFFileBase *, 0> &files);
 242 void initSymbolAnchors();
 243
 244 LLVM_LIBRARY_VISIBILITY extern const TargetInfo *target;
 245 TargetInfo *getTarget();
 246
 247 template <class ELFT> bool isMipsPIC(const Defined *sym);
 248
 249 void reportRangeError(uint8_t *loc, const Relocation &rel, const Twine &v,
 250                       int64_t min, uint64_t max);
 251 void reportRangeError(uint8_t *loc, int64_t v, int n, const Symbol &sym,
 252                       const Twine &msg);
 253
 254 // Make sure that V can be represented as an N bit signed integer.
 255 inline void checkInt(uint8_t *loc, int64_t v, int n, const Relocation &rel) {
 256   if (v != llvm::SignExtend64(v, n))
 257     reportRangeError(loc, rel, Twine(v), llvm::minIntN(n), llvm::maxIntN(n));
 258 }
 259
 260 // Make sure that V can be represented as an N bit unsigned integer.
 261 inline void checkUInt(uint8_t *loc, uint64_t v, int n, const Relocation &rel) {
 262   if ((v >> n) != 0)
 263     reportRangeError(loc, rel, Twine(v), 0, llvm::maxUIntN(n));
 264 }
 265
 266 // Make sure that V can be represented as an N bit signed or unsigned integer.
 267 inline void checkIntUInt(uint8_t *loc, uint64_t v, int n,
 268                          const Relocation &rel) {
 269   // For the error message we should cast V to a signed integer so that error
 270   // messages show a small negative value rather than an extremely large one
 271   if (v != (uint64_t)llvm::SignExtend64(v, n) && (v >> n) != 0)
 272     reportRangeError(loc, rel, Twine((int64_t)v), llvm::minIntN(n),
 273                      llvm::maxUIntN(n));
 274 }
 275
 276 inline void checkAlignment(uint8_t *loc, uint64_t v, int n,
 277                            const Relocation &rel) {
 278   if ((v & (n - 1)) != 0)
 279     error(getErrorLocation(loc) + "improper alignment for relocation " +
 280           lld::toString(rel.type) + ": 0x" + llvm::utohexstr(v) +
 281           " is not aligned to " + Twine(n) + " bytes");
 282 }
 283
 284 // Endianness-aware read/write.
 285 inline uint16_t read16(const void *p) {
 286   return llvm::support::endian::read16(p, config->endianness);
 287 }
 288
 289 inline uint32_t read32(const void *p) {
 290   return llvm::support::endian::read32(p, config->endianness);
 291 }
 292
 293 inline uint64_t read64(const void *p) {
 294   return llvm::support::endian::read64(p, config->endianness);
 295 }
 296
 297 inline void write16(void *p, uint16_t v) {
 298   llvm::support::endian::write16(p, v, config->endianness);
 299 }
 300
 301 inline void write32(void *p, uint32_t v) {
 302   llvm::support::endian::write32(p, v, config->endianness);
 303 }
 304
 305 inline void write64(void *p, uint64_t v) {
 306   llvm::support::endian::write64(p, v, config->endianness);
 307 }
 308
 309 // Overwrite a ULEB128 value and keep the original length.
 310 inline uint64_t overwriteULEB128(uint8_t *bufLoc, uint64_t val) {
 311   while (*bufLoc & 0x80) {
 312     *bufLoc++ = 0x80 | (val & 0x7f);
 313     val >>= 7;
 314   }
 315   *bufLoc = val;
 316   return val;
 317 }
 318 } // namespace elf
 319 } // namespace lld
 320
 321 #ifdef __clang__
 322 #pragma clang diagnostic ignored "-Wgnu-zero-variadic-macro-arguments"
 323 #endif
 324 #define invokeELFT(f, ...)                                                     \
 325   switch (config->ekind) {                                                     \
 326   case lld::elf::ELF32LEKind:                                                  \
 327     f<llvm::object::ELF32LE>(__VA_ARGS__);                                     \
 328     break;                                                                     \
 329   case lld::elf::ELF32BEKind:                                                  \
 330     f<llvm::object::ELF32BE>(__VA_ARGS__);                                     \
 331     break;                                                                     \
 332   case lld::elf::ELF64LEKind:                                                  \
 333     f<llvm::object::ELF64LE>(__VA_ARGS__);                                     \
 334     break;                                                                     \
 335   case lld::elf::ELF64BEKind:                                                  \
 336     f<llvm::object::ELF64BE>(__VA_ARGS__);                                     \
 337     break;                                                                     \
 338   default:                                                                     \
 339     llvm_unreachable("unknown config->ekind");                                 \
 340   }
 341
 342 #endif