1 //===- Target.h -------------------------------------------------*- C++ -*-===//
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
7 //===----------------------------------------------------------------------===//
9 #ifndef LLD_ELF_TARGET_H
10 #define LLD_ELF_TARGET_H
12 #include "InputSection.h"
13 #include "lld/Common/ErrorHandler.h"
14 #include "llvm/Object/ELF.h"
15 #include "llvm/Support/MathExtras.h"
19 std::string toString(elf::RelType type);
28 virtual uint32_t calcEFlags() const { return 0; }
29 virtual RelExpr getRelExpr(RelType type, const Symbol &s,
30 const uint8_t *loc) const = 0;
31 virtual RelType getDynRel(RelType type) const { return 0; }
32 virtual void writeGotPltHeader(uint8_t *buf) const {}
33 virtual void writeGotHeader(uint8_t *buf) const {}
34 virtual void writeGotPlt(uint8_t *buf, const Symbol &s) const {};
35 virtual void writeIgotPlt(uint8_t *buf, const Symbol &s) const;
36 virtual int64_t getImplicitAddend(const uint8_t *buf, RelType type) const;
37 virtual int getTlsGdRelaxSkip(RelType type) const { return 1; }
39 // If lazy binding is supported, the first entry of the PLT has code
40 // to call the dynamic linker to resolve PLT entries the first time
41 // they are called. This function writes that code.
42 virtual void writePltHeader(uint8_t *buf) const {}
44 virtual void writePlt(uint8_t *buf, uint64_t gotEntryAddr,
45 uint64_t pltEntryAddr, int32_t index,
46 unsigned relOff) const {}
47 virtual void addPltHeaderSymbols(InputSection &isec) const {}
48 virtual void addPltSymbols(InputSection &isec, uint64_t off) const {}
50 // Returns true if a relocation only uses the low bits of a value such that
51 // all those bits are in the same page. For example, if the relocation
52 // only uses the low 12 bits in a system with 4k pages. If this is true, the
53 // bits will always have the same value at runtime and we don't have to emit
54 // a dynamic relocation.
55 virtual bool usesOnlyLowPageBits(RelType type) const;
57 // Decide whether a Thunk is needed for the relocation from File
59 virtual bool needsThunk(RelExpr expr, RelType relocType,
60 const InputFile *file, uint64_t branchAddr,
61 const Symbol &s) const;
63 // On systems with range extensions we place collections of Thunks at
64 // regular spacings that enable the majority of branches reach the Thunks.
65 // a value of 0 means range extension thunks are not supported.
66 virtual uint32_t getThunkSectionSpacing() const { return 0; }
68 // The function with a prologue starting at Loc was compiled with
69 // -fsplit-stack and it calls a function compiled without. Adjust the prologue
70 // to do the right thing. See https://gcc.gnu.org/wiki/SplitStacks.
71 // The symbols st_other flags are needed on PowerPC64 for determining the
72 // offset to the split-stack prologue.
73 virtual bool adjustPrologueForCrossSplitStack(uint8_t *loc, uint8_t *end,
74 uint8_t stOther) const;
76 // Return true if we can reach dst from src with RelType type.
77 virtual bool inBranchRange(RelType type, uint64_t src,
80 virtual void relocateOne(uint8_t *loc, RelType type, uint64_t val) const = 0;
82 virtual ~TargetInfo();
84 unsigned defaultCommonPageSize = 4096;
85 unsigned defaultMaxPageSize = 4096;
87 uint64_t getImageBase() const;
89 // True if _GLOBAL_OFFSET_TABLE_ is relative to .got.plt, false if .got.
90 bool gotBaseSymInGotPlt = true;
101 RelType tlsModuleIndexRel;
102 RelType tlsOffsetRel;
103 unsigned pltEntrySize;
104 unsigned pltHeaderSize;
106 // At least on x86_64 positions 1 and 2 are used by the first plt entry
107 // to support lazy loading.
108 unsigned gotPltHeaderEntriesNum = 3;
110 // On PPC ELF V2 abi, the first entry in the .got is the .TOC.
111 unsigned gotHeaderEntriesNum = 0;
113 bool needsThunks = false;
115 // A 4-byte field corresponding to one or more trap instructions, used to pad
116 // executable OutputSections.
117 std::array<uint8_t, 4> trapInstr;
119 // If a target needs to rewrite calls to __morestack to instead call
120 // __morestack_non_split when a split-stack enabled caller calls a
121 // non-split-stack callee this will return true. Otherwise returns false.
122 bool needsMoreStackNonSplit = true;
124 virtual RelExpr adjustRelaxExpr(RelType type, const uint8_t *data,
126 virtual void relaxGot(uint8_t *loc, RelType type, uint64_t val) const;
127 virtual void relaxTlsGdToIe(uint8_t *loc, RelType type, uint64_t val) const;
128 virtual void relaxTlsGdToLe(uint8_t *loc, RelType type, uint64_t val) const;
129 virtual void relaxTlsIeToLe(uint8_t *loc, RelType type, uint64_t val) const;
130 virtual void relaxTlsLdToLe(uint8_t *loc, RelType type, uint64_t val) const;
133 // On FreeBSD x86_64 the first page cannot be mmaped.
134 // On Linux that is controled by vm.mmap_min_addr. At least on some x86_64
135 // installs that is 65536, so the first 15 pages cannot be used.
136 // Given that, the smallest value that can be used in here is 0x10000.
137 uint64_t defaultImageBase = 0x10000;
140 TargetInfo *getAArch64TargetInfo();
141 TargetInfo *getAMDGPUTargetInfo();
142 TargetInfo *getARMTargetInfo();
143 TargetInfo *getAVRTargetInfo();
144 TargetInfo *getHexagonTargetInfo();
145 TargetInfo *getMSP430TargetInfo();
146 TargetInfo *getPPC64TargetInfo();
147 TargetInfo *getPPCTargetInfo();
148 TargetInfo *getRISCVTargetInfo();
149 TargetInfo *getSPARCV9TargetInfo();
150 TargetInfo *getX86TargetInfo();
151 TargetInfo *getX86_64TargetInfo();
152 template <class ELFT> TargetInfo *getMipsTargetInfo();
155 InputSectionBase *isec;
159 // Returns input section and corresponding source string for the given location.
160 ErrorPlace getErrorPlace(const uint8_t *loc);
162 static inline std::string getErrorLocation(const uint8_t *loc) {
163 return getErrorPlace(loc).loc;
166 void writePPC32GlinkSection(uint8_t *buf, size_t numEntries);
168 bool tryRelaxPPC64TocIndirection(RelType type, const Relocation &rel,
170 unsigned getPPCDFormOp(unsigned secondaryOp);
172 // In the PowerPC64 Elf V2 abi a function can have 2 entry points. The first
173 // is a global entry point (GEP) which typically is used to initialize the TOC
174 // pointer in general purpose register 2. The second is a local entry
175 // point (LEP) which bypasses the TOC pointer initialization code. The
176 // offset between GEP and LEP is encoded in a function's st_other flags.
177 // This function will return the offset (in bytes) from the global entry-point
178 // to the local entry-point.
179 unsigned getPPC64GlobalEntryToLocalEntryOffset(uint8_t stOther);
181 // Returns true if a relocation is a small code model relocation that accesses
183 bool isPPC64SmallCodeModelTocReloc(RelType type);
185 uint64_t getPPC64TocBase();
186 uint64_t getAArch64Page(uint64_t expr);
188 extern const TargetInfo *target;
189 TargetInfo *getTarget();
191 template <class ELFT> bool isMipsPIC(const Defined *sym);
193 static inline void reportRangeError(uint8_t *loc, RelType type, const Twine &v,
194 int64_t min, uint64_t max) {
195 ErrorPlace errPlace = getErrorPlace(loc);
197 if (errPlace.isec && errPlace.isec->name.startswith(".debug"))
198 hint = "; consider recompiling with -fdebug-types-section to reduce size "
201 errorOrWarn(errPlace.loc + "relocation " + lld::toString(type) +
202 " out of range: " + v.str() + " is not in [" + Twine(min).str() +
203 ", " + Twine(max).str() + "]" + hint);
206 // Make sure that V can be represented as an N bit signed integer.
207 inline void checkInt(uint8_t *loc, int64_t v, int n, RelType type) {
208 if (v != llvm::SignExtend64(v, n))
209 reportRangeError(loc, type, Twine(v), llvm::minIntN(n), llvm::maxIntN(n));
212 // Make sure that V can be represented as an N bit unsigned integer.
213 inline void checkUInt(uint8_t *loc, uint64_t v, int n, RelType type) {
215 reportRangeError(loc, type, Twine(v), 0, llvm::maxUIntN(n));
218 // Make sure that V can be represented as an N bit signed or unsigned integer.
219 inline void checkIntUInt(uint8_t *loc, uint64_t v, int n, RelType type) {
220 // For the error message we should cast V to a signed integer so that error
221 // messages show a small negative value rather than an extremely large one
222 if (v != (uint64_t)llvm::SignExtend64(v, n) && (v >> n) != 0)
223 reportRangeError(loc, type, Twine((int64_t)v), llvm::minIntN(n),
227 inline void checkAlignment(uint8_t *loc, uint64_t v, int n, RelType type) {
228 if ((v & (n - 1)) != 0)
229 error(getErrorLocation(loc) + "improper alignment for relocation " +
230 lld::toString(type) + ": 0x" + llvm::utohexstr(v) +
231 " is not aligned to " + Twine(n) + " bytes");
234 // Endianness-aware read/write.
235 inline uint16_t read16(const void *p) {
236 return llvm::support::endian::read16(p, config->endianness);
239 inline uint32_t read32(const void *p) {
240 return llvm::support::endian::read32(p, config->endianness);
243 inline uint64_t read64(const void *p) {
244 return llvm::support::endian::read64(p, config->endianness);
247 inline void write16(void *p, uint16_t v) {
248 llvm::support::endian::write16(p, v, config->endianness);
251 inline void write32(void *p, uint32_t v) {
252 llvm::support::endian::write32(p, v, config->endianness);
255 inline void write64(void *p, uint64_t v) {
256 llvm::support::endian::write64(p, v, config->endianness);