xref: /freebsd/contrib/llvm-project/lld/ELF/Target.h (revision 643ac419fafba89f5adda0e0ea75b538727453fb)
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 "InputSection.h"
13 #include "lld/Common/ErrorHandler.h"
14 #include "llvm/Object/ELF.h"
15 #include "llvm/Support/MathExtras.h"
16 #include <array>
17 
18 namespace lld {
19 std::string toString(elf::RelType type);
20 
21 namespace elf {
22 class Defined;
23 class InputFile;
24 class Symbol;
25 
26 class TargetInfo {
27 public:
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; }
38 
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 {}
43 
44   virtual void writePlt(uint8_t *buf, const Symbol &sym,
45                         uint64_t pltEntryAddr) const {}
46   virtual void writeIplt(uint8_t *buf, const Symbol &sym,
47                          uint64_t pltEntryAddr) const {
48     // All but PPC32 and PPC64 use the same format for .plt and .iplt entries.
49     writePlt(buf, sym, pltEntryAddr);
50   }
51   virtual void writeIBTPlt(uint8_t *buf, size_t numEntries) const {}
52   virtual void addPltHeaderSymbols(InputSection &isec) const {}
53   virtual void addPltSymbols(InputSection &isec, uint64_t off) const {}
54 
55   // Returns true if a relocation only uses the low bits of a value such that
56   // all those bits are in the same page. For example, if the relocation
57   // only uses the low 12 bits in a system with 4k pages. If this is true, the
58   // bits will always have the same value at runtime and we don't have to emit
59   // a dynamic relocation.
60   virtual bool usesOnlyLowPageBits(RelType type) const;
61 
62   // Decide whether a Thunk is needed for the relocation from File
63   // targeting S.
64   virtual bool needsThunk(RelExpr expr, RelType relocType,
65                           const InputFile *file, uint64_t branchAddr,
66                           const Symbol &s, int64_t a) const;
67 
68   // On systems with range extensions we place collections of Thunks at
69   // regular spacings that enable the majority of branches reach the Thunks.
70   // a value of 0 means range extension thunks are not supported.
71   virtual uint32_t getThunkSectionSpacing() const { return 0; }
72 
73   // The function with a prologue starting at Loc was compiled with
74   // -fsplit-stack and it calls a function compiled without. Adjust the prologue
75   // to do the right thing. See https://gcc.gnu.org/wiki/SplitStacks.
76   // The symbols st_other flags are needed on PowerPC64 for determining the
77   // offset to the split-stack prologue.
78   virtual bool adjustPrologueForCrossSplitStack(uint8_t *loc, uint8_t *end,
79                                                 uint8_t stOther) const;
80 
81   // Return true if we can reach dst from src with RelType type.
82   virtual bool inBranchRange(RelType type, uint64_t src,
83                              uint64_t dst) const;
84 
85   virtual void relocate(uint8_t *loc, const Relocation &rel,
86                         uint64_t val) const = 0;
87   void relocateNoSym(uint8_t *loc, RelType type, uint64_t val) const {
88     relocate(loc, Relocation{R_NONE, type, 0, 0, nullptr}, val);
89   }
90 
91   virtual void applyJumpInstrMod(uint8_t *loc, JumpModType type,
92                                  JumpModType val) const {}
93 
94   virtual ~TargetInfo();
95 
96   // This deletes a jump insn at the end of the section if it is a fall thru to
97   // the next section.  Further, if there is a conditional jump and a direct
98   // jump consecutively, it tries to flip the conditional jump to convert the
99   // direct jump into a fall thru and delete it.  Returns true if a jump
100   // instruction can be deleted.
101   virtual bool deleteFallThruJmpInsn(InputSection &is, InputFile *file,
102                                      InputSection *nextIS) const {
103     return false;
104   }
105 
106   unsigned defaultCommonPageSize = 4096;
107   unsigned defaultMaxPageSize = 4096;
108 
109   uint64_t getImageBase() const;
110 
111   // True if _GLOBAL_OFFSET_TABLE_ is relative to .got.plt, false if .got.
112   bool gotBaseSymInGotPlt = false;
113 
114   static constexpr RelType noneRel = 0;
115   RelType copyRel;
116   RelType gotRel;
117   RelType pltRel;
118   RelType relativeRel;
119   RelType iRelativeRel;
120   RelType symbolicRel;
121   RelType tlsDescRel;
122   RelType tlsGotRel;
123   RelType tlsModuleIndexRel;
124   RelType tlsOffsetRel;
125   unsigned gotEntrySize = config->wordsize;
126   unsigned pltEntrySize;
127   unsigned pltHeaderSize;
128   unsigned ipltEntrySize;
129 
130   // At least on x86_64 positions 1 and 2 are used by the first plt entry
131   // to support lazy loading.
132   unsigned gotPltHeaderEntriesNum = 3;
133 
134   // On PPC ELF V2 abi, the first entry in the .got is the .TOC.
135   unsigned gotHeaderEntriesNum = 0;
136 
137   bool needsThunks = false;
138 
139   // A 4-byte field corresponding to one or more trap instructions, used to pad
140   // executable OutputSections.
141   std::array<uint8_t, 4> trapInstr;
142 
143   // Stores the NOP instructions of different sizes for the target and is used
144   // to pad sections that are relaxed.
145   llvm::Optional<std::vector<std::vector<uint8_t>>> nopInstrs;
146 
147   // If a target needs to rewrite calls to __morestack to instead call
148   // __morestack_non_split when a split-stack enabled caller calls a
149   // non-split-stack callee this will return true. Otherwise returns false.
150   bool needsMoreStackNonSplit = true;
151 
152   virtual RelExpr adjustTlsExpr(RelType type, RelExpr expr) const;
153   virtual RelExpr adjustGotPcExpr(RelType type, int64_t addend,
154                                   const uint8_t *loc) const;
155   virtual void relaxGot(uint8_t *loc, const Relocation &rel,
156                         uint64_t val) const;
157   virtual void relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
158                               uint64_t val) const;
159   virtual void relaxTlsGdToLe(uint8_t *loc, const Relocation &rel,
160                               uint64_t val) const;
161   virtual void relaxTlsIeToLe(uint8_t *loc, const Relocation &rel,
162                               uint64_t val) const;
163   virtual void relaxTlsLdToLe(uint8_t *loc, const Relocation &rel,
164                               uint64_t val) const;
165 
166 protected:
167   // On FreeBSD x86_64 the first page cannot be mmaped.
168   // On Linux this is controlled by vm.mmap_min_addr. At least on some x86_64
169   // installs this is set to 65536, so the first 15 pages cannot be used.
170   // Given that, the smallest value that can be used in here is 0x10000.
171   uint64_t defaultImageBase = 0x10000;
172 };
173 
174 TargetInfo *getAArch64TargetInfo();
175 TargetInfo *getAMDGPUTargetInfo();
176 TargetInfo *getARMTargetInfo();
177 TargetInfo *getAVRTargetInfo();
178 TargetInfo *getHexagonTargetInfo();
179 TargetInfo *getMSP430TargetInfo();
180 TargetInfo *getPPC64TargetInfo();
181 TargetInfo *getPPCTargetInfo();
182 TargetInfo *getRISCVTargetInfo();
183 TargetInfo *getSPARCV9TargetInfo();
184 TargetInfo *getX86TargetInfo();
185 TargetInfo *getX86_64TargetInfo();
186 template <class ELFT> TargetInfo *getMipsTargetInfo();
187 
188 struct ErrorPlace {
189   InputSectionBase *isec;
190   std::string loc;
191   std::string srcLoc;
192 };
193 
194 // Returns input section and corresponding source string for the given location.
195 ErrorPlace getErrorPlace(const uint8_t *loc);
196 
197 static inline std::string getErrorLocation(const uint8_t *loc) {
198   return getErrorPlace(loc).loc;
199 }
200 
201 void writePPC32GlinkSection(uint8_t *buf, size_t numEntries);
202 
203 bool tryRelaxPPC64TocIndirection(const Relocation &rel, uint8_t *bufLoc);
204 unsigned getPPCDFormOp(unsigned secondaryOp);
205 
206 // In the PowerPC64 Elf V2 abi a function can have 2 entry points.  The first
207 // is a global entry point (GEP) which typically is used to initialize the TOC
208 // pointer in general purpose register 2.  The second is a local entry
209 // point (LEP) which bypasses the TOC pointer initialization code. The
210 // offset between GEP and LEP is encoded in a function's st_other flags.
211 // This function will return the offset (in bytes) from the global entry-point
212 // to the local entry-point.
213 unsigned getPPC64GlobalEntryToLocalEntryOffset(uint8_t stOther);
214 
215 // Write a prefixed instruction, which is a 4-byte prefix followed by a 4-byte
216 // instruction (regardless of endianness). Therefore, the prefix is always in
217 // lower memory than the instruction.
218 void writePrefixedInstruction(uint8_t *loc, uint64_t insn);
219 
220 void addPPC64SaveRestore();
221 uint64_t getPPC64TocBase();
222 uint64_t getAArch64Page(uint64_t expr);
223 
224 class AArch64Relaxer {
225   bool safeToRelaxAdrpLdr = true;
226 
227 public:
228   explicit AArch64Relaxer(ArrayRef<Relocation> relocs);
229 
230   bool tryRelaxAdrpAdd(const Relocation &adrpRel, const Relocation &addRel,
231                        uint64_t secAddr, uint8_t *buf) const;
232   bool tryRelaxAdrpLdr(const Relocation &adrpRel, const Relocation &ldrRel,
233                        uint64_t secAddr, uint8_t *buf) const;
234 };
235 
236 extern const TargetInfo *target;
237 TargetInfo *getTarget();
238 
239 template <class ELFT> bool isMipsPIC(const Defined *sym);
240 
241 void reportRangeError(uint8_t *loc, const Relocation &rel, const Twine &v,
242                       int64_t min, uint64_t max);
243 void reportRangeError(uint8_t *loc, int64_t v, int n, const Symbol &sym,
244                       const Twine &msg);
245 
246 // Make sure that V can be represented as an N bit signed integer.
247 inline void checkInt(uint8_t *loc, int64_t v, int n, const Relocation &rel) {
248   if (v != llvm::SignExtend64(v, n))
249     reportRangeError(loc, rel, Twine(v), llvm::minIntN(n), llvm::maxIntN(n));
250 }
251 
252 // Make sure that V can be represented as an N bit unsigned integer.
253 inline void checkUInt(uint8_t *loc, uint64_t v, int n, const Relocation &rel) {
254   if ((v >> n) != 0)
255     reportRangeError(loc, rel, Twine(v), 0, llvm::maxUIntN(n));
256 }
257 
258 // Make sure that V can be represented as an N bit signed or unsigned integer.
259 inline void checkIntUInt(uint8_t *loc, uint64_t v, int n,
260                          const Relocation &rel) {
261   // For the error message we should cast V to a signed integer so that error
262   // messages show a small negative value rather than an extremely large one
263   if (v != (uint64_t)llvm::SignExtend64(v, n) && (v >> n) != 0)
264     reportRangeError(loc, rel, Twine((int64_t)v), llvm::minIntN(n),
265                      llvm::maxUIntN(n));
266 }
267 
268 inline void checkAlignment(uint8_t *loc, uint64_t v, int n,
269                            const Relocation &rel) {
270   if ((v & (n - 1)) != 0)
271     error(getErrorLocation(loc) + "improper alignment for relocation " +
272           lld::toString(rel.type) + ": 0x" + llvm::utohexstr(v) +
273           " is not aligned to " + Twine(n) + " bytes");
274 }
275 
276 // Endianness-aware read/write.
277 inline uint16_t read16(const void *p) {
278   return llvm::support::endian::read16(p, config->endianness);
279 }
280 
281 inline uint32_t read32(const void *p) {
282   return llvm::support::endian::read32(p, config->endianness);
283 }
284 
285 inline uint64_t read64(const void *p) {
286   return llvm::support::endian::read64(p, config->endianness);
287 }
288 
289 inline void write16(void *p, uint16_t v) {
290   llvm::support::endian::write16(p, v, config->endianness);
291 }
292 
293 inline void write32(void *p, uint32_t v) {
294   llvm::support::endian::write32(p, v, config->endianness);
295 }
296 
297 inline void write64(void *p, uint64_t v) {
298   llvm::support::endian::write64(p, v, config->endianness);
299 }
300 } // namespace elf
301 } // namespace lld
302 
303 #ifdef __clang__
304 #pragma clang diagnostic ignored "-Wgnu-zero-variadic-macro-arguments"
305 #endif
306 #define invokeELFT(f, ...)                                                     \
307   switch (config->ekind) {                                                     \
308   case ELF32LEKind:                                                            \
309     f<ELF32LE>(__VA_ARGS__);                                                   \
310     break;                                                                     \
311   case ELF32BEKind:                                                            \
312     f<ELF32BE>(__VA_ARGS__);                                                   \
313     break;                                                                     \
314   case ELF64LEKind:                                                            \
315     f<ELF64LE>(__VA_ARGS__);                                                   \
316     break;                                                                     \
317   case ELF64BEKind:                                                            \
318     f<ELF64BE>(__VA_ARGS__);                                                   \
319     break;                                                                     \
320   default:                                                                     \
321     llvm_unreachable("unknown config->ekind");                                 \
322   }
323 
324 #endif
325