1//===----- RuntimeDyldMachOARM.h ---- MachO/ARM specific code. ----*- 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 LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_TARGETS_RUNTIMEDYLDMACHOARM_H
10#define LLVM_LIB_EXECUTIONENGINE_RUNTIMEDYLD_TARGETS_RUNTIMEDYLDMACHOARM_H
11
12#include "../RuntimeDyldMachO.h"
13#include <string>
14
15#define DEBUG_TYPE "dyld"
16
17namespace llvm {
18
19class RuntimeDyldMachOARM
20 : public RuntimeDyldMachOCRTPBase<RuntimeDyldMachOARM> {
21private:
22 typedef RuntimeDyldMachOCRTPBase<RuntimeDyldMachOARM> ParentT;
23
24public:
25
26 typedef uint32_t TargetPtrT;
27
28 RuntimeDyldMachOARM(RuntimeDyld::MemoryManager &MM,
29 JITSymbolResolver &Resolver)
30 : RuntimeDyldMachOCRTPBase(MM, Resolver) {}
31
32 unsigned getMaxStubSize() const override { return 8; }
33
34 unsigned getStubAlignment() override { return 4; }
35
36 Expected<JITSymbolFlags> getJITSymbolFlags(const SymbolRef &SR) override {
37 auto Flags = RuntimeDyldImpl::getJITSymbolFlags(SR);
38 if (!Flags)
39 return Flags.takeError();
40 Flags->getTargetFlags() = ARMJITSymbolFlags::fromObjectSymbol(SR);
41 return Flags;
42 }
43
44 uint64_t modifyAddressBasedOnFlags(uint64_t Addr,
45 JITSymbolFlags Flags) const override {
46 if (Flags.getTargetFlags() & ARMJITSymbolFlags::Thumb)
47 Addr |= 0x1;
48 return Addr;
49 }
50
51 bool isAddrTargetThumb(unsigned SectionID, uint64_t Offset) {
52 auto TargetObjAddr = Sections[SectionID].getObjAddress() + Offset;
53 for (auto &KV : GlobalSymbolTable) {
54 auto &Entry = KV.second;
55 auto SymbolObjAddr =
56 Sections[Entry.getSectionID()].getObjAddress() + Entry.getOffset();
57 if (TargetObjAddr == SymbolObjAddr)
58 return (Entry.getFlags().getTargetFlags() & ARMJITSymbolFlags::Thumb);
59 }
60 return false;
61 }
62
63 Expected<int64_t> decodeAddend(const RelocationEntry &RE) const {
64 const SectionEntry &Section = Sections[RE.SectionID];
65 uint8_t *LocalAddress = Section.getAddressWithOffset(RE.Offset);
66
67 switch (RE.RelType) {
68 default:
69 return memcpyAddend(RE);
70 case MachO::ARM_RELOC_BR24: {
71 uint32_t Temp = readBytesUnaligned(LocalAddress, 4);
72 Temp &= 0x00ffffff; // Mask out the opcode.
73 // Now we've got the shifted immediate, shift by 2, sign extend and ret.
74 return SignExtend32<26>(Temp << 2);
75 }
76
77 case MachO::ARM_THUMB_RELOC_BR22: {
78 // This is a pair of instructions whose operands combine to provide 22
79 // bits of displacement:
80 // Encoding for high bits 1111 0XXX XXXX XXXX
81 // Encoding for low bits 1111 1XXX XXXX XXXX
82 uint16_t HighInsn = readBytesUnaligned(LocalAddress, 2);
83 if ((HighInsn & 0xf800) != 0xf000)
84 return make_error<StringError>("Unrecognized thumb branch encoding "
85 "(BR22 high bits)",
86 inconvertibleErrorCode());
87
88 uint16_t LowInsn = readBytesUnaligned(LocalAddress + 2, 2);
89 if ((LowInsn & 0xf800) != 0xf800)
90 return make_error<StringError>("Unrecognized thumb branch encoding "
91 "(BR22 low bits)",
92 inconvertibleErrorCode());
93
94 return SignExtend64<23>(((HighInsn & 0x7ff) << 12) |
95 ((LowInsn & 0x7ff) << 1));
96 }
97 }
98 }
99
100 Expected<relocation_iterator>
101 processRelocationRef(unsigned SectionID, relocation_iterator RelI,
102 const ObjectFile &BaseObjT,
103 ObjSectionToIDMap &ObjSectionToID,
104 StubMap &Stubs) override {
105 const MachOObjectFile &Obj =
106 static_cast<const MachOObjectFile &>(BaseObjT);
107 MachO::any_relocation_info RelInfo =
108 Obj.getRelocation(RelI->getRawDataRefImpl());
109 uint32_t RelType = Obj.getAnyRelocationType(RelInfo);
110
111 // Set to true for thumb functions in this (or previous) TUs.
112 // Will be used to set the TargetIsThumbFunc member on the relocation entry.
113 bool TargetIsLocalThumbFunc = false;
114 if (Obj.getPlainRelocationExternal(RelInfo)) {
115 auto Symbol = RelI->getSymbol();
116 StringRef TargetName;
117 if (auto TargetNameOrErr = Symbol->getName())
118 TargetName = *TargetNameOrErr;
119 else
120 return TargetNameOrErr.takeError();
121
122 // If the target is external but the value doesn't have a name then we've
123 // converted the value to a section/offset pair, but we still need to set
124 // the IsTargetThumbFunc bit, so look the value up in the globla symbol table.
125 auto EntryItr = GlobalSymbolTable.find(TargetName);
126 if (EntryItr != GlobalSymbolTable.end()) {
127 TargetIsLocalThumbFunc =
128 EntryItr->second.getFlags().getTargetFlags() &
129 ARMJITSymbolFlags::Thumb;
130 }
131 }
132
133 if (Obj.isRelocationScattered(RelInfo)) {
134 if (RelType == MachO::ARM_RELOC_HALF_SECTDIFF)
135 return processHALFSECTDIFFRelocation(SectionID, RelI, Obj,
136 ObjSectionToID);
137 else if (RelType == MachO::GENERIC_RELOC_VANILLA)
138 return processScatteredVANILLA(SectionID, RelI, Obj, ObjSectionToID,
139 TargetIsLocalThumbFunc);
140 else
141 return ++RelI;
142 }
143
144 // Sanity check relocation type.
145 switch (RelType) {
146 UNIMPLEMENTED_RELOC(MachO::ARM_RELOC_PAIR);
147 UNIMPLEMENTED_RELOC(MachO::ARM_RELOC_SECTDIFF);
148 UNIMPLEMENTED_RELOC(MachO::ARM_RELOC_LOCAL_SECTDIFF);
149 UNIMPLEMENTED_RELOC(MachO::ARM_RELOC_PB_LA_PTR);
150 UNIMPLEMENTED_RELOC(MachO::ARM_THUMB_32BIT_BRANCH);
151 UNIMPLEMENTED_RELOC(MachO::ARM_RELOC_HALF);
152 default:
153 if (RelType > MachO::ARM_RELOC_HALF_SECTDIFF)
154 return make_error<RuntimeDyldError>(("MachO ARM relocation type " +
155 Twine(RelType) +
156 " is out of range").str());
157 break;
158 }
159
160 RelocationEntry RE(getRelocationEntry(SectionID, Obj, RelI));
161 if (auto AddendOrErr = decodeAddend(RE))
162 RE.Addend = *AddendOrErr;
163 else
164 return AddendOrErr.takeError();
165 RE.IsTargetThumbFunc = TargetIsLocalThumbFunc;
166
167 RelocationValueRef Value;
168 if (auto ValueOrErr = getRelocationValueRef(Obj, RelI, RE, ObjSectionToID))
169 Value = *ValueOrErr;
170 else
171 return ValueOrErr.takeError();
172
173 // If this is a branch from a thumb function (BR22) then make sure we mark
174 // the value as being a thumb stub: we don't want to mix it up with an ARM
175 // stub targeting the same function.
176 if (RE.RelType == MachO::ARM_THUMB_RELOC_BR22)
177 Value.IsStubThumb = true;
178
179 if (RE.IsPCRel)
180 makeValueAddendPCRel(Value, RelI,
181 (RE.RelType == MachO::ARM_THUMB_RELOC_BR22) ? 4 : 8);
182
183 // If this is a non-external branch target check whether Value points to a
184 // thumb func.
185 if (!Value.SymbolName && (RelType == MachO::ARM_RELOC_BR24 ||
186 RelType == MachO::ARM_THUMB_RELOC_BR22))
187 RE.IsTargetThumbFunc = isAddrTargetThumb(Value.SectionID, Value.Offset);
188
189 if (RE.RelType == MachO::ARM_RELOC_BR24 ||
190 RE.RelType == MachO::ARM_THUMB_RELOC_BR22)
191 processBranchRelocation(RE, Value, Stubs);
192 else {
193 RE.Addend = Value.Offset;
194 if (Value.SymbolName)
195 addRelocationForSymbol(RE, Value.SymbolName);
196 else
197 addRelocationForSection(RE, Value.SectionID);
198 }
199
200 return ++RelI;
201 }
202
203 void resolveRelocation(const RelocationEntry &RE, uint64_t Value) override {
204 LLVM_DEBUG(dumpRelocationToResolve(RE, Value));
205 const SectionEntry &Section = Sections[RE.SectionID];
206 uint8_t *LocalAddress = Section.getAddressWithOffset(RE.Offset);
207
208 // If the relocation is PC-relative, the value to be encoded is the
209 // pointer difference.
210 if (RE.IsPCRel) {
211 uint64_t FinalAddress = Section.getLoadAddressWithOffset(RE.Offset);
212 Value -= FinalAddress;
213 // ARM PCRel relocations have an effective-PC offset of two instructions
214 // (four bytes in Thumb mode, 8 bytes in ARM mode).
215 Value -= (RE.RelType == MachO::ARM_THUMB_RELOC_BR22) ? 4 : 8;
216 }
217
218 switch (RE.RelType) {
219 case MachO::ARM_THUMB_RELOC_BR22: {
220 Value += RE.Addend;
221 uint16_t HighInsn = readBytesUnaligned(LocalAddress, 2);
222 assert((HighInsn & 0xf800) == 0xf000 &&
223 "Unrecognized thumb branch encoding (BR22 high bits)");
224 HighInsn = (HighInsn & 0xf800) | ((Value >> 12) & 0x7ff);
225
226 uint16_t LowInsn = readBytesUnaligned(LocalAddress + 2, 2);
227 assert((LowInsn & 0xf800) == 0xf800 &&
228 "Unrecognized thumb branch encoding (BR22 low bits)");
229 LowInsn = (LowInsn & 0xf800) | ((Value >> 1) & 0x7ff);
230
231 writeBytesUnaligned(HighInsn, LocalAddress, 2);
232 writeBytesUnaligned(LowInsn, LocalAddress + 2, 2);
233 break;
234 }
235
236 case MachO::ARM_RELOC_VANILLA:
237 if (RE.IsTargetThumbFunc)
238 Value |= 0x01;
239 writeBytesUnaligned(Value + RE.Addend, LocalAddress, 1 << RE.Size);
240 break;
241 case MachO::ARM_RELOC_BR24: {
242 // Mask the value into the target address. We know instructions are
243 // 32-bit aligned, so we can do it all at once.
244 Value += RE.Addend;
245 // The low two bits of the value are not encoded.
246 Value >>= 2;
247 // Mask the value to 24 bits.
248 uint64_t FinalValue = Value & 0xffffff;
249 // FIXME: If the destination is a Thumb function (and the instruction
250 // is a non-predicated BL instruction), we need to change it to a BLX
251 // instruction instead.
252
253 // Insert the value into the instruction.
254 uint32_t Temp = readBytesUnaligned(LocalAddress, 4);
255 writeBytesUnaligned((Temp & ~0xffffff) | FinalValue, LocalAddress, 4);
256
257 break;
258 }
259 case MachO::ARM_RELOC_HALF_SECTDIFF: {
260 uint64_t SectionABase = Sections[RE.Sections.SectionA].getLoadAddress();
261 uint64_t SectionBBase = Sections[RE.Sections.SectionB].getLoadAddress();
262 assert((Value == SectionABase || Value == SectionBBase) &&
263 "Unexpected HALFSECTDIFF relocation value.");
264 Value = SectionABase - SectionBBase + RE.Addend;
265 if (RE.Size & 0x1) // :upper16:
266 Value = (Value >> 16);
267
268 bool IsThumb = RE.Size & 0x2;
269
270 Value &= 0xffff;
271
272 uint32_t Insn = readBytesUnaligned(LocalAddress, 4);
273
274 if (IsThumb)
275 Insn = (Insn & 0x8f00fbf0) | ((Value & 0xf000) >> 12) |
276 ((Value & 0x0800) >> 1) | ((Value & 0x0700) << 20) |
277 ((Value & 0x00ff) << 16);
278 else
279 Insn = (Insn & 0xfff0f000) | ((Value & 0xf000) << 4) | (Value & 0x0fff);
280 writeBytesUnaligned(Insn, LocalAddress, 4);
281 break;
282 }
283
284 default:
285 llvm_unreachable("Invalid relocation type");
286 }
287 }
288
289 Error finalizeSection(const ObjectFile &Obj, unsigned SectionID,
290 const SectionRef &Section) {
291 StringRef Name;
292 if (Expected<StringRef> NameOrErr = Section.getName())
293 Name = *NameOrErr;
294 else
295 consumeError(NameOrErr.takeError());
296
297 if (Name == "__nl_symbol_ptr")
298 return populateIndirectSymbolPointersSection(cast<MachOObjectFile>(Obj),
299 Section, SectionID);
300 return Error::success();
301 }
302
303private:
304
305 void processBranchRelocation(const RelocationEntry &RE,
306 const RelocationValueRef &Value,
307 StubMap &Stubs) {
308 // This is an ARM branch relocation, need to use a stub function.
309 // Look up for existing stub.
310 SectionEntry &Section = Sections[RE.SectionID];
311 RuntimeDyldMachO::StubMap::const_iterator i = Stubs.find(Value);
312 uint8_t *Addr;
313 if (i != Stubs.end()) {
314 Addr = Section.getAddressWithOffset(i->second);
315 } else {
316 // Create a new stub function.
317 assert(Section.getStubOffset() % 4 == 0 && "Misaligned stub");
318 Stubs[Value] = Section.getStubOffset();
319 uint32_t StubOpcode = 0;
320 if (RE.RelType == MachO::ARM_RELOC_BR24)
321 StubOpcode = 0xe51ff004; // ldr pc, [pc, #-4]
322 else if (RE.RelType == MachO::ARM_THUMB_RELOC_BR22)
323 StubOpcode = 0xf000f8df; // ldr pc, [pc]
324 else
325 llvm_unreachable("Unrecognized relocation");
326 Addr = Section.getAddressWithOffset(Section.getStubOffset());
327 writeBytesUnaligned(StubOpcode, Addr, 4);
328 uint8_t *StubTargetAddr = Addr + 4;
329 RelocationEntry StubRE(
330 RE.SectionID, StubTargetAddr - Section.getAddress(),
331 MachO::GENERIC_RELOC_VANILLA, Value.Offset, false, 2);
332 StubRE.IsTargetThumbFunc = RE.IsTargetThumbFunc;
333 if (Value.SymbolName)
334 addRelocationForSymbol(StubRE, Value.SymbolName);
335 else
336 addRelocationForSection(StubRE, Value.SectionID);
337 Section.advanceStubOffset(getMaxStubSize());
338 }
339 RelocationEntry TargetRE(RE.SectionID, RE.Offset, RE.RelType, 0,
340 RE.IsPCRel, RE.Size);
341 resolveRelocation(TargetRE, (uint64_t)Addr);
342 }
343
344 Expected<relocation_iterator>
345 processHALFSECTDIFFRelocation(unsigned SectionID, relocation_iterator RelI,
346 const ObjectFile &BaseTObj,
347 ObjSectionToIDMap &ObjSectionToID) {
348 const MachOObjectFile &MachO =
349 static_cast<const MachOObjectFile&>(BaseTObj);
350 MachO::any_relocation_info RE =
351 MachO.getRelocation(RelI->getRawDataRefImpl());
352
353 // For a half-diff relocation the length bits actually record whether this
354 // is a movw/movt, and whether this is arm or thumb.
355 // Bit 0 indicates movw (b0 == 0) or movt (b0 == 1).
356 // Bit 1 indicates arm (b1 == 0) or thumb (b1 == 1).
357 unsigned HalfDiffKindBits = MachO.getAnyRelocationLength(RE);
358 bool IsThumb = HalfDiffKindBits & 0x2;
359
360 SectionEntry &Section = Sections[SectionID];
361 uint32_t RelocType = MachO.getAnyRelocationType(RE);
362 bool IsPCRel = MachO.getAnyRelocationPCRel(RE);
363 uint64_t Offset = RelI->getOffset();
364 uint8_t *LocalAddress = Section.getAddressWithOffset(Offset);
365 int64_t Immediate = readBytesUnaligned(LocalAddress, 4); // Copy the whole instruction out.
366
367 if (IsThumb)
368 Immediate = ((Immediate & 0x0000000f) << 12) |
369 ((Immediate & 0x00000400) << 1) |
370 ((Immediate & 0x70000000) >> 20) |
371 ((Immediate & 0x00ff0000) >> 16);
372 else
373 Immediate = ((Immediate >> 4) & 0xf000) | (Immediate & 0xfff);
374
375 ++RelI;
376 MachO::any_relocation_info RE2 =
377 MachO.getRelocation(RelI->getRawDataRefImpl());
378 uint32_t AddrA = MachO.getScatteredRelocationValue(RE);
379 section_iterator SAI = getSectionByAddress(MachO, AddrA);
380 assert(SAI != MachO.section_end() && "Can't find section for address A");
381 uint64_t SectionABase = SAI->getAddress();
382 uint64_t SectionAOffset = AddrA - SectionABase;
383 SectionRef SectionA = *SAI;
384 bool IsCode = SectionA.isText();
385 uint32_t SectionAID = ~0U;
386 if (auto SectionAIDOrErr =
387 findOrEmitSection(MachO, SectionA, IsCode, ObjSectionToID))
388 SectionAID = *SectionAIDOrErr;
389 else
390 return SectionAIDOrErr.takeError();
391
392 uint32_t AddrB = MachO.getScatteredRelocationValue(RE2);
393 section_iterator SBI = getSectionByAddress(MachO, AddrB);
394 assert(SBI != MachO.section_end() && "Can't find section for address B");
395 uint64_t SectionBBase = SBI->getAddress();
396 uint64_t SectionBOffset = AddrB - SectionBBase;
397 SectionRef SectionB = *SBI;
398 uint32_t SectionBID = ~0U;
399 if (auto SectionBIDOrErr =
400 findOrEmitSection(MachO, SectionB, IsCode, ObjSectionToID))
401 SectionBID = *SectionBIDOrErr;
402 else
403 return SectionBIDOrErr.takeError();
404
405 uint32_t OtherHalf = MachO.getAnyRelocationAddress(RE2) & 0xffff;
406 unsigned Shift = (HalfDiffKindBits & 0x1) ? 16 : 0;
407 uint32_t FullImmVal = (Immediate << Shift) | (OtherHalf << (16 - Shift));
408 int64_t Addend = FullImmVal - (AddrA - AddrB);
409
410 // addend = Encoded - Expected
411 // = Encoded - (AddrA - AddrB)
412
413 LLVM_DEBUG(dbgs() << "Found SECTDIFF: AddrA: " << AddrA
414 << ", AddrB: " << AddrB << ", Addend: " << Addend
415 << ", SectionA ID: " << SectionAID << ", SectionAOffset: "
416 << SectionAOffset << ", SectionB ID: " << SectionBID
417 << ", SectionBOffset: " << SectionBOffset << "\n");
418 RelocationEntry R(SectionID, Offset, RelocType, Addend, SectionAID,
419 SectionAOffset, SectionBID, SectionBOffset, IsPCRel,
420 HalfDiffKindBits);
421
422 addRelocationForSection(R, SectionAID);
423
424 return ++RelI;
425 }
426
427};
428}
429
430#undef DEBUG_TYPE
431
432#endif
433