1 //===-- JITMemoryManager.cpp - Memory Allocator for JIT'd code ------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file defines the DefaultJITMemoryManager class. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #define DEBUG_TYPE "jit" 15 #include "llvm/ExecutionEngine/JITMemoryManager.h" 16 #include "llvm/ADT/SmallPtrSet.h" 17 #include "llvm/ADT/Statistic.h" 18 #include "llvm/ADT/Twine.h" 19 #include "llvm/Config/config.h" 20 #include "llvm/IR/GlobalValue.h" 21 #include "llvm/Support/Allocator.h" 22 #include "llvm/Support/Compiler.h" 23 #include "llvm/Support/Debug.h" 24 #include "llvm/Support/DynamicLibrary.h" 25 #include "llvm/Support/ErrorHandling.h" 26 #include "llvm/Support/Memory.h" 27 #include "llvm/Support/raw_ostream.h" 28 #include <cassert> 29 #include <climits> 30 #include <cstring> 31 #include <vector> 32 33 #if defined(__linux__) 34 #if defined(HAVE_SYS_STAT_H) 35 #include <sys/stat.h> 36 #endif 37 #include <fcntl.h> 38 #include <unistd.h> 39 #endif 40 41 using namespace llvm; 42 43 STATISTIC(NumSlabs, "Number of slabs of memory allocated by the JIT"); 44 45 JITMemoryManager::~JITMemoryManager() {} 46 47 //===----------------------------------------------------------------------===// 48 // Memory Block Implementation. 49 //===----------------------------------------------------------------------===// 50 51 namespace { 52 /// MemoryRangeHeader - For a range of memory, this is the header that we put 53 /// on the block of memory. It is carefully crafted to be one word of memory. 54 /// Allocated blocks have just this header, free'd blocks have FreeRangeHeader 55 /// which starts with this. 56 struct FreeRangeHeader; 57 struct MemoryRangeHeader { 58 /// ThisAllocated - This is true if this block is currently allocated. If 59 /// not, this can be converted to a FreeRangeHeader. 60 unsigned ThisAllocated : 1; 61 62 /// PrevAllocated - Keep track of whether the block immediately before us is 63 /// allocated. If not, the word immediately before this header is the size 64 /// of the previous block. 65 unsigned PrevAllocated : 1; 66 67 /// BlockSize - This is the size in bytes of this memory block, 68 /// including this header. 69 uintptr_t BlockSize : (sizeof(intptr_t)*CHAR_BIT - 2); 70 71 72 /// getBlockAfter - Return the memory block immediately after this one. 73 /// 74 MemoryRangeHeader &getBlockAfter() const { 75 return *reinterpret_cast<MemoryRangeHeader *>( 76 reinterpret_cast<char*>( 77 const_cast<MemoryRangeHeader *>(this))+BlockSize); 78 } 79 80 /// getFreeBlockBefore - If the block before this one is free, return it, 81 /// otherwise return null. 82 FreeRangeHeader *getFreeBlockBefore() const { 83 if (PrevAllocated) return 0; 84 intptr_t PrevSize = reinterpret_cast<intptr_t *>( 85 const_cast<MemoryRangeHeader *>(this))[-1]; 86 return reinterpret_cast<FreeRangeHeader *>( 87 reinterpret_cast<char*>( 88 const_cast<MemoryRangeHeader *>(this))-PrevSize); 89 } 90 91 /// FreeBlock - Turn an allocated block into a free block, adjusting 92 /// bits in the object headers, and adding an end of region memory block. 93 FreeRangeHeader *FreeBlock(FreeRangeHeader *FreeList); 94 95 /// TrimAllocationToSize - If this allocated block is significantly larger 96 /// than NewSize, split it into two pieces (where the former is NewSize 97 /// bytes, including the header), and add the new block to the free list. 98 FreeRangeHeader *TrimAllocationToSize(FreeRangeHeader *FreeList, 99 uint64_t NewSize); 100 }; 101 102 /// FreeRangeHeader - For a memory block that isn't already allocated, this 103 /// keeps track of the current block and has a pointer to the next free block. 104 /// Free blocks are kept on a circularly linked list. 105 struct FreeRangeHeader : public MemoryRangeHeader { 106 FreeRangeHeader *Prev; 107 FreeRangeHeader *Next; 108 109 /// getMinBlockSize - Get the minimum size for a memory block. Blocks 110 /// smaller than this size cannot be created. 111 static unsigned getMinBlockSize() { 112 return sizeof(FreeRangeHeader)+sizeof(intptr_t); 113 } 114 115 /// SetEndOfBlockSizeMarker - The word at the end of every free block is 116 /// known to be the size of the free block. Set it for this block. 117 void SetEndOfBlockSizeMarker() { 118 void *EndOfBlock = (char*)this + BlockSize; 119 ((intptr_t *)EndOfBlock)[-1] = BlockSize; 120 } 121 122 FreeRangeHeader *RemoveFromFreeList() { 123 assert(Next->Prev == this && Prev->Next == this && "Freelist broken!"); 124 Next->Prev = Prev; 125 return Prev->Next = Next; 126 } 127 128 void AddToFreeList(FreeRangeHeader *FreeList) { 129 Next = FreeList; 130 Prev = FreeList->Prev; 131 Prev->Next = this; 132 Next->Prev = this; 133 } 134 135 /// GrowBlock - The block after this block just got deallocated. Merge it 136 /// into the current block. 137 void GrowBlock(uintptr_t NewSize); 138 139 /// AllocateBlock - Mark this entire block allocated, updating freelists 140 /// etc. This returns a pointer to the circular free-list. 141 FreeRangeHeader *AllocateBlock(); 142 }; 143 } 144 145 146 /// AllocateBlock - Mark this entire block allocated, updating freelists 147 /// etc. This returns a pointer to the circular free-list. 148 FreeRangeHeader *FreeRangeHeader::AllocateBlock() { 149 assert(!ThisAllocated && !getBlockAfter().PrevAllocated && 150 "Cannot allocate an allocated block!"); 151 // Mark this block allocated. 152 ThisAllocated = 1; 153 getBlockAfter().PrevAllocated = 1; 154 155 // Remove it from the free list. 156 return RemoveFromFreeList(); 157 } 158 159 /// FreeBlock - Turn an allocated block into a free block, adjusting 160 /// bits in the object headers, and adding an end of region memory block. 161 /// If possible, coalesce this block with neighboring blocks. Return the 162 /// FreeRangeHeader to allocate from. 163 FreeRangeHeader *MemoryRangeHeader::FreeBlock(FreeRangeHeader *FreeList) { 164 MemoryRangeHeader *FollowingBlock = &getBlockAfter(); 165 assert(ThisAllocated && "This block is already free!"); 166 assert(FollowingBlock->PrevAllocated && "Flags out of sync!"); 167 168 FreeRangeHeader *FreeListToReturn = FreeList; 169 170 // If the block after this one is free, merge it into this block. 171 if (!FollowingBlock->ThisAllocated) { 172 FreeRangeHeader &FollowingFreeBlock = *(FreeRangeHeader *)FollowingBlock; 173 // "FreeList" always needs to be a valid free block. If we're about to 174 // coalesce with it, update our notion of what the free list is. 175 if (&FollowingFreeBlock == FreeList) { 176 FreeList = FollowingFreeBlock.Next; 177 FreeListToReturn = 0; 178 assert(&FollowingFreeBlock != FreeList && "No tombstone block?"); 179 } 180 FollowingFreeBlock.RemoveFromFreeList(); 181 182 // Include the following block into this one. 183 BlockSize += FollowingFreeBlock.BlockSize; 184 FollowingBlock = &FollowingFreeBlock.getBlockAfter(); 185 186 // Tell the block after the block we are coalescing that this block is 187 // allocated. 188 FollowingBlock->PrevAllocated = 1; 189 } 190 191 assert(FollowingBlock->ThisAllocated && "Missed coalescing?"); 192 193 if (FreeRangeHeader *PrevFreeBlock = getFreeBlockBefore()) { 194 PrevFreeBlock->GrowBlock(PrevFreeBlock->BlockSize + BlockSize); 195 return FreeListToReturn ? FreeListToReturn : PrevFreeBlock; 196 } 197 198 // Otherwise, mark this block free. 199 FreeRangeHeader &FreeBlock = *(FreeRangeHeader*)this; 200 FollowingBlock->PrevAllocated = 0; 201 FreeBlock.ThisAllocated = 0; 202 203 // Link this into the linked list of free blocks. 204 FreeBlock.AddToFreeList(FreeList); 205 206 // Add a marker at the end of the block, indicating the size of this free 207 // block. 208 FreeBlock.SetEndOfBlockSizeMarker(); 209 return FreeListToReturn ? FreeListToReturn : &FreeBlock; 210 } 211 212 /// GrowBlock - The block after this block just got deallocated. Merge it 213 /// into the current block. 214 void FreeRangeHeader::GrowBlock(uintptr_t NewSize) { 215 assert(NewSize > BlockSize && "Not growing block?"); 216 BlockSize = NewSize; 217 SetEndOfBlockSizeMarker(); 218 getBlockAfter().PrevAllocated = 0; 219 } 220 221 /// TrimAllocationToSize - If this allocated block is significantly larger 222 /// than NewSize, split it into two pieces (where the former is NewSize 223 /// bytes, including the header), and add the new block to the free list. 224 FreeRangeHeader *MemoryRangeHeader:: 225 TrimAllocationToSize(FreeRangeHeader *FreeList, uint64_t NewSize) { 226 assert(ThisAllocated && getBlockAfter().PrevAllocated && 227 "Cannot deallocate part of an allocated block!"); 228 229 // Don't allow blocks to be trimmed below minimum required size 230 NewSize = std::max<uint64_t>(FreeRangeHeader::getMinBlockSize(), NewSize); 231 232 // Round up size for alignment of header. 233 unsigned HeaderAlign = __alignof(FreeRangeHeader); 234 NewSize = (NewSize+ (HeaderAlign-1)) & ~(HeaderAlign-1); 235 236 // Size is now the size of the block we will remove from the start of the 237 // current block. 238 assert(NewSize <= BlockSize && 239 "Allocating more space from this block than exists!"); 240 241 // If splitting this block will cause the remainder to be too small, do not 242 // split the block. 243 if (BlockSize <= NewSize+FreeRangeHeader::getMinBlockSize()) 244 return FreeList; 245 246 // Otherwise, we splice the required number of bytes out of this block, form 247 // a new block immediately after it, then mark this block allocated. 248 MemoryRangeHeader &FormerNextBlock = getBlockAfter(); 249 250 // Change the size of this block. 251 BlockSize = NewSize; 252 253 // Get the new block we just sliced out and turn it into a free block. 254 FreeRangeHeader &NewNextBlock = (FreeRangeHeader &)getBlockAfter(); 255 NewNextBlock.BlockSize = (char*)&FormerNextBlock - (char*)&NewNextBlock; 256 NewNextBlock.ThisAllocated = 0; 257 NewNextBlock.PrevAllocated = 1; 258 NewNextBlock.SetEndOfBlockSizeMarker(); 259 FormerNextBlock.PrevAllocated = 0; 260 NewNextBlock.AddToFreeList(FreeList); 261 return &NewNextBlock; 262 } 263 264 //===----------------------------------------------------------------------===// 265 // Memory Block Implementation. 266 //===----------------------------------------------------------------------===// 267 268 namespace { 269 270 class DefaultJITMemoryManager; 271 272 class JITSlabAllocator : public SlabAllocator { 273 DefaultJITMemoryManager &JMM; 274 public: 275 JITSlabAllocator(DefaultJITMemoryManager &jmm) : JMM(jmm) { } 276 virtual ~JITSlabAllocator() { } 277 virtual MemSlab *Allocate(size_t Size); 278 virtual void Deallocate(MemSlab *Slab); 279 }; 280 281 /// DefaultJITMemoryManager - Manage memory for the JIT code generation. 282 /// This splits a large block of MAP_NORESERVE'd memory into two 283 /// sections, one for function stubs, one for the functions themselves. We 284 /// have to do this because we may need to emit a function stub while in the 285 /// middle of emitting a function, and we don't know how large the function we 286 /// are emitting is. 287 class DefaultJITMemoryManager : public JITMemoryManager { 288 289 // Whether to poison freed memory. 290 bool PoisonMemory; 291 292 /// LastSlab - This points to the last slab allocated and is used as the 293 /// NearBlock parameter to AllocateRWX so that we can attempt to lay out all 294 /// stubs, data, and code contiguously in memory. In general, however, this 295 /// is not possible because the NearBlock parameter is ignored on Windows 296 /// platforms and even on Unix it works on a best-effort pasis. 297 sys::MemoryBlock LastSlab; 298 299 // Memory slabs allocated by the JIT. We refer to them as slabs so we don't 300 // confuse them with the blocks of memory described above. 301 std::vector<sys::MemoryBlock> CodeSlabs; 302 JITSlabAllocator BumpSlabAllocator; 303 BumpPtrAllocator StubAllocator; 304 BumpPtrAllocator DataAllocator; 305 306 // Circular list of free blocks. 307 FreeRangeHeader *FreeMemoryList; 308 309 // When emitting code into a memory block, this is the block. 310 MemoryRangeHeader *CurBlock; 311 312 uint8_t *GOTBase; // Target Specific reserved memory 313 public: 314 DefaultJITMemoryManager(); 315 ~DefaultJITMemoryManager(); 316 317 /// allocateNewSlab - Allocates a new MemoryBlock and remembers it as the 318 /// last slab it allocated, so that subsequent allocations follow it. 319 sys::MemoryBlock allocateNewSlab(size_t size); 320 321 /// DefaultCodeSlabSize - When we have to go map more memory, we allocate at 322 /// least this much unless more is requested. 323 static const size_t DefaultCodeSlabSize; 324 325 /// DefaultSlabSize - Allocate data into slabs of this size unless we get 326 /// an allocation above SizeThreshold. 327 static const size_t DefaultSlabSize; 328 329 /// DefaultSizeThreshold - For any allocation larger than this threshold, we 330 /// should allocate a separate slab. 331 static const size_t DefaultSizeThreshold; 332 333 /// getPointerToNamedFunction - This method returns the address of the 334 /// specified function by using the dlsym function call. 335 virtual void *getPointerToNamedFunction(const std::string &Name, 336 bool AbortOnFailure = true); 337 338 void AllocateGOT(); 339 340 // Testing methods. 341 virtual bool CheckInvariants(std::string &ErrorStr); 342 size_t GetDefaultCodeSlabSize() { return DefaultCodeSlabSize; } 343 size_t GetDefaultDataSlabSize() { return DefaultSlabSize; } 344 size_t GetDefaultStubSlabSize() { return DefaultSlabSize; } 345 unsigned GetNumCodeSlabs() { return CodeSlabs.size(); } 346 unsigned GetNumDataSlabs() { return DataAllocator.GetNumSlabs(); } 347 unsigned GetNumStubSlabs() { return StubAllocator.GetNumSlabs(); } 348 349 /// startFunctionBody - When a function starts, allocate a block of free 350 /// executable memory, returning a pointer to it and its actual size. 351 uint8_t *startFunctionBody(const Function *F, uintptr_t &ActualSize) { 352 353 FreeRangeHeader* candidateBlock = FreeMemoryList; 354 FreeRangeHeader* head = FreeMemoryList; 355 FreeRangeHeader* iter = head->Next; 356 357 uintptr_t largest = candidateBlock->BlockSize; 358 359 // Search for the largest free block 360 while (iter != head) { 361 if (iter->BlockSize > largest) { 362 largest = iter->BlockSize; 363 candidateBlock = iter; 364 } 365 iter = iter->Next; 366 } 367 368 largest = largest - sizeof(MemoryRangeHeader); 369 370 // If this block isn't big enough for the allocation desired, allocate 371 // another block of memory and add it to the free list. 372 if (largest < ActualSize || 373 largest <= FreeRangeHeader::getMinBlockSize()) { 374 DEBUG(dbgs() << "JIT: Allocating another slab of memory for function."); 375 candidateBlock = allocateNewCodeSlab((size_t)ActualSize); 376 } 377 378 // Select this candidate block for allocation 379 CurBlock = candidateBlock; 380 381 // Allocate the entire memory block. 382 FreeMemoryList = candidateBlock->AllocateBlock(); 383 ActualSize = CurBlock->BlockSize - sizeof(MemoryRangeHeader); 384 return (uint8_t *)(CurBlock + 1); 385 } 386 387 /// allocateNewCodeSlab - Helper method to allocate a new slab of code 388 /// memory from the OS and add it to the free list. Returns the new 389 /// FreeRangeHeader at the base of the slab. 390 FreeRangeHeader *allocateNewCodeSlab(size_t MinSize) { 391 // If the user needs at least MinSize free memory, then we account for 392 // two MemoryRangeHeaders: the one in the user's block, and the one at the 393 // end of the slab. 394 size_t PaddedMin = MinSize + 2 * sizeof(MemoryRangeHeader); 395 size_t SlabSize = std::max(DefaultCodeSlabSize, PaddedMin); 396 sys::MemoryBlock B = allocateNewSlab(SlabSize); 397 CodeSlabs.push_back(B); 398 char *MemBase = (char*)(B.base()); 399 400 // Put a tiny allocated block at the end of the memory chunk, so when 401 // FreeBlock calls getBlockAfter it doesn't fall off the end. 402 MemoryRangeHeader *EndBlock = 403 (MemoryRangeHeader*)(MemBase + B.size()) - 1; 404 EndBlock->ThisAllocated = 1; 405 EndBlock->PrevAllocated = 0; 406 EndBlock->BlockSize = sizeof(MemoryRangeHeader); 407 408 // Start out with a vast new block of free memory. 409 FreeRangeHeader *NewBlock = (FreeRangeHeader*)MemBase; 410 NewBlock->ThisAllocated = 0; 411 // Make sure getFreeBlockBefore doesn't look into unmapped memory. 412 NewBlock->PrevAllocated = 1; 413 NewBlock->BlockSize = (uintptr_t)EndBlock - (uintptr_t)NewBlock; 414 NewBlock->SetEndOfBlockSizeMarker(); 415 NewBlock->AddToFreeList(FreeMemoryList); 416 417 assert(NewBlock->BlockSize - sizeof(MemoryRangeHeader) >= MinSize && 418 "The block was too small!"); 419 return NewBlock; 420 } 421 422 /// endFunctionBody - The function F is now allocated, and takes the memory 423 /// in the range [FunctionStart,FunctionEnd). 424 void endFunctionBody(const Function *F, uint8_t *FunctionStart, 425 uint8_t *FunctionEnd) { 426 assert(FunctionEnd > FunctionStart); 427 assert(FunctionStart == (uint8_t *)(CurBlock+1) && 428 "Mismatched function start/end!"); 429 430 uintptr_t BlockSize = FunctionEnd - (uint8_t *)CurBlock; 431 432 // Release the memory at the end of this block that isn't needed. 433 FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize); 434 } 435 436 /// allocateSpace - Allocate a memory block of the given size. This method 437 /// cannot be called between calls to startFunctionBody and endFunctionBody. 438 uint8_t *allocateSpace(intptr_t Size, unsigned Alignment) { 439 CurBlock = FreeMemoryList; 440 FreeMemoryList = FreeMemoryList->AllocateBlock(); 441 442 uint8_t *result = (uint8_t *)(CurBlock + 1); 443 444 if (Alignment == 0) Alignment = 1; 445 result = (uint8_t*)(((intptr_t)result+Alignment-1) & 446 ~(intptr_t)(Alignment-1)); 447 448 uintptr_t BlockSize = result + Size - (uint8_t *)CurBlock; 449 FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize); 450 451 return result; 452 } 453 454 /// allocateStub - Allocate memory for a function stub. 455 uint8_t *allocateStub(const GlobalValue* F, unsigned StubSize, 456 unsigned Alignment) { 457 return (uint8_t*)StubAllocator.Allocate(StubSize, Alignment); 458 } 459 460 /// allocateGlobal - Allocate memory for a global. 461 uint8_t *allocateGlobal(uintptr_t Size, unsigned Alignment) { 462 return (uint8_t*)DataAllocator.Allocate(Size, Alignment); 463 } 464 465 /// allocateCodeSection - Allocate memory for a code section. 466 uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment, 467 unsigned SectionID) { 468 // Grow the required block size to account for the block header 469 Size += sizeof(*CurBlock); 470 471 // FIXME: Alignement handling. 472 FreeRangeHeader* candidateBlock = FreeMemoryList; 473 FreeRangeHeader* head = FreeMemoryList; 474 FreeRangeHeader* iter = head->Next; 475 476 uintptr_t largest = candidateBlock->BlockSize; 477 478 // Search for the largest free block. 479 while (iter != head) { 480 if (iter->BlockSize > largest) { 481 largest = iter->BlockSize; 482 candidateBlock = iter; 483 } 484 iter = iter->Next; 485 } 486 487 largest = largest - sizeof(MemoryRangeHeader); 488 489 // If this block isn't big enough for the allocation desired, allocate 490 // another block of memory and add it to the free list. 491 if (largest < Size || largest <= FreeRangeHeader::getMinBlockSize()) { 492 DEBUG(dbgs() << "JIT: Allocating another slab of memory for function."); 493 candidateBlock = allocateNewCodeSlab((size_t)Size); 494 } 495 496 // Select this candidate block for allocation 497 CurBlock = candidateBlock; 498 499 // Allocate the entire memory block. 500 FreeMemoryList = candidateBlock->AllocateBlock(); 501 // Release the memory at the end of this block that isn't needed. 502 FreeMemoryList = CurBlock->TrimAllocationToSize(FreeMemoryList, Size); 503 return (uint8_t *)(CurBlock + 1); 504 } 505 506 /// allocateDataSection - Allocate memory for a data section. 507 uint8_t *allocateDataSection(uintptr_t Size, unsigned Alignment, 508 unsigned SectionID, bool IsReadOnly) { 509 return (uint8_t*)DataAllocator.Allocate(Size, Alignment); 510 } 511 512 bool applyPermissions(std::string *ErrMsg) { 513 return false; 514 } 515 516 /// startExceptionTable - Use startFunctionBody to allocate memory for the 517 /// function's exception table. 518 uint8_t* startExceptionTable(const Function* F, uintptr_t &ActualSize) { 519 return startFunctionBody(F, ActualSize); 520 } 521 522 /// endExceptionTable - The exception table of F is now allocated, 523 /// and takes the memory in the range [TableStart,TableEnd). 524 void endExceptionTable(const Function *F, uint8_t *TableStart, 525 uint8_t *TableEnd, uint8_t* FrameRegister) { 526 assert(TableEnd > TableStart); 527 assert(TableStart == (uint8_t *)(CurBlock+1) && 528 "Mismatched table start/end!"); 529 530 uintptr_t BlockSize = TableEnd - (uint8_t *)CurBlock; 531 532 // Release the memory at the end of this block that isn't needed. 533 FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize); 534 } 535 536 uint8_t *getGOTBase() const { 537 return GOTBase; 538 } 539 540 void deallocateBlock(void *Block) { 541 // Find the block that is allocated for this function. 542 MemoryRangeHeader *MemRange = static_cast<MemoryRangeHeader*>(Block) - 1; 543 assert(MemRange->ThisAllocated && "Block isn't allocated!"); 544 545 // Fill the buffer with garbage! 546 if (PoisonMemory) { 547 memset(MemRange+1, 0xCD, MemRange->BlockSize-sizeof(*MemRange)); 548 } 549 550 // Free the memory. 551 FreeMemoryList = MemRange->FreeBlock(FreeMemoryList); 552 } 553 554 /// deallocateFunctionBody - Deallocate all memory for the specified 555 /// function body. 556 void deallocateFunctionBody(void *Body) { 557 if (Body) deallocateBlock(Body); 558 } 559 560 /// deallocateExceptionTable - Deallocate memory for the specified 561 /// exception table. 562 void deallocateExceptionTable(void *ET) { 563 if (ET) deallocateBlock(ET); 564 } 565 566 /// setMemoryWritable - When code generation is in progress, 567 /// the code pages may need permissions changed. 568 void setMemoryWritable() 569 { 570 for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i) 571 sys::Memory::setWritable(CodeSlabs[i]); 572 } 573 /// setMemoryExecutable - When code generation is done and we're ready to 574 /// start execution, the code pages may need permissions changed. 575 void setMemoryExecutable() 576 { 577 for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i) 578 sys::Memory::setExecutable(CodeSlabs[i]); 579 } 580 581 /// setPoisonMemory - Controls whether we write garbage over freed memory. 582 /// 583 void setPoisonMemory(bool poison) { 584 PoisonMemory = poison; 585 } 586 }; 587 } 588 589 MemSlab *JITSlabAllocator::Allocate(size_t Size) { 590 sys::MemoryBlock B = JMM.allocateNewSlab(Size); 591 MemSlab *Slab = (MemSlab*)B.base(); 592 Slab->Size = B.size(); 593 Slab->NextPtr = 0; 594 return Slab; 595 } 596 597 void JITSlabAllocator::Deallocate(MemSlab *Slab) { 598 sys::MemoryBlock B(Slab, Slab->Size); 599 sys::Memory::ReleaseRWX(B); 600 } 601 602 DefaultJITMemoryManager::DefaultJITMemoryManager() 603 : 604 #ifdef NDEBUG 605 PoisonMemory(false), 606 #else 607 PoisonMemory(true), 608 #endif 609 LastSlab(0, 0), 610 BumpSlabAllocator(*this), 611 StubAllocator(DefaultSlabSize, DefaultSizeThreshold, BumpSlabAllocator), 612 DataAllocator(DefaultSlabSize, DefaultSizeThreshold, BumpSlabAllocator) { 613 614 // Allocate space for code. 615 sys::MemoryBlock MemBlock = allocateNewSlab(DefaultCodeSlabSize); 616 CodeSlabs.push_back(MemBlock); 617 uint8_t *MemBase = (uint8_t*)MemBlock.base(); 618 619 // We set up the memory chunk with 4 mem regions, like this: 620 // [ START 621 // [ Free #0 ] -> Large space to allocate functions from. 622 // [ Allocated #1 ] -> Tiny space to separate regions. 623 // [ Free #2 ] -> Tiny space so there is always at least 1 free block. 624 // [ Allocated #3 ] -> Tiny space to prevent looking past end of block. 625 // END ] 626 // 627 // The last three blocks are never deallocated or touched. 628 629 // Add MemoryRangeHeader to the end of the memory region, indicating that 630 // the space after the block of memory is allocated. This is block #3. 631 MemoryRangeHeader *Mem3 = (MemoryRangeHeader*)(MemBase+MemBlock.size())-1; 632 Mem3->ThisAllocated = 1; 633 Mem3->PrevAllocated = 0; 634 Mem3->BlockSize = sizeof(MemoryRangeHeader); 635 636 /// Add a tiny free region so that the free list always has one entry. 637 FreeRangeHeader *Mem2 = 638 (FreeRangeHeader *)(((char*)Mem3)-FreeRangeHeader::getMinBlockSize()); 639 Mem2->ThisAllocated = 0; 640 Mem2->PrevAllocated = 1; 641 Mem2->BlockSize = FreeRangeHeader::getMinBlockSize(); 642 Mem2->SetEndOfBlockSizeMarker(); 643 Mem2->Prev = Mem2; // Mem2 *is* the free list for now. 644 Mem2->Next = Mem2; 645 646 /// Add a tiny allocated region so that Mem2 is never coalesced away. 647 MemoryRangeHeader *Mem1 = (MemoryRangeHeader*)Mem2-1; 648 Mem1->ThisAllocated = 1; 649 Mem1->PrevAllocated = 0; 650 Mem1->BlockSize = sizeof(MemoryRangeHeader); 651 652 // Add a FreeRangeHeader to the start of the function body region, indicating 653 // that the space is free. Mark the previous block allocated so we never look 654 // at it. 655 FreeRangeHeader *Mem0 = (FreeRangeHeader*)MemBase; 656 Mem0->ThisAllocated = 0; 657 Mem0->PrevAllocated = 1; 658 Mem0->BlockSize = (char*)Mem1-(char*)Mem0; 659 Mem0->SetEndOfBlockSizeMarker(); 660 Mem0->AddToFreeList(Mem2); 661 662 // Start out with the freelist pointing to Mem0. 663 FreeMemoryList = Mem0; 664 665 GOTBase = NULL; 666 } 667 668 void DefaultJITMemoryManager::AllocateGOT() { 669 assert(GOTBase == 0 && "Cannot allocate the got multiple times"); 670 GOTBase = new uint8_t[sizeof(void*) * 8192]; 671 HasGOT = true; 672 } 673 674 DefaultJITMemoryManager::~DefaultJITMemoryManager() { 675 for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i) 676 sys::Memory::ReleaseRWX(CodeSlabs[i]); 677 678 delete[] GOTBase; 679 } 680 681 sys::MemoryBlock DefaultJITMemoryManager::allocateNewSlab(size_t size) { 682 // Allocate a new block close to the last one. 683 std::string ErrMsg; 684 sys::MemoryBlock *LastSlabPtr = LastSlab.base() ? &LastSlab : 0; 685 sys::MemoryBlock B = sys::Memory::AllocateRWX(size, LastSlabPtr, &ErrMsg); 686 if (B.base() == 0) { 687 report_fatal_error("Allocation failed when allocating new memory in the" 688 " JIT\n" + Twine(ErrMsg)); 689 } 690 LastSlab = B; 691 ++NumSlabs; 692 // Initialize the slab to garbage when debugging. 693 if (PoisonMemory) { 694 memset(B.base(), 0xCD, B.size()); 695 } 696 return B; 697 } 698 699 /// CheckInvariants - For testing only. Return "" if all internal invariants 700 /// are preserved, and a helpful error message otherwise. For free and 701 /// allocated blocks, make sure that adding BlockSize gives a valid block. 702 /// For free blocks, make sure they're in the free list and that their end of 703 /// block size marker is correct. This function should return an error before 704 /// accessing bad memory. This function is defined here instead of in 705 /// JITMemoryManagerTest.cpp so that we don't have to expose all of the 706 /// implementation details of DefaultJITMemoryManager. 707 bool DefaultJITMemoryManager::CheckInvariants(std::string &ErrorStr) { 708 raw_string_ostream Err(ErrorStr); 709 710 // Construct a the set of FreeRangeHeader pointers so we can query it 711 // efficiently. 712 llvm::SmallPtrSet<MemoryRangeHeader*, 16> FreeHdrSet; 713 FreeRangeHeader* FreeHead = FreeMemoryList; 714 FreeRangeHeader* FreeRange = FreeHead; 715 716 do { 717 // Check that the free range pointer is in the blocks we've allocated. 718 bool Found = false; 719 for (std::vector<sys::MemoryBlock>::iterator I = CodeSlabs.begin(), 720 E = CodeSlabs.end(); I != E && !Found; ++I) { 721 char *Start = (char*)I->base(); 722 char *End = Start + I->size(); 723 Found = (Start <= (char*)FreeRange && (char*)FreeRange < End); 724 } 725 if (!Found) { 726 Err << "Corrupt free list; points to " << FreeRange; 727 return false; 728 } 729 730 if (FreeRange->Next->Prev != FreeRange) { 731 Err << "Next and Prev pointers do not match."; 732 return false; 733 } 734 735 // Otherwise, add it to the set. 736 FreeHdrSet.insert(FreeRange); 737 FreeRange = FreeRange->Next; 738 } while (FreeRange != FreeHead); 739 740 // Go over each block, and look at each MemoryRangeHeader. 741 for (std::vector<sys::MemoryBlock>::iterator I = CodeSlabs.begin(), 742 E = CodeSlabs.end(); I != E; ++I) { 743 char *Start = (char*)I->base(); 744 char *End = Start + I->size(); 745 746 // Check each memory range. 747 for (MemoryRangeHeader *Hdr = (MemoryRangeHeader*)Start, *LastHdr = NULL; 748 Start <= (char*)Hdr && (char*)Hdr < End; 749 Hdr = &Hdr->getBlockAfter()) { 750 if (Hdr->ThisAllocated == 0) { 751 // Check that this range is in the free list. 752 if (!FreeHdrSet.count(Hdr)) { 753 Err << "Found free header at " << Hdr << " that is not in free list."; 754 return false; 755 } 756 757 // Now make sure the size marker at the end of the block is correct. 758 uintptr_t *Marker = ((uintptr_t*)&Hdr->getBlockAfter()) - 1; 759 if (!(Start <= (char*)Marker && (char*)Marker < End)) { 760 Err << "Block size in header points out of current MemoryBlock."; 761 return false; 762 } 763 if (Hdr->BlockSize != *Marker) { 764 Err << "End of block size marker (" << *Marker << ") " 765 << "and BlockSize (" << Hdr->BlockSize << ") don't match."; 766 return false; 767 } 768 } 769 770 if (LastHdr && LastHdr->ThisAllocated != Hdr->PrevAllocated) { 771 Err << "Hdr->PrevAllocated (" << Hdr->PrevAllocated << ") != " 772 << "LastHdr->ThisAllocated (" << LastHdr->ThisAllocated << ")"; 773 return false; 774 } else if (!LastHdr && !Hdr->PrevAllocated) { 775 Err << "The first header should have PrevAllocated true."; 776 return false; 777 } 778 779 // Remember the last header. 780 LastHdr = Hdr; 781 } 782 } 783 784 // All invariants are preserved. 785 return true; 786 } 787 788 //===----------------------------------------------------------------------===// 789 // getPointerToNamedFunction() implementation. 790 //===----------------------------------------------------------------------===// 791 792 // AtExitHandlers - List of functions to call when the program exits, 793 // registered with the atexit() library function. 794 static std::vector<void (*)()> AtExitHandlers; 795 796 /// runAtExitHandlers - Run any functions registered by the program's 797 /// calls to atexit(3), which we intercept and store in 798 /// AtExitHandlers. 799 /// 800 static void runAtExitHandlers() { 801 while (!AtExitHandlers.empty()) { 802 void (*Fn)() = AtExitHandlers.back(); 803 AtExitHandlers.pop_back(); 804 Fn(); 805 } 806 } 807 808 //===----------------------------------------------------------------------===// 809 // Function stubs that are invoked instead of certain library calls 810 // 811 // Force the following functions to be linked in to anything that uses the 812 // JIT. This is a hack designed to work around the all-too-clever Glibc 813 // strategy of making these functions work differently when inlined vs. when 814 // not inlined, and hiding their real definitions in a separate archive file 815 // that the dynamic linker can't see. For more info, search for 816 // 'libc_nonshared.a' on Google, or read http://llvm.org/PR274. 817 #if defined(__linux__) 818 /* stat functions are redirecting to __xstat with a version number. On x86-64 819 * linking with libc_nonshared.a and -Wl,--export-dynamic doesn't make 'stat' 820 * available as an exported symbol, so we have to add it explicitly. 821 */ 822 namespace { 823 class StatSymbols { 824 public: 825 StatSymbols() { 826 sys::DynamicLibrary::AddSymbol("stat", (void*)(intptr_t)stat); 827 sys::DynamicLibrary::AddSymbol("fstat", (void*)(intptr_t)fstat); 828 sys::DynamicLibrary::AddSymbol("lstat", (void*)(intptr_t)lstat); 829 sys::DynamicLibrary::AddSymbol("stat64", (void*)(intptr_t)stat64); 830 sys::DynamicLibrary::AddSymbol("\x1stat64", (void*)(intptr_t)stat64); 831 sys::DynamicLibrary::AddSymbol("\x1open64", (void*)(intptr_t)open64); 832 sys::DynamicLibrary::AddSymbol("\x1lseek64", (void*)(intptr_t)lseek64); 833 sys::DynamicLibrary::AddSymbol("fstat64", (void*)(intptr_t)fstat64); 834 sys::DynamicLibrary::AddSymbol("lstat64", (void*)(intptr_t)lstat64); 835 sys::DynamicLibrary::AddSymbol("atexit", (void*)(intptr_t)atexit); 836 sys::DynamicLibrary::AddSymbol("mknod", (void*)(intptr_t)mknod); 837 } 838 }; 839 } 840 static StatSymbols initStatSymbols; 841 #endif // __linux__ 842 843 // jit_exit - Used to intercept the "exit" library call. 844 static void jit_exit(int Status) { 845 runAtExitHandlers(); // Run atexit handlers... 846 exit(Status); 847 } 848 849 // jit_atexit - Used to intercept the "atexit" library call. 850 static int jit_atexit(void (*Fn)()) { 851 AtExitHandlers.push_back(Fn); // Take note of atexit handler... 852 return 0; // Always successful 853 } 854 855 static int jit_noop() { 856 return 0; 857 } 858 859 //===----------------------------------------------------------------------===// 860 // 861 /// getPointerToNamedFunction - This method returns the address of the specified 862 /// function by using the dynamic loader interface. As such it is only useful 863 /// for resolving library symbols, not code generated symbols. 864 /// 865 void *DefaultJITMemoryManager::getPointerToNamedFunction(const std::string &Name, 866 bool AbortOnFailure) { 867 // Check to see if this is one of the functions we want to intercept. Note, 868 // we cast to intptr_t here to silence a -pedantic warning that complains 869 // about casting a function pointer to a normal pointer. 870 if (Name == "exit") return (void*)(intptr_t)&jit_exit; 871 if (Name == "atexit") return (void*)(intptr_t)&jit_atexit; 872 873 // We should not invoke parent's ctors/dtors from generated main()! 874 // On Mingw and Cygwin, the symbol __main is resolved to 875 // callee's(eg. tools/lli) one, to invoke wrong duplicated ctors 876 // (and register wrong callee's dtors with atexit(3)). 877 // We expect ExecutionEngine::runStaticConstructorsDestructors() 878 // is called before ExecutionEngine::runFunctionAsMain() is called. 879 if (Name == "__main") return (void*)(intptr_t)&jit_noop; 880 881 const char *NameStr = Name.c_str(); 882 // If this is an asm specifier, skip the sentinal. 883 if (NameStr[0] == 1) ++NameStr; 884 885 // If it's an external function, look it up in the process image... 886 void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr); 887 if (Ptr) return Ptr; 888 889 // If it wasn't found and if it starts with an underscore ('_') character, 890 // try again without the underscore. 891 if (NameStr[0] == '_') { 892 Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1); 893 if (Ptr) return Ptr; 894 } 895 896 // Darwin/PPC adds $LDBLStub suffixes to various symbols like printf. These 897 // are references to hidden visibility symbols that dlsym cannot resolve. 898 // If we have one of these, strip off $LDBLStub and try again. 899 #if defined(__APPLE__) && defined(__ppc__) 900 if (Name.size() > 9 && Name[Name.size()-9] == '$' && 901 memcmp(&Name[Name.size()-8], "LDBLStub", 8) == 0) { 902 // First try turning $LDBLStub into $LDBL128. If that fails, strip it off. 903 // This mirrors logic in libSystemStubs.a. 904 std::string Prefix = std::string(Name.begin(), Name.end()-9); 905 if (void *Ptr = getPointerToNamedFunction(Prefix+"$LDBL128", false)) 906 return Ptr; 907 if (void *Ptr = getPointerToNamedFunction(Prefix, false)) 908 return Ptr; 909 } 910 #endif 911 912 if (AbortOnFailure) { 913 report_fatal_error("Program used external function '"+Name+ 914 "' which could not be resolved!"); 915 } 916 return 0; 917 } 918 919 920 921 JITMemoryManager *JITMemoryManager::CreateDefaultMemManager() { 922 return new DefaultJITMemoryManager(); 923 } 924 925 // Allocate memory for code in 512K slabs. 926 const size_t DefaultJITMemoryManager::DefaultCodeSlabSize = 512 * 1024; 927 928 // Allocate globals and stubs in slabs of 64K. (probably 16 pages) 929 const size_t DefaultJITMemoryManager::DefaultSlabSize = 64 * 1024; 930 931 // Waste at most 16K at the end of each bump slab. (probably 4 pages) 932 const size_t DefaultJITMemoryManager::DefaultSizeThreshold = 16 * 1024; 933