1 //===-- JITMemoryManager.cpp - Memory Allocator for JIT'd code ------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the DefaultJITMemoryManager class.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/ExecutionEngine/JITMemoryManager.h"
15 #include "llvm/ADT/SmallPtrSet.h"
16 #include "llvm/ADT/Statistic.h"
17 #include "llvm/ADT/Twine.h"
18 #include "llvm/Config/config.h"
19 #include "llvm/IR/GlobalValue.h"
20 #include "llvm/Support/Allocator.h"
21 #include "llvm/Support/Compiler.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Support/DynamicLibrary.h"
24 #include "llvm/Support/ErrorHandling.h"
25 #include "llvm/Support/Memory.h"
26 #include "llvm/Support/raw_ostream.h"
32 #if defined(__linux__)
33 #if defined(HAVE_SYS_STAT_H)
42 #define DEBUG_TYPE "jit"
44 STATISTIC(NumSlabs, "Number of slabs of memory allocated by the JIT");
46 JITMemoryManager::~JITMemoryManager() {}
48 //===----------------------------------------------------------------------===//
49 // Memory Block Implementation.
50 //===----------------------------------------------------------------------===//
53 /// MemoryRangeHeader - For a range of memory, this is the header that we put
54 /// on the block of memory. It is carefully crafted to be one word of memory.
55 /// Allocated blocks have just this header, free'd blocks have FreeRangeHeader
56 /// which starts with this.
57 struct FreeRangeHeader;
58 struct MemoryRangeHeader {
59 /// ThisAllocated - This is true if this block is currently allocated. If
60 /// not, this can be converted to a FreeRangeHeader.
61 unsigned ThisAllocated : 1;
63 /// PrevAllocated - Keep track of whether the block immediately before us is
64 /// allocated. If not, the word immediately before this header is the size
65 /// of the previous block.
66 unsigned PrevAllocated : 1;
68 /// BlockSize - This is the size in bytes of this memory block,
69 /// including this header.
70 uintptr_t BlockSize : (sizeof(intptr_t)*CHAR_BIT - 2);
73 /// getBlockAfter - Return the memory block immediately after this one.
75 MemoryRangeHeader &getBlockAfter() const {
76 return *reinterpret_cast<MemoryRangeHeader *>(
77 reinterpret_cast<char*>(
78 const_cast<MemoryRangeHeader *>(this))+BlockSize);
81 /// getFreeBlockBefore - If the block before this one is free, return it,
82 /// otherwise return null.
83 FreeRangeHeader *getFreeBlockBefore() const {
84 if (PrevAllocated) return nullptr;
85 intptr_t PrevSize = reinterpret_cast<intptr_t *>(
86 const_cast<MemoryRangeHeader *>(this))[-1];
87 return reinterpret_cast<FreeRangeHeader *>(
88 reinterpret_cast<char*>(
89 const_cast<MemoryRangeHeader *>(this))-PrevSize);
92 /// FreeBlock - Turn an allocated block into a free block, adjusting
93 /// bits in the object headers, and adding an end of region memory block.
94 FreeRangeHeader *FreeBlock(FreeRangeHeader *FreeList);
96 /// TrimAllocationToSize - If this allocated block is significantly larger
97 /// than NewSize, split it into two pieces (where the former is NewSize
98 /// bytes, including the header), and add the new block to the free list.
99 FreeRangeHeader *TrimAllocationToSize(FreeRangeHeader *FreeList,
103 /// FreeRangeHeader - For a memory block that isn't already allocated, this
104 /// keeps track of the current block and has a pointer to the next free block.
105 /// Free blocks are kept on a circularly linked list.
106 struct FreeRangeHeader : public MemoryRangeHeader {
107 FreeRangeHeader *Prev;
108 FreeRangeHeader *Next;
110 /// getMinBlockSize - Get the minimum size for a memory block. Blocks
111 /// smaller than this size cannot be created.
112 static unsigned getMinBlockSize() {
113 return sizeof(FreeRangeHeader)+sizeof(intptr_t);
116 /// SetEndOfBlockSizeMarker - The word at the end of every free block is
117 /// known to be the size of the free block. Set it for this block.
118 void SetEndOfBlockSizeMarker() {
119 void *EndOfBlock = (char*)this + BlockSize;
120 ((intptr_t *)EndOfBlock)[-1] = BlockSize;
123 FreeRangeHeader *RemoveFromFreeList() {
124 assert(Next->Prev == this && Prev->Next == this && "Freelist broken!");
126 return Prev->Next = Next;
129 void AddToFreeList(FreeRangeHeader *FreeList) {
131 Prev = FreeList->Prev;
136 /// GrowBlock - The block after this block just got deallocated. Merge it
137 /// into the current block.
138 void GrowBlock(uintptr_t NewSize);
140 /// AllocateBlock - Mark this entire block allocated, updating freelists
141 /// etc. This returns a pointer to the circular free-list.
142 FreeRangeHeader *AllocateBlock();
147 /// AllocateBlock - Mark this entire block allocated, updating freelists
148 /// etc. This returns a pointer to the circular free-list.
149 FreeRangeHeader *FreeRangeHeader::AllocateBlock() {
150 assert(!ThisAllocated && !getBlockAfter().PrevAllocated &&
151 "Cannot allocate an allocated block!");
152 // Mark this block allocated.
154 getBlockAfter().PrevAllocated = 1;
156 // Remove it from the free list.
157 return RemoveFromFreeList();
160 /// FreeBlock - Turn an allocated block into a free block, adjusting
161 /// bits in the object headers, and adding an end of region memory block.
162 /// If possible, coalesce this block with neighboring blocks. Return the
163 /// FreeRangeHeader to allocate from.
164 FreeRangeHeader *MemoryRangeHeader::FreeBlock(FreeRangeHeader *FreeList) {
165 MemoryRangeHeader *FollowingBlock = &getBlockAfter();
166 assert(ThisAllocated && "This block is already free!");
167 assert(FollowingBlock->PrevAllocated && "Flags out of sync!");
169 FreeRangeHeader *FreeListToReturn = FreeList;
171 // If the block after this one is free, merge it into this block.
172 if (!FollowingBlock->ThisAllocated) {
173 FreeRangeHeader &FollowingFreeBlock = *(FreeRangeHeader *)FollowingBlock;
174 // "FreeList" always needs to be a valid free block. If we're about to
175 // coalesce with it, update our notion of what the free list is.
176 if (&FollowingFreeBlock == FreeList) {
177 FreeList = FollowingFreeBlock.Next;
178 FreeListToReturn = nullptr;
179 assert(&FollowingFreeBlock != FreeList && "No tombstone block?");
181 FollowingFreeBlock.RemoveFromFreeList();
183 // Include the following block into this one.
184 BlockSize += FollowingFreeBlock.BlockSize;
185 FollowingBlock = &FollowingFreeBlock.getBlockAfter();
187 // Tell the block after the block we are coalescing that this block is
189 FollowingBlock->PrevAllocated = 1;
192 assert(FollowingBlock->ThisAllocated && "Missed coalescing?");
194 if (FreeRangeHeader *PrevFreeBlock = getFreeBlockBefore()) {
195 PrevFreeBlock->GrowBlock(PrevFreeBlock->BlockSize + BlockSize);
196 return FreeListToReturn ? FreeListToReturn : PrevFreeBlock;
199 // Otherwise, mark this block free.
200 FreeRangeHeader &FreeBlock = *(FreeRangeHeader*)this;
201 FollowingBlock->PrevAllocated = 0;
202 FreeBlock.ThisAllocated = 0;
204 // Link this into the linked list of free blocks.
205 FreeBlock.AddToFreeList(FreeList);
207 // Add a marker at the end of the block, indicating the size of this free
209 FreeBlock.SetEndOfBlockSizeMarker();
210 return FreeListToReturn ? FreeListToReturn : &FreeBlock;
213 /// GrowBlock - The block after this block just got deallocated. Merge it
214 /// into the current block.
215 void FreeRangeHeader::GrowBlock(uintptr_t NewSize) {
216 assert(NewSize > BlockSize && "Not growing block?");
218 SetEndOfBlockSizeMarker();
219 getBlockAfter().PrevAllocated = 0;
222 /// TrimAllocationToSize - If this allocated block is significantly larger
223 /// than NewSize, split it into two pieces (where the former is NewSize
224 /// bytes, including the header), and add the new block to the free list.
225 FreeRangeHeader *MemoryRangeHeader::
226 TrimAllocationToSize(FreeRangeHeader *FreeList, uint64_t NewSize) {
227 assert(ThisAllocated && getBlockAfter().PrevAllocated &&
228 "Cannot deallocate part of an allocated block!");
230 // Don't allow blocks to be trimmed below minimum required size
231 NewSize = std::max<uint64_t>(FreeRangeHeader::getMinBlockSize(), NewSize);
233 // Round up size for alignment of header.
234 unsigned HeaderAlign = __alignof(FreeRangeHeader);
235 NewSize = (NewSize+ (HeaderAlign-1)) & ~(HeaderAlign-1);
237 // Size is now the size of the block we will remove from the start of the
239 assert(NewSize <= BlockSize &&
240 "Allocating more space from this block than exists!");
242 // If splitting this block will cause the remainder to be too small, do not
244 if (BlockSize <= NewSize+FreeRangeHeader::getMinBlockSize())
247 // Otherwise, we splice the required number of bytes out of this block, form
248 // a new block immediately after it, then mark this block allocated.
249 MemoryRangeHeader &FormerNextBlock = getBlockAfter();
251 // Change the size of this block.
254 // Get the new block we just sliced out and turn it into a free block.
255 FreeRangeHeader &NewNextBlock = (FreeRangeHeader &)getBlockAfter();
256 NewNextBlock.BlockSize = (char*)&FormerNextBlock - (char*)&NewNextBlock;
257 NewNextBlock.ThisAllocated = 0;
258 NewNextBlock.PrevAllocated = 1;
259 NewNextBlock.SetEndOfBlockSizeMarker();
260 FormerNextBlock.PrevAllocated = 0;
261 NewNextBlock.AddToFreeList(FreeList);
262 return &NewNextBlock;
265 //===----------------------------------------------------------------------===//
266 // Memory Block Implementation.
267 //===----------------------------------------------------------------------===//
271 class DefaultJITMemoryManager;
274 DefaultJITMemoryManager &JMM;
276 JITAllocator(DefaultJITMemoryManager &jmm) : JMM(jmm) { }
277 void *Allocate(size_t Size, size_t /*Alignment*/);
278 void Deallocate(void *Slab, size_t Size);
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
287 class DefaultJITMemoryManager : public JITMemoryManager {
289 /// DefaultCodeSlabSize - When we have to go map more memory, we allocate at
290 /// least this much unless more is requested. Currently, in 512k slabs.
291 static const size_t DefaultCodeSlabSize = 512 * 1024;
293 /// DefaultSlabSize - Allocate globals and stubs into slabs of 64K (probably
294 /// 16 pages) unless we get an allocation above SizeThreshold.
295 static const size_t DefaultSlabSize = 64 * 1024;
297 /// DefaultSizeThreshold - For any allocation larger than 16K (probably
298 /// 4 pages), we should allocate a separate slab to avoid wasted space at
299 /// the end of a normal slab.
300 static const size_t DefaultSizeThreshold = 16 * 1024;
303 // Whether to poison freed memory.
306 /// LastSlab - This points to the last slab allocated and is used as the
307 /// NearBlock parameter to AllocateRWX so that we can attempt to lay out all
308 /// stubs, data, and code contiguously in memory. In general, however, this
309 /// is not possible because the NearBlock parameter is ignored on Windows
310 /// platforms and even on Unix it works on a best-effort pasis.
311 sys::MemoryBlock LastSlab;
313 // Memory slabs allocated by the JIT. We refer to them as slabs so we don't
314 // confuse them with the blocks of memory described above.
315 std::vector<sys::MemoryBlock> CodeSlabs;
316 BumpPtrAllocatorImpl<JITAllocator, DefaultSlabSize,
317 DefaultSizeThreshold> StubAllocator;
318 BumpPtrAllocatorImpl<JITAllocator, DefaultSlabSize,
319 DefaultSizeThreshold> DataAllocator;
321 // Circular list of free blocks.
322 FreeRangeHeader *FreeMemoryList;
324 // When emitting code into a memory block, this is the block.
325 MemoryRangeHeader *CurBlock;
327 std::unique_ptr<uint8_t[]> GOTBase; // Target Specific reserved memory
329 DefaultJITMemoryManager();
330 ~DefaultJITMemoryManager();
332 /// allocateNewSlab - Allocates a new MemoryBlock and remembers it as the
333 /// last slab it allocated, so that subsequent allocations follow it.
334 sys::MemoryBlock allocateNewSlab(size_t size);
336 /// getPointerToNamedFunction - This method returns the address of the
337 /// specified function by using the dlsym function call.
338 void *getPointerToNamedFunction(const std::string &Name,
339 bool AbortOnFailure = true) override;
341 void AllocateGOT() override;
344 bool CheckInvariants(std::string &ErrorStr) override;
345 size_t GetDefaultCodeSlabSize() override { return DefaultCodeSlabSize; }
346 size_t GetDefaultDataSlabSize() override { return DefaultSlabSize; }
347 size_t GetDefaultStubSlabSize() override { return DefaultSlabSize; }
348 unsigned GetNumCodeSlabs() override { return CodeSlabs.size(); }
349 unsigned GetNumDataSlabs() override { return DataAllocator.GetNumSlabs(); }
350 unsigned GetNumStubSlabs() override { return StubAllocator.GetNumSlabs(); }
352 /// startFunctionBody - When a function starts, allocate a block of free
353 /// executable memory, returning a pointer to it and its actual size.
354 uint8_t *startFunctionBody(const Function *F,
355 uintptr_t &ActualSize) override {
357 FreeRangeHeader* candidateBlock = FreeMemoryList;
358 FreeRangeHeader* head = FreeMemoryList;
359 FreeRangeHeader* iter = head->Next;
361 uintptr_t largest = candidateBlock->BlockSize;
363 // Search for the largest free block
364 while (iter != head) {
365 if (iter->BlockSize > largest) {
366 largest = iter->BlockSize;
367 candidateBlock = iter;
372 largest = largest - sizeof(MemoryRangeHeader);
374 // If this block isn't big enough for the allocation desired, allocate
375 // another block of memory and add it to the free list.
376 if (largest < ActualSize ||
377 largest <= FreeRangeHeader::getMinBlockSize()) {
378 DEBUG(dbgs() << "JIT: Allocating another slab of memory for function.");
379 candidateBlock = allocateNewCodeSlab((size_t)ActualSize);
382 // Select this candidate block for allocation
383 CurBlock = candidateBlock;
385 // Allocate the entire memory block.
386 FreeMemoryList = candidateBlock->AllocateBlock();
387 ActualSize = CurBlock->BlockSize - sizeof(MemoryRangeHeader);
388 return (uint8_t *)(CurBlock + 1);
391 /// allocateNewCodeSlab - Helper method to allocate a new slab of code
392 /// memory from the OS and add it to the free list. Returns the new
393 /// FreeRangeHeader at the base of the slab.
394 FreeRangeHeader *allocateNewCodeSlab(size_t MinSize) {
395 // If the user needs at least MinSize free memory, then we account for
396 // two MemoryRangeHeaders: the one in the user's block, and the one at the
398 size_t PaddedMin = MinSize + 2 * sizeof(MemoryRangeHeader);
399 size_t SlabSize = std::max(DefaultCodeSlabSize, PaddedMin);
400 sys::MemoryBlock B = allocateNewSlab(SlabSize);
401 CodeSlabs.push_back(B);
402 char *MemBase = (char*)(B.base());
404 // Put a tiny allocated block at the end of the memory chunk, so when
405 // FreeBlock calls getBlockAfter it doesn't fall off the end.
406 MemoryRangeHeader *EndBlock =
407 (MemoryRangeHeader*)(MemBase + B.size()) - 1;
408 EndBlock->ThisAllocated = 1;
409 EndBlock->PrevAllocated = 0;
410 EndBlock->BlockSize = sizeof(MemoryRangeHeader);
412 // Start out with a vast new block of free memory.
413 FreeRangeHeader *NewBlock = (FreeRangeHeader*)MemBase;
414 NewBlock->ThisAllocated = 0;
415 // Make sure getFreeBlockBefore doesn't look into unmapped memory.
416 NewBlock->PrevAllocated = 1;
417 NewBlock->BlockSize = (uintptr_t)EndBlock - (uintptr_t)NewBlock;
418 NewBlock->SetEndOfBlockSizeMarker();
419 NewBlock->AddToFreeList(FreeMemoryList);
421 assert(NewBlock->BlockSize - sizeof(MemoryRangeHeader) >= MinSize &&
422 "The block was too small!");
426 /// endFunctionBody - The function F is now allocated, and takes the memory
427 /// in the range [FunctionStart,FunctionEnd).
428 void endFunctionBody(const Function *F, uint8_t *FunctionStart,
429 uint8_t *FunctionEnd) override {
430 assert(FunctionEnd > FunctionStart);
431 assert(FunctionStart == (uint8_t *)(CurBlock+1) &&
432 "Mismatched function start/end!");
434 uintptr_t BlockSize = FunctionEnd - (uint8_t *)CurBlock;
436 // Release the memory at the end of this block that isn't needed.
437 FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize);
440 /// allocateSpace - Allocate a memory block of the given size. This method
441 /// cannot be called between calls to startFunctionBody and endFunctionBody.
442 uint8_t *allocateSpace(intptr_t Size, unsigned Alignment) override {
443 CurBlock = FreeMemoryList;
444 FreeMemoryList = FreeMemoryList->AllocateBlock();
446 uint8_t *result = (uint8_t *)(CurBlock + 1);
448 if (Alignment == 0) Alignment = 1;
449 result = (uint8_t*)(((intptr_t)result+Alignment-1) &
450 ~(intptr_t)(Alignment-1));
452 uintptr_t BlockSize = result + Size - (uint8_t *)CurBlock;
453 FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize);
458 /// allocateStub - Allocate memory for a function stub.
459 uint8_t *allocateStub(const GlobalValue* F, unsigned StubSize,
460 unsigned Alignment) override {
461 return (uint8_t*)StubAllocator.Allocate(StubSize, Alignment);
464 /// allocateGlobal - Allocate memory for a global.
465 uint8_t *allocateGlobal(uintptr_t Size, unsigned Alignment) override {
466 return (uint8_t*)DataAllocator.Allocate(Size, Alignment);
469 /// allocateCodeSection - Allocate memory for a code section.
470 uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment,
472 StringRef SectionName) override {
473 // Grow the required block size to account for the block header
474 Size += sizeof(*CurBlock);
476 // Alignment handling.
479 Size += Alignment - 1;
481 FreeRangeHeader* candidateBlock = FreeMemoryList;
482 FreeRangeHeader* head = FreeMemoryList;
483 FreeRangeHeader* iter = head->Next;
485 uintptr_t largest = candidateBlock->BlockSize;
487 // Search for the largest free block.
488 while (iter != head) {
489 if (iter->BlockSize > largest) {
490 largest = iter->BlockSize;
491 candidateBlock = iter;
496 largest = largest - sizeof(MemoryRangeHeader);
498 // If this block isn't big enough for the allocation desired, allocate
499 // another block of memory and add it to the free list.
500 if (largest < Size || largest <= FreeRangeHeader::getMinBlockSize()) {
501 DEBUG(dbgs() << "JIT: Allocating another slab of memory for function.");
502 candidateBlock = allocateNewCodeSlab((size_t)Size);
505 // Select this candidate block for allocation
506 CurBlock = candidateBlock;
508 // Allocate the entire memory block.
509 FreeMemoryList = candidateBlock->AllocateBlock();
510 // Release the memory at the end of this block that isn't needed.
511 FreeMemoryList = CurBlock->TrimAllocationToSize(FreeMemoryList, Size);
512 uintptr_t unalignedAddr = (uintptr_t)CurBlock + sizeof(*CurBlock);
513 return (uint8_t*)RoundUpToAlignment((uint64_t)unalignedAddr, Alignment);
516 /// allocateDataSection - Allocate memory for a data section.
517 uint8_t *allocateDataSection(uintptr_t Size, unsigned Alignment,
518 unsigned SectionID, StringRef SectionName,
519 bool IsReadOnly) override {
520 return (uint8_t*)DataAllocator.Allocate(Size, Alignment);
523 bool finalizeMemory(std::string *ErrMsg) override {
527 uint8_t *getGOTBase() const override {
528 return GOTBase.get();
531 void deallocateBlock(void *Block) {
532 // Find the block that is allocated for this function.
533 MemoryRangeHeader *MemRange = static_cast<MemoryRangeHeader*>(Block) - 1;
534 assert(MemRange->ThisAllocated && "Block isn't allocated!");
536 // Fill the buffer with garbage!
538 memset(MemRange+1, 0xCD, MemRange->BlockSize-sizeof(*MemRange));
542 FreeMemoryList = MemRange->FreeBlock(FreeMemoryList);
545 /// deallocateFunctionBody - Deallocate all memory for the specified
547 void deallocateFunctionBody(void *Body) override {
548 if (Body) deallocateBlock(Body);
551 /// setMemoryWritable - When code generation is in progress,
552 /// the code pages may need permissions changed.
553 void setMemoryWritable() override {
554 for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
555 sys::Memory::setWritable(CodeSlabs[i]);
557 /// setMemoryExecutable - When code generation is done and we're ready to
558 /// start execution, the code pages may need permissions changed.
559 void setMemoryExecutable() override {
560 for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
561 sys::Memory::setExecutable(CodeSlabs[i]);
564 /// setPoisonMemory - Controls whether we write garbage over freed memory.
566 void setPoisonMemory(bool poison) override {
567 PoisonMemory = poison;
572 void *JITAllocator::Allocate(size_t Size, size_t /*Alignment*/) {
573 sys::MemoryBlock B = JMM.allocateNewSlab(Size);
577 void JITAllocator::Deallocate(void *Slab, size_t Size) {
578 sys::MemoryBlock B(Slab, Size);
579 sys::Memory::ReleaseRWX(B);
582 DefaultJITMemoryManager::DefaultJITMemoryManager()
589 LastSlab(nullptr, 0), StubAllocator(*this), DataAllocator(*this) {
591 // Allocate space for code.
592 sys::MemoryBlock MemBlock = allocateNewSlab(DefaultCodeSlabSize);
593 CodeSlabs.push_back(MemBlock);
594 uint8_t *MemBase = (uint8_t*)MemBlock.base();
596 // We set up the memory chunk with 4 mem regions, like this:
598 // [ Free #0 ] -> Large space to allocate functions from.
599 // [ Allocated #1 ] -> Tiny space to separate regions.
600 // [ Free #2 ] -> Tiny space so there is always at least 1 free block.
601 // [ Allocated #3 ] -> Tiny space to prevent looking past end of block.
604 // The last three blocks are never deallocated or touched.
606 // Add MemoryRangeHeader to the end of the memory region, indicating that
607 // the space after the block of memory is allocated. This is block #3.
608 MemoryRangeHeader *Mem3 = (MemoryRangeHeader*)(MemBase+MemBlock.size())-1;
609 Mem3->ThisAllocated = 1;
610 Mem3->PrevAllocated = 0;
611 Mem3->BlockSize = sizeof(MemoryRangeHeader);
613 /// Add a tiny free region so that the free list always has one entry.
614 FreeRangeHeader *Mem2 =
615 (FreeRangeHeader *)(((char*)Mem3)-FreeRangeHeader::getMinBlockSize());
616 Mem2->ThisAllocated = 0;
617 Mem2->PrevAllocated = 1;
618 Mem2->BlockSize = FreeRangeHeader::getMinBlockSize();
619 Mem2->SetEndOfBlockSizeMarker();
620 Mem2->Prev = Mem2; // Mem2 *is* the free list for now.
623 /// Add a tiny allocated region so that Mem2 is never coalesced away.
624 MemoryRangeHeader *Mem1 = (MemoryRangeHeader*)Mem2-1;
625 Mem1->ThisAllocated = 1;
626 Mem1->PrevAllocated = 0;
627 Mem1->BlockSize = sizeof(MemoryRangeHeader);
629 // Add a FreeRangeHeader to the start of the function body region, indicating
630 // that the space is free. Mark the previous block allocated so we never look
632 FreeRangeHeader *Mem0 = (FreeRangeHeader*)MemBase;
633 Mem0->ThisAllocated = 0;
634 Mem0->PrevAllocated = 1;
635 Mem0->BlockSize = (char*)Mem1-(char*)Mem0;
636 Mem0->SetEndOfBlockSizeMarker();
637 Mem0->AddToFreeList(Mem2);
639 // Start out with the freelist pointing to Mem0.
640 FreeMemoryList = Mem0;
643 void DefaultJITMemoryManager::AllocateGOT() {
644 assert(!GOTBase && "Cannot allocate the got multiple times");
645 GOTBase = make_unique<uint8_t[]>(sizeof(void*) * 8192);
649 DefaultJITMemoryManager::~DefaultJITMemoryManager() {
650 for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
651 sys::Memory::ReleaseRWX(CodeSlabs[i]);
654 sys::MemoryBlock DefaultJITMemoryManager::allocateNewSlab(size_t size) {
655 // Allocate a new block close to the last one.
657 sys::MemoryBlock *LastSlabPtr = LastSlab.base() ? &LastSlab : nullptr;
658 sys::MemoryBlock B = sys::Memory::AllocateRWX(size, LastSlabPtr, &ErrMsg);
660 report_fatal_error("Allocation failed when allocating new memory in the"
661 " JIT\n" + Twine(ErrMsg));
665 // Initialize the slab to garbage when debugging.
667 memset(B.base(), 0xCD, B.size());
672 /// CheckInvariants - For testing only. Return "" if all internal invariants
673 /// are preserved, and a helpful error message otherwise. For free and
674 /// allocated blocks, make sure that adding BlockSize gives a valid block.
675 /// For free blocks, make sure they're in the free list and that their end of
676 /// block size marker is correct. This function should return an error before
677 /// accessing bad memory. This function is defined here instead of in
678 /// JITMemoryManagerTest.cpp so that we don't have to expose all of the
679 /// implementation details of DefaultJITMemoryManager.
680 bool DefaultJITMemoryManager::CheckInvariants(std::string &ErrorStr) {
681 raw_string_ostream Err(ErrorStr);
683 // Construct the set of FreeRangeHeader pointers so we can query it
685 llvm::SmallPtrSet<MemoryRangeHeader*, 16> FreeHdrSet;
686 FreeRangeHeader* FreeHead = FreeMemoryList;
687 FreeRangeHeader* FreeRange = FreeHead;
690 // Check that the free range pointer is in the blocks we've allocated.
692 for (std::vector<sys::MemoryBlock>::iterator I = CodeSlabs.begin(),
693 E = CodeSlabs.end(); I != E && !Found; ++I) {
694 char *Start = (char*)I->base();
695 char *End = Start + I->size();
696 Found = (Start <= (char*)FreeRange && (char*)FreeRange < End);
699 Err << "Corrupt free list; points to " << FreeRange;
703 if (FreeRange->Next->Prev != FreeRange) {
704 Err << "Next and Prev pointers do not match.";
708 // Otherwise, add it to the set.
709 FreeHdrSet.insert(FreeRange);
710 FreeRange = FreeRange->Next;
711 } while (FreeRange != FreeHead);
713 // Go over each block, and look at each MemoryRangeHeader.
714 for (std::vector<sys::MemoryBlock>::iterator I = CodeSlabs.begin(),
715 E = CodeSlabs.end(); I != E; ++I) {
716 char *Start = (char*)I->base();
717 char *End = Start + I->size();
719 // Check each memory range.
720 for (MemoryRangeHeader *Hdr = (MemoryRangeHeader*)Start, *LastHdr = nullptr;
721 Start <= (char*)Hdr && (char*)Hdr < End;
722 Hdr = &Hdr->getBlockAfter()) {
723 if (Hdr->ThisAllocated == 0) {
724 // Check that this range is in the free list.
725 if (!FreeHdrSet.count(Hdr)) {
726 Err << "Found free header at " << Hdr << " that is not in free list.";
730 // Now make sure the size marker at the end of the block is correct.
731 uintptr_t *Marker = ((uintptr_t*)&Hdr->getBlockAfter()) - 1;
732 if (!(Start <= (char*)Marker && (char*)Marker < End)) {
733 Err << "Block size in header points out of current MemoryBlock.";
736 if (Hdr->BlockSize != *Marker) {
737 Err << "End of block size marker (" << *Marker << ") "
738 << "and BlockSize (" << Hdr->BlockSize << ") don't match.";
743 if (LastHdr && LastHdr->ThisAllocated != Hdr->PrevAllocated) {
744 Err << "Hdr->PrevAllocated (" << Hdr->PrevAllocated << ") != "
745 << "LastHdr->ThisAllocated (" << LastHdr->ThisAllocated << ")";
747 } else if (!LastHdr && !Hdr->PrevAllocated) {
748 Err << "The first header should have PrevAllocated true.";
752 // Remember the last header.
757 // All invariants are preserved.
761 //===----------------------------------------------------------------------===//
762 // getPointerToNamedFunction() implementation.
763 //===----------------------------------------------------------------------===//
765 // AtExitHandlers - List of functions to call when the program exits,
766 // registered with the atexit() library function.
767 static std::vector<void (*)()> AtExitHandlers;
769 /// runAtExitHandlers - Run any functions registered by the program's
770 /// calls to atexit(3), which we intercept and store in
773 static void runAtExitHandlers() {
774 while (!AtExitHandlers.empty()) {
775 void (*Fn)() = AtExitHandlers.back();
776 AtExitHandlers.pop_back();
781 //===----------------------------------------------------------------------===//
782 // Function stubs that are invoked instead of certain library calls
784 // Force the following functions to be linked in to anything that uses the
785 // JIT. This is a hack designed to work around the all-too-clever Glibc
786 // strategy of making these functions work differently when inlined vs. when
787 // not inlined, and hiding their real definitions in a separate archive file
788 // that the dynamic linker can't see. For more info, search for
789 // 'libc_nonshared.a' on Google, or read http://llvm.org/PR274.
790 #if defined(__linux__) && defined(__GLIBC__)
791 /* stat functions are redirecting to __xstat with a version number. On x86-64
792 * linking with libc_nonshared.a and -Wl,--export-dynamic doesn't make 'stat'
793 * available as an exported symbol, so we have to add it explicitly.
799 sys::DynamicLibrary::AddSymbol("stat", (void*)(intptr_t)stat);
800 sys::DynamicLibrary::AddSymbol("fstat", (void*)(intptr_t)fstat);
801 sys::DynamicLibrary::AddSymbol("lstat", (void*)(intptr_t)lstat);
802 sys::DynamicLibrary::AddSymbol("stat64", (void*)(intptr_t)stat64);
803 sys::DynamicLibrary::AddSymbol("\x1stat64", (void*)(intptr_t)stat64);
804 sys::DynamicLibrary::AddSymbol("\x1open64", (void*)(intptr_t)open64);
805 sys::DynamicLibrary::AddSymbol("\x1lseek64", (void*)(intptr_t)lseek64);
806 sys::DynamicLibrary::AddSymbol("fstat64", (void*)(intptr_t)fstat64);
807 sys::DynamicLibrary::AddSymbol("lstat64", (void*)(intptr_t)lstat64);
808 sys::DynamicLibrary::AddSymbol("atexit", (void*)(intptr_t)atexit);
809 sys::DynamicLibrary::AddSymbol("mknod", (void*)(intptr_t)mknod);
813 static StatSymbols initStatSymbols;
816 // jit_exit - Used to intercept the "exit" library call.
817 static void jit_exit(int Status) {
818 runAtExitHandlers(); // Run atexit handlers...
822 // jit_atexit - Used to intercept the "atexit" library call.
823 static int jit_atexit(void (*Fn)()) {
824 AtExitHandlers.push_back(Fn); // Take note of atexit handler...
825 return 0; // Always successful
828 static int jit_noop() {
832 //===----------------------------------------------------------------------===//
834 /// getPointerToNamedFunction - This method returns the address of the specified
835 /// function by using the dynamic loader interface. As such it is only useful
836 /// for resolving library symbols, not code generated symbols.
838 void *DefaultJITMemoryManager::getPointerToNamedFunction(const std::string &Name,
839 bool AbortOnFailure) {
840 // Check to see if this is one of the functions we want to intercept. Note,
841 // we cast to intptr_t here to silence a -pedantic warning that complains
842 // about casting a function pointer to a normal pointer.
843 if (Name == "exit") return (void*)(intptr_t)&jit_exit;
844 if (Name == "atexit") return (void*)(intptr_t)&jit_atexit;
846 // We should not invoke parent's ctors/dtors from generated main()!
847 // On Mingw and Cygwin, the symbol __main is resolved to
848 // callee's(eg. tools/lli) one, to invoke wrong duplicated ctors
849 // (and register wrong callee's dtors with atexit(3)).
850 // We expect ExecutionEngine::runStaticConstructorsDestructors()
851 // is called before ExecutionEngine::runFunctionAsMain() is called.
852 if (Name == "__main") return (void*)(intptr_t)&jit_noop;
854 const char *NameStr = Name.c_str();
855 // If this is an asm specifier, skip the sentinal.
856 if (NameStr[0] == 1) ++NameStr;
858 // If it's an external function, look it up in the process image...
859 void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr);
862 // If it wasn't found and if it starts with an underscore ('_') character,
863 // try again without the underscore.
864 if (NameStr[0] == '_') {
865 Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1);
869 // Darwin/PPC adds $LDBLStub suffixes to various symbols like printf. These
870 // are references to hidden visibility symbols that dlsym cannot resolve.
871 // If we have one of these, strip off $LDBLStub and try again.
872 #if defined(__APPLE__) && defined(__ppc__)
873 if (Name.size() > 9 && Name[Name.size()-9] == '$' &&
874 memcmp(&Name[Name.size()-8], "LDBLStub", 8) == 0) {
875 // First try turning $LDBLStub into $LDBL128. If that fails, strip it off.
876 // This mirrors logic in libSystemStubs.a.
877 std::string Prefix = std::string(Name.begin(), Name.end()-9);
878 if (void *Ptr = getPointerToNamedFunction(Prefix+"$LDBL128", false))
880 if (void *Ptr = getPointerToNamedFunction(Prefix, false))
885 if (AbortOnFailure) {
886 report_fatal_error("Program used external function '"+Name+
887 "' which could not be resolved!");
894 JITMemoryManager *JITMemoryManager::CreateDefaultMemManager() {
895 return new DefaultJITMemoryManager();
898 const size_t DefaultJITMemoryManager::DefaultCodeSlabSize;
899 const size_t DefaultJITMemoryManager::DefaultSlabSize;
900 const size_t DefaultJITMemoryManager::DefaultSizeThreshold;