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 #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"
33 #if defined(__linux__)
34 #if defined(HAVE_SYS_STAT_H)
43 STATISTIC(NumSlabs, "Number of slabs of memory allocated by the JIT");
45 JITMemoryManager::~JITMemoryManager() {}
47 //===----------------------------------------------------------------------===//
48 // Memory Block Implementation.
49 //===----------------------------------------------------------------------===//
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;
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;
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);
72 /// getBlockAfter - Return the memory block immediately after this one.
74 MemoryRangeHeader &getBlockAfter() const {
75 return *reinterpret_cast<MemoryRangeHeader *>(
76 reinterpret_cast<char*>(
77 const_cast<MemoryRangeHeader *>(this))+BlockSize);
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);
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);
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,
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;
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);
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;
122 FreeRangeHeader *RemoveFromFreeList() {
123 assert(Next->Prev == this && Prev->Next == this && "Freelist broken!");
125 return Prev->Next = Next;
128 void AddToFreeList(FreeRangeHeader *FreeList) {
130 Prev = FreeList->Prev;
135 /// GrowBlock - The block after this block just got deallocated. Merge it
136 /// into the current block.
137 void GrowBlock(uintptr_t NewSize);
139 /// AllocateBlock - Mark this entire block allocated, updating freelists
140 /// etc. This returns a pointer to the circular free-list.
141 FreeRangeHeader *AllocateBlock();
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.
153 getBlockAfter().PrevAllocated = 1;
155 // Remove it from the free list.
156 return RemoveFromFreeList();
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!");
168 FreeRangeHeader *FreeListToReturn = FreeList;
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?");
180 FollowingFreeBlock.RemoveFromFreeList();
182 // Include the following block into this one.
183 BlockSize += FollowingFreeBlock.BlockSize;
184 FollowingBlock = &FollowingFreeBlock.getBlockAfter();
186 // Tell the block after the block we are coalescing that this block is
188 FollowingBlock->PrevAllocated = 1;
191 assert(FollowingBlock->ThisAllocated && "Missed coalescing?");
193 if (FreeRangeHeader *PrevFreeBlock = getFreeBlockBefore()) {
194 PrevFreeBlock->GrowBlock(PrevFreeBlock->BlockSize + BlockSize);
195 return FreeListToReturn ? FreeListToReturn : PrevFreeBlock;
198 // Otherwise, mark this block free.
199 FreeRangeHeader &FreeBlock = *(FreeRangeHeader*)this;
200 FollowingBlock->PrevAllocated = 0;
201 FreeBlock.ThisAllocated = 0;
203 // Link this into the linked list of free blocks.
204 FreeBlock.AddToFreeList(FreeList);
206 // Add a marker at the end of the block, indicating the size of this free
208 FreeBlock.SetEndOfBlockSizeMarker();
209 return FreeListToReturn ? FreeListToReturn : &FreeBlock;
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?");
217 SetEndOfBlockSizeMarker();
218 getBlockAfter().PrevAllocated = 0;
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!");
229 // Don't allow blocks to be trimmed below minimum required size
230 NewSize = std::max<uint64_t>(FreeRangeHeader::getMinBlockSize(), NewSize);
232 // Round up size for alignment of header.
233 unsigned HeaderAlign = __alignof(FreeRangeHeader);
234 NewSize = (NewSize+ (HeaderAlign-1)) & ~(HeaderAlign-1);
236 // Size is now the size of the block we will remove from the start of the
238 assert(NewSize <= BlockSize &&
239 "Allocating more space from this block than exists!");
241 // If splitting this block will cause the remainder to be too small, do not
243 if (BlockSize <= NewSize+FreeRangeHeader::getMinBlockSize())
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();
250 // Change the size of this block.
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;
264 //===----------------------------------------------------------------------===//
265 // Memory Block Implementation.
266 //===----------------------------------------------------------------------===//
270 class DefaultJITMemoryManager;
272 class JITSlabAllocator : public SlabAllocator {
273 DefaultJITMemoryManager &JMM;
275 JITSlabAllocator(DefaultJITMemoryManager &jmm) : JMM(jmm) { }
276 virtual ~JITSlabAllocator() { }
277 virtual MemSlab *Allocate(size_t Size);
278 virtual void Deallocate(MemSlab *Slab);
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 // Whether to poison freed memory.
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;
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;
306 // Circular list of free blocks.
307 FreeRangeHeader *FreeMemoryList;
309 // When emitting code into a memory block, this is the block.
310 MemoryRangeHeader *CurBlock;
312 uint8_t *GOTBase; // Target Specific reserved memory
314 DefaultJITMemoryManager();
315 ~DefaultJITMemoryManager();
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);
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;
325 /// DefaultSlabSize - Allocate data into slabs of this size unless we get
326 /// an allocation above SizeThreshold.
327 static const size_t DefaultSlabSize;
329 /// DefaultSizeThreshold - For any allocation larger than this threshold, we
330 /// should allocate a separate slab.
331 static const size_t DefaultSizeThreshold;
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);
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(); }
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) {
353 FreeRangeHeader* candidateBlock = FreeMemoryList;
354 FreeRangeHeader* head = FreeMemoryList;
355 FreeRangeHeader* iter = head->Next;
357 uintptr_t largest = candidateBlock->BlockSize;
359 // Search for the largest free block
360 while (iter != head) {
361 if (iter->BlockSize > largest) {
362 largest = iter->BlockSize;
363 candidateBlock = iter;
368 largest = largest - sizeof(MemoryRangeHeader);
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);
378 // Select this candidate block for allocation
379 CurBlock = candidateBlock;
381 // Allocate the entire memory block.
382 FreeMemoryList = candidateBlock->AllocateBlock();
383 ActualSize = CurBlock->BlockSize - sizeof(MemoryRangeHeader);
384 return (uint8_t *)(CurBlock + 1);
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
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());
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);
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);
417 assert(NewBlock->BlockSize - sizeof(MemoryRangeHeader) >= MinSize &&
418 "The block was too small!");
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!");
430 uintptr_t BlockSize = FunctionEnd - (uint8_t *)CurBlock;
432 // Release the memory at the end of this block that isn't needed.
433 FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize);
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();
442 uint8_t *result = (uint8_t *)(CurBlock + 1);
444 if (Alignment == 0) Alignment = 1;
445 result = (uint8_t*)(((intptr_t)result+Alignment-1) &
446 ~(intptr_t)(Alignment-1));
448 uintptr_t BlockSize = result + Size - (uint8_t *)CurBlock;
449 FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize);
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);
460 /// allocateGlobal - Allocate memory for a global.
461 uint8_t *allocateGlobal(uintptr_t Size, unsigned Alignment) {
462 return (uint8_t*)DataAllocator.Allocate(Size, Alignment);
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);
471 // FIXME: Alignement handling.
472 FreeRangeHeader* candidateBlock = FreeMemoryList;
473 FreeRangeHeader* head = FreeMemoryList;
474 FreeRangeHeader* iter = head->Next;
476 uintptr_t largest = candidateBlock->BlockSize;
478 // Search for the largest free block.
479 while (iter != head) {
480 if (iter->BlockSize > largest) {
481 largest = iter->BlockSize;
482 candidateBlock = iter;
487 largest = largest - sizeof(MemoryRangeHeader);
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);
496 // Select this candidate block for allocation
497 CurBlock = candidateBlock;
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);
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);
512 bool applyPermissions(std::string *ErrMsg) {
516 uint8_t *getGOTBase() const {
520 void deallocateBlock(void *Block) {
521 // Find the block that is allocated for this function.
522 MemoryRangeHeader *MemRange = static_cast<MemoryRangeHeader*>(Block) - 1;
523 assert(MemRange->ThisAllocated && "Block isn't allocated!");
525 // Fill the buffer with garbage!
527 memset(MemRange+1, 0xCD, MemRange->BlockSize-sizeof(*MemRange));
531 FreeMemoryList = MemRange->FreeBlock(FreeMemoryList);
534 /// deallocateFunctionBody - Deallocate all memory for the specified
536 void deallocateFunctionBody(void *Body) {
537 if (Body) deallocateBlock(Body);
540 /// setMemoryWritable - When code generation is in progress,
541 /// the code pages may need permissions changed.
542 void setMemoryWritable()
544 for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
545 sys::Memory::setWritable(CodeSlabs[i]);
547 /// setMemoryExecutable - When code generation is done and we're ready to
548 /// start execution, the code pages may need permissions changed.
549 void setMemoryExecutable()
551 for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
552 sys::Memory::setExecutable(CodeSlabs[i]);
555 /// setPoisonMemory - Controls whether we write garbage over freed memory.
557 void setPoisonMemory(bool poison) {
558 PoisonMemory = poison;
563 MemSlab *JITSlabAllocator::Allocate(size_t Size) {
564 sys::MemoryBlock B = JMM.allocateNewSlab(Size);
565 MemSlab *Slab = (MemSlab*)B.base();
566 Slab->Size = B.size();
571 void JITSlabAllocator::Deallocate(MemSlab *Slab) {
572 sys::MemoryBlock B(Slab, Slab->Size);
573 sys::Memory::ReleaseRWX(B);
576 DefaultJITMemoryManager::DefaultJITMemoryManager()
584 BumpSlabAllocator(*this),
585 StubAllocator(DefaultSlabSize, DefaultSizeThreshold, BumpSlabAllocator),
586 DataAllocator(DefaultSlabSize, DefaultSizeThreshold, BumpSlabAllocator) {
588 // Allocate space for code.
589 sys::MemoryBlock MemBlock = allocateNewSlab(DefaultCodeSlabSize);
590 CodeSlabs.push_back(MemBlock);
591 uint8_t *MemBase = (uint8_t*)MemBlock.base();
593 // We set up the memory chunk with 4 mem regions, like this:
595 // [ Free #0 ] -> Large space to allocate functions from.
596 // [ Allocated #1 ] -> Tiny space to separate regions.
597 // [ Free #2 ] -> Tiny space so there is always at least 1 free block.
598 // [ Allocated #3 ] -> Tiny space to prevent looking past end of block.
601 // The last three blocks are never deallocated or touched.
603 // Add MemoryRangeHeader to the end of the memory region, indicating that
604 // the space after the block of memory is allocated. This is block #3.
605 MemoryRangeHeader *Mem3 = (MemoryRangeHeader*)(MemBase+MemBlock.size())-1;
606 Mem3->ThisAllocated = 1;
607 Mem3->PrevAllocated = 0;
608 Mem3->BlockSize = sizeof(MemoryRangeHeader);
610 /// Add a tiny free region so that the free list always has one entry.
611 FreeRangeHeader *Mem2 =
612 (FreeRangeHeader *)(((char*)Mem3)-FreeRangeHeader::getMinBlockSize());
613 Mem2->ThisAllocated = 0;
614 Mem2->PrevAllocated = 1;
615 Mem2->BlockSize = FreeRangeHeader::getMinBlockSize();
616 Mem2->SetEndOfBlockSizeMarker();
617 Mem2->Prev = Mem2; // Mem2 *is* the free list for now.
620 /// Add a tiny allocated region so that Mem2 is never coalesced away.
621 MemoryRangeHeader *Mem1 = (MemoryRangeHeader*)Mem2-1;
622 Mem1->ThisAllocated = 1;
623 Mem1->PrevAllocated = 0;
624 Mem1->BlockSize = sizeof(MemoryRangeHeader);
626 // Add a FreeRangeHeader to the start of the function body region, indicating
627 // that the space is free. Mark the previous block allocated so we never look
629 FreeRangeHeader *Mem0 = (FreeRangeHeader*)MemBase;
630 Mem0->ThisAllocated = 0;
631 Mem0->PrevAllocated = 1;
632 Mem0->BlockSize = (char*)Mem1-(char*)Mem0;
633 Mem0->SetEndOfBlockSizeMarker();
634 Mem0->AddToFreeList(Mem2);
636 // Start out with the freelist pointing to Mem0.
637 FreeMemoryList = Mem0;
642 void DefaultJITMemoryManager::AllocateGOT() {
643 assert(GOTBase == 0 && "Cannot allocate the got multiple times");
644 GOTBase = new uint8_t[sizeof(void*) * 8192];
648 DefaultJITMemoryManager::~DefaultJITMemoryManager() {
649 for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
650 sys::Memory::ReleaseRWX(CodeSlabs[i]);
655 sys::MemoryBlock DefaultJITMemoryManager::allocateNewSlab(size_t size) {
656 // Allocate a new block close to the last one.
658 sys::MemoryBlock *LastSlabPtr = LastSlab.base() ? &LastSlab : 0;
659 sys::MemoryBlock B = sys::Memory::AllocateRWX(size, LastSlabPtr, &ErrMsg);
661 report_fatal_error("Allocation failed when allocating new memory in the"
662 " JIT\n" + Twine(ErrMsg));
666 // Initialize the slab to garbage when debugging.
668 memset(B.base(), 0xCD, B.size());
673 /// CheckInvariants - For testing only. Return "" if all internal invariants
674 /// are preserved, and a helpful error message otherwise. For free and
675 /// allocated blocks, make sure that adding BlockSize gives a valid block.
676 /// For free blocks, make sure they're in the free list and that their end of
677 /// block size marker is correct. This function should return an error before
678 /// accessing bad memory. This function is defined here instead of in
679 /// JITMemoryManagerTest.cpp so that we don't have to expose all of the
680 /// implementation details of DefaultJITMemoryManager.
681 bool DefaultJITMemoryManager::CheckInvariants(std::string &ErrorStr) {
682 raw_string_ostream Err(ErrorStr);
684 // Construct a the set of FreeRangeHeader pointers so we can query it
686 llvm::SmallPtrSet<MemoryRangeHeader*, 16> FreeHdrSet;
687 FreeRangeHeader* FreeHead = FreeMemoryList;
688 FreeRangeHeader* FreeRange = FreeHead;
691 // Check that the free range pointer is in the blocks we've allocated.
693 for (std::vector<sys::MemoryBlock>::iterator I = CodeSlabs.begin(),
694 E = CodeSlabs.end(); I != E && !Found; ++I) {
695 char *Start = (char*)I->base();
696 char *End = Start + I->size();
697 Found = (Start <= (char*)FreeRange && (char*)FreeRange < End);
700 Err << "Corrupt free list; points to " << FreeRange;
704 if (FreeRange->Next->Prev != FreeRange) {
705 Err << "Next and Prev pointers do not match.";
709 // Otherwise, add it to the set.
710 FreeHdrSet.insert(FreeRange);
711 FreeRange = FreeRange->Next;
712 } while (FreeRange != FreeHead);
714 // Go over each block, and look at each MemoryRangeHeader.
715 for (std::vector<sys::MemoryBlock>::iterator I = CodeSlabs.begin(),
716 E = CodeSlabs.end(); I != E; ++I) {
717 char *Start = (char*)I->base();
718 char *End = Start + I->size();
720 // Check each memory range.
721 for (MemoryRangeHeader *Hdr = (MemoryRangeHeader*)Start, *LastHdr = NULL;
722 Start <= (char*)Hdr && (char*)Hdr < End;
723 Hdr = &Hdr->getBlockAfter()) {
724 if (Hdr->ThisAllocated == 0) {
725 // Check that this range is in the free list.
726 if (!FreeHdrSet.count(Hdr)) {
727 Err << "Found free header at " << Hdr << " that is not in free list.";
731 // Now make sure the size marker at the end of the block is correct.
732 uintptr_t *Marker = ((uintptr_t*)&Hdr->getBlockAfter()) - 1;
733 if (!(Start <= (char*)Marker && (char*)Marker < End)) {
734 Err << "Block size in header points out of current MemoryBlock.";
737 if (Hdr->BlockSize != *Marker) {
738 Err << "End of block size marker (" << *Marker << ") "
739 << "and BlockSize (" << Hdr->BlockSize << ") don't match.";
744 if (LastHdr && LastHdr->ThisAllocated != Hdr->PrevAllocated) {
745 Err << "Hdr->PrevAllocated (" << Hdr->PrevAllocated << ") != "
746 << "LastHdr->ThisAllocated (" << LastHdr->ThisAllocated << ")";
748 } else if (!LastHdr && !Hdr->PrevAllocated) {
749 Err << "The first header should have PrevAllocated true.";
753 // Remember the last header.
758 // All invariants are preserved.
762 //===----------------------------------------------------------------------===//
763 // getPointerToNamedFunction() implementation.
764 //===----------------------------------------------------------------------===//
766 // AtExitHandlers - List of functions to call when the program exits,
767 // registered with the atexit() library function.
768 static std::vector<void (*)()> AtExitHandlers;
770 /// runAtExitHandlers - Run any functions registered by the program's
771 /// calls to atexit(3), which we intercept and store in
774 static void runAtExitHandlers() {
775 while (!AtExitHandlers.empty()) {
776 void (*Fn)() = AtExitHandlers.back();
777 AtExitHandlers.pop_back();
782 //===----------------------------------------------------------------------===//
783 // Function stubs that are invoked instead of certain library calls
785 // Force the following functions to be linked in to anything that uses the
786 // JIT. This is a hack designed to work around the all-too-clever Glibc
787 // strategy of making these functions work differently when inlined vs. when
788 // not inlined, and hiding their real definitions in a separate archive file
789 // that the dynamic linker can't see. For more info, search for
790 // 'libc_nonshared.a' on Google, or read http://llvm.org/PR274.
791 #if defined(__linux__)
792 /* stat functions are redirecting to __xstat with a version number. On x86-64
793 * linking with libc_nonshared.a and -Wl,--export-dynamic doesn't make 'stat'
794 * available as an exported symbol, so we have to add it explicitly.
800 sys::DynamicLibrary::AddSymbol("stat", (void*)(intptr_t)stat);
801 sys::DynamicLibrary::AddSymbol("fstat", (void*)(intptr_t)fstat);
802 sys::DynamicLibrary::AddSymbol("lstat", (void*)(intptr_t)lstat);
803 sys::DynamicLibrary::AddSymbol("stat64", (void*)(intptr_t)stat64);
804 sys::DynamicLibrary::AddSymbol("\x1stat64", (void*)(intptr_t)stat64);
805 sys::DynamicLibrary::AddSymbol("\x1open64", (void*)(intptr_t)open64);
806 sys::DynamicLibrary::AddSymbol("\x1lseek64", (void*)(intptr_t)lseek64);
807 sys::DynamicLibrary::AddSymbol("fstat64", (void*)(intptr_t)fstat64);
808 sys::DynamicLibrary::AddSymbol("lstat64", (void*)(intptr_t)lstat64);
809 sys::DynamicLibrary::AddSymbol("atexit", (void*)(intptr_t)atexit);
810 sys::DynamicLibrary::AddSymbol("mknod", (void*)(intptr_t)mknod);
814 static StatSymbols initStatSymbols;
817 // jit_exit - Used to intercept the "exit" library call.
818 static void jit_exit(int Status) {
819 runAtExitHandlers(); // Run atexit handlers...
823 // jit_atexit - Used to intercept the "atexit" library call.
824 static int jit_atexit(void (*Fn)()) {
825 AtExitHandlers.push_back(Fn); // Take note of atexit handler...
826 return 0; // Always successful
829 static int jit_noop() {
833 //===----------------------------------------------------------------------===//
835 /// getPointerToNamedFunction - This method returns the address of the specified
836 /// function by using the dynamic loader interface. As such it is only useful
837 /// for resolving library symbols, not code generated symbols.
839 void *DefaultJITMemoryManager::getPointerToNamedFunction(const std::string &Name,
840 bool AbortOnFailure) {
841 // Check to see if this is one of the functions we want to intercept. Note,
842 // we cast to intptr_t here to silence a -pedantic warning that complains
843 // about casting a function pointer to a normal pointer.
844 if (Name == "exit") return (void*)(intptr_t)&jit_exit;
845 if (Name == "atexit") return (void*)(intptr_t)&jit_atexit;
847 // We should not invoke parent's ctors/dtors from generated main()!
848 // On Mingw and Cygwin, the symbol __main is resolved to
849 // callee's(eg. tools/lli) one, to invoke wrong duplicated ctors
850 // (and register wrong callee's dtors with atexit(3)).
851 // We expect ExecutionEngine::runStaticConstructorsDestructors()
852 // is called before ExecutionEngine::runFunctionAsMain() is called.
853 if (Name == "__main") return (void*)(intptr_t)&jit_noop;
855 const char *NameStr = Name.c_str();
856 // If this is an asm specifier, skip the sentinal.
857 if (NameStr[0] == 1) ++NameStr;
859 // If it's an external function, look it up in the process image...
860 void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr);
863 // If it wasn't found and if it starts with an underscore ('_') character,
864 // try again without the underscore.
865 if (NameStr[0] == '_') {
866 Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1);
870 // Darwin/PPC adds $LDBLStub suffixes to various symbols like printf. These
871 // are references to hidden visibility symbols that dlsym cannot resolve.
872 // If we have one of these, strip off $LDBLStub and try again.
873 #if defined(__APPLE__) && defined(__ppc__)
874 if (Name.size() > 9 && Name[Name.size()-9] == '$' &&
875 memcmp(&Name[Name.size()-8], "LDBLStub", 8) == 0) {
876 // First try turning $LDBLStub into $LDBL128. If that fails, strip it off.
877 // This mirrors logic in libSystemStubs.a.
878 std::string Prefix = std::string(Name.begin(), Name.end()-9);
879 if (void *Ptr = getPointerToNamedFunction(Prefix+"$LDBL128", false))
881 if (void *Ptr = getPointerToNamedFunction(Prefix, false))
886 if (AbortOnFailure) {
887 report_fatal_error("Program used external function '"+Name+
888 "' which could not be resolved!");
895 JITMemoryManager *JITMemoryManager::CreateDefaultMemManager() {
896 return new DefaultJITMemoryManager();
899 // Allocate memory for code in 512K slabs.
900 const size_t DefaultJITMemoryManager::DefaultCodeSlabSize = 512 * 1024;
902 // Allocate globals and stubs in slabs of 64K. (probably 16 pages)
903 const size_t DefaultJITMemoryManager::DefaultSlabSize = 64 * 1024;
905 // Waste at most 16K at the end of each bump slab. (probably 4 pages)
906 const size_t DefaultJITMemoryManager::DefaultSizeThreshold = 16 * 1024;