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 MemSlab *Allocate(size_t Size) override;
278 void Deallocate(MemSlab *Slab) override;
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 JITSlabAllocator BumpSlabAllocator;
317 BumpPtrAllocatorImpl<DefaultSlabSize, DefaultSizeThreshold> StubAllocator;
318 BumpPtrAllocatorImpl<DefaultSlabSize, DefaultSizeThreshold> DataAllocator;
320 // Circular list of free blocks.
321 FreeRangeHeader *FreeMemoryList;
323 // When emitting code into a memory block, this is the block.
324 MemoryRangeHeader *CurBlock;
326 uint8_t *GOTBase; // Target Specific reserved memory
328 DefaultJITMemoryManager();
329 ~DefaultJITMemoryManager();
331 /// allocateNewSlab - Allocates a new MemoryBlock and remembers it as the
332 /// last slab it allocated, so that subsequent allocations follow it.
333 sys::MemoryBlock allocateNewSlab(size_t size);
335 /// getPointerToNamedFunction - This method returns the address of the
336 /// specified function by using the dlsym function call.
337 void *getPointerToNamedFunction(const std::string &Name,
338 bool AbortOnFailure = true) override;
340 void AllocateGOT() override;
343 bool CheckInvariants(std::string &ErrorStr) override;
344 size_t GetDefaultCodeSlabSize() override { return DefaultCodeSlabSize; }
345 size_t GetDefaultDataSlabSize() override { return DefaultSlabSize; }
346 size_t GetDefaultStubSlabSize() override { return DefaultSlabSize; }
347 unsigned GetNumCodeSlabs() override { return CodeSlabs.size(); }
348 unsigned GetNumDataSlabs() override { return DataAllocator.GetNumSlabs(); }
349 unsigned GetNumStubSlabs() override { return StubAllocator.GetNumSlabs(); }
351 /// startFunctionBody - When a function starts, allocate a block of free
352 /// executable memory, returning a pointer to it and its actual size.
353 uint8_t *startFunctionBody(const Function *F,
354 uintptr_t &ActualSize) override {
356 FreeRangeHeader* candidateBlock = FreeMemoryList;
357 FreeRangeHeader* head = FreeMemoryList;
358 FreeRangeHeader* iter = head->Next;
360 uintptr_t largest = candidateBlock->BlockSize;
362 // Search for the largest free block
363 while (iter != head) {
364 if (iter->BlockSize > largest) {
365 largest = iter->BlockSize;
366 candidateBlock = iter;
371 largest = largest - sizeof(MemoryRangeHeader);
373 // If this block isn't big enough for the allocation desired, allocate
374 // another block of memory and add it to the free list.
375 if (largest < ActualSize ||
376 largest <= FreeRangeHeader::getMinBlockSize()) {
377 DEBUG(dbgs() << "JIT: Allocating another slab of memory for function.");
378 candidateBlock = allocateNewCodeSlab((size_t)ActualSize);
381 // Select this candidate block for allocation
382 CurBlock = candidateBlock;
384 // Allocate the entire memory block.
385 FreeMemoryList = candidateBlock->AllocateBlock();
386 ActualSize = CurBlock->BlockSize - sizeof(MemoryRangeHeader);
387 return (uint8_t *)(CurBlock + 1);
390 /// allocateNewCodeSlab - Helper method to allocate a new slab of code
391 /// memory from the OS and add it to the free list. Returns the new
392 /// FreeRangeHeader at the base of the slab.
393 FreeRangeHeader *allocateNewCodeSlab(size_t MinSize) {
394 // If the user needs at least MinSize free memory, then we account for
395 // two MemoryRangeHeaders: the one in the user's block, and the one at the
397 size_t PaddedMin = MinSize + 2 * sizeof(MemoryRangeHeader);
398 size_t SlabSize = std::max(DefaultCodeSlabSize, PaddedMin);
399 sys::MemoryBlock B = allocateNewSlab(SlabSize);
400 CodeSlabs.push_back(B);
401 char *MemBase = (char*)(B.base());
403 // Put a tiny allocated block at the end of the memory chunk, so when
404 // FreeBlock calls getBlockAfter it doesn't fall off the end.
405 MemoryRangeHeader *EndBlock =
406 (MemoryRangeHeader*)(MemBase + B.size()) - 1;
407 EndBlock->ThisAllocated = 1;
408 EndBlock->PrevAllocated = 0;
409 EndBlock->BlockSize = sizeof(MemoryRangeHeader);
411 // Start out with a vast new block of free memory.
412 FreeRangeHeader *NewBlock = (FreeRangeHeader*)MemBase;
413 NewBlock->ThisAllocated = 0;
414 // Make sure getFreeBlockBefore doesn't look into unmapped memory.
415 NewBlock->PrevAllocated = 1;
416 NewBlock->BlockSize = (uintptr_t)EndBlock - (uintptr_t)NewBlock;
417 NewBlock->SetEndOfBlockSizeMarker();
418 NewBlock->AddToFreeList(FreeMemoryList);
420 assert(NewBlock->BlockSize - sizeof(MemoryRangeHeader) >= MinSize &&
421 "The block was too small!");
425 /// endFunctionBody - The function F is now allocated, and takes the memory
426 /// in the range [FunctionStart,FunctionEnd).
427 void endFunctionBody(const Function *F, uint8_t *FunctionStart,
428 uint8_t *FunctionEnd) override {
429 assert(FunctionEnd > FunctionStart);
430 assert(FunctionStart == (uint8_t *)(CurBlock+1) &&
431 "Mismatched function start/end!");
433 uintptr_t BlockSize = FunctionEnd - (uint8_t *)CurBlock;
435 // Release the memory at the end of this block that isn't needed.
436 FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize);
439 /// allocateSpace - Allocate a memory block of the given size. This method
440 /// cannot be called between calls to startFunctionBody and endFunctionBody.
441 uint8_t *allocateSpace(intptr_t Size, unsigned Alignment) override {
442 CurBlock = FreeMemoryList;
443 FreeMemoryList = FreeMemoryList->AllocateBlock();
445 uint8_t *result = (uint8_t *)(CurBlock + 1);
447 if (Alignment == 0) Alignment = 1;
448 result = (uint8_t*)(((intptr_t)result+Alignment-1) &
449 ~(intptr_t)(Alignment-1));
451 uintptr_t BlockSize = result + Size - (uint8_t *)CurBlock;
452 FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize);
457 /// allocateStub - Allocate memory for a function stub.
458 uint8_t *allocateStub(const GlobalValue* F, unsigned StubSize,
459 unsigned Alignment) override {
460 return (uint8_t*)StubAllocator.Allocate(StubSize, Alignment);
463 /// allocateGlobal - Allocate memory for a global.
464 uint8_t *allocateGlobal(uintptr_t Size, unsigned Alignment) override {
465 return (uint8_t*)DataAllocator.Allocate(Size, Alignment);
468 /// allocateCodeSection - Allocate memory for a code section.
469 uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment,
471 StringRef SectionName) override {
472 // Grow the required block size to account for the block header
473 Size += sizeof(*CurBlock);
475 // Alignment handling.
478 Size += Alignment - 1;
480 FreeRangeHeader* candidateBlock = FreeMemoryList;
481 FreeRangeHeader* head = FreeMemoryList;
482 FreeRangeHeader* iter = head->Next;
484 uintptr_t largest = candidateBlock->BlockSize;
486 // Search for the largest free block.
487 while (iter != head) {
488 if (iter->BlockSize > largest) {
489 largest = iter->BlockSize;
490 candidateBlock = iter;
495 largest = largest - sizeof(MemoryRangeHeader);
497 // If this block isn't big enough for the allocation desired, allocate
498 // another block of memory and add it to the free list.
499 if (largest < Size || largest <= FreeRangeHeader::getMinBlockSize()) {
500 DEBUG(dbgs() << "JIT: Allocating another slab of memory for function.");
501 candidateBlock = allocateNewCodeSlab((size_t)Size);
504 // Select this candidate block for allocation
505 CurBlock = candidateBlock;
507 // Allocate the entire memory block.
508 FreeMemoryList = candidateBlock->AllocateBlock();
509 // Release the memory at the end of this block that isn't needed.
510 FreeMemoryList = CurBlock->TrimAllocationToSize(FreeMemoryList, Size);
511 uintptr_t unalignedAddr = (uintptr_t)CurBlock + sizeof(*CurBlock);
512 return (uint8_t*)RoundUpToAlignment((uint64_t)unalignedAddr, Alignment);
515 /// allocateDataSection - Allocate memory for a data section.
516 uint8_t *allocateDataSection(uintptr_t Size, unsigned Alignment,
517 unsigned SectionID, StringRef SectionName,
518 bool IsReadOnly) override {
519 return (uint8_t*)DataAllocator.Allocate(Size, Alignment);
522 bool finalizeMemory(std::string *ErrMsg) override {
526 uint8_t *getGOTBase() const override {
530 void deallocateBlock(void *Block) {
531 // Find the block that is allocated for this function.
532 MemoryRangeHeader *MemRange = static_cast<MemoryRangeHeader*>(Block) - 1;
533 assert(MemRange->ThisAllocated && "Block isn't allocated!");
535 // Fill the buffer with garbage!
537 memset(MemRange+1, 0xCD, MemRange->BlockSize-sizeof(*MemRange));
541 FreeMemoryList = MemRange->FreeBlock(FreeMemoryList);
544 /// deallocateFunctionBody - Deallocate all memory for the specified
546 void deallocateFunctionBody(void *Body) override {
547 if (Body) deallocateBlock(Body);
550 /// setMemoryWritable - When code generation is in progress,
551 /// the code pages may need permissions changed.
552 void setMemoryWritable() override {
553 for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
554 sys::Memory::setWritable(CodeSlabs[i]);
556 /// setMemoryExecutable - When code generation is done and we're ready to
557 /// start execution, the code pages may need permissions changed.
558 void setMemoryExecutable() override {
559 for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
560 sys::Memory::setExecutable(CodeSlabs[i]);
563 /// setPoisonMemory - Controls whether we write garbage over freed memory.
565 void setPoisonMemory(bool poison) override {
566 PoisonMemory = poison;
571 MemSlab *JITSlabAllocator::Allocate(size_t Size) {
572 sys::MemoryBlock B = JMM.allocateNewSlab(Size);
573 MemSlab *Slab = (MemSlab*)B.base();
574 Slab->Size = B.size();
579 void JITSlabAllocator::Deallocate(MemSlab *Slab) {
580 sys::MemoryBlock B(Slab, Slab->Size);
581 sys::Memory::ReleaseRWX(B);
584 DefaultJITMemoryManager::DefaultJITMemoryManager()
592 BumpSlabAllocator(*this),
593 StubAllocator(BumpSlabAllocator),
594 DataAllocator(BumpSlabAllocator) {
596 // Allocate space for code.
597 sys::MemoryBlock MemBlock = allocateNewSlab(DefaultCodeSlabSize);
598 CodeSlabs.push_back(MemBlock);
599 uint8_t *MemBase = (uint8_t*)MemBlock.base();
601 // We set up the memory chunk with 4 mem regions, like this:
603 // [ Free #0 ] -> Large space to allocate functions from.
604 // [ Allocated #1 ] -> Tiny space to separate regions.
605 // [ Free #2 ] -> Tiny space so there is always at least 1 free block.
606 // [ Allocated #3 ] -> Tiny space to prevent looking past end of block.
609 // The last three blocks are never deallocated or touched.
611 // Add MemoryRangeHeader to the end of the memory region, indicating that
612 // the space after the block of memory is allocated. This is block #3.
613 MemoryRangeHeader *Mem3 = (MemoryRangeHeader*)(MemBase+MemBlock.size())-1;
614 Mem3->ThisAllocated = 1;
615 Mem3->PrevAllocated = 0;
616 Mem3->BlockSize = sizeof(MemoryRangeHeader);
618 /// Add a tiny free region so that the free list always has one entry.
619 FreeRangeHeader *Mem2 =
620 (FreeRangeHeader *)(((char*)Mem3)-FreeRangeHeader::getMinBlockSize());
621 Mem2->ThisAllocated = 0;
622 Mem2->PrevAllocated = 1;
623 Mem2->BlockSize = FreeRangeHeader::getMinBlockSize();
624 Mem2->SetEndOfBlockSizeMarker();
625 Mem2->Prev = Mem2; // Mem2 *is* the free list for now.
628 /// Add a tiny allocated region so that Mem2 is never coalesced away.
629 MemoryRangeHeader *Mem1 = (MemoryRangeHeader*)Mem2-1;
630 Mem1->ThisAllocated = 1;
631 Mem1->PrevAllocated = 0;
632 Mem1->BlockSize = sizeof(MemoryRangeHeader);
634 // Add a FreeRangeHeader to the start of the function body region, indicating
635 // that the space is free. Mark the previous block allocated so we never look
637 FreeRangeHeader *Mem0 = (FreeRangeHeader*)MemBase;
638 Mem0->ThisAllocated = 0;
639 Mem0->PrevAllocated = 1;
640 Mem0->BlockSize = (char*)Mem1-(char*)Mem0;
641 Mem0->SetEndOfBlockSizeMarker();
642 Mem0->AddToFreeList(Mem2);
644 // Start out with the freelist pointing to Mem0.
645 FreeMemoryList = Mem0;
650 void DefaultJITMemoryManager::AllocateGOT() {
651 assert(GOTBase == 0 && "Cannot allocate the got multiple times");
652 GOTBase = new uint8_t[sizeof(void*) * 8192];
656 DefaultJITMemoryManager::~DefaultJITMemoryManager() {
657 for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
658 sys::Memory::ReleaseRWX(CodeSlabs[i]);
663 sys::MemoryBlock DefaultJITMemoryManager::allocateNewSlab(size_t size) {
664 // Allocate a new block close to the last one.
666 sys::MemoryBlock *LastSlabPtr = LastSlab.base() ? &LastSlab : 0;
667 sys::MemoryBlock B = sys::Memory::AllocateRWX(size, LastSlabPtr, &ErrMsg);
669 report_fatal_error("Allocation failed when allocating new memory in the"
670 " JIT\n" + Twine(ErrMsg));
674 // Initialize the slab to garbage when debugging.
676 memset(B.base(), 0xCD, B.size());
681 /// CheckInvariants - For testing only. Return "" if all internal invariants
682 /// are preserved, and a helpful error message otherwise. For free and
683 /// allocated blocks, make sure that adding BlockSize gives a valid block.
684 /// For free blocks, make sure they're in the free list and that their end of
685 /// block size marker is correct. This function should return an error before
686 /// accessing bad memory. This function is defined here instead of in
687 /// JITMemoryManagerTest.cpp so that we don't have to expose all of the
688 /// implementation details of DefaultJITMemoryManager.
689 bool DefaultJITMemoryManager::CheckInvariants(std::string &ErrorStr) {
690 raw_string_ostream Err(ErrorStr);
692 // Construct a the set of FreeRangeHeader pointers so we can query it
694 llvm::SmallPtrSet<MemoryRangeHeader*, 16> FreeHdrSet;
695 FreeRangeHeader* FreeHead = FreeMemoryList;
696 FreeRangeHeader* FreeRange = FreeHead;
699 // Check that the free range pointer is in the blocks we've allocated.
701 for (std::vector<sys::MemoryBlock>::iterator I = CodeSlabs.begin(),
702 E = CodeSlabs.end(); I != E && !Found; ++I) {
703 char *Start = (char*)I->base();
704 char *End = Start + I->size();
705 Found = (Start <= (char*)FreeRange && (char*)FreeRange < End);
708 Err << "Corrupt free list; points to " << FreeRange;
712 if (FreeRange->Next->Prev != FreeRange) {
713 Err << "Next and Prev pointers do not match.";
717 // Otherwise, add it to the set.
718 FreeHdrSet.insert(FreeRange);
719 FreeRange = FreeRange->Next;
720 } while (FreeRange != FreeHead);
722 // Go over each block, and look at each MemoryRangeHeader.
723 for (std::vector<sys::MemoryBlock>::iterator I = CodeSlabs.begin(),
724 E = CodeSlabs.end(); I != E; ++I) {
725 char *Start = (char*)I->base();
726 char *End = Start + I->size();
728 // Check each memory range.
729 for (MemoryRangeHeader *Hdr = (MemoryRangeHeader*)Start, *LastHdr = NULL;
730 Start <= (char*)Hdr && (char*)Hdr < End;
731 Hdr = &Hdr->getBlockAfter()) {
732 if (Hdr->ThisAllocated == 0) {
733 // Check that this range is in the free list.
734 if (!FreeHdrSet.count(Hdr)) {
735 Err << "Found free header at " << Hdr << " that is not in free list.";
739 // Now make sure the size marker at the end of the block is correct.
740 uintptr_t *Marker = ((uintptr_t*)&Hdr->getBlockAfter()) - 1;
741 if (!(Start <= (char*)Marker && (char*)Marker < End)) {
742 Err << "Block size in header points out of current MemoryBlock.";
745 if (Hdr->BlockSize != *Marker) {
746 Err << "End of block size marker (" << *Marker << ") "
747 << "and BlockSize (" << Hdr->BlockSize << ") don't match.";
752 if (LastHdr && LastHdr->ThisAllocated != Hdr->PrevAllocated) {
753 Err << "Hdr->PrevAllocated (" << Hdr->PrevAllocated << ") != "
754 << "LastHdr->ThisAllocated (" << LastHdr->ThisAllocated << ")";
756 } else if (!LastHdr && !Hdr->PrevAllocated) {
757 Err << "The first header should have PrevAllocated true.";
761 // Remember the last header.
766 // All invariants are preserved.
770 //===----------------------------------------------------------------------===//
771 // getPointerToNamedFunction() implementation.
772 //===----------------------------------------------------------------------===//
774 // AtExitHandlers - List of functions to call when the program exits,
775 // registered with the atexit() library function.
776 static std::vector<void (*)()> AtExitHandlers;
778 /// runAtExitHandlers - Run any functions registered by the program's
779 /// calls to atexit(3), which we intercept and store in
782 static void runAtExitHandlers() {
783 while (!AtExitHandlers.empty()) {
784 void (*Fn)() = AtExitHandlers.back();
785 AtExitHandlers.pop_back();
790 //===----------------------------------------------------------------------===//
791 // Function stubs that are invoked instead of certain library calls
793 // Force the following functions to be linked in to anything that uses the
794 // JIT. This is a hack designed to work around the all-too-clever Glibc
795 // strategy of making these functions work differently when inlined vs. when
796 // not inlined, and hiding their real definitions in a separate archive file
797 // that the dynamic linker can't see. For more info, search for
798 // 'libc_nonshared.a' on Google, or read http://llvm.org/PR274.
799 #if defined(__linux__) && defined(__GLIBC__)
800 /* stat functions are redirecting to __xstat with a version number. On x86-64
801 * linking with libc_nonshared.a and -Wl,--export-dynamic doesn't make 'stat'
802 * available as an exported symbol, so we have to add it explicitly.
808 sys::DynamicLibrary::AddSymbol("stat", (void*)(intptr_t)stat);
809 sys::DynamicLibrary::AddSymbol("fstat", (void*)(intptr_t)fstat);
810 sys::DynamicLibrary::AddSymbol("lstat", (void*)(intptr_t)lstat);
811 sys::DynamicLibrary::AddSymbol("stat64", (void*)(intptr_t)stat64);
812 sys::DynamicLibrary::AddSymbol("\x1stat64", (void*)(intptr_t)stat64);
813 sys::DynamicLibrary::AddSymbol("\x1open64", (void*)(intptr_t)open64);
814 sys::DynamicLibrary::AddSymbol("\x1lseek64", (void*)(intptr_t)lseek64);
815 sys::DynamicLibrary::AddSymbol("fstat64", (void*)(intptr_t)fstat64);
816 sys::DynamicLibrary::AddSymbol("lstat64", (void*)(intptr_t)lstat64);
817 sys::DynamicLibrary::AddSymbol("atexit", (void*)(intptr_t)atexit);
818 sys::DynamicLibrary::AddSymbol("mknod", (void*)(intptr_t)mknod);
822 static StatSymbols initStatSymbols;
825 // jit_exit - Used to intercept the "exit" library call.
826 static void jit_exit(int Status) {
827 runAtExitHandlers(); // Run atexit handlers...
831 // jit_atexit - Used to intercept the "atexit" library call.
832 static int jit_atexit(void (*Fn)()) {
833 AtExitHandlers.push_back(Fn); // Take note of atexit handler...
834 return 0; // Always successful
837 static int jit_noop() {
841 //===----------------------------------------------------------------------===//
843 /// getPointerToNamedFunction - This method returns the address of the specified
844 /// function by using the dynamic loader interface. As such it is only useful
845 /// for resolving library symbols, not code generated symbols.
847 void *DefaultJITMemoryManager::getPointerToNamedFunction(const std::string &Name,
848 bool AbortOnFailure) {
849 // Check to see if this is one of the functions we want to intercept. Note,
850 // we cast to intptr_t here to silence a -pedantic warning that complains
851 // about casting a function pointer to a normal pointer.
852 if (Name == "exit") return (void*)(intptr_t)&jit_exit;
853 if (Name == "atexit") return (void*)(intptr_t)&jit_atexit;
855 // We should not invoke parent's ctors/dtors from generated main()!
856 // On Mingw and Cygwin, the symbol __main is resolved to
857 // callee's(eg. tools/lli) one, to invoke wrong duplicated ctors
858 // (and register wrong callee's dtors with atexit(3)).
859 // We expect ExecutionEngine::runStaticConstructorsDestructors()
860 // is called before ExecutionEngine::runFunctionAsMain() is called.
861 if (Name == "__main") return (void*)(intptr_t)&jit_noop;
863 const char *NameStr = Name.c_str();
864 // If this is an asm specifier, skip the sentinal.
865 if (NameStr[0] == 1) ++NameStr;
867 // If it's an external function, look it up in the process image...
868 void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr);
871 // If it wasn't found and if it starts with an underscore ('_') character,
872 // try again without the underscore.
873 if (NameStr[0] == '_') {
874 Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1);
878 // Darwin/PPC adds $LDBLStub suffixes to various symbols like printf. These
879 // are references to hidden visibility symbols that dlsym cannot resolve.
880 // If we have one of these, strip off $LDBLStub and try again.
881 #if defined(__APPLE__) && defined(__ppc__)
882 if (Name.size() > 9 && Name[Name.size()-9] == '$' &&
883 memcmp(&Name[Name.size()-8], "LDBLStub", 8) == 0) {
884 // First try turning $LDBLStub into $LDBL128. If that fails, strip it off.
885 // This mirrors logic in libSystemStubs.a.
886 std::string Prefix = std::string(Name.begin(), Name.end()-9);
887 if (void *Ptr = getPointerToNamedFunction(Prefix+"$LDBL128", false))
889 if (void *Ptr = getPointerToNamedFunction(Prefix, false))
894 if (AbortOnFailure) {
895 report_fatal_error("Program used external function '"+Name+
896 "' which could not be resolved!");
903 JITMemoryManager *JITMemoryManager::CreateDefaultMemManager() {
904 return new DefaultJITMemoryManager();
907 const size_t DefaultJITMemoryManager::DefaultCodeSlabSize;
908 const size_t DefaultJITMemoryManager::DefaultSlabSize;
909 const size_t DefaultJITMemoryManager::DefaultSizeThreshold;