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llvm-project/llvm/lib/ExecutionEngine/JIT/JITMemoryManager.cpp

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//===-- JITMemoryManager.cpp - Memory Allocator for JIT'd code ------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the DefaultJITMemoryManager class.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "jit"
#include "llvm/ExecutionEngine/JITMemoryManager.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Config/config.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/DynamicLibrary.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Memory.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <climits>
#include <cstring>
#include <vector>
#if defined(__linux__)
#if defined(HAVE_SYS_STAT_H)
#include <sys/stat.h>
#endif
#include <fcntl.h>
#include <unistd.h>
#endif
using namespace llvm;
STATISTIC(NumSlabs, "Number of slabs of memory allocated by the JIT");
JITMemoryManager::~JITMemoryManager() {}
//===----------------------------------------------------------------------===//
// Memory Block Implementation.
//===----------------------------------------------------------------------===//
namespace {
/// MemoryRangeHeader - For a range of memory, this is the header that we put
/// on the block of memory. It is carefully crafted to be one word of memory.
/// Allocated blocks have just this header, free'd blocks have FreeRangeHeader
/// which starts with this.
struct FreeRangeHeader;
struct MemoryRangeHeader {
/// ThisAllocated - This is true if this block is currently allocated. If
/// not, this can be converted to a FreeRangeHeader.
unsigned ThisAllocated : 1;
/// PrevAllocated - Keep track of whether the block immediately before us is
/// allocated. If not, the word immediately before this header is the size
/// of the previous block.
unsigned PrevAllocated : 1;
/// BlockSize - This is the size in bytes of this memory block,
/// including this header.
uintptr_t BlockSize : (sizeof(intptr_t)*CHAR_BIT - 2);
/// getBlockAfter - Return the memory block immediately after this one.
///
MemoryRangeHeader &getBlockAfter() const {
return *reinterpret_cast<MemoryRangeHeader *>(
reinterpret_cast<char*>(
const_cast<MemoryRangeHeader *>(this))+BlockSize);
}
/// getFreeBlockBefore - If the block before this one is free, return it,
/// otherwise return null.
FreeRangeHeader *getFreeBlockBefore() const {
if (PrevAllocated) return 0;
intptr_t PrevSize = reinterpret_cast<intptr_t *>(
const_cast<MemoryRangeHeader *>(this))[-1];
return reinterpret_cast<FreeRangeHeader *>(
reinterpret_cast<char*>(
const_cast<MemoryRangeHeader *>(this))-PrevSize);
}
/// FreeBlock - Turn an allocated block into a free block, adjusting
/// bits in the object headers, and adding an end of region memory block.
FreeRangeHeader *FreeBlock(FreeRangeHeader *FreeList);
/// TrimAllocationToSize - If this allocated block is significantly larger
/// than NewSize, split it into two pieces (where the former is NewSize
/// bytes, including the header), and add the new block to the free list.
FreeRangeHeader *TrimAllocationToSize(FreeRangeHeader *FreeList,
uint64_t NewSize);
};
/// FreeRangeHeader - For a memory block that isn't already allocated, this
/// keeps track of the current block and has a pointer to the next free block.
/// Free blocks are kept on a circularly linked list.
struct FreeRangeHeader : public MemoryRangeHeader {
FreeRangeHeader *Prev;
FreeRangeHeader *Next;
/// getMinBlockSize - Get the minimum size for a memory block. Blocks
/// smaller than this size cannot be created.
static unsigned getMinBlockSize() {
return sizeof(FreeRangeHeader)+sizeof(intptr_t);
}
/// SetEndOfBlockSizeMarker - The word at the end of every free block is
/// known to be the size of the free block. Set it for this block.
void SetEndOfBlockSizeMarker() {
void *EndOfBlock = (char*)this + BlockSize;
((intptr_t *)EndOfBlock)[-1] = BlockSize;
}
FreeRangeHeader *RemoveFromFreeList() {
assert(Next->Prev == this && Prev->Next == this && "Freelist broken!");
Next->Prev = Prev;
return Prev->Next = Next;
}
void AddToFreeList(FreeRangeHeader *FreeList) {
Next = FreeList;
Prev = FreeList->Prev;
Prev->Next = this;
Next->Prev = this;
}
/// GrowBlock - The block after this block just got deallocated. Merge it
/// into the current block.
void GrowBlock(uintptr_t NewSize);
/// AllocateBlock - Mark this entire block allocated, updating freelists
/// etc. This returns a pointer to the circular free-list.
FreeRangeHeader *AllocateBlock();
};
}
/// AllocateBlock - Mark this entire block allocated, updating freelists
/// etc. This returns a pointer to the circular free-list.
FreeRangeHeader *FreeRangeHeader::AllocateBlock() {
assert(!ThisAllocated && !getBlockAfter().PrevAllocated &&
"Cannot allocate an allocated block!");
// Mark this block allocated.
ThisAllocated = 1;
getBlockAfter().PrevAllocated = 1;
// Remove it from the free list.
return RemoveFromFreeList();
}
/// FreeBlock - Turn an allocated block into a free block, adjusting
/// bits in the object headers, and adding an end of region memory block.
/// If possible, coalesce this block with neighboring blocks. Return the
/// FreeRangeHeader to allocate from.
FreeRangeHeader *MemoryRangeHeader::FreeBlock(FreeRangeHeader *FreeList) {
MemoryRangeHeader *FollowingBlock = &getBlockAfter();
assert(ThisAllocated && "This block is already free!");
assert(FollowingBlock->PrevAllocated && "Flags out of sync!");
FreeRangeHeader *FreeListToReturn = FreeList;
// If the block after this one is free, merge it into this block.
if (!FollowingBlock->ThisAllocated) {
FreeRangeHeader &FollowingFreeBlock = *(FreeRangeHeader *)FollowingBlock;
// "FreeList" always needs to be a valid free block. If we're about to
// coalesce with it, update our notion of what the free list is.
if (&FollowingFreeBlock == FreeList) {
FreeList = FollowingFreeBlock.Next;
FreeListToReturn = 0;
assert(&FollowingFreeBlock != FreeList && "No tombstone block?");
}
FollowingFreeBlock.RemoveFromFreeList();
// Include the following block into this one.
BlockSize += FollowingFreeBlock.BlockSize;
FollowingBlock = &FollowingFreeBlock.getBlockAfter();
// Tell the block after the block we are coalescing that this block is
// allocated.
FollowingBlock->PrevAllocated = 1;
}
assert(FollowingBlock->ThisAllocated && "Missed coalescing?");
if (FreeRangeHeader *PrevFreeBlock = getFreeBlockBefore()) {
PrevFreeBlock->GrowBlock(PrevFreeBlock->BlockSize + BlockSize);
return FreeListToReturn ? FreeListToReturn : PrevFreeBlock;
}
// Otherwise, mark this block free.
FreeRangeHeader &FreeBlock = *(FreeRangeHeader*)this;
FollowingBlock->PrevAllocated = 0;
FreeBlock.ThisAllocated = 0;
// Link this into the linked list of free blocks.
FreeBlock.AddToFreeList(FreeList);
// Add a marker at the end of the block, indicating the size of this free
// block.
FreeBlock.SetEndOfBlockSizeMarker();
return FreeListToReturn ? FreeListToReturn : &FreeBlock;
}
/// GrowBlock - The block after this block just got deallocated. Merge it
/// into the current block.
void FreeRangeHeader::GrowBlock(uintptr_t NewSize) {
assert(NewSize > BlockSize && "Not growing block?");
BlockSize = NewSize;
SetEndOfBlockSizeMarker();
getBlockAfter().PrevAllocated = 0;
}
/// TrimAllocationToSize - If this allocated block is significantly larger
/// than NewSize, split it into two pieces (where the former is NewSize
/// bytes, including the header), and add the new block to the free list.
FreeRangeHeader *MemoryRangeHeader::
TrimAllocationToSize(FreeRangeHeader *FreeList, uint64_t NewSize) {
assert(ThisAllocated && getBlockAfter().PrevAllocated &&
"Cannot deallocate part of an allocated block!");
// Don't allow blocks to be trimmed below minimum required size
NewSize = std::max<uint64_t>(FreeRangeHeader::getMinBlockSize(), NewSize);
// Round up size for alignment of header.
unsigned HeaderAlign = __alignof(FreeRangeHeader);
NewSize = (NewSize+ (HeaderAlign-1)) & ~(HeaderAlign-1);
// Size is now the size of the block we will remove from the start of the
// current block.
assert(NewSize <= BlockSize &&
"Allocating more space from this block than exists!");
// If splitting this block will cause the remainder to be too small, do not
// split the block.
if (BlockSize <= NewSize+FreeRangeHeader::getMinBlockSize())
return FreeList;
// Otherwise, we splice the required number of bytes out of this block, form
// a new block immediately after it, then mark this block allocated.
MemoryRangeHeader &FormerNextBlock = getBlockAfter();
// Change the size of this block.
BlockSize = NewSize;
// Get the new block we just sliced out and turn it into a free block.
FreeRangeHeader &NewNextBlock = (FreeRangeHeader &)getBlockAfter();
NewNextBlock.BlockSize = (char*)&FormerNextBlock - (char*)&NewNextBlock;
NewNextBlock.ThisAllocated = 0;
NewNextBlock.PrevAllocated = 1;
NewNextBlock.SetEndOfBlockSizeMarker();
FormerNextBlock.PrevAllocated = 0;
NewNextBlock.AddToFreeList(FreeList);
return &NewNextBlock;
}
//===----------------------------------------------------------------------===//
// Memory Block Implementation.
//===----------------------------------------------------------------------===//
namespace {
class DefaultJITMemoryManager;
class JITSlabAllocator : public SlabAllocator {
DefaultJITMemoryManager &JMM;
public:
JITSlabAllocator(DefaultJITMemoryManager &jmm) : JMM(jmm) { }
virtual ~JITSlabAllocator() { }
MemSlab *Allocate(size_t Size) override;
void Deallocate(MemSlab *Slab) override;
};
/// DefaultJITMemoryManager - Manage memory for the JIT code generation.
/// This splits a large block of MAP_NORESERVE'd memory into two
/// sections, one for function stubs, one for the functions themselves. We
/// have to do this because we may need to emit a function stub while in the
/// middle of emitting a function, and we don't know how large the function we
/// are emitting is.
class DefaultJITMemoryManager : public JITMemoryManager {
public:
/// DefaultCodeSlabSize - When we have to go map more memory, we allocate at
/// least this much unless more is requested. Currently, in 512k slabs.
static const size_t DefaultCodeSlabSize = 512 * 1024;
/// DefaultSlabSize - Allocate globals and stubs into slabs of 64K (probably
/// 16 pages) unless we get an allocation above SizeThreshold.
static const size_t DefaultSlabSize = 64 * 1024;
/// DefaultSizeThreshold - For any allocation larger than 16K (probably
/// 4 pages), we should allocate a separate slab to avoid wasted space at
/// the end of a normal slab.
static const size_t DefaultSizeThreshold = 16 * 1024;
private:
// Whether to poison freed memory.
bool PoisonMemory;
/// LastSlab - This points to the last slab allocated and is used as the
/// NearBlock parameter to AllocateRWX so that we can attempt to lay out all
/// stubs, data, and code contiguously in memory. In general, however, this
/// is not possible because the NearBlock parameter is ignored on Windows
/// platforms and even on Unix it works on a best-effort pasis.
sys::MemoryBlock LastSlab;
// Memory slabs allocated by the JIT. We refer to them as slabs so we don't
// confuse them with the blocks of memory described above.
std::vector<sys::MemoryBlock> CodeSlabs;
JITSlabAllocator BumpSlabAllocator;
BumpPtrAllocator StubAllocator;
BumpPtrAllocator DataAllocator;
// Circular list of free blocks.
FreeRangeHeader *FreeMemoryList;
// When emitting code into a memory block, this is the block.
MemoryRangeHeader *CurBlock;
uint8_t *GOTBase; // Target Specific reserved memory
public:
DefaultJITMemoryManager();
~DefaultJITMemoryManager();
/// allocateNewSlab - Allocates a new MemoryBlock and remembers it as the
/// last slab it allocated, so that subsequent allocations follow it.
sys::MemoryBlock allocateNewSlab(size_t size);
/// getPointerToNamedFunction - This method returns the address of the
/// specified function by using the dlsym function call.
void *getPointerToNamedFunction(const std::string &Name,
bool AbortOnFailure = true) override;
void AllocateGOT() override;
// Testing methods.
bool CheckInvariants(std::string &ErrorStr) override;
size_t GetDefaultCodeSlabSize() override { return DefaultCodeSlabSize; }
size_t GetDefaultDataSlabSize() override { return DefaultSlabSize; }
size_t GetDefaultStubSlabSize() override { return DefaultSlabSize; }
unsigned GetNumCodeSlabs() override { return CodeSlabs.size(); }
unsigned GetNumDataSlabs() override { return DataAllocator.GetNumSlabs(); }
unsigned GetNumStubSlabs() override { return StubAllocator.GetNumSlabs(); }
/// startFunctionBody - When a function starts, allocate a block of free
/// executable memory, returning a pointer to it and its actual size.
uint8_t *startFunctionBody(const Function *F,
uintptr_t &ActualSize) override {
FreeRangeHeader* candidateBlock = FreeMemoryList;
FreeRangeHeader* head = FreeMemoryList;
FreeRangeHeader* iter = head->Next;
uintptr_t largest = candidateBlock->BlockSize;
// Search for the largest free block
while (iter != head) {
if (iter->BlockSize > largest) {
largest = iter->BlockSize;
candidateBlock = iter;
}
iter = iter->Next;
}
largest = largest - sizeof(MemoryRangeHeader);
// If this block isn't big enough for the allocation desired, allocate
// another block of memory and add it to the free list.
if (largest < ActualSize ||
largest <= FreeRangeHeader::getMinBlockSize()) {
DEBUG(dbgs() << "JIT: Allocating another slab of memory for function.");
candidateBlock = allocateNewCodeSlab((size_t)ActualSize);
}
// Select this candidate block for allocation
CurBlock = candidateBlock;
// Allocate the entire memory block.
FreeMemoryList = candidateBlock->AllocateBlock();
ActualSize = CurBlock->BlockSize - sizeof(MemoryRangeHeader);
return (uint8_t *)(CurBlock + 1);
}
/// allocateNewCodeSlab - Helper method to allocate a new slab of code
/// memory from the OS and add it to the free list. Returns the new
/// FreeRangeHeader at the base of the slab.
FreeRangeHeader *allocateNewCodeSlab(size_t MinSize) {
// If the user needs at least MinSize free memory, then we account for
// two MemoryRangeHeaders: the one in the user's block, and the one at the
// end of the slab.
size_t PaddedMin = MinSize + 2 * sizeof(MemoryRangeHeader);
size_t SlabSize = std::max(DefaultCodeSlabSize, PaddedMin);
sys::MemoryBlock B = allocateNewSlab(SlabSize);
CodeSlabs.push_back(B);
char *MemBase = (char*)(B.base());
// Put a tiny allocated block at the end of the memory chunk, so when
// FreeBlock calls getBlockAfter it doesn't fall off the end.
MemoryRangeHeader *EndBlock =
(MemoryRangeHeader*)(MemBase + B.size()) - 1;
EndBlock->ThisAllocated = 1;
EndBlock->PrevAllocated = 0;
EndBlock->BlockSize = sizeof(MemoryRangeHeader);
// Start out with a vast new block of free memory.
FreeRangeHeader *NewBlock = (FreeRangeHeader*)MemBase;
NewBlock->ThisAllocated = 0;
// Make sure getFreeBlockBefore doesn't look into unmapped memory.
NewBlock->PrevAllocated = 1;
NewBlock->BlockSize = (uintptr_t)EndBlock - (uintptr_t)NewBlock;
NewBlock->SetEndOfBlockSizeMarker();
NewBlock->AddToFreeList(FreeMemoryList);
assert(NewBlock->BlockSize - sizeof(MemoryRangeHeader) >= MinSize &&
"The block was too small!");
return NewBlock;
}
/// endFunctionBody - The function F is now allocated, and takes the memory
/// in the range [FunctionStart,FunctionEnd).
void endFunctionBody(const Function *F, uint8_t *FunctionStart,
uint8_t *FunctionEnd) override {
assert(FunctionEnd > FunctionStart);
assert(FunctionStart == (uint8_t *)(CurBlock+1) &&
"Mismatched function start/end!");
uintptr_t BlockSize = FunctionEnd - (uint8_t *)CurBlock;
// Release the memory at the end of this block that isn't needed.
FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize);
}
/// allocateSpace - Allocate a memory block of the given size. This method
/// cannot be called between calls to startFunctionBody and endFunctionBody.
uint8_t *allocateSpace(intptr_t Size, unsigned Alignment) override {
CurBlock = FreeMemoryList;
FreeMemoryList = FreeMemoryList->AllocateBlock();
uint8_t *result = (uint8_t *)(CurBlock + 1);
if (Alignment == 0) Alignment = 1;
result = (uint8_t*)(((intptr_t)result+Alignment-1) &
~(intptr_t)(Alignment-1));
uintptr_t BlockSize = result + Size - (uint8_t *)CurBlock;
FreeMemoryList =CurBlock->TrimAllocationToSize(FreeMemoryList, BlockSize);
return result;
}
/// allocateStub - Allocate memory for a function stub.
uint8_t *allocateStub(const GlobalValue* F, unsigned StubSize,
unsigned Alignment) override {
return (uint8_t*)StubAllocator.Allocate(StubSize, Alignment);
}
/// allocateGlobal - Allocate memory for a global.
uint8_t *allocateGlobal(uintptr_t Size, unsigned Alignment) override {
return (uint8_t*)DataAllocator.Allocate(Size, Alignment);
}
/// allocateCodeSection - Allocate memory for a code section.
uint8_t *allocateCodeSection(uintptr_t Size, unsigned Alignment,
unsigned SectionID,
StringRef SectionName) override {
// Grow the required block size to account for the block header
Size += sizeof(*CurBlock);
// Alignment handling.
if (!Alignment)
Alignment = 16;
Size += Alignment - 1;
FreeRangeHeader* candidateBlock = FreeMemoryList;
FreeRangeHeader* head = FreeMemoryList;
FreeRangeHeader* iter = head->Next;
uintptr_t largest = candidateBlock->BlockSize;
// Search for the largest free block.
while (iter != head) {
if (iter->BlockSize > largest) {
largest = iter->BlockSize;
candidateBlock = iter;
}
iter = iter->Next;
}
largest = largest - sizeof(MemoryRangeHeader);
// If this block isn't big enough for the allocation desired, allocate
// another block of memory and add it to the free list.
if (largest < Size || largest <= FreeRangeHeader::getMinBlockSize()) {
DEBUG(dbgs() << "JIT: Allocating another slab of memory for function.");
candidateBlock = allocateNewCodeSlab((size_t)Size);
}
// Select this candidate block for allocation
CurBlock = candidateBlock;
// Allocate the entire memory block.
FreeMemoryList = candidateBlock->AllocateBlock();
// Release the memory at the end of this block that isn't needed.
FreeMemoryList = CurBlock->TrimAllocationToSize(FreeMemoryList, Size);
uintptr_t unalignedAddr = (uintptr_t)CurBlock + sizeof(*CurBlock);
return (uint8_t*)RoundUpToAlignment((uint64_t)unalignedAddr, Alignment);
}
/// allocateDataSection - Allocate memory for a data section.
uint8_t *allocateDataSection(uintptr_t Size, unsigned Alignment,
unsigned SectionID, StringRef SectionName,
bool IsReadOnly) override {
return (uint8_t*)DataAllocator.Allocate(Size, Alignment);
}
bool finalizeMemory(std::string *ErrMsg) override {
return false;
}
uint8_t *getGOTBase() const override {
return GOTBase;
}
void deallocateBlock(void *Block) {
// Find the block that is allocated for this function.
MemoryRangeHeader *MemRange = static_cast<MemoryRangeHeader*>(Block) - 1;
assert(MemRange->ThisAllocated && "Block isn't allocated!");
// Fill the buffer with garbage!
if (PoisonMemory) {
memset(MemRange+1, 0xCD, MemRange->BlockSize-sizeof(*MemRange));
}
// Free the memory.
FreeMemoryList = MemRange->FreeBlock(FreeMemoryList);
}
/// deallocateFunctionBody - Deallocate all memory for the specified
/// function body.
void deallocateFunctionBody(void *Body) override {
if (Body) deallocateBlock(Body);
}
/// setMemoryWritable - When code generation is in progress,
/// the code pages may need permissions changed.
void setMemoryWritable() override {
for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
sys::Memory::setWritable(CodeSlabs[i]);
}
/// setMemoryExecutable - When code generation is done and we're ready to
/// start execution, the code pages may need permissions changed.
void setMemoryExecutable() override {
for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
sys::Memory::setExecutable(CodeSlabs[i]);
}
/// setPoisonMemory - Controls whether we write garbage over freed memory.
///
void setPoisonMemory(bool poison) override {
PoisonMemory = poison;
}
};
}
MemSlab *JITSlabAllocator::Allocate(size_t Size) {
sys::MemoryBlock B = JMM.allocateNewSlab(Size);
MemSlab *Slab = (MemSlab*)B.base();
Slab->Size = B.size();
Slab->NextPtr = 0;
return Slab;
}
void JITSlabAllocator::Deallocate(MemSlab *Slab) {
sys::MemoryBlock B(Slab, Slab->Size);
sys::Memory::ReleaseRWX(B);
}
DefaultJITMemoryManager::DefaultJITMemoryManager()
:
#ifdef NDEBUG
PoisonMemory(false),
#else
PoisonMemory(true),
#endif
LastSlab(0, 0),
BumpSlabAllocator(*this),
StubAllocator(DefaultSlabSize, DefaultSizeThreshold, BumpSlabAllocator),
DataAllocator(DefaultSlabSize, DefaultSizeThreshold, BumpSlabAllocator) {
// Allocate space for code.
sys::MemoryBlock MemBlock = allocateNewSlab(DefaultCodeSlabSize);
CodeSlabs.push_back(MemBlock);
uint8_t *MemBase = (uint8_t*)MemBlock.base();
// We set up the memory chunk with 4 mem regions, like this:
// [ START
// [ Free #0 ] -> Large space to allocate functions from.
// [ Allocated #1 ] -> Tiny space to separate regions.
// [ Free #2 ] -> Tiny space so there is always at least 1 free block.
// [ Allocated #3 ] -> Tiny space to prevent looking past end of block.
// END ]
//
// The last three blocks are never deallocated or touched.
// Add MemoryRangeHeader to the end of the memory region, indicating that
// the space after the block of memory is allocated. This is block #3.
MemoryRangeHeader *Mem3 = (MemoryRangeHeader*)(MemBase+MemBlock.size())-1;
Mem3->ThisAllocated = 1;
Mem3->PrevAllocated = 0;
Mem3->BlockSize = sizeof(MemoryRangeHeader);
/// Add a tiny free region so that the free list always has one entry.
FreeRangeHeader *Mem2 =
(FreeRangeHeader *)(((char*)Mem3)-FreeRangeHeader::getMinBlockSize());
Mem2->ThisAllocated = 0;
Mem2->PrevAllocated = 1;
Mem2->BlockSize = FreeRangeHeader::getMinBlockSize();
Mem2->SetEndOfBlockSizeMarker();
Mem2->Prev = Mem2; // Mem2 *is* the free list for now.
Mem2->Next = Mem2;
/// Add a tiny allocated region so that Mem2 is never coalesced away.
MemoryRangeHeader *Mem1 = (MemoryRangeHeader*)Mem2-1;
Mem1->ThisAllocated = 1;
Mem1->PrevAllocated = 0;
Mem1->BlockSize = sizeof(MemoryRangeHeader);
// Add a FreeRangeHeader to the start of the function body region, indicating
// that the space is free. Mark the previous block allocated so we never look
// at it.
FreeRangeHeader *Mem0 = (FreeRangeHeader*)MemBase;
Mem0->ThisAllocated = 0;
Mem0->PrevAllocated = 1;
Mem0->BlockSize = (char*)Mem1-(char*)Mem0;
Mem0->SetEndOfBlockSizeMarker();
Mem0->AddToFreeList(Mem2);
// Start out with the freelist pointing to Mem0.
FreeMemoryList = Mem0;
GOTBase = NULL;
}
void DefaultJITMemoryManager::AllocateGOT() {
assert(GOTBase == 0 && "Cannot allocate the got multiple times");
GOTBase = new uint8_t[sizeof(void*) * 8192];
HasGOT = true;
}
DefaultJITMemoryManager::~DefaultJITMemoryManager() {
for (unsigned i = 0, e = CodeSlabs.size(); i != e; ++i)
sys::Memory::ReleaseRWX(CodeSlabs[i]);
delete[] GOTBase;
}
sys::MemoryBlock DefaultJITMemoryManager::allocateNewSlab(size_t size) {
// Allocate a new block close to the last one.
std::string ErrMsg;
sys::MemoryBlock *LastSlabPtr = LastSlab.base() ? &LastSlab : 0;
sys::MemoryBlock B = sys::Memory::AllocateRWX(size, LastSlabPtr, &ErrMsg);
if (B.base() == 0) {
report_fatal_error("Allocation failed when allocating new memory in the"
" JIT\n" + Twine(ErrMsg));
}
LastSlab = B;
++NumSlabs;
// Initialize the slab to garbage when debugging.
if (PoisonMemory) {
memset(B.base(), 0xCD, B.size());
}
return B;
}
/// CheckInvariants - For testing only. Return "" if all internal invariants
/// are preserved, and a helpful error message otherwise. For free and
/// allocated blocks, make sure that adding BlockSize gives a valid block.
/// For free blocks, make sure they're in the free list and that their end of
/// block size marker is correct. This function should return an error before
/// accessing bad memory. This function is defined here instead of in
/// JITMemoryManagerTest.cpp so that we don't have to expose all of the
/// implementation details of DefaultJITMemoryManager.
bool DefaultJITMemoryManager::CheckInvariants(std::string &ErrorStr) {
raw_string_ostream Err(ErrorStr);
// Construct a the set of FreeRangeHeader pointers so we can query it
// efficiently.
llvm::SmallPtrSet<MemoryRangeHeader*, 16> FreeHdrSet;
FreeRangeHeader* FreeHead = FreeMemoryList;
FreeRangeHeader* FreeRange = FreeHead;
do {
// Check that the free range pointer is in the blocks we've allocated.
bool Found = false;
for (std::vector<sys::MemoryBlock>::iterator I = CodeSlabs.begin(),
E = CodeSlabs.end(); I != E && !Found; ++I) {
char *Start = (char*)I->base();
char *End = Start + I->size();
Found = (Start <= (char*)FreeRange && (char*)FreeRange < End);
}
if (!Found) {
Err << "Corrupt free list; points to " << FreeRange;
return false;
}
if (FreeRange->Next->Prev != FreeRange) {
Err << "Next and Prev pointers do not match.";
return false;
}
// Otherwise, add it to the set.
FreeHdrSet.insert(FreeRange);
FreeRange = FreeRange->Next;
} while (FreeRange != FreeHead);
// Go over each block, and look at each MemoryRangeHeader.
for (std::vector<sys::MemoryBlock>::iterator I = CodeSlabs.begin(),
E = CodeSlabs.end(); I != E; ++I) {
char *Start = (char*)I->base();
char *End = Start + I->size();
// Check each memory range.
for (MemoryRangeHeader *Hdr = (MemoryRangeHeader*)Start, *LastHdr = NULL;
Start <= (char*)Hdr && (char*)Hdr < End;
Hdr = &Hdr->getBlockAfter()) {
if (Hdr->ThisAllocated == 0) {
// Check that this range is in the free list.
if (!FreeHdrSet.count(Hdr)) {
Err << "Found free header at " << Hdr << " that is not in free list.";
return false;
}
// Now make sure the size marker at the end of the block is correct.
uintptr_t *Marker = ((uintptr_t*)&Hdr->getBlockAfter()) - 1;
if (!(Start <= (char*)Marker && (char*)Marker < End)) {
Err << "Block size in header points out of current MemoryBlock.";
return false;
}
if (Hdr->BlockSize != *Marker) {
Err << "End of block size marker (" << *Marker << ") "
<< "and BlockSize (" << Hdr->BlockSize << ") don't match.";
return false;
}
}
if (LastHdr && LastHdr->ThisAllocated != Hdr->PrevAllocated) {
Err << "Hdr->PrevAllocated (" << Hdr->PrevAllocated << ") != "
<< "LastHdr->ThisAllocated (" << LastHdr->ThisAllocated << ")";
return false;
} else if (!LastHdr && !Hdr->PrevAllocated) {
Err << "The first header should have PrevAllocated true.";
return false;
}
// Remember the last header.
LastHdr = Hdr;
}
}
// All invariants are preserved.
return true;
}
//===----------------------------------------------------------------------===//
// getPointerToNamedFunction() implementation.
//===----------------------------------------------------------------------===//
// AtExitHandlers - List of functions to call when the program exits,
// registered with the atexit() library function.
static std::vector<void (*)()> AtExitHandlers;
/// runAtExitHandlers - Run any functions registered by the program's
/// calls to atexit(3), which we intercept and store in
/// AtExitHandlers.
///
static void runAtExitHandlers() {
while (!AtExitHandlers.empty()) {
void (*Fn)() = AtExitHandlers.back();
AtExitHandlers.pop_back();
Fn();
}
}
//===----------------------------------------------------------------------===//
// Function stubs that are invoked instead of certain library calls
//
// Force the following functions to be linked in to anything that uses the
// JIT. This is a hack designed to work around the all-too-clever Glibc
// strategy of making these functions work differently when inlined vs. when
// not inlined, and hiding their real definitions in a separate archive file
// that the dynamic linker can't see. For more info, search for
// 'libc_nonshared.a' on Google, or read http://llvm.org/PR274.
#if defined(__linux__) && defined(__GLIBC__)
/* stat functions are redirecting to __xstat with a version number. On x86-64
* linking with libc_nonshared.a and -Wl,--export-dynamic doesn't make 'stat'
* available as an exported symbol, so we have to add it explicitly.
*/
namespace {
class StatSymbols {
public:
StatSymbols() {
sys::DynamicLibrary::AddSymbol("stat", (void*)(intptr_t)stat);
sys::DynamicLibrary::AddSymbol("fstat", (void*)(intptr_t)fstat);
sys::DynamicLibrary::AddSymbol("lstat", (void*)(intptr_t)lstat);
sys::DynamicLibrary::AddSymbol("stat64", (void*)(intptr_t)stat64);
sys::DynamicLibrary::AddSymbol("\x1stat64", (void*)(intptr_t)stat64);
sys::DynamicLibrary::AddSymbol("\x1open64", (void*)(intptr_t)open64);
sys::DynamicLibrary::AddSymbol("\x1lseek64", (void*)(intptr_t)lseek64);
sys::DynamicLibrary::AddSymbol("fstat64", (void*)(intptr_t)fstat64);
sys::DynamicLibrary::AddSymbol("lstat64", (void*)(intptr_t)lstat64);
sys::DynamicLibrary::AddSymbol("atexit", (void*)(intptr_t)atexit);
sys::DynamicLibrary::AddSymbol("mknod", (void*)(intptr_t)mknod);
}
};
}
static StatSymbols initStatSymbols;
#endif // __linux__
// jit_exit - Used to intercept the "exit" library call.
static void jit_exit(int Status) {
runAtExitHandlers(); // Run atexit handlers...
exit(Status);
}
// jit_atexit - Used to intercept the "atexit" library call.
static int jit_atexit(void (*Fn)()) {
AtExitHandlers.push_back(Fn); // Take note of atexit handler...
return 0; // Always successful
}
static int jit_noop() {
return 0;
}
//===----------------------------------------------------------------------===//
//
/// getPointerToNamedFunction - This method returns the address of the specified
/// function by using the dynamic loader interface. As such it is only useful
/// for resolving library symbols, not code generated symbols.
///
void *DefaultJITMemoryManager::getPointerToNamedFunction(const std::string &Name,
bool AbortOnFailure) {
// Check to see if this is one of the functions we want to intercept. Note,
// we cast to intptr_t here to silence a -pedantic warning that complains
// about casting a function pointer to a normal pointer.
if (Name == "exit") return (void*)(intptr_t)&jit_exit;
if (Name == "atexit") return (void*)(intptr_t)&jit_atexit;
// We should not invoke parent's ctors/dtors from generated main()!
// On Mingw and Cygwin, the symbol __main is resolved to
// callee's(eg. tools/lli) one, to invoke wrong duplicated ctors
// (and register wrong callee's dtors with atexit(3)).
// We expect ExecutionEngine::runStaticConstructorsDestructors()
// is called before ExecutionEngine::runFunctionAsMain() is called.
if (Name == "__main") return (void*)(intptr_t)&jit_noop;
const char *NameStr = Name.c_str();
// If this is an asm specifier, skip the sentinal.
if (NameStr[0] == 1) ++NameStr;
// If it's an external function, look it up in the process image...
void *Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr);
if (Ptr) return Ptr;
// If it wasn't found and if it starts with an underscore ('_') character,
// try again without the underscore.
if (NameStr[0] == '_') {
Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(NameStr+1);
if (Ptr) return Ptr;
}
// Darwin/PPC adds $LDBLStub suffixes to various symbols like printf. These
// are references to hidden visibility symbols that dlsym cannot resolve.
// If we have one of these, strip off $LDBLStub and try again.
#if defined(__APPLE__) && defined(__ppc__)
if (Name.size() > 9 && Name[Name.size()-9] == '$' &&
memcmp(&Name[Name.size()-8], "LDBLStub", 8) == 0) {
// First try turning $LDBLStub into $LDBL128. If that fails, strip it off.
// This mirrors logic in libSystemStubs.a.
std::string Prefix = std::string(Name.begin(), Name.end()-9);
if (void *Ptr = getPointerToNamedFunction(Prefix+"$LDBL128", false))
return Ptr;
if (void *Ptr = getPointerToNamedFunction(Prefix, false))
return Ptr;
}
#endif
if (AbortOnFailure) {
report_fatal_error("Program used external function '"+Name+
"' which could not be resolved!");
}
return 0;
}
JITMemoryManager *JITMemoryManager::CreateDefaultMemManager() {
return new DefaultJITMemoryManager();
}
const size_t DefaultJITMemoryManager::DefaultCodeSlabSize;
const size_t DefaultJITMemoryManager::DefaultSlabSize;
const size_t DefaultJITMemoryManager::DefaultSizeThreshold;
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