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llvm-6502/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
Keno Fischer 4edb309c27 [RuntimeDyldELF] Improve GOT support 
Summary:
This is the first in a series of patches to eventually add support for TLS relocations to RuntimeDyld. This patch resolves an issue in the current GOT handling, where GOT entries would be reused between object files, which leads to the same situation that necessitates the GOT in the first place, i.e. that the 32-bit offset can not cover all of the address space. Thus this patch makes the GOT object-file-local.
Unfortunately, this still isn't quite enough, because the MemoryManager does not yet guarantee that sections are allocated sufficiently close to each other, even if they belong to the same object file. To address this concern, this patch also adds a small API abstraction on top of the GOT allocation mechanism that will allow (temporarily, until the MemoryManager is improved) using the stub mechanism instead of allocating a different section. The actual switch from separate section to stub mechanism will be part of a follow-on commit, so that it can be easily reverted independently at the appropriate time.

Test Plan: Includes a test case where the GOT of two object files is artificially forced to be apart by several GB.

Reviewers: lhames

Reviewed By: lhames

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8813

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234839 91177308-0d34-0410-b5e6-96231b3b80d8
2015-04-14 02:10:35 +00:00

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//===-- RuntimeDyld.cpp - Run-time dynamic linker for MC-JIT ----*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Implementation of the MC-JIT runtime dynamic linker.
//
//===----------------------------------------------------------------------===//
#include "llvm/ExecutionEngine/RuntimeDyld.h"
#include "RuntimeDyldCheckerImpl.h"
#include "RuntimeDyldCOFF.h"
#include "RuntimeDyldELF.h"
#include "RuntimeDyldImpl.h"
#include "RuntimeDyldMachO.h"
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/Object/COFF.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/MutexGuard.h"
using namespace llvm;
using namespace llvm::object;
#define DEBUG_TYPE "dyld"
// Empty out-of-line virtual destructor as the key function.
RuntimeDyldImpl::~RuntimeDyldImpl() {}
// Pin LoadedObjectInfo's vtables to this file.
void RuntimeDyld::LoadedObjectInfo::anchor() {}
namespace llvm {
void RuntimeDyldImpl::registerEHFrames() {}
void RuntimeDyldImpl::deregisterEHFrames() {}
#ifndef NDEBUG
static void dumpSectionMemory(const SectionEntry &S, StringRef State) {
dbgs() << "----- Contents of section " << S.Name << " " << State << " -----";
if (S.Address == nullptr) {
dbgs() << "\n <section not emitted>\n";
return;
}
const unsigned ColsPerRow = 16;
uint8_t *DataAddr = S.Address;
uint64_t LoadAddr = S.LoadAddress;
unsigned StartPadding = LoadAddr & (ColsPerRow - 1);
unsigned BytesRemaining = S.Size;
if (StartPadding) {
dbgs() << "\n" << format("0x%016" PRIx64,
LoadAddr & ~(uint64_t)(ColsPerRow - 1)) << ":";
while (StartPadding--)
dbgs() << " ";
}
while (BytesRemaining > 0) {
if ((LoadAddr & (ColsPerRow - 1)) == 0)
dbgs() << "\n" << format("0x%016" PRIx64, LoadAddr) << ":";
dbgs() << " " << format("%02x", *DataAddr);
++DataAddr;
++LoadAddr;
--BytesRemaining;
}
dbgs() << "\n";
}
#endif
// Resolve the relocations for all symbols we currently know about.
void RuntimeDyldImpl::resolveRelocations() {
MutexGuard locked(lock);
// First, resolve relocations associated with external symbols.
resolveExternalSymbols();
// Just iterate over the sections we have and resolve all the relocations
// in them. Gross overkill, but it gets the job done.
for (int i = 0, e = Sections.size(); i != e; ++i) {
// The Section here (Sections[i]) refers to the section in which the
// symbol for the relocation is located. The SectionID in the relocation
// entry provides the section to which the relocation will be applied.
uint64_t Addr = Sections[i].LoadAddress;
DEBUG(dbgs() << "Resolving relocations Section #" << i << "\t"
<< format("%p", (uintptr_t)Addr) << "\n");
DEBUG(dumpSectionMemory(Sections[i], "before relocations"));
resolveRelocationList(Relocations[i], Addr);
DEBUG(dumpSectionMemory(Sections[i], "after relocations"));
Relocations.erase(i);
}
}
void RuntimeDyldImpl::mapSectionAddress(const void *LocalAddress,
uint64_t TargetAddress) {
MutexGuard locked(lock);
for (unsigned i = 0, e = Sections.size(); i != e; ++i) {
if (Sections[i].Address == LocalAddress) {
reassignSectionAddress(i, TargetAddress);
return;
}
}
llvm_unreachable("Attempting to remap address of unknown section!");
}
static std::error_code getOffset(const SymbolRef &Sym, uint64_t &Result) {
uint64_t Address;
if (std::error_code EC = Sym.getAddress(Address))
return EC;
if (Address == UnknownAddressOrSize) {
Result = UnknownAddressOrSize;
return object_error::success;
}
const ObjectFile *Obj = Sym.getObject();
section_iterator SecI(Obj->section_begin());
if (std::error_code EC = Sym.getSection(SecI))
return EC;
if (SecI == Obj->section_end()) {
Result = UnknownAddressOrSize;
return object_error::success;
}
uint64_t SectionAddress = SecI->getAddress();
Result = Address - SectionAddress;
return object_error::success;
}
std::pair<unsigned, unsigned>
RuntimeDyldImpl::loadObjectImpl(const object::ObjectFile &Obj) {
MutexGuard locked(lock);
// Grab the first Section ID. We'll use this later to construct the underlying
// range for the returned LoadedObjectInfo.
unsigned SectionsAddedBeginIdx = Sections.size();
// Save information about our target
Arch = (Triple::ArchType)Obj.getArch();
IsTargetLittleEndian = Obj.isLittleEndian();
// Compute the memory size required to load all sections to be loaded
// and pass this information to the memory manager
if (MemMgr.needsToReserveAllocationSpace()) {
uint64_t CodeSize = 0, DataSizeRO = 0, DataSizeRW = 0;
computeTotalAllocSize(Obj, CodeSize, DataSizeRO, DataSizeRW);
MemMgr.reserveAllocationSpace(CodeSize, DataSizeRO, DataSizeRW);
}
// Used sections from the object file
ObjSectionToIDMap LocalSections;
// Common symbols requiring allocation, with their sizes and alignments
CommonSymbolList CommonSymbols;
// Parse symbols
DEBUG(dbgs() << "Parse symbols:\n");
for (symbol_iterator I = Obj.symbol_begin(), E = Obj.symbol_end(); I != E;
++I) {
uint32_t Flags = I->getFlags();
bool IsCommon = Flags & SymbolRef::SF_Common;
if (IsCommon)
CommonSymbols.push_back(*I);
else {
object::SymbolRef::Type SymType;
Check(I->getType(SymType));
if (SymType == object::SymbolRef::ST_Function ||
SymType == object::SymbolRef::ST_Data ||
SymType == object::SymbolRef::ST_Unknown) {
StringRef Name;
uint64_t SectOffset;
Check(I->getName(Name));
Check(getOffset(*I, SectOffset));
section_iterator SI = Obj.section_end();
Check(I->getSection(SI));
if (SI == Obj.section_end())
continue;
StringRef SectionData;
Check(SI->getContents(SectionData));
bool IsCode = SI->isText();
unsigned SectionID =
findOrEmitSection(Obj, *SI, IsCode, LocalSections);
DEBUG(dbgs() << "\tType: " << SymType << " Name: " << Name
<< " SID: " << SectionID << " Offset: "
<< format("%p", (uintptr_t)SectOffset)
<< " flags: " << Flags << "\n");
JITSymbolFlags RTDyldSymFlags = JITSymbolFlags::None;
if (Flags & SymbolRef::SF_Weak)
RTDyldSymFlags |= JITSymbolFlags::Weak;
if (Flags & SymbolRef::SF_Exported)
RTDyldSymFlags |= JITSymbolFlags::Exported;
GlobalSymbolTable[Name] =
SymbolTableEntry(SectionID, SectOffset, RTDyldSymFlags);
}
}
}
// Allocate common symbols
emitCommonSymbols(Obj, CommonSymbols);
// Parse and process relocations
DEBUG(dbgs() << "Parse relocations:\n");
for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
SI != SE; ++SI) {
unsigned SectionID = 0;
StubMap Stubs;
section_iterator RelocatedSection = SI->getRelocatedSection();
if (RelocatedSection == SE)
continue;
relocation_iterator I = SI->relocation_begin();
relocation_iterator E = SI->relocation_end();
if (I == E && !ProcessAllSections)
continue;
bool IsCode = RelocatedSection->isText();
SectionID =
findOrEmitSection(Obj, *RelocatedSection, IsCode, LocalSections);
DEBUG(dbgs() << "\tSectionID: " << SectionID << "\n");
for (; I != E;)
I = processRelocationRef(SectionID, I, Obj, LocalSections, Stubs);
// If there is an attached checker, notify it about the stubs for this
// section so that they can be verified.
if (Checker)
Checker->registerStubMap(Obj.getFileName(), SectionID, Stubs);
}
// Give the subclasses a chance to tie-up any loose ends.
finalizeLoad(Obj, LocalSections);
unsigned SectionsAddedEndIdx = Sections.size();
return std::make_pair(SectionsAddedBeginIdx, SectionsAddedEndIdx);
}
// A helper method for computeTotalAllocSize.
// Computes the memory size required to allocate sections with the given sizes,
// assuming that all sections are allocated with the given alignment
static uint64_t
computeAllocationSizeForSections(std::vector<uint64_t> &SectionSizes,
uint64_t Alignment) {
uint64_t TotalSize = 0;
for (size_t Idx = 0, Cnt = SectionSizes.size(); Idx < Cnt; Idx++) {
uint64_t AlignedSize =
(SectionSizes[Idx] + Alignment - 1) / Alignment * Alignment;
TotalSize += AlignedSize;
}
return TotalSize;
}
static bool isRequiredForExecution(const SectionRef &Section) {
const ObjectFile *Obj = Section.getObject();
if (auto *ELFObj = dyn_cast<object::ELFObjectFileBase>(Obj))
return ELFObj->getSectionFlags(Section) & ELF::SHF_ALLOC;
if (auto *COFFObj = dyn_cast<object::COFFObjectFile>(Obj)) {
const coff_section *CoffSection = COFFObj->getCOFFSection(Section);
// Avoid loading zero-sized COFF sections.
// In PE files, VirtualSize gives the section size, and SizeOfRawData
// may be zero for sections with content. In Obj files, SizeOfRawData
// gives the section size, and VirtualSize is always zero. Hence
// the need to check for both cases below.
bool HasContent = (CoffSection->VirtualSize > 0)
|| (CoffSection->SizeOfRawData > 0);
bool IsDiscardable = CoffSection->Characteristics &
(COFF::IMAGE_SCN_MEM_DISCARDABLE | COFF::IMAGE_SCN_LNK_INFO);
return HasContent && !IsDiscardable;
}
assert(isa<MachOObjectFile>(Obj));
return true;
}
static bool isReadOnlyData(const SectionRef &Section) {
const ObjectFile *Obj = Section.getObject();
if (auto *ELFObj = dyn_cast<object::ELFObjectFileBase>(Obj))
return !(ELFObj->getSectionFlags(Section) &
(ELF::SHF_WRITE | ELF::SHF_EXECINSTR));
if (auto *COFFObj = dyn_cast<object::COFFObjectFile>(Obj))
return ((COFFObj->getCOFFSection(Section)->Characteristics &
(COFF::IMAGE_SCN_CNT_INITIALIZED_DATA
| COFF::IMAGE_SCN_MEM_READ
| COFF::IMAGE_SCN_MEM_WRITE))
==
(COFF::IMAGE_SCN_CNT_INITIALIZED_DATA
| COFF::IMAGE_SCN_MEM_READ));
assert(isa<MachOObjectFile>(Obj));
return false;
}
static bool isZeroInit(const SectionRef &Section) {
const ObjectFile *Obj = Section.getObject();
if (auto *ELFObj = dyn_cast<object::ELFObjectFileBase>(Obj))
return ELFObj->getSectionType(Section) == ELF::SHT_NOBITS;
if (auto *COFFObj = dyn_cast<object::COFFObjectFile>(Obj))
return COFFObj->getCOFFSection(Section)->Characteristics &
COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA;
auto *MachO = cast<MachOObjectFile>(Obj);
unsigned SectionType = MachO->getSectionType(Section);
return SectionType == MachO::S_ZEROFILL ||
SectionType == MachO::S_GB_ZEROFILL;
}
// Compute an upper bound of the memory size that is required to load all
// sections
void RuntimeDyldImpl::computeTotalAllocSize(const ObjectFile &Obj,
uint64_t &CodeSize,
uint64_t &DataSizeRO,
uint64_t &DataSizeRW) {
// Compute the size of all sections required for execution
std::vector<uint64_t> CodeSectionSizes;
std::vector<uint64_t> ROSectionSizes;
std::vector<uint64_t> RWSectionSizes;
uint64_t MaxAlignment = sizeof(void *);
// Collect sizes of all sections to be loaded;
// also determine the max alignment of all sections
for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
SI != SE; ++SI) {
const SectionRef &Section = *SI;
bool IsRequired = isRequiredForExecution(Section);
// Consider only the sections that are required to be loaded for execution
if (IsRequired) {
StringRef Name;
uint64_t DataSize = Section.getSize();
uint64_t Alignment64 = Section.getAlignment();
bool IsCode = Section.isText();
bool IsReadOnly = isReadOnlyData(Section);
Check(Section.getName(Name));
unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
uint64_t StubBufSize = computeSectionStubBufSize(Obj, Section);
uint64_t SectionSize = DataSize + StubBufSize;
// The .eh_frame section (at least on Linux) needs an extra four bytes
// padded
// with zeroes added at the end. For MachO objects, this section has a
// slightly different name, so this won't have any effect for MachO
// objects.
if (Name == ".eh_frame")
SectionSize += 4;
if (!SectionSize)
SectionSize = 1;
if (IsCode) {
CodeSectionSizes.push_back(SectionSize);
} else if (IsReadOnly) {
ROSectionSizes.push_back(SectionSize);
} else {
RWSectionSizes.push_back(SectionSize);
}
// update the max alignment
if (Alignment > MaxAlignment) {
MaxAlignment = Alignment;
}
}
}
// Compute the size of all common symbols
uint64_t CommonSize = 0;
for (symbol_iterator I = Obj.symbol_begin(), E = Obj.symbol_end(); I != E;
++I) {
uint32_t Flags = I->getFlags();
if (Flags & SymbolRef::SF_Common) {
// Add the common symbols to a list. We'll allocate them all below.
uint64_t Size = 0;
Check(I->getSize(Size));
CommonSize += Size;
}
}
if (CommonSize != 0) {
RWSectionSizes.push_back(CommonSize);
}
// Compute the required allocation space for each different type of sections
// (code, read-only data, read-write data) assuming that all sections are
// allocated with the max alignment. Note that we cannot compute with the
// individual alignments of the sections, because then the required size
// depends on the order, in which the sections are allocated.
CodeSize = computeAllocationSizeForSections(CodeSectionSizes, MaxAlignment);
DataSizeRO = computeAllocationSizeForSections(ROSectionSizes, MaxAlignment);
DataSizeRW = computeAllocationSizeForSections(RWSectionSizes, MaxAlignment);
}
// compute stub buffer size for the given section
unsigned RuntimeDyldImpl::computeSectionStubBufSize(const ObjectFile &Obj,
const SectionRef &Section) {
unsigned StubSize = getMaxStubSize();
if (StubSize == 0) {
return 0;
}
// FIXME: this is an inefficient way to handle this. We should computed the
// necessary section allocation size in loadObject by walking all the sections
// once.
unsigned StubBufSize = 0;
for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
SI != SE; ++SI) {
section_iterator RelSecI = SI->getRelocatedSection();
if (!(RelSecI == Section))
continue;
for (const RelocationRef &Reloc : SI->relocations()) {
(void)Reloc;
StubBufSize += StubSize;
}
}
// Get section data size and alignment
uint64_t DataSize = Section.getSize();
uint64_t Alignment64 = Section.getAlignment();
// Add stubbuf size alignment
unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
unsigned StubAlignment = getStubAlignment();
unsigned EndAlignment = (DataSize | Alignment) & -(DataSize | Alignment);
if (StubAlignment > EndAlignment)
StubBufSize += StubAlignment - EndAlignment;
return StubBufSize;
}
uint64_t RuntimeDyldImpl::readBytesUnaligned(uint8_t *Src,
unsigned Size) const {
uint64_t Result = 0;
if (IsTargetLittleEndian) {
Src += Size - 1;
while (Size--)
Result = (Result << 8) | *Src--;
} else
while (Size--)
Result = (Result << 8) | *Src++;
return Result;
}
void RuntimeDyldImpl::writeBytesUnaligned(uint64_t Value, uint8_t *Dst,
unsigned Size) const {
if (IsTargetLittleEndian) {
while (Size--) {
*Dst++ = Value & 0xFF;
Value >>= 8;
}
} else {
Dst += Size - 1;
while (Size--) {
*Dst-- = Value & 0xFF;
Value >>= 8;
}
}
}
void RuntimeDyldImpl::emitCommonSymbols(const ObjectFile &Obj,
CommonSymbolList &CommonSymbols) {
if (CommonSymbols.empty())
return;
uint64_t CommonSize = 0;
CommonSymbolList SymbolsToAllocate;
DEBUG(dbgs() << "Processing common symbols...\n");
for (const auto &Sym : CommonSymbols) {
StringRef Name;
Check(Sym.getName(Name));
// Skip common symbols already elsewhere.
if (GlobalSymbolTable.count(Name) ||
Resolver.findSymbolInLogicalDylib(Name)) {
DEBUG(dbgs() << "\tSkipping already emitted common symbol '" << Name
<< "'\n");
continue;
}
uint32_t Align = 0;
uint64_t Size = 0;
Check(Sym.getAlignment(Align));
Check(Sym.getSize(Size));
CommonSize += Align + Size;
SymbolsToAllocate.push_back(Sym);
}
// Allocate memory for the section
unsigned SectionID = Sections.size();
uint8_t *Addr = MemMgr.allocateDataSection(CommonSize, sizeof(void *),
SectionID, StringRef(), false);
if (!Addr)
report_fatal_error("Unable to allocate memory for common symbols!");
uint64_t Offset = 0;
Sections.push_back(SectionEntry("<common symbols>", Addr, CommonSize, 0));
memset(Addr, 0, CommonSize);
DEBUG(dbgs() << "emitCommonSection SectionID: " << SectionID << " new addr: "
<< format("%p", Addr) << " DataSize: " << CommonSize << "\n");
// Assign the address of each symbol
for (auto &Sym : SymbolsToAllocate) {
uint32_t Align;
uint64_t Size;
StringRef Name;
Check(Sym.getAlignment(Align));
Check(Sym.getSize(Size));
Check(Sym.getName(Name));
if (Align) {
// This symbol has an alignment requirement.
uint64_t AlignOffset = OffsetToAlignment((uint64_t)Addr, Align);
Addr += AlignOffset;
Offset += AlignOffset;
}
uint32_t Flags = Sym.getFlags();
JITSymbolFlags RTDyldSymFlags = JITSymbolFlags::None;
if (Flags & SymbolRef::SF_Weak)
RTDyldSymFlags |= JITSymbolFlags::Weak;
if (Flags & SymbolRef::SF_Exported)
RTDyldSymFlags |= JITSymbolFlags::Exported;
DEBUG(dbgs() << "Allocating common symbol " << Name << " address "
<< format("%p", Addr) << "\n");
GlobalSymbolTable[Name] =
SymbolTableEntry(SectionID, Offset, RTDyldSymFlags);
Offset += Size;
Addr += Size;
}
}
unsigned RuntimeDyldImpl::emitSection(const ObjectFile &Obj,
const SectionRef &Section, bool IsCode) {
StringRef data;
uint64_t Alignment64 = Section.getAlignment();
unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
unsigned PaddingSize = 0;
unsigned StubBufSize = 0;
StringRef Name;
bool IsRequired = isRequiredForExecution(Section);
bool IsVirtual = Section.isVirtual();
bool IsZeroInit = isZeroInit(Section);
bool IsReadOnly = isReadOnlyData(Section);
uint64_t DataSize = Section.getSize();
Check(Section.getName(Name));
StubBufSize = computeSectionStubBufSize(Obj, Section);
// The .eh_frame section (at least on Linux) needs an extra four bytes padded
// with zeroes added at the end. For MachO objects, this section has a
// slightly different name, so this won't have any effect for MachO objects.
if (Name == ".eh_frame")
PaddingSize = 4;
uintptr_t Allocate;
unsigned SectionID = Sections.size();
uint8_t *Addr;
const char *pData = nullptr;
// Some sections, such as debug info, don't need to be loaded for execution.
// Leave those where they are.
if (IsRequired) {
Check(Section.getContents(data));
Allocate = DataSize + PaddingSize + StubBufSize;
if (!Allocate)
Allocate = 1;
Addr = IsCode ? MemMgr.allocateCodeSection(Allocate, Alignment, SectionID,
Name)
: MemMgr.allocateDataSection(Allocate, Alignment, SectionID,
Name, IsReadOnly);
if (!Addr)
report_fatal_error("Unable to allocate section memory!");
// Virtual sections have no data in the object image, so leave pData = 0
if (!IsVirtual)
pData = data.data();
// Zero-initialize or copy the data from the image
if (IsZeroInit || IsVirtual)
memset(Addr, 0, DataSize);
else
memcpy(Addr, pData, DataSize);
// Fill in any extra bytes we allocated for padding
if (PaddingSize != 0) {
memset(Addr + DataSize, 0, PaddingSize);
// Update the DataSize variable so that the stub offset is set correctly.
DataSize += PaddingSize;
}
DEBUG(dbgs() << "emitSection SectionID: " << SectionID << " Name: " << Name
<< " obj addr: " << format("%p", pData)
<< " new addr: " << format("%p", Addr)
<< " DataSize: " << DataSize << " StubBufSize: " << StubBufSize
<< " Allocate: " << Allocate << "\n");
} else {
// Even if we didn't load the section, we need to record an entry for it
// to handle later processing (and by 'handle' I mean don't do anything
// with these sections).
Allocate = 0;
Addr = nullptr;
DEBUG(dbgs() << "emitSection SectionID: " << SectionID << " Name: " << Name
<< " obj addr: " << format("%p", data.data()) << " new addr: 0"
<< " DataSize: " << DataSize << " StubBufSize: " << StubBufSize
<< " Allocate: " << Allocate << "\n");
}
Sections.push_back(SectionEntry(Name, Addr, DataSize, (uintptr_t)pData));
if (Checker)
Checker->registerSection(Obj.getFileName(), SectionID);
return SectionID;
}
unsigned RuntimeDyldImpl::findOrEmitSection(const ObjectFile &Obj,
const SectionRef &Section,
bool IsCode,
ObjSectionToIDMap &LocalSections) {
unsigned SectionID = 0;
ObjSectionToIDMap::iterator i = LocalSections.find(Section);
if (i != LocalSections.end())
SectionID = i->second;
else {
SectionID = emitSection(Obj, Section, IsCode);
LocalSections[Section] = SectionID;
}
return SectionID;
}
void RuntimeDyldImpl::addRelocationForSection(const RelocationEntry &RE,
unsigned SectionID) {
Relocations[SectionID].push_back(RE);
}
void RuntimeDyldImpl::addRelocationForSymbol(const RelocationEntry &RE,
StringRef SymbolName) {
// Relocation by symbol. If the symbol is found in the global symbol table,
// create an appropriate section relocation. Otherwise, add it to
// ExternalSymbolRelocations.
RTDyldSymbolTable::const_iterator Loc = GlobalSymbolTable.find(SymbolName);
if (Loc == GlobalSymbolTable.end()) {
ExternalSymbolRelocations[SymbolName].push_back(RE);
} else {
// Copy the RE since we want to modify its addend.
RelocationEntry RECopy = RE;
const auto &SymInfo = Loc->second;
RECopy.Addend += SymInfo.getOffset();
Relocations[SymInfo.getSectionID()].push_back(RECopy);
}
}
uint8_t *RuntimeDyldImpl::createStubFunction(uint8_t *Addr,
unsigned AbiVariant) {
if (Arch == Triple::aarch64 || Arch == Triple::aarch64_be) {
// This stub has to be able to access the full address space,
// since symbol lookup won't necessarily find a handy, in-range,
// PLT stub for functions which could be anywhere.
// Stub can use ip0 (== x16) to calculate address
writeBytesUnaligned(0xd2e00010, Addr, 4); // movz ip0, #:abs_g3:<addr>
writeBytesUnaligned(0xf2c00010, Addr+4, 4); // movk ip0, #:abs_g2_nc:<addr>
writeBytesUnaligned(0xf2a00010, Addr+8, 4); // movk ip0, #:abs_g1_nc:<addr>
writeBytesUnaligned(0xf2800010, Addr+12, 4); // movk ip0, #:abs_g0_nc:<addr>
writeBytesUnaligned(0xd61f0200, Addr+16, 4); // br ip0
return Addr;
} else if (Arch == Triple::arm || Arch == Triple::armeb) {
// TODO: There is only ARM far stub now. We should add the Thumb stub,
// and stubs for branches Thumb - ARM and ARM - Thumb.
writeBytesUnaligned(0xe51ff004, Addr, 4); // ldr pc,<label>
return Addr + 4;
} else if (Arch == Triple::mipsel || Arch == Triple::mips) {
// 0: 3c190000 lui t9,%hi(addr).
// 4: 27390000 addiu t9,t9,%lo(addr).
// 8: 03200008 jr t9.
// c: 00000000 nop.
const unsigned LuiT9Instr = 0x3c190000, AdduiT9Instr = 0x27390000;
const unsigned JrT9Instr = 0x03200008, NopInstr = 0x0;
writeBytesUnaligned(LuiT9Instr, Addr, 4);
writeBytesUnaligned(AdduiT9Instr, Addr+4, 4);
writeBytesUnaligned(JrT9Instr, Addr+8, 4);
writeBytesUnaligned(NopInstr, Addr+12, 4);
return Addr;
} else if (Arch == Triple::ppc64 || Arch == Triple::ppc64le) {
// Depending on which version of the ELF ABI is in use, we need to
// generate one of two variants of the stub. They both start with
// the same sequence to load the target address into r12.
writeInt32BE(Addr, 0x3D800000); // lis r12, highest(addr)
writeInt32BE(Addr+4, 0x618C0000); // ori r12, higher(addr)
writeInt32BE(Addr+8, 0x798C07C6); // sldi r12, r12, 32
writeInt32BE(Addr+12, 0x658C0000); // oris r12, r12, h(addr)
writeInt32BE(Addr+16, 0x618C0000); // ori r12, r12, l(addr)
if (AbiVariant == 2) {
// PowerPC64 stub ELFv2 ABI: The address points to the function itself.
// The address is already in r12 as required by the ABI. Branch to it.
writeInt32BE(Addr+20, 0xF8410018); // std r2, 24(r1)
writeInt32BE(Addr+24, 0x7D8903A6); // mtctr r12
writeInt32BE(Addr+28, 0x4E800420); // bctr
} else {
// PowerPC64 stub ELFv1 ABI: The address points to a function descriptor.
// Load the function address on r11 and sets it to control register. Also
// loads the function TOC in r2 and environment pointer to r11.
writeInt32BE(Addr+20, 0xF8410028); // std r2, 40(r1)
writeInt32BE(Addr+24, 0xE96C0000); // ld r11, 0(r12)
writeInt32BE(Addr+28, 0xE84C0008); // ld r2, 0(r12)
writeInt32BE(Addr+32, 0x7D6903A6); // mtctr r11
writeInt32BE(Addr+36, 0xE96C0010); // ld r11, 16(r2)
writeInt32BE(Addr+40, 0x4E800420); // bctr
}
return Addr;
} else if (Arch == Triple::systemz) {
writeInt16BE(Addr, 0xC418); // lgrl %r1,.+8
writeInt16BE(Addr+2, 0x0000);
writeInt16BE(Addr+4, 0x0004);
writeInt16BE(Addr+6, 0x07F1); // brc 15,%r1
// 8-byte address stored at Addr + 8
return Addr;
} else if (Arch == Triple::x86_64) {
*Addr = 0xFF; // jmp
*(Addr+1) = 0x25; // rip
// 32-bit PC-relative address of the GOT entry will be stored at Addr+2
} else if (Arch == Triple::x86) {
*Addr = 0xE9; // 32-bit pc-relative jump.
}
return Addr;
}
// Assign an address to a symbol name and resolve all the relocations
// associated with it.
void RuntimeDyldImpl::reassignSectionAddress(unsigned SectionID,
uint64_t Addr) {
// The address to use for relocation resolution is not
// the address of the local section buffer. We must be doing
// a remote execution environment of some sort. Relocations can't
// be applied until all the sections have been moved. The client must
// trigger this with a call to MCJIT::finalize() or
// RuntimeDyld::resolveRelocations().
//
// Addr is a uint64_t because we can't assume the pointer width
// of the target is the same as that of the host. Just use a generic
// "big enough" type.
DEBUG(dbgs() << "Reassigning address for section "
<< SectionID << " (" << Sections[SectionID].Name << "): "
<< format("0x%016" PRIx64, Sections[SectionID].LoadAddress) << " -> "
<< format("0x%016" PRIx64, Addr) << "\n");
Sections[SectionID].LoadAddress = Addr;
}
void RuntimeDyldImpl::resolveRelocationList(const RelocationList &Relocs,
uint64_t Value) {
for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
const RelocationEntry &RE = Relocs[i];
// Ignore relocations for sections that were not loaded
if (Sections[RE.SectionID].Address == nullptr)
continue;
resolveRelocation(RE, Value);
}
}
void RuntimeDyldImpl::resolveExternalSymbols() {
while (!ExternalSymbolRelocations.empty()) {
StringMap<RelocationList>::iterator i = ExternalSymbolRelocations.begin();
StringRef Name = i->first();
if (Name.size() == 0) {
// This is an absolute symbol, use an address of zero.
DEBUG(dbgs() << "Resolving absolute relocations."
<< "\n");
RelocationList &Relocs = i->second;
resolveRelocationList(Relocs, 0);
} else {
uint64_t Addr = 0;
RTDyldSymbolTable::const_iterator Loc = GlobalSymbolTable.find(Name);
if (Loc == GlobalSymbolTable.end()) {
// This is an external symbol, try to get its address from the symbol
// resolver.
Addr = Resolver.findSymbol(Name.data()).getAddress();
// The call to getSymbolAddress may have caused additional modules to
// be loaded, which may have added new entries to the
// ExternalSymbolRelocations map. Consquently, we need to update our
// iterator. This is also why retrieval of the relocation list
// associated with this symbol is deferred until below this point.
// New entries may have been added to the relocation list.
i = ExternalSymbolRelocations.find(Name);
} else {
// We found the symbol in our global table. It was probably in a
// Module that we loaded previously.
const auto &SymInfo = Loc->second;
Addr = getSectionLoadAddress(SymInfo.getSectionID()) +
SymInfo.getOffset();
}
// FIXME: Implement error handling that doesn't kill the host program!
if (!Addr)
report_fatal_error("Program used external function '" + Name +
"' which could not be resolved!");
DEBUG(dbgs() << "Resolving relocations Name: " << Name << "\t"
<< format("0x%lx", Addr) << "\n");
// This list may have been updated when we called getSymbolAddress, so
// don't change this code to get the list earlier.
RelocationList &Relocs = i->second;
resolveRelocationList(Relocs, Addr);
}
ExternalSymbolRelocations.erase(i);
}
}
//===----------------------------------------------------------------------===//
// RuntimeDyld class implementation
uint64_t RuntimeDyld::LoadedObjectInfo::getSectionLoadAddress(
StringRef SectionName) const {
for (unsigned I = BeginIdx; I != EndIdx; ++I)
if (RTDyld.Sections[I].Name == SectionName)
return RTDyld.Sections[I].LoadAddress;
return 0;
}
void RuntimeDyld::MemoryManager::anchor() {}
void RuntimeDyld::SymbolResolver::anchor() {}
RuntimeDyld::RuntimeDyld(RuntimeDyld::MemoryManager &MemMgr,
RuntimeDyld::SymbolResolver &Resolver)
: MemMgr(MemMgr), Resolver(Resolver) {
// FIXME: There's a potential issue lurking here if a single instance of
// RuntimeDyld is used to load multiple objects. The current implementation
// associates a single memory manager with a RuntimeDyld instance. Even
// though the public class spawns a new 'impl' instance for each load,
// they share a single memory manager. This can become a problem when page
// permissions are applied.
Dyld = nullptr;
ProcessAllSections = false;
Checker = nullptr;
}
RuntimeDyld::~RuntimeDyld() {}
static std::unique_ptr<RuntimeDyldCOFF>
createRuntimeDyldCOFF(Triple::ArchType Arch, RuntimeDyld::MemoryManager &MM,
RuntimeDyld::SymbolResolver &Resolver,
bool ProcessAllSections, RuntimeDyldCheckerImpl *Checker) {
std::unique_ptr<RuntimeDyldCOFF> Dyld =
RuntimeDyldCOFF::create(Arch, MM, Resolver);
Dyld->setProcessAllSections(ProcessAllSections);
Dyld->setRuntimeDyldChecker(Checker);
return Dyld;
}
static std::unique_ptr<RuntimeDyldELF>
createRuntimeDyldELF(RuntimeDyld::MemoryManager &MM,
RuntimeDyld::SymbolResolver &Resolver,
bool ProcessAllSections, RuntimeDyldCheckerImpl *Checker) {
std::unique_ptr<RuntimeDyldELF> Dyld(new RuntimeDyldELF(MM, Resolver));
Dyld->setProcessAllSections(ProcessAllSections);
Dyld->setRuntimeDyldChecker(Checker);
return Dyld;
}
static std::unique_ptr<RuntimeDyldMachO>
createRuntimeDyldMachO(Triple::ArchType Arch, RuntimeDyld::MemoryManager &MM,
RuntimeDyld::SymbolResolver &Resolver,
bool ProcessAllSections,
RuntimeDyldCheckerImpl *Checker) {
std::unique_ptr<RuntimeDyldMachO> Dyld =
RuntimeDyldMachO::create(Arch, MM, Resolver);
Dyld->setProcessAllSections(ProcessAllSections);
Dyld->setRuntimeDyldChecker(Checker);
return Dyld;
}
std::unique_ptr<RuntimeDyld::LoadedObjectInfo>
RuntimeDyld::loadObject(const ObjectFile &Obj) {
if (!Dyld) {
if (Obj.isELF())
Dyld = createRuntimeDyldELF(MemMgr, Resolver, ProcessAllSections, Checker);
else if (Obj.isMachO())
Dyld = createRuntimeDyldMachO(
static_cast<Triple::ArchType>(Obj.getArch()), MemMgr, Resolver,
ProcessAllSections, Checker);
else if (Obj.isCOFF())
Dyld = createRuntimeDyldCOFF(
static_cast<Triple::ArchType>(Obj.getArch()), MemMgr, Resolver,
ProcessAllSections, Checker);
else
report_fatal_error("Incompatible object format!");
}
if (!Dyld->isCompatibleFile(Obj))
report_fatal_error("Incompatible object format!");
return Dyld->loadObject(Obj);
}
void *RuntimeDyld::getSymbolLocalAddress(StringRef Name) const {
if (!Dyld)
return nullptr;
return Dyld->getSymbolLocalAddress(Name);
}
RuntimeDyld::SymbolInfo RuntimeDyld::getSymbol(StringRef Name) const {
if (!Dyld)
return nullptr;
return Dyld->getSymbol(Name);
}
void RuntimeDyld::resolveRelocations() { Dyld->resolveRelocations(); }
void RuntimeDyld::reassignSectionAddress(unsigned SectionID, uint64_t Addr) {
Dyld->reassignSectionAddress(SectionID, Addr);
}
void RuntimeDyld::mapSectionAddress(const void *LocalAddress,
uint64_t TargetAddress) {
Dyld->mapSectionAddress(LocalAddress, TargetAddress);
}
bool RuntimeDyld::hasError() { return Dyld->hasError(); }
StringRef RuntimeDyld::getErrorString() { return Dyld->getErrorString(); }
void RuntimeDyld::registerEHFrames() {
if (Dyld)
Dyld->registerEHFrames();
}
void RuntimeDyld::deregisterEHFrames() {
if (Dyld)
Dyld->deregisterEHFrames();
}
} // end namespace llvm
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