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RuntimeDyld.cpp
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//===-- RuntimeDyld.cpp - Run-time dynamic linker for MC-JIT ----*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Implementation of the MC-JIT runtime dynamic linker.
//
//===----------------------------------------------------------------------===//
#include "llvm/ExecutionEngine/RuntimeDyld.h"
#include "RuntimeDyldCOFF.h"
#include "RuntimeDyldELF.h"
#include "RuntimeDyldImpl.h"
#include "RuntimeDyldMachO.h"
#include "llvm/Object/COFF.h"
#include "llvm/Object/ELFObjectFile.h"
#include "llvm/Support/Alignment.h"
#include "llvm/Support/MSVCErrorWorkarounds.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/MathExtras.h"
#include <mutex>
#include <future>
using namespace llvm;
using namespace llvm::object;
#define DEBUG_TYPE "dyld"
namespace {
enum RuntimeDyldErrorCode {
GenericRTDyldError = 1
};
// FIXME: This class is only here to support the transition to llvm::Error. It
// will be removed once this transition is complete. Clients should prefer to
// deal with the Error value directly, rather than converting to error_code.
class RuntimeDyldErrorCategory : public std::error_category {
public:
const char *name() const noexcept override { return "runtimedyld"; }
std::string message(int Condition) const override {
switch (static_cast<RuntimeDyldErrorCode>(Condition)) {
case GenericRTDyldError: return "Generic RuntimeDyld error";
}
llvm_unreachable("Unrecognized RuntimeDyldErrorCode");
}
};
static ManagedStatic<RuntimeDyldErrorCategory> RTDyldErrorCategory;
}
char RuntimeDyldError::ID = 0;
void RuntimeDyldError::log(raw_ostream &OS) const {
OS << ErrMsg << "\n";
}
std::error_code RuntimeDyldError::convertToErrorCode() const {
return std::error_code(GenericRTDyldError, *RTDyldErrorCategory);
}
// 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() {
MemMgr.deregisterEHFrames();
}
#ifndef NDEBUG
static void dumpSectionMemory(const SectionEntry &S, StringRef State) {
dbgs() << "----- Contents of section " << S.getName() << " " << State
<< " -----";
if (S.getAddress() == nullptr) {
dbgs() << "\n <section not emitted>\n";
return;
}
const unsigned ColsPerRow = 16;
uint8_t *DataAddr = S.getAddress();
uint64_t LoadAddr = S.getLoadAddress();
unsigned StartPadding = LoadAddr & (ColsPerRow - 1);
unsigned BytesRemaining = S.getSize();
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() {
std::lock_guard<sys::Mutex> locked(lock);
// Print out the sections prior to relocation.
LLVM_DEBUG(for (int i = 0, e = Sections.size(); i != e; ++i)
dumpSectionMemory(Sections[i], "before relocations"););
// First, resolve relocations associated with external symbols.
if (auto Err = resolveExternalSymbols()) {
HasError = true;
ErrorStr = toString(std::move(Err));
}
resolveLocalRelocations();
// Print out sections after relocation.
LLVM_DEBUG(for (int i = 0, e = Sections.size(); i != e; ++i)
dumpSectionMemory(Sections[i], "after relocations"););
}
void RuntimeDyldImpl::resolveLocalRelocations() {
// Iterate over all outstanding relocations
for (auto it = Relocations.begin(), e = Relocations.end(); it != e; ++it) {
// 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.
int Idx = it->first;
uint64_t Addr = Sections[Idx].getLoadAddress();
LLVM_DEBUG(dbgs() << "Resolving relocations Section #" << Idx << "\t"
<< format("%p", (uintptr_t)Addr) << "\n");
resolveRelocationList(it->second, Addr);
}
Relocations.clear();
}
void RuntimeDyldImpl::mapSectionAddress(const void *LocalAddress,
uint64_t TargetAddress) {
std::lock_guard<sys::Mutex> locked(lock);
for (unsigned i = 0, e = Sections.size(); i != e; ++i) {
if (Sections[i].getAddress() == LocalAddress) {
reassignSectionAddress(i, TargetAddress);
return;
}
}
llvm_unreachable("Attempting to remap address of unknown section!");
}
static Error getOffset(const SymbolRef &Sym, SectionRef Sec,
uint64_t &Result) {
Expected<uint64_t> AddressOrErr = Sym.getAddress();
if (!AddressOrErr)
return AddressOrErr.takeError();
Result = *AddressOrErr - Sec.getAddress();
return Error::success();
}
Expected<RuntimeDyldImpl::ObjSectionToIDMap>
RuntimeDyldImpl::loadObjectImpl(const object::ObjectFile &Obj) {
std::lock_guard<sys::Mutex> locked(lock);
// Save information about our target
Arch = (Triple::ArchType)Obj.getArch();
IsTargetLittleEndian = Obj.isLittleEndian();
setMipsABI(Obj);
// 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, RODataSize = 0, RWDataSize = 0;
uint32_t CodeAlign = 1, RODataAlign = 1, RWDataAlign = 1;
if (auto Err = computeTotalAllocSize(Obj,
CodeSize, CodeAlign,
RODataSize, RODataAlign,
RWDataSize, RWDataAlign))
return std::move(Err);
MemMgr.reserveAllocationSpace(CodeSize, CodeAlign, RODataSize, RODataAlign,
RWDataSize, RWDataAlign);
}
// Used sections from the object file
ObjSectionToIDMap LocalSections;
// Common symbols requiring allocation, with their sizes and alignments
CommonSymbolList CommonSymbolsToAllocate;
uint64_t CommonSize = 0;
uint32_t CommonAlign = 0;
// First, collect all weak and common symbols. We need to know if stronger
// definitions occur elsewhere.
JITSymbolResolver::LookupSet ResponsibilitySet;
{
JITSymbolResolver::LookupSet Symbols;
for (auto &Sym : Obj.symbols()) {
Expected<uint32_t> FlagsOrErr = Sym.getFlags();
if (!FlagsOrErr)
// TODO: Test this error.
return FlagsOrErr.takeError();
if ((*FlagsOrErr & SymbolRef::SF_Common) ||
(*FlagsOrErr & SymbolRef::SF_Weak)) {
// Get symbol name.
if (auto NameOrErr = Sym.getName())
Symbols.insert(*NameOrErr);
else
return NameOrErr.takeError();
}
}
if (auto ResultOrErr = Resolver.getResponsibilitySet(Symbols))
ResponsibilitySet = std::move(*ResultOrErr);
else
return ResultOrErr.takeError();
}
// Parse symbols
LLVM_DEBUG(dbgs() << "Parse symbols:\n");
for (symbol_iterator I = Obj.symbol_begin(), E = Obj.symbol_end(); I != E;
++I) {
Expected<uint32_t> FlagsOrErr = I->getFlags();
if (!FlagsOrErr)
// TODO: Test this error.
return FlagsOrErr.takeError();
// Skip undefined symbols.
if (*FlagsOrErr & SymbolRef::SF_Undefined)
continue;
// Get the symbol type.
object::SymbolRef::Type SymType;
if (auto SymTypeOrErr = I->getType())
SymType = *SymTypeOrErr;
else
return SymTypeOrErr.takeError();
// Get symbol name.
StringRef Name;
if (auto NameOrErr = I->getName())
Name = *NameOrErr;
else
return NameOrErr.takeError();
// Compute JIT symbol flags.
auto JITSymFlags = getJITSymbolFlags(*I);
if (!JITSymFlags)
return JITSymFlags.takeError();
// If this is a weak definition, check to see if there's a strong one.
// If there is, skip this symbol (we won't be providing it: the strong
// definition will). If there's no strong definition, make this definition
// strong.
if (JITSymFlags->isWeak() || JITSymFlags->isCommon()) {
// First check whether there's already a definition in this instance.
if (GlobalSymbolTable.count(Name))
continue;
// If we're not responsible for this symbol, skip it.
if (!ResponsibilitySet.count(Name))
continue;
// Otherwise update the flags on the symbol to make this definition
// strong.
if (JITSymFlags->isWeak())
*JITSymFlags &= ~JITSymbolFlags::Weak;
if (JITSymFlags->isCommon()) {
*JITSymFlags &= ~JITSymbolFlags::Common;
uint32_t Align = I->getAlignment();
uint64_t Size = I->getCommonSize();
if (!CommonAlign)
CommonAlign = Align;
CommonSize = alignTo(CommonSize, Align) + Size;
CommonSymbolsToAllocate.push_back(*I);
}
}
if (*FlagsOrErr & SymbolRef::SF_Absolute &&
SymType != object::SymbolRef::ST_File) {
uint64_t Addr = 0;
if (auto AddrOrErr = I->getAddress())
Addr = *AddrOrErr;
else
return AddrOrErr.takeError();
unsigned SectionID = AbsoluteSymbolSection;
LLVM_DEBUG(dbgs() << "\tType: " << SymType << " (absolute) Name: " << Name
<< " SID: " << SectionID
<< " Offset: " << format("%p", (uintptr_t)Addr)
<< " flags: " << *FlagsOrErr << "\n");
if (!Name.empty()) // Skip absolute symbol relocations.
GlobalSymbolTable[Name] =
SymbolTableEntry(SectionID, Addr, *JITSymFlags);
} else if (SymType == object::SymbolRef::ST_Function ||
SymType == object::SymbolRef::ST_Data ||
SymType == object::SymbolRef::ST_Unknown ||
SymType == object::SymbolRef::ST_Other) {
section_iterator SI = Obj.section_end();
if (auto SIOrErr = I->getSection())
SI = *SIOrErr;
else
return SIOrErr.takeError();
if (SI == Obj.section_end())
continue;
// Get symbol offset.
uint64_t SectOffset;
if (auto Err = getOffset(*I, *SI, SectOffset))
return std::move(Err);
bool IsCode = SI->isText();
unsigned SectionID;
if (auto SectionIDOrErr =
findOrEmitSection(Obj, *SI, IsCode, LocalSections))
SectionID = *SectionIDOrErr;
else
return SectionIDOrErr.takeError();
LLVM_DEBUG(dbgs() << "\tType: " << SymType << " Name: " << Name
<< " SID: " << SectionID
<< " Offset: " << format("%p", (uintptr_t)SectOffset)
<< " flags: " << *FlagsOrErr << "\n");
if (!Name.empty()) // Skip absolute symbol relocations
GlobalSymbolTable[Name] =
SymbolTableEntry(SectionID, SectOffset, *JITSymFlags);
}
}
// Allocate common symbols
if (auto Err = emitCommonSymbols(Obj, CommonSymbolsToAllocate, CommonSize,
CommonAlign))
return std::move(Err);
// Parse and process relocations
LLVM_DEBUG(dbgs() << "Parse relocations:\n");
for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
SI != SE; ++SI) {
StubMap Stubs;
Expected<section_iterator> RelSecOrErr = SI->getRelocatedSection();
if (!RelSecOrErr)
return RelSecOrErr.takeError();
section_iterator RelocatedSection = *RelSecOrErr;
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();
unsigned SectionID = 0;
if (auto SectionIDOrErr = findOrEmitSection(Obj, *RelocatedSection, IsCode,
LocalSections))
SectionID = *SectionIDOrErr;
else
return SectionIDOrErr.takeError();
LLVM_DEBUG(dbgs() << "\tSectionID: " << SectionID << "\n");
for (; I != E;)
if (auto IOrErr = processRelocationRef(SectionID, I, Obj, LocalSections, Stubs))
I = *IOrErr;
else
return IOrErr.takeError();
// If there is a NotifyStubEmitted callback set, call it to register any
// stubs created for this section.
if (NotifyStubEmitted) {
StringRef FileName = Obj.getFileName();
StringRef SectionName = Sections[SectionID].getName();
for (auto &KV : Stubs) {
auto &VR = KV.first;
uint64_t StubAddr = KV.second;
// If this is a named stub, just call NotifyStubEmitted.
if (VR.SymbolName) {
NotifyStubEmitted(FileName, SectionName, VR.SymbolName, SectionID,
StubAddr);
continue;
}
// Otherwise we will have to try a reverse lookup on the globla symbol table.
for (auto &GSTMapEntry : GlobalSymbolTable) {
StringRef SymbolName = GSTMapEntry.first();
auto &GSTEntry = GSTMapEntry.second;
if (GSTEntry.getSectionID() == VR.SectionID &&
GSTEntry.getOffset() == VR.Offset) {
NotifyStubEmitted(FileName, SectionName, SymbolName, SectionID,
StubAddr);
break;
}
}
}
}
}
// Process remaining sections
if (ProcessAllSections) {
LLVM_DEBUG(dbgs() << "Process remaining sections:\n");
for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
SI != SE; ++SI) {
/* Ignore already loaded sections */
if (LocalSections.find(*SI) != LocalSections.end())
continue;
bool IsCode = SI->isText();
if (auto SectionIDOrErr =
findOrEmitSection(Obj, *SI, IsCode, LocalSections))
LLVM_DEBUG(dbgs() << "\tSectionID: " << (*SectionIDOrErr) << "\n");
else
return SectionIDOrErr.takeError();
}
}
// Give the subclasses a chance to tie-up any loose ends.
if (auto Err = finalizeLoad(Obj, LocalSections))
return std::move(Err);
// for (auto E : LocalSections)
// llvm::dbgs() << "Added: " << E.first.getRawDataRefImpl() << " -> " << E.second << "\n";
return LocalSections;
}
// 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 (isa<object::ELFObjectFileBase>(Obj))
return ELFSectionRef(Section).getFlags() & 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 (isa<object::ELFObjectFileBase>(Obj))
return !(ELFSectionRef(Section).getFlags() &
(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 (isa<object::ELFObjectFileBase>(Obj))
return ELFSectionRef(Section).getType() == 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
Error RuntimeDyldImpl::computeTotalAllocSize(const ObjectFile &Obj,
uint64_t &CodeSize,
uint32_t &CodeAlign,
uint64_t &RODataSize,
uint32_t &RODataAlign,
uint64_t &RWDataSize,
uint32_t &RWDataAlign) {
// Compute the size of all sections required for execution
std::vector<uint64_t> CodeSectionSizes;
std::vector<uint64_t> ROSectionSizes;
std::vector<uint64_t> RWSectionSizes;
// 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) || ProcessAllSections;
// Consider only the sections that are required to be loaded for execution
if (IsRequired) {
uint64_t DataSize = Section.getSize();
uint64_t Alignment64 = Section.getAlignment();
unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
bool IsCode = Section.isText();
bool IsReadOnly = isReadOnlyData(Section);
Expected<StringRef> NameOrErr = Section.getName();
if (!NameOrErr)
return NameOrErr.takeError();
StringRef Name = *NameOrErr;
uint64_t StubBufSize = computeSectionStubBufSize(Obj, Section);
uint64_t PaddingSize = 0;
if (Name == ".eh_frame")
PaddingSize += 4;
if (StubBufSize != 0)
PaddingSize += getStubAlignment() - 1;
uint64_t SectionSize = DataSize + PaddingSize + 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) {
CodeAlign = std::max(CodeAlign, Alignment);
CodeSectionSizes.push_back(SectionSize);
} else if (IsReadOnly) {
RODataAlign = std::max(RODataAlign, Alignment);
ROSectionSizes.push_back(SectionSize);
} else {
RWDataAlign = std::max(RWDataAlign, Alignment);
RWSectionSizes.push_back(SectionSize);
}
}
}
// Compute Global Offset Table size. If it is not zero we
// also update alignment, which is equal to a size of a
// single GOT entry.
if (unsigned GotSize = computeGOTSize(Obj)) {
RWSectionSizes.push_back(GotSize);
RWDataAlign = std::max<uint32_t>(RWDataAlign, getGOTEntrySize());
}
// Compute the size of all common symbols
uint64_t CommonSize = 0;
uint32_t CommonAlign = 1;
for (symbol_iterator I = Obj.symbol_begin(), E = Obj.symbol_end(); I != E;
++I) {
Expected<uint32_t> FlagsOrErr = I->getFlags();
if (!FlagsOrErr)
// TODO: Test this error.
return FlagsOrErr.takeError();
if (*FlagsOrErr & SymbolRef::SF_Common) {
// Add the common symbols to a list. We'll allocate them all below.
uint64_t Size = I->getCommonSize();
uint32_t Align = I->getAlignment();
// If this is the first common symbol, use its alignment as the alignment
// for the common symbols section.
if (CommonSize == 0)
CommonAlign = Align;
CommonSize = alignTo(CommonSize, Align) + Size;
}
}
if (CommonSize != 0) {
RWSectionSizes.push_back(CommonSize);
RWDataAlign = std::max(RWDataAlign, CommonAlign);
}
// 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, CodeAlign);
RODataSize = computeAllocationSizeForSections(ROSectionSizes, RODataAlign);
RWDataSize = computeAllocationSizeForSections(RWSectionSizes, RWDataAlign);
return Error::success();
}
// compute GOT size
unsigned RuntimeDyldImpl::computeGOTSize(const ObjectFile &Obj) {
size_t GotEntrySize = getGOTEntrySize();
if (!GotEntrySize)
return 0;
size_t GotSize = 0;
for (section_iterator SI = Obj.section_begin(), SE = Obj.section_end();
SI != SE; ++SI) {
for (const RelocationRef &Reloc : SI->relocations())
if (relocationNeedsGot(Reloc))
GotSize += GotEntrySize;
}
return GotSize;
}
// 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) {
Expected<section_iterator> RelSecOrErr = SI->getRelocatedSection();
if (!RelSecOrErr)
report_fatal_error(toString(RelSecOrErr.takeError()));
section_iterator RelSecI = *RelSecOrErr;
if (!(RelSecI == Section))
continue;
for (const RelocationRef &Reloc : SI->relocations())
if (relocationNeedsStub(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;
}
}
}
Expected<JITSymbolFlags>
RuntimeDyldImpl::getJITSymbolFlags(const SymbolRef &SR) {
return JITSymbolFlags::fromObjectSymbol(SR);
}
Error RuntimeDyldImpl::emitCommonSymbols(const ObjectFile &Obj,
CommonSymbolList &SymbolsToAllocate,
uint64_t CommonSize,
uint32_t CommonAlign) {
if (SymbolsToAllocate.empty())
return Error::success();
// Allocate memory for the section
unsigned SectionID = Sections.size();
uint8_t *Addr = MemMgr.allocateDataSection(CommonSize, CommonAlign, SectionID,
"<common symbols>", 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, CommonSize, 0));
memset(Addr, 0, CommonSize);
LLVM_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 Alignment = Sym.getAlignment();
uint64_t Size = Sym.getCommonSize();
StringRef Name;
if (auto NameOrErr = Sym.getName())
Name = *NameOrErr;
else
return NameOrErr.takeError();
if (Alignment) {
// This symbol has an alignment requirement.
uint64_t AlignOffset =
offsetToAlignment((uint64_t)Addr, Align(Alignment));
Addr += AlignOffset;
Offset += AlignOffset;
}
auto JITSymFlags = getJITSymbolFlags(Sym);
if (!JITSymFlags)
return JITSymFlags.takeError();
LLVM_DEBUG(dbgs() << "Allocating common symbol " << Name << " address "
<< format("%p", Addr) << "\n");
if (!Name.empty()) // Skip absolute symbol relocations.
GlobalSymbolTable[Name] =
SymbolTableEntry(SectionID, Offset, std::move(*JITSymFlags));
Offset += Size;
Addr += Size;
}
return Error::success();
}
Expected<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;
bool IsRequired = isRequiredForExecution(Section);
bool IsVirtual = Section.isVirtual();
bool IsZeroInit = isZeroInit(Section);
bool IsReadOnly = isReadOnlyData(Section);
uint64_t DataSize = Section.getSize();
// An alignment of 0 (at least with ELF) is identical to an alignment of 1,
// while being more "polite". Other formats do not support 0-aligned sections
// anyway, so we should guarantee that the alignment is always at least 1.
Alignment = std::max(1u, Alignment);
Expected<StringRef> NameOrErr = Section.getName();
if (!NameOrErr)
return NameOrErr.takeError();
StringRef Name = *NameOrErr;
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;
// If this section contains any bits (i.e. isn't a virtual or bss section),
// grab a reference to them.
if (!IsVirtual && !IsZeroInit) {
// In either case, set the location of the unrelocated section in memory,
// since we still process relocations for it even if we're not applying them.
if (Expected<StringRef> E = Section.getContents())
data = *E;
else
return E.takeError();
pData = data.data();
}
// If there are any stubs then the section alignment needs to be at least as
// high as stub alignment or padding calculations may by incorrect when the
// section is remapped.
if (StubBufSize != 0) {
Alignment = std::max(Alignment, getStubAlignment());
PaddingSize += getStubAlignment() - 1;
}
// Some sections, such as debug info, don't need to be loaded for execution.
// Process those only if explicitly requested.
if (IsRequired || ProcessAllSections) {
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!");
// 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 to include padding.
DataSize += PaddingSize;
// Align DataSize to stub alignment if we have any stubs (PaddingSize will
// have been increased above to account for this).
if (StubBufSize > 0)
DataSize &= -(uint64_t)getStubAlignment();
}
LLVM_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;
LLVM_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, Allocate, (uintptr_t)pData));
// Debug info sections are linked as if their load address was zero
if (!IsRequired)
Sections.back().setLoadAddress(0);
return SectionID;
}
Expected<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 {
if (auto SectionIDOrErr = emitSection(Obj, Section, IsCode))
SectionID = *SectionIDOrErr;
else
return SectionIDOrErr.takeError();
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 {
assert(!SymbolName.empty() &&
"Empty symbol should not be in GlobalSymbolTable");
// 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 ||
Arch == Triple::aarch64_32) {
// 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, [pc, #-4]
return Addr + 4;
} else if (IsMipsO32ABI || IsMipsN32ABI) {
// 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 NopInstr = 0x0;
unsigned JrT9Instr = 0x03200008;
if ((AbiVariant & ELF::EF_MIPS_ARCH) == ELF::EF_MIPS_ARCH_32R6 ||
(AbiVariant & ELF::EF_MIPS_ARCH) == ELF::EF_MIPS_ARCH_64R6)
JrT9Instr = 0x03200009;
writeBytesUnaligned(LuiT9Instr, Addr, 4);
writeBytesUnaligned(AdduiT9Instr, Addr + 4, 4);
writeBytesUnaligned(JrT9Instr, Addr + 8, 4);
writeBytesUnaligned(NopInstr, Addr + 12, 4);
return Addr;
} else if (IsMipsN64ABI) {
// 0: 3c190000 lui t9,%highest(addr).
// 4: 67390000 daddiu t9,t9,%higher(addr).
// 8: 0019CC38 dsll t9,t9,16.
// c: 67390000 daddiu t9,t9,%hi(addr).
// 10: 0019CC38 dsll t9,t9,16.
// 14: 67390000 daddiu t9,t9,%lo(addr).
// 18: 03200008 jr t9.
// 1c: 00000000 nop.
const unsigned LuiT9Instr = 0x3c190000, DaddiuT9Instr = 0x67390000,
DsllT9Instr = 0x19CC38;
const unsigned NopInstr = 0x0;
unsigned JrT9Instr = 0x03200008;
if ((AbiVariant & ELF::EF_MIPS_ARCH) == ELF::EF_MIPS_ARCH_64R6)
JrT9Instr = 0x03200009;
writeBytesUnaligned(LuiT9Instr, Addr, 4);