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llvm-project/llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp

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//===-- RuntimeDyldMachO.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.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "dyld"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/STLExtras.h"
#include "RuntimeDyldImpl.h"
using namespace llvm;
using namespace llvm::object;
namespace llvm {
bool RuntimeDyldMachO::
resolveRelocation(uint8_t *Address, uint8_t *Value, bool isPCRel,
unsigned Type, unsigned Size) {
// This just dispatches to the proper target specific routine.
switch (CPUType) {
default: assert(0 && "Unsupported CPU type!");
case mach::CTM_x86_64:
return resolveX86_64Relocation((uintptr_t)Address, (uintptr_t)Value,
isPCRel, Type, Size);
case mach::CTM_ARM:
return resolveARMRelocation((uintptr_t)Address, (uintptr_t)Value,
isPCRel, Type, Size);
}
llvm_unreachable("");
}
bool RuntimeDyldMachO::
resolveX86_64Relocation(uintptr_t Address, uintptr_t Value,
bool isPCRel, unsigned Type,
unsigned Size) {
// If the relocation is PC-relative, the value to be encoded is the
// pointer difference.
if (isPCRel)
// FIXME: It seems this value needs to be adjusted by 4 for an effective PC
// address. Is that expected? Only for branches, perhaps?
Value -= Address + 4;
switch(Type) {
default:
llvm_unreachable("Invalid relocation type!");
case macho::RIT_X86_64_Unsigned:
case macho::RIT_X86_64_Branch: {
// Mask in the target value a byte at a time (we don't have an alignment
// guarantee for the target address, so this is safest).
uint8_t *p = (uint8_t*)Address;
for (unsigned i = 0; i < Size; ++i) {
*p++ = (uint8_t)Value;
Value >>= 8;
}
return false;
}
case macho::RIT_X86_64_Signed:
case macho::RIT_X86_64_GOTLoad:
case macho::RIT_X86_64_GOT:
case macho::RIT_X86_64_Subtractor:
case macho::RIT_X86_64_Signed1:
case macho::RIT_X86_64_Signed2:
case macho::RIT_X86_64_Signed4:
case macho::RIT_X86_64_TLV:
return Error("Relocation type not implemented yet!");
}
return false;
}
bool RuntimeDyldMachO::resolveARMRelocation(uintptr_t Address, uintptr_t Value,
bool isPCRel, unsigned Type,
unsigned Size) {
// If the relocation is PC-relative, the value to be encoded is the
// pointer difference.
if (isPCRel) {
Value -= Address;
// ARM PCRel relocations have an effective-PC offset of two instructions
// (four bytes in Thumb mode, 8 bytes in ARM mode).
// FIXME: For now, assume ARM mode.
Value -= 8;
}
switch(Type) {
default:
llvm_unreachable("Invalid relocation type!");
case macho::RIT_Vanilla: {
llvm_unreachable("Invalid relocation type!");
// Mask in the target value a byte at a time (we don't have an alignment
// guarantee for the target address, so this is safest).
uint8_t *p = (uint8_t*)Address;
for (unsigned i = 0; i < Size; ++i) {
*p++ = (uint8_t)Value;
Value >>= 8;
}
break;
}
case macho::RIT_ARM_Branch24Bit: {
// Mask the value into the target address. We know instructions are
// 32-bit aligned, so we can do it all at once.
uint32_t *p = (uint32_t*)Address;
// The low two bits of the value are not encoded.
Value >>= 2;
// Mask the value to 24 bits.
Value &= 0xffffff;
// FIXME: If the destination is a Thumb function (and the instruction
// is a non-predicated BL instruction), we need to change it to a BLX
// instruction instead.
// Insert the value into the instruction.
*p = (*p & ~0xffffff) | Value;
break;
}
case macho::RIT_ARM_ThumbBranch22Bit:
case macho::RIT_ARM_ThumbBranch32Bit:
case macho::RIT_ARM_Half:
case macho::RIT_ARM_HalfDifference:
case macho::RIT_Pair:
case macho::RIT_Difference:
case macho::RIT_ARM_LocalDifference:
case macho::RIT_ARM_PreboundLazyPointer:
return Error("Relocation type not implemented yet!");
}
return false;
}
bool RuntimeDyldMachO::
loadSegment32(const MachOObject *Obj,
const MachOObject::LoadCommandInfo *SegmentLCI,
const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC) {
InMemoryStruct<macho::SegmentLoadCommand> SegmentLC;
Obj->ReadSegmentLoadCommand(*SegmentLCI, SegmentLC);
if (!SegmentLC)
return Error("unable to load segment load command");
for (unsigned SectNum = 0; SectNum != SegmentLC->NumSections; ++SectNum) {
InMemoryStruct<macho::Section> Sect;
Obj->ReadSection(*SegmentLCI, SectNum, Sect);
if (!Sect)
return Error("unable to load section: '" + Twine(SectNum) + "'");
// FIXME: For the time being, we're only loading text segments.
if (Sect->Flags != 0x80000400)
continue;
// Address and names of symbols in the section.
typedef std::pair<uint64_t, StringRef> SymbolEntry;
SmallVector<SymbolEntry, 64> Symbols;
// Index of all the names, in this section or not. Used when we're
// dealing with relocation entries.
SmallVector<StringRef, 64> SymbolNames;
for (unsigned i = 0; i != SymtabLC->NumSymbolTableEntries; ++i) {
InMemoryStruct<macho::SymbolTableEntry> STE;
Obj->ReadSymbolTableEntry(SymtabLC->SymbolTableOffset, i, STE);
if (!STE)
return Error("unable to read symbol: '" + Twine(i) + "'");
if (STE->SectionIndex > SegmentLC->NumSections)
return Error("invalid section index for symbol: '" + Twine(i) + "'");
// Get the symbol name.
StringRef Name = Obj->getStringAtIndex(STE->StringIndex);
SymbolNames.push_back(Name);
// Just skip symbols not defined in this section.
if ((unsigned)STE->SectionIndex - 1 != SectNum)
continue;
// FIXME: Check the symbol type and flags.
if (STE->Type != 0xF) // external, defined in this section.
continue;
// Flags == 0x8 marks a thumb function for ARM, which is fine as it
// doesn't require any special handling here.
// Flags in the upper nibble we don't care about.
if ((STE->Flags & 0xf) != 0x0 && STE->Flags != 0x8)
continue;
// Remember the symbol.
Symbols.push_back(SymbolEntry(STE->Value, Name));
DEBUG(dbgs() << "Function sym: '" << Name << "' @ " <<
(Sect->Address + STE->Value) << "\n");
}
// Sort the symbols by address, just in case they didn't come in that way.
array_pod_sort(Symbols.begin(), Symbols.end());
// If there weren't any functions (odd, but just in case...)
if (!Symbols.size())
continue;
// Extract the function data.
uint8_t *Base = (uint8_t*)Obj->getData(SegmentLC->FileOffset,
SegmentLC->FileSize).data();
for (unsigned i = 0, e = Symbols.size() - 1; i != e; ++i) {
uint64_t StartOffset = Sect->Address + Symbols[i].first;
uint64_t EndOffset = Symbols[i + 1].first - 1;
DEBUG(dbgs() << "Extracting function: " << Symbols[i].second
<< " from [" << StartOffset << ", " << EndOffset << "]\n");
extractFunction(Symbols[i].second, Base + StartOffset, Base + EndOffset);
}
// The last symbol we do after since the end address is calculated
// differently because there is no next symbol to reference.
uint64_t StartOffset = Symbols[Symbols.size() - 1].first;
uint64_t EndOffset = Sect->Size - 1;
DEBUG(dbgs() << "Extracting function: " << Symbols[Symbols.size()-1].second
<< " from [" << StartOffset << ", " << EndOffset << "]\n");
extractFunction(Symbols[Symbols.size()-1].second,
Base + StartOffset, Base + EndOffset);
// Now extract the relocation information for each function and process it.
for (unsigned j = 0; j != Sect->NumRelocationTableEntries; ++j) {
InMemoryStruct<macho::RelocationEntry> RE;
Obj->ReadRelocationEntry(Sect->RelocationTableOffset, j, RE);
if (RE->Word0 & macho::RF_Scattered)
return Error("NOT YET IMPLEMENTED: scattered relocations.");
// Word0 of the relocation is the offset into the section where the
// relocation should be applied. We need to translate that into an
// offset into a function since that's our atom.
uint32_t Offset = RE->Word0;
// Look for the function containing the address. This is used for JIT
// code, so the number of functions in section is almost always going
// to be very small (usually just one), so until we have use cases
// where that's not true, just use a trivial linear search.
unsigned SymbolNum;
unsigned NumSymbols = Symbols.size();
assert(NumSymbols > 0 && Symbols[0].first <= Offset &&
"No symbol containing relocation!");
for (SymbolNum = 0; SymbolNum < NumSymbols - 1; ++SymbolNum)
if (Symbols[SymbolNum + 1].first > Offset)
break;
// Adjust the offset to be relative to the symbol.
Offset -= Symbols[SymbolNum].first;
// Get the name of the symbol containing the relocation.
StringRef TargetName = SymbolNames[SymbolNum];
bool isExtern = (RE->Word1 >> 27) & 1;
// Figure out the source symbol of the relocation. If isExtern is true,
// this relocation references the symbol table, otherwise it references
// a section in the same object, numbered from 1 through NumSections
// (SectionBases is [0, NumSections-1]).
// FIXME: Some targets (ARM) use internal relocations even for
// externally visible symbols, if the definition is in the same
// file as the reference. We need to convert those back to by-name
// references. We can resolve the address based on the section
// offset and see if we have a symbol at that address. If we do,
// use that; otherwise, puke.
if (!isExtern)
return Error("Internal relocations not supported.");
uint32_t SourceNum = RE->Word1 & 0xffffff; // 24-bit value
StringRef SourceName = SymbolNames[SourceNum];
// FIXME: Get the relocation addend from the target address.
// Now store the relocation information. Associate it with the source
// symbol.
Relocations[SourceName].push_back(RelocationEntry(TargetName,
Offset,
RE->Word1,
0 /*Addend*/));
DEBUG(dbgs() << "Relocation at '" << TargetName << "' + " << Offset
<< " from '" << SourceName << "(Word1: "
<< format("0x%x", RE->Word1) << ")\n");
}
}
return false;
}
bool RuntimeDyldMachO::
loadSegment64(const MachOObject *Obj,
const MachOObject::LoadCommandInfo *SegmentLCI,
const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC) {
InMemoryStruct<macho::Segment64LoadCommand> Segment64LC;
Obj->ReadSegment64LoadCommand(*SegmentLCI, Segment64LC);
if (!Segment64LC)
return Error("unable to load segment load command");
for (unsigned SectNum = 0; SectNum != Segment64LC->NumSections; ++SectNum) {
InMemoryStruct<macho::Section64> Sect;
Obj->ReadSection64(*SegmentLCI, SectNum, Sect);
if (!Sect)
return Error("unable to load section: '" + Twine(SectNum) + "'");
// FIXME: For the time being, we're only loading text segments.
if (Sect->Flags != 0x80000400)
continue;
// Address and names of symbols in the section.
typedef std::pair<uint64_t, StringRef> SymbolEntry;
SmallVector<SymbolEntry, 64> Symbols;
// Index of all the names, in this section or not. Used when we're
// dealing with relocation entries.
SmallVector<StringRef, 64> SymbolNames;
for (unsigned i = 0; i != SymtabLC->NumSymbolTableEntries; ++i) {
InMemoryStruct<macho::Symbol64TableEntry> STE;
Obj->ReadSymbol64TableEntry(SymtabLC->SymbolTableOffset, i, STE);
if (!STE)
return Error("unable to read symbol: '" + Twine(i) + "'");
if (STE->SectionIndex > Segment64LC->NumSections)
return Error("invalid section index for symbol: '" + Twine(i) + "'");
// Get the symbol name.
StringRef Name = Obj->getStringAtIndex(STE->StringIndex);
SymbolNames.push_back(Name);
// Just skip symbols not defined in this section.
if ((unsigned)STE->SectionIndex - 1 != SectNum)
continue;
// FIXME: Check the symbol type and flags.
if (STE->Type != 0xF) // external, defined in this section.
continue;
// Flags in the upper nibble we don't care about.
if ((STE->Flags & 0xf) != 0x0)
continue;
// Remember the symbol.
Symbols.push_back(SymbolEntry(STE->Value, Name));
DEBUG(dbgs() << "Function sym: '" << Name << "' @ " <<
(Sect->Address + STE->Value) << "\n");
}
// Sort the symbols by address, just in case they didn't come in that way.
array_pod_sort(Symbols.begin(), Symbols.end());
// If there weren't any functions (odd, but just in case...)
if (!Symbols.size())
continue;
// Extract the function data.
uint8_t *Base = (uint8_t*)Obj->getData(Segment64LC->FileOffset,
Segment64LC->FileSize).data();
for (unsigned i = 0, e = Symbols.size() - 1; i != e; ++i) {
uint64_t StartOffset = Sect->Address + Symbols[i].first;
uint64_t EndOffset = Symbols[i + 1].first - 1;
DEBUG(dbgs() << "Extracting function: " << Symbols[i].second
<< " from [" << StartOffset << ", " << EndOffset << "]\n");
extractFunction(Symbols[i].second, Base + StartOffset, Base + EndOffset);
}
// The last symbol we do after since the end address is calculated
// differently because there is no next symbol to reference.
uint64_t StartOffset = Symbols[Symbols.size() - 1].first;
uint64_t EndOffset = Sect->Size - 1;
DEBUG(dbgs() << "Extracting function: " << Symbols[Symbols.size()-1].second
<< " from [" << StartOffset << ", " << EndOffset << "]\n");
extractFunction(Symbols[Symbols.size()-1].second,
Base + StartOffset, Base + EndOffset);
// Now extract the relocation information for each function and process it.
for (unsigned j = 0; j != Sect->NumRelocationTableEntries; ++j) {
InMemoryStruct<macho::RelocationEntry> RE;
Obj->ReadRelocationEntry(Sect->RelocationTableOffset, j, RE);
if (RE->Word0 & macho::RF_Scattered)
return Error("NOT YET IMPLEMENTED: scattered relocations.");
// Word0 of the relocation is the offset into the section where the
// relocation should be applied. We need to translate that into an
// offset into a function since that's our atom.
uint32_t Offset = RE->Word0;
// Look for the function containing the address. This is used for JIT
// code, so the number of functions in section is almost always going
// to be very small (usually just one), so until we have use cases
// where that's not true, just use a trivial linear search.
unsigned SymbolNum;
unsigned NumSymbols = Symbols.size();
assert(NumSymbols > 0 && Symbols[0].first <= Offset &&
"No symbol containing relocation!");
for (SymbolNum = 0; SymbolNum < NumSymbols - 1; ++SymbolNum)
if (Symbols[SymbolNum + 1].first > Offset)
break;
// Adjust the offset to be relative to the symbol.
Offset -= Symbols[SymbolNum].first;
// Get the name of the symbol containing the relocation.
StringRef TargetName = SymbolNames[SymbolNum];
bool isExtern = (RE->Word1 >> 27) & 1;
// Figure out the source symbol of the relocation. If isExtern is true,
// this relocation references the symbol table, otherwise it references
// a section in the same object, numbered from 1 through NumSections
// (SectionBases is [0, NumSections-1]).
if (!isExtern)
return Error("Internal relocations not supported.");
uint32_t SourceNum = RE->Word1 & 0xffffff; // 24-bit value
StringRef SourceName = SymbolNames[SourceNum];
// FIXME: Get the relocation addend from the target address.
// Now store the relocation information. Associate it with the source
// symbol.
Relocations[SourceName].push_back(RelocationEntry(TargetName,
Offset,
RE->Word1,
0 /*Addend*/));
DEBUG(dbgs() << "Relocation at '" << TargetName << "' + " << Offset
<< " from '" << SourceName << "(Word1: "
<< format("0x%x", RE->Word1) << ")\n");
}
}
return false;
}
bool RuntimeDyldMachO::loadObject(MemoryBuffer *InputBuffer) {
// If the linker is in an error state, don't do anything.
if (hasError())
return true;
// Load the Mach-O wrapper object.
std::string ErrorStr;
OwningPtr<MachOObject> Obj(
MachOObject::LoadFromBuffer(InputBuffer, &ErrorStr));
if (!Obj)
return Error("unable to load object: '" + ErrorStr + "'");
// Get the CPU type information from the header.
const macho::Header &Header = Obj->getHeader();
// FIXME: Error checking that the loaded object is compatible with
// the system we're running on.
CPUType = Header.CPUType;
CPUSubtype = Header.CPUSubtype;
// Validate that the load commands match what we expect.
const MachOObject::LoadCommandInfo *SegmentLCI = 0, *SymtabLCI = 0,
*DysymtabLCI = 0;
for (unsigned i = 0; i != Header.NumLoadCommands; ++i) {
const MachOObject::LoadCommandInfo &LCI = Obj->getLoadCommandInfo(i);
switch (LCI.Command.Type) {
case macho::LCT_Segment:
case macho::LCT_Segment64:
if (SegmentLCI)
return Error("unexpected input object (multiple segments)");
SegmentLCI = &LCI;
break;
case macho::LCT_Symtab:
if (SymtabLCI)
return Error("unexpected input object (multiple symbol tables)");
SymtabLCI = &LCI;
break;
case macho::LCT_Dysymtab:
if (DysymtabLCI)
return Error("unexpected input object (multiple symbol tables)");
DysymtabLCI = &LCI;
break;
default:
return Error("unexpected input object (unexpected load command");
}
}
if (!SymtabLCI)
return Error("no symbol table found in object");
if (!SegmentLCI)
return Error("no symbol table found in object");
// Read and register the symbol table data.
InMemoryStruct<macho::SymtabLoadCommand> SymtabLC;
Obj->ReadSymtabLoadCommand(*SymtabLCI, SymtabLC);
if (!SymtabLC)
return Error("unable to load symbol table load command");
Obj->RegisterStringTable(*SymtabLC);
// Read the dynamic link-edit information, if present (not present in static
// objects).
if (DysymtabLCI) {
InMemoryStruct<macho::DysymtabLoadCommand> DysymtabLC;
Obj->ReadDysymtabLoadCommand(*DysymtabLCI, DysymtabLC);
if (!DysymtabLC)
return Error("unable to load dynamic link-exit load command");
// FIXME: We don't support anything interesting yet.
// if (DysymtabLC->LocalSymbolsIndex != 0)
// return Error("NOT YET IMPLEMENTED: local symbol entries");
// if (DysymtabLC->ExternalSymbolsIndex != 0)
// return Error("NOT YET IMPLEMENTED: non-external symbol entries");
// if (DysymtabLC->UndefinedSymbolsIndex != SymtabLC->NumSymbolTableEntries)
// return Error("NOT YET IMPLEMENTED: undefined symbol entries");
}
// Load the segment load command.
if (SegmentLCI->Command.Type == macho::LCT_Segment) {
if (loadSegment32(Obj.get(), SegmentLCI, SymtabLC))
return true;
} else {
if (loadSegment64(Obj.get(), SegmentLCI, SymtabLC))
return true;
}
return false;
}
// Assign an address to a symbol name and resolve all the relocations
// associated with it.
void RuntimeDyldMachO::reassignSymbolAddress(StringRef Name, uint8_t *Addr) {
// Assign the address in our symbol table.
SymbolTable[Name] = Addr;
RelocationList &Relocs = Relocations[Name];
for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
RelocationEntry &RE = Relocs[i];
uint8_t *Target = SymbolTable[RE.Target] + RE.Offset;
bool isPCRel = (RE.Data >> 24) & 1;
unsigned Type = (RE.Data >> 28) & 0xf;
unsigned Size = 1 << ((RE.Data >> 25) & 3);
DEBUG(dbgs() << "Resolving relocation at '" << RE.Target
<< "' + " << RE.Offset << " (" << format("%p", Target) << ")"
<< " from '" << Name << " (" << format("%p", Addr) << ")"
<< "(" << (isPCRel ? "pcrel" : "absolute")
<< ", type: " << Type << ", Size: " << Size << ").\n");
resolveRelocation(Target, Addr, isPCRel, Type, Size);
RE.isResolved = true;
}
}
bool RuntimeDyldMachO::isKnownFormat(const MemoryBuffer *InputBuffer) {
StringRef Magic = InputBuffer->getBuffer().slice(0, 4);
if (Magic == "\xFE\xED\xFA\xCE") return true;
if (Magic == "\xCE\xFA\xED\xFE") return true;
if (Magic == "\xFE\xED\xFA\xCF") return true;
if (Magic == "\xCF\xFA\xED\xFE") return true;
return false;
}
} // end namespace llvm
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