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Diffstat (limited to 'lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp')
| -rw-r--r-- | lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp | 524 |
1 files changed, 524 insertions, 0 deletions
diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp new file mode 100644 index 0000000000..623e9b2acc --- /dev/null +++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp @@ -0,0 +1,524 @@ +//===-- 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. + if (STE->Flags != 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; + if (STE->Flags != 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 |