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324 lines
12 KiB
C++
324 lines
12 KiB
C++
//===-- ELFWriter.h - Target-independent ELF writer support -----*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by Chris Lattner and is distributed under the
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// University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the ELFWriter class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_ELFWRITER_H
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#define LLVM_CODEGEN_ELFWRITER_H
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include <list>
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namespace llvm {
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class GlobalVariable;
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class Mangler;
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class MachineCodeEmitter;
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class ELFCodeEmitter;
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/// ELFWriter - This class implements the common target-independent code for
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/// writing ELF files. Targets should derive a class from this to
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/// parameterize the output format.
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///
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class ELFWriter : public MachineFunctionPass {
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friend class ELFCodeEmitter;
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public:
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MachineCodeEmitter &getMachineCodeEmitter() const {
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return *(MachineCodeEmitter*)MCE;
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}
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~ELFWriter();
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typedef std::vector<unsigned char> DataBuffer;
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protected:
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ELFWriter(std::ostream &O, TargetMachine &TM);
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/// Output stream to send the resultant object file to.
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///
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std::ostream &O;
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/// Target machine description.
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///
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TargetMachine &TM;
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/// Mang - The object used to perform name mangling for this module.
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///
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Mangler *Mang;
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/// MCE - The MachineCodeEmitter object that we are exposing to emit machine
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/// code for functions to the .o file.
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ELFCodeEmitter *MCE;
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//===------------------------------------------------------------------===//
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// Properties to be set by the derived class ctor, used to configure the
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// ELFWriter.
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// e_machine - This field is the target specific value to emit as the
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// e_machine member of the ELF header.
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unsigned short e_machine;
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// e_flags - The machine flags for the target. This defaults to zero.
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unsigned e_flags;
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//===------------------------------------------------------------------===//
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// Properties inferred automatically from the target machine.
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//
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/// is64Bit/isLittleEndian - This information is inferred from the target
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/// machine directly, indicating whether to emit a 32- or 64-bit ELF file.
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bool is64Bit, isLittleEndian;
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/// doInitialization - Emit the file header and all of the global variables
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/// for the module to the ELF file.
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bool doInitialization(Module &M);
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bool runOnMachineFunction(MachineFunction &MF);
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/// doFinalization - Now that the module has been completely processed, emit
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/// the ELF file to 'O'.
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bool doFinalization(Module &M);
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private:
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// The buffer we accumulate the file header into. Note that this should be
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// changed into something much more efficient later (and the bytecode writer
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// as well!).
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DataBuffer FileHeader;
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/// ELFSection - This struct contains information about each section that is
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/// emitted to the file. This is eventually turned into the section header
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/// table at the end of the file.
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struct ELFSection {
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std::string Name; // Name of the section.
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unsigned NameIdx; // Index in .shstrtab of name, once emitted.
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unsigned Type;
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unsigned Flags;
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uint64_t Addr;
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unsigned Offset;
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unsigned Size;
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unsigned Link;
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unsigned Info;
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unsigned Align;
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unsigned EntSize;
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/// SectionIdx - The number of the section in the Section Table.
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///
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unsigned short SectionIdx;
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/// SectionData - The actual data for this section which we are building
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/// up for emission to the file.
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DataBuffer SectionData;
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enum { SHT_NULL = 0, SHT_PROGBITS = 1, SHT_SYMTAB = 2, SHT_STRTAB = 3,
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SHT_RELA = 4, SHT_HASH = 5, SHT_DYNAMIC = 6, SHT_NOTE = 7,
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SHT_NOBITS = 8, SHT_REL = 9, SHT_SHLIB = 10, SHT_DYNSYM = 11 };
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enum { SHN_UNDEF = 0, SHN_ABS = 0xFFF1, SHN_COMMON = 0xFFF2 };
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enum { // SHF - ELF Section Header Flags
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SHF_WRITE = 1 << 0, // Writable
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SHF_ALLOC = 1 << 1, // Mapped into the process addr space
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SHF_EXECINSTR = 1 << 2, // Executable
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SHF_MERGE = 1 << 4, // Might be merged if equal
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SHF_STRINGS = 1 << 5, // Contains null-terminated strings
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SHF_INFO_LINK = 1 << 6, // 'sh_info' contains SHT index
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SHF_LINK_ORDER = 1 << 7, // Preserve order after combining
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SHF_OS_NONCONFORMING = 1 << 8, // nonstandard OS support required
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SHF_GROUP = 1 << 9, // Section is a member of a group
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SHF_TLS = 1 << 10 // Section holds thread-local data
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};
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ELFSection(const std::string &name)
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: Name(name), Type(0), Flags(0), Addr(0), Offset(0), Size(0),
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Link(0), Info(0), Align(0), EntSize(0) {
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}
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};
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/// SectionList - This is the list of sections that we have emitted to the
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/// file. Once the file has been completely built, the section header table
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/// is constructed from this info.
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std::list<ELFSection> SectionList;
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unsigned NumSections; // Always = SectionList.size()
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/// SectionLookup - This is a mapping from section name to section number in
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/// the SectionList.
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std::map<std::string, ELFSection*> SectionLookup;
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/// getSection - Return the section with the specified name, creating a new
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/// section if one does not already exist.
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ELFSection &getSection(const std::string &Name,
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unsigned Type, unsigned Flags = 0) {
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ELFSection *&SN = SectionLookup[Name];
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if (SN) return *SN;
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SectionList.push_back(Name);
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SN = &SectionList.back();
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SN->SectionIdx = NumSections++;
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SN->Type = Type;
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SN->Flags = Flags;
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return *SN;
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}
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ELFSection &getDataSection() {
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return getSection(".data", ELFSection::SHT_PROGBITS,
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ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC);
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}
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ELFSection &getBSSSection() {
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return getSection(".bss", ELFSection::SHT_NOBITS,
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ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC);
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}
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/// ELFSym - This struct contains information about each symbol that is
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/// added to logical symbol table for the module. This is eventually
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/// turned into a real symbol table in the file.
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struct ELFSym {
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const GlobalValue *GV; // The global value this corresponds to.
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unsigned NameIdx; // Index in .strtab of name, once emitted.
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uint64_t Value;
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unsigned Size;
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unsigned char Info;
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unsigned char Other;
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unsigned short SectionIdx;
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enum { STB_LOCAL = 0, STB_GLOBAL = 1, STB_WEAK = 2 };
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enum { STT_NOTYPE = 0, STT_OBJECT = 1, STT_FUNC = 2, STT_SECTION = 3,
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STT_FILE = 4 };
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ELFSym(const GlobalValue *gv) : GV(gv), Value(0), Size(0), Info(0),
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Other(0), SectionIdx(0) {}
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void SetBind(unsigned X) {
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assert(X == (X & 0xF) && "Bind value out of range!");
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Info = (Info & 0x0F) | (X << 4);
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}
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void SetType(unsigned X) {
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assert(X == (X & 0xF) && "Type value out of range!");
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Info = (Info & 0xF0) | X;
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}
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};
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/// SymbolTable - This is the list of symbols we have emitted to the file.
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/// This actually gets rearranged before emission to the file (to put the
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/// local symbols first in the list).
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std::vector<ELFSym> SymbolTable;
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// As we complete the ELF file, we need to update fields in the ELF header
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// (e.g. the location of the section table). These members keep track of
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// the offset in ELFHeader of these various pieces to update and other
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// locations in the file.
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unsigned ELFHeader_e_shoff_Offset; // e_shoff in ELF header.
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unsigned ELFHeader_e_shstrndx_Offset; // e_shstrndx in ELF header.
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unsigned ELFHeader_e_shnum_Offset; // e_shnum in ELF header.
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// align - Emit padding into the file until the current output position is
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// aligned to the specified power of two boundary.
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static void align(DataBuffer &Output, unsigned Boundary) {
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assert(Boundary && (Boundary & (Boundary-1)) == 0 &&
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"Must align to 2^k boundary");
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size_t Size = Output.size();
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if (Size & (Boundary-1)) {
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// Add padding to get alignment to the correct place.
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size_t Pad = Boundary-(Size & (Boundary-1));
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Output.resize(Size+Pad);
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}
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}
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static void outbyte(DataBuffer &Output, unsigned char X) {
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Output.push_back(X);
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}
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void outhalf(DataBuffer &Output, unsigned short X) {
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if (isLittleEndian) {
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Output.push_back(X&255);
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Output.push_back(X >> 8);
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} else {
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Output.push_back(X >> 8);
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Output.push_back(X&255);
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}
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}
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void outword(DataBuffer &Output, unsigned X) {
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if (isLittleEndian) {
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Output.push_back((X >> 0) & 255);
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Output.push_back((X >> 8) & 255);
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Output.push_back((X >> 16) & 255);
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Output.push_back((X >> 24) & 255);
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} else {
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Output.push_back((X >> 24) & 255);
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Output.push_back((X >> 16) & 255);
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Output.push_back((X >> 8) & 255);
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Output.push_back((X >> 0) & 255);
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}
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}
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void outxword(DataBuffer &Output, uint64_t X) {
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if (isLittleEndian) {
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Output.push_back(unsigned(X >> 0) & 255);
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Output.push_back(unsigned(X >> 8) & 255);
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Output.push_back(unsigned(X >> 16) & 255);
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Output.push_back(unsigned(X >> 24) & 255);
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Output.push_back(unsigned(X >> 32) & 255);
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Output.push_back(unsigned(X >> 40) & 255);
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Output.push_back(unsigned(X >> 48) & 255);
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Output.push_back(unsigned(X >> 56) & 255);
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} else {
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Output.push_back(unsigned(X >> 56) & 255);
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Output.push_back(unsigned(X >> 48) & 255);
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Output.push_back(unsigned(X >> 40) & 255);
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Output.push_back(unsigned(X >> 32) & 255);
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Output.push_back(unsigned(X >> 24) & 255);
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Output.push_back(unsigned(X >> 16) & 255);
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Output.push_back(unsigned(X >> 8) & 255);
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Output.push_back(unsigned(X >> 0) & 255);
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}
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}
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void outaddr32(DataBuffer &Output, unsigned X) {
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outword(Output, X);
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}
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void outaddr64(DataBuffer &Output, uint64_t X) {
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outxword(Output, X);
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}
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void outaddr(DataBuffer &Output, uint64_t X) {
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if (!is64Bit)
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outword(Output, (unsigned)X);
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else
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outxword(Output, X);
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}
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// fix functions - Replace an existing entry at an offset.
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void fixhalf(DataBuffer &Output, unsigned short X, unsigned Offset) {
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unsigned char *P = &Output[Offset];
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P[0] = (X >> (isLittleEndian ? 0 : 8)) & 255;
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P[1] = (X >> (isLittleEndian ? 8 : 0)) & 255;
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}
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void fixword(DataBuffer &Output, unsigned X, unsigned Offset) {
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unsigned char *P = &Output[Offset];
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P[0] = (X >> (isLittleEndian ? 0 : 24)) & 255;
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P[1] = (X >> (isLittleEndian ? 8 : 16)) & 255;
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P[2] = (X >> (isLittleEndian ? 16 : 8)) & 255;
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P[3] = (X >> (isLittleEndian ? 24 : 0)) & 255;
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}
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void fixaddr(DataBuffer &Output, uint64_t X, unsigned Offset) {
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if (!is64Bit)
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fixword(Output, (unsigned)X, Offset);
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else
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assert(0 && "Emission of 64-bit data not implemented yet!");
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}
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private:
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void EmitGlobal(GlobalVariable *GV);
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void EmitSymbolTable();
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void EmitSectionTableStringTable();
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void OutputSectionsAndSectionTable();
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};
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}
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#endif
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