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256 lines
9.2 KiB
C++
256 lines
9.2 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 is distributed under the University of Illinois Open Source
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// 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 ELFWRITER_H
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#define ELFWRITER_H
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#include "llvm/ADT/SetVector.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include <map>
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namespace llvm {
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class BinaryObject;
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class Constant;
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class ConstantStruct;
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class ELFCodeEmitter;
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class ELFRelocation;
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class ELFSection;
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struct ELFSym;
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class GlobalVariable;
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class Mangler;
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class MachineCodeEmitter;
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class ObjectCodeEmitter;
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class TargetAsmInfo;
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class TargetELFWriterInfo;
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class raw_ostream;
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typedef std::vector<ELFSym*>::iterator ELFSymIter;
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typedef std::vector<ELFSection*>::iterator ELFSectionIter;
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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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static char ID;
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/// Return the ELFCodeEmitter as an instance of ObjectCodeEmitter
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ObjectCodeEmitter *getObjectCodeEmitter() {
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return reinterpret_cast<ObjectCodeEmitter*>(ElfCE);
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}
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ELFWriter(raw_ostream &O, TargetMachine &TM);
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~ELFWriter();
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protected:
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/// Output stream to send the resultant object file to.
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raw_ostream &O;
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/// Target machine description.
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TargetMachine &TM;
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/// Target Elf Writer description.
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const TargetELFWriterInfo *TEW;
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/// Mang - The object used to perform name mangling for this module.
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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 *ElfCE;
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/// TAI - Target Asm Info, provide information about section names for
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/// globals and other target specific stuff.
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const TargetAsmInfo *TAI;
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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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/// Blob containing the Elf header
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BinaryObject ElfHdr;
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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::vector<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. Used to quickly gather the Section Index from TAI names
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std::map<std::string, ELFSection*> SectionLookup;
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/// GblSymLookup - This is a mapping from global value to a symbol index
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/// in the symbol table. This is useful since relocations symbol references
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/// must be quickly mapped to a symbol table index
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std::map<const GlobalValue*, uint32_t> GblSymLookup;
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/// SymbolList - This is the list of symbols emitted to the symbol table.
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/// When the SymbolList is finally built, local symbols must be placed in
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/// the beginning while non-locals at the end.
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std::vector<ELFSym*> SymbolList;
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/// PendingGlobals - List of externally defined symbols that we have been
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/// asked to emit, but have not seen a reference to. When a reference
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/// is seen, the symbol will move from this list to the SymbolList.
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SetVector<GlobalValue*> PendingGlobals;
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// Remove tab from section name prefix. This is necessary becase TAI
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// sometimes return a section name prefixed with elf unused chars. This is
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// a little bit dirty. FIXME: find a better approach, maybe add more
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// methods to TAI to get the clean name?
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void fixNameForSection(std::string &Name) {
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size_t Pos = Name.find("\t");
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if (Pos != std::string::npos)
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Name.erase(Pos, 1);
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Pos = Name.find(".section ");
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if (Pos != std::string::npos)
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Name.erase(Pos, 9);
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Pos = Name.find("\n");
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if (Pos != std::string::npos)
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Name.erase(Pos, 1);
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}
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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, unsigned Type,
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unsigned Flags = 0, unsigned Align = 0) {
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std::string SName(Name);
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fixNameForSection(SName);
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ELFSection *&SN = SectionLookup[SName];
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if (SN) return *SN;
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SectionList.push_back(new ELFSection(SName, isLittleEndian, is64Bit));
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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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SN->Link = ELFSection::SHN_UNDEF;
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SN->Align = Align;
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return *SN;
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}
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/// TODO: support mangled names here to emit the right .text section
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/// for c++ object files.
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ELFSection &getTextSection() {
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return getSection(".text", ELFSection::SHT_PROGBITS,
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ELFSection::SHF_EXECINSTR | ELFSection::SHF_ALLOC);
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}
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/// Get jump table section on the section name returned by TAI
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ELFSection &getJumpTableSection(std::string SName, unsigned Align) {
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return getSection(SName, ELFSection::SHT_PROGBITS,
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ELFSection::SHF_ALLOC, Align);
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}
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/// Get a constant pool section based on the section name returned by TAI
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ELFSection &getConstantPoolSection(std::string SName, unsigned Align) {
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return getSection(SName, ELFSection::SHT_PROGBITS,
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ELFSection::SHF_MERGE | ELFSection::SHF_ALLOC, Align);
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}
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/// Return the relocation section of section 'S'. 'RelA' is true
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/// if the relocation section contains entries with addends.
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ELFSection &getRelocSection(std::string SName, bool RelA, unsigned Align) {
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std::string RelSName(".rel");
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unsigned SHdrTy = RelA ? ELFSection::SHT_RELA : ELFSection::SHT_REL;
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if (RelA) RelSName.append("a");
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RelSName.append(SName);
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return getSection(RelSName, SHdrTy, 0, Align);
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}
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ELFSection &getNonExecStackSection() {
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return getSection(".note.GNU-stack", ELFSection::SHT_PROGBITS, 0, 1);
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}
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ELFSection &getSymbolTableSection() {
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return getSection(".symtab", ELFSection::SHT_SYMTAB, 0);
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}
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ELFSection &getStringTableSection() {
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return getSection(".strtab", ELFSection::SHT_STRTAB, 0, 1);
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}
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ELFSection &getSectionHeaderStringTableSection() {
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return getSection(".shstrtab", ELFSection::SHT_STRTAB, 0, 1);
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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, 4);
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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, 4);
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}
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ELFSection &getNullSection() {
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return getSection("", ELFSection::SHT_NULL, 0);
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}
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// Helpers for obtaining ELF specific info.
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unsigned getGlobalELFBinding(const GlobalValue *GV);
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unsigned getGlobalELFType(const GlobalValue *GV);
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unsigned getGlobalELFVisibility(const GlobalValue *GV);
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unsigned getElfSectionFlags(unsigned Flags);
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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 ELFHdr_e_shoff_Offset; // e_shoff in ELF header.
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unsigned ELFHdr_e_shstrndx_Offset; // e_shstrndx in ELF header.
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unsigned ELFHdr_e_shnum_Offset; // e_shnum in ELF header.
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private:
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void EmitGlobal(const GlobalValue *GV);
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void EmitGlobalConstant(const Constant *C, ELFSection &GblS);
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void EmitGlobalConstantStruct(const ConstantStruct *CVS,
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ELFSection &GblS);
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ELFSection &getGlobalSymELFSection(const GlobalVariable *GV, ELFSym &Sym);
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void EmitRelocations();
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void EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel, bool HasRelA);
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void EmitSectionHeader(BinaryObject &SHdrTab, const ELFSection &SHdr);
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void EmitSectionTableStringTable();
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void EmitSymbol(BinaryObject &SymbolTable, ELFSym &Sym);
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void EmitSymbolTable();
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void EmitStringTable();
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void OutputSectionsAndSectionTable();
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unsigned SortSymbols();
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};
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}
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#endif
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