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For now, the elf writer is only capable of emitting an empty elf file, with a section table and a section table string table. This will be enhanced in the future :) git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@22290 91177308-0d34-0410-b5e6-96231b3b80d8
175 lines
6.0 KiB
C++
175 lines
6.0 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 the LLVM research group and is distributed under
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// the 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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namespace llvm {
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class GlobalVariable;
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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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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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//===------------------------------------------------------------------===//
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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 are accumulating the file 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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std::vector<unsigned char> OutputBuffer;
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/// ELFSection - This struct contains information about each section that is
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/// emitted to the OutputBuffer. This is eventually turned into the section
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/// header 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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ELFSection() : Type(0), Flags(0), Addr(0), Offset(0), Size(0), Link(0),
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Info(0), Align(0), EntSize(0) {
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}
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ELFSection(const char *name, unsigned offset)
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: Name(name), Type(0), Flags(0), Addr(0), Offset(offset), 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::vector<ELFSection> SectionList;
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// As we accumulate the ELF file into OutputBuffer, we occasionally need to
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// keep track of locations to update later (e.g. the location of the section
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// table in the ELF header. These members keep track of the offset in
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// OffsetBuffer of these various pieces to update and other locations in the
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// 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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void outbyte(unsigned char X) { OutputBuffer.push_back(X); }
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void outhalf(unsigned short X) {
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if (isLittleEndian) {
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OutputBuffer.push_back(X&255);
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OutputBuffer.push_back(X >> 8);
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} else {
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OutputBuffer.push_back(X >> 8);
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OutputBuffer.push_back(X&255);
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}
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}
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void outword(unsigned X) {
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if (isLittleEndian) {
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OutputBuffer.push_back((X >> 0) & 255);
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OutputBuffer.push_back((X >> 8) & 255);
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OutputBuffer.push_back((X >> 16) & 255);
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OutputBuffer.push_back((X >> 24) & 255);
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} else {
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OutputBuffer.push_back((X >> 24) & 255);
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OutputBuffer.push_back((X >> 16) & 255);
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OutputBuffer.push_back((X >> 8) & 255);
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OutputBuffer.push_back((X >> 0) & 255);
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}
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}
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void outaddr(uint64_t X) {
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if (!is64Bit)
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outword((unsigned)X);
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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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// fix functions - Replace an existing entry at an offset.
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void fixhalf(unsigned short X, unsigned Offset) {
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unsigned char *P = &OutputBuffer[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(unsigned X, unsigned Offset) {
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unsigned char *P = &OutputBuffer[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(uint64_t X, unsigned Offset) {
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if (!is64Bit)
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fixword((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 EmitDATASectionGlobal(GlobalVariable *GV);
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void EmitBSSSectionGlobal(GlobalVariable *GV);
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void EmitGlobal(GlobalVariable *GV);
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void EmitSectionTableStringTable();
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void EmitSectionTable();
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};
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}
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#endif
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