Remove elf specific info from ELFWriter.h to Elf.h. Code cleanup and more comments added
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72982 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/ELFWriter.cpp b/lib/CodeGen/ELFWriter.cpp
index be8edce..24f12a3 100644
--- a/lib/CodeGen/ELFWriter.cpp
+++ b/lib/CodeGen/ELFWriter.cpp
@@ -33,6 +33,7 @@
#include "ELFWriter.h"
#include "ELFCodeEmitter.h"
+#include "ELF.h"
#include "llvm/Module.h"
#include "llvm/PassManager.h"
#include "llvm/DerivedTypes.h"
@@ -67,7 +68,8 @@
ELFWriter::ELFWriter(raw_ostream &o, TargetMachine &tm)
: MachineFunctionPass(&ID), O(o), TM(tm) {
- e_flags = 0; // e_flags defaults to 0, no flags.
+ e_flags = 0; // e_flags defaults to 0, no flags.
+ e_machine = TM.getELFWriterInfo()->getEMachine();
is64Bit = TM.getTargetData()->getPointerSizeInBits() == 64;
isLittleEndian = TM.getTargetData()->isLittleEndian();
@@ -90,24 +92,39 @@
std::vector<unsigned char> &FH = FileHeader;
OutputBuffer FHOut(FH, is64Bit, isLittleEndian);
- FHOut.outbyte(0x7F); // EI_MAG0
- FHOut.outbyte('E'); // EI_MAG1
- FHOut.outbyte('L'); // EI_MAG2
- FHOut.outbyte('F'); // EI_MAG3
- FHOut.outbyte(is64Bit ? 2 : 1); // EI_CLASS
- FHOut.outbyte(isLittleEndian ? 1 : 2); // EI_DATA
- FHOut.outbyte(1); // EI_VERSION
- FH.resize(16); // EI_PAD up to 16 bytes.
+ unsigned ElfClass = is64Bit ? ELFCLASS64 : ELFCLASS32;
+ unsigned ElfEndian = isLittleEndian ? ELFDATA2LSB : ELFDATA2MSB;
- // This should change for shared objects.
- FHOut.outhalf(1); // e_type = ET_REL
- FHOut.outhalf(TM.getELFWriterInfo()->getEMachine()); // target-defined
- FHOut.outword(1); // e_version = 1
- FHOut.outaddr(0); // e_entry = 0 -> no entry point in .o file
- FHOut.outaddr(0); // e_phoff = 0 -> no program header for .o
+ // ELF Header
+ // ----------
+ // Fields e_shnum e_shstrndx are only known after all section have
+ // been emitted. They locations in the ouput buffer are recorded so
+ // to be patched up later.
+ //
+ // Note
+ // ----
+ // FHOut.outaddr method behaves differently for ELF32 and ELF64 writing
+ // 4 bytes in the former and 8 in the last for *_off and *_addr elf types
- ELFHeader_e_shoff_Offset = FH.size();
- FHOut.outaddr(0); // e_shoff
+ FHOut.outbyte(0x7f); // e_ident[EI_MAG0]
+ FHOut.outbyte('E'); // e_ident[EI_MAG1]
+ FHOut.outbyte('L'); // e_ident[EI_MAG2]
+ FHOut.outbyte('F'); // e_ident[EI_MAG3]
+
+ FHOut.outbyte(ElfClass); // e_ident[EI_CLASS]
+ FHOut.outbyte(ElfEndian); // e_ident[EI_DATA]
+ FHOut.outbyte(EV_CURRENT); // e_ident[EI_VERSION]
+
+ FH.resize(16); // e_ident[EI_NIDENT-EI_PAD]
+
+ FHOut.outhalf(ET_REL); // e_type
+ FHOut.outhalf(e_machine); // e_machine = target
+ FHOut.outword(EV_CURRENT); // e_version
+ FHOut.outaddr(0); // e_entry = 0 -> no entry point in .o file
+ FHOut.outaddr(0); // e_phoff = 0 -> no program header for .o
+
+ ELFHdr_e_shoff_Offset = FH.size();
+ FHOut.outaddr(0); // e_shoff = sec hdr table off in bytes
FHOut.outword(e_flags); // e_flags = whatever the target wants
FHOut.outhalf(is64Bit ? 64 : 52); // e_ehsize = ELF header size
@@ -115,14 +132,16 @@
FHOut.outhalf(0); // e_phnum = # prog header entries = 0
FHOut.outhalf(is64Bit ? 64 : 40); // e_shentsize = sect hdr entry size
+ // e_shnum = # of section header ents
+ ELFHdr_e_shnum_Offset = FH.size();
+ FHOut.outhalf(0);
- ELFHeader_e_shnum_Offset = FH.size();
- FHOut.outhalf(0); // e_shnum = # of section header ents
- ELFHeader_e_shstrndx_Offset = FH.size();
- FHOut.outhalf(0); // e_shstrndx = Section # of '.shstrtab'
+ // e_shstrndx = Section # of '.shstrtab'
+ ELFHdr_e_shstrndx_Offset = FH.size();
+ FHOut.outhalf(0);
// Add the null section, which is required to be first in the file.
- getSection("", 0, 0);
+ getSection("", ELFSection::SHT_NULL, 0);
// Start up the symbol table. The first entry in the symtab is the null
// entry.
@@ -334,7 +353,7 @@
// Now that we know which section number is the .shstrtab section, update the
// e_shstrndx entry in the ELF header.
OutputBuffer FHOut(FileHeader, is64Bit, isLittleEndian);
- FHOut.fixhalf(SHStrTab.SectionIdx, ELFHeader_e_shstrndx_Offset);
+ FHOut.fixhalf(SHStrTab.SectionIdx, ELFHdr_e_shstrndx_Offset);
// Set the NameIdx of each section in the string table and emit the bytes for
// the string table.
@@ -386,11 +405,11 @@
// Now that we know where all of the sections will be emitted, set the e_shnum
// entry in the ELF header.
OutputBuffer FHOut(FileHeader, is64Bit, isLittleEndian);
- FHOut.fixhalf(NumSections, ELFHeader_e_shnum_Offset);
+ FHOut.fixhalf(NumSections, ELFHdr_e_shnum_Offset);
// Now that we know the offset in the file of the section table, update the
// e_shoff address in the ELF header.
- FHOut.fixaddr(FileOff, ELFHeader_e_shoff_Offset);
+ FHOut.fixaddr(FileOff, ELFHdr_e_shoff_Offset);
// Now that we know all of the data in the file header, emit it and all of the
// sections!