mirror of
https://github.com/RPCS3/llvm.git
synced 2024-12-23 20:45:06 +00:00
35f0a4f24e
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@22291 91177308-0d34-0410-b5e6-96231b3b80d8
231 lines
8.7 KiB
C++
231 lines
8.7 KiB
C++
//===-- ELFWriter.cpp - Target-independent ELF Writer code ----------------===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file was developed by the LLVM research group and is distributed under
|
|
// the University of Illinois Open Source License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements the target-independent ELF writer. This file writes out
|
|
// the ELF file in the following order:
|
|
//
|
|
// #1. ELF Header
|
|
// #2. '.data' section
|
|
// #3. '.bss' section
|
|
// ...
|
|
// #X. '.shstrtab' section
|
|
// #Y. Section Table
|
|
//
|
|
// The entries in the section table are laid out as:
|
|
// #0. Null entry [required]
|
|
// #1. ".data" entry - global variables with initializers. [ if needed ]
|
|
// #2. ".bss" entry - global variables without initializers. [ if needed ]
|
|
// #3. ".text" entry - the program code
|
|
// ...
|
|
// #N. ".shstrtab" entry - String table for the section names.
|
|
|
|
//
|
|
// NOTE: This code should eventually be extended to support 64-bit ELF (this
|
|
// won't be hard), but we haven't done so yet!
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/CodeGen/ELFWriter.h"
|
|
#include "llvm/Module.h"
|
|
#include "llvm/Target/TargetMachine.h"
|
|
using namespace llvm;
|
|
|
|
ELFWriter::ELFWriter(std::ostream &o, TargetMachine &tm) : O(o), TM(tm) {
|
|
e_machine = 0; // e_machine defaults to 'No Machine'
|
|
e_flags = 0; // e_flags defaults to 0, no flags.
|
|
|
|
is64Bit = TM.getTargetData().getPointerSizeInBits() == 64;
|
|
isLittleEndian = TM.getTargetData().isLittleEndian();
|
|
}
|
|
|
|
// doInitialization - Emit the file header and all of the global variables for
|
|
// the module to the ELF file.
|
|
bool ELFWriter::doInitialization(Module &M) {
|
|
outbyte(0x7F); // EI_MAG0
|
|
outbyte('E'); // EI_MAG1
|
|
outbyte('L'); // EI_MAG2
|
|
outbyte('F'); // EI_MAG3
|
|
outbyte(is64Bit ? 2 : 1); // EI_CLASS
|
|
outbyte(isLittleEndian ? 1 : 2); // EI_DATA
|
|
outbyte(1); // EI_VERSION
|
|
for (unsigned i = OutputBuffer.size(); i != 16; ++i)
|
|
outbyte(0); // EI_PAD up to 16 bytes.
|
|
|
|
// This should change for shared objects.
|
|
outhalf(1); // e_type = ET_REL
|
|
outhalf(e_machine); // e_machine = whatever the target wants
|
|
outword(1); // e_version = 1
|
|
outaddr(0); // e_entry = 0 -> no entry point in .o file
|
|
outaddr(0); // e_phoff = 0 -> no program header for .o
|
|
|
|
ELFHeader_e_shoff_Offset = OutputBuffer.size();
|
|
outaddr(0); // e_shoff
|
|
outword(e_flags); // e_flags = whatever the target wants
|
|
|
|
assert(!is64Bit && "These sizes need to be adjusted for 64-bit!");
|
|
outhalf(52); // e_ehsize = ELF header size
|
|
outhalf(0); // e_phentsize = prog header entry size
|
|
outhalf(0); // e_phnum = # prog header entries = 0
|
|
outhalf(40); // e_shentsize = sect header entry size
|
|
|
|
|
|
ELFHeader_e_shnum_Offset = OutputBuffer.size();
|
|
outhalf(0); // e_shnum = # of section header ents
|
|
ELFHeader_e_shstrndx_Offset = OutputBuffer.size();
|
|
outhalf(0); // e_shstrndx = Section # of '.shstrtab'
|
|
|
|
// Add the null section.
|
|
SectionList.push_back(ELFSection());
|
|
|
|
// Okay, the ELF header has been completed, emit the .data section next.
|
|
ELFSection DataSection(".data", OutputBuffer.size());
|
|
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
|
|
I != E; ++I)
|
|
EmitDATASectionGlobal(I);
|
|
|
|
// If the .data section is nonempty, add it to our list.
|
|
if ((DataSection.Size = OutputBuffer.size()-DataSection.Offset)) {
|
|
DataSection.Align = 4; // FIXME: Compute!
|
|
SectionList.push_back(DataSection);
|
|
}
|
|
|
|
// Okay, emit the .bss section next.
|
|
ELFSection BSSSection(".bss", OutputBuffer.size());
|
|
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
|
|
I != E; ++I)
|
|
EmitBSSSectionGlobal(I);
|
|
|
|
// If the .bss section is nonempty, add it to our list.
|
|
if ((BSSSection.Size = OutputBuffer.size()-BSSSection.Offset)) {
|
|
BSSSection.Align = 4; // FIXME: Compute!
|
|
SectionList.push_back(BSSSection);
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
// isCOMM - A global variable should be emitted to the common area if it is zero
|
|
// initialized and has linkage that permits it to be merged with other globals.
|
|
static bool isCOMM(GlobalVariable *GV) {
|
|
return GV->getInitializer()->isNullValue() &&
|
|
(GV->hasLinkOnceLinkage() || GV->hasInternalLinkage() ||
|
|
GV->hasWeakLinkage());
|
|
}
|
|
|
|
// EmitDATASectionGlobal - Emit a global variable to the .data section if it
|
|
// belongs there.
|
|
void ELFWriter::EmitDATASectionGlobal(GlobalVariable *GV) {
|
|
if (!GV->hasInitializer()) return;
|
|
|
|
// Do not emit a symbol here if it should be emitted to the common area.
|
|
if (isCOMM(GV)) return;
|
|
|
|
EmitGlobal(GV);
|
|
}
|
|
|
|
void ELFWriter::EmitBSSSectionGlobal(GlobalVariable *GV) {
|
|
if (!GV->hasInitializer()) return;
|
|
|
|
// FIXME: We don't support BSS yet!
|
|
return;
|
|
|
|
EmitGlobal(GV);
|
|
}
|
|
|
|
void ELFWriter::EmitGlobal(GlobalVariable *GV) {
|
|
}
|
|
|
|
|
|
bool ELFWriter::runOnMachineFunction(MachineFunction &MF) {
|
|
return false;
|
|
}
|
|
|
|
/// doFinalization - Now that the module has been completely processed, emit
|
|
/// the ELF file to 'O'.
|
|
bool ELFWriter::doFinalization(Module &M) {
|
|
// Emit the string table for the sections in the ELF file we have.
|
|
EmitSectionTableStringTable();
|
|
|
|
// Emit the .o file section table.
|
|
EmitSectionTable();
|
|
|
|
// Emit the .o file to the specified stream.
|
|
O.write((char*)&OutputBuffer[0], OutputBuffer.size());
|
|
|
|
// Free the output buffer.
|
|
std::vector<unsigned char>().swap(OutputBuffer);
|
|
return false;
|
|
}
|
|
|
|
/// EmitSectionTableStringTable - This method adds and emits a section for the
|
|
/// ELF Section Table string table: the string table that holds all of the
|
|
/// section names.
|
|
void ELFWriter::EmitSectionTableStringTable() {
|
|
// First step: add the section for the string table to the list of sections:
|
|
SectionList.push_back(ELFSection(".shstrtab", OutputBuffer.size()));
|
|
SectionList.back().Type = 3; // SHT_STRTAB
|
|
|
|
// Now that we know which section number is the .shstrtab section, update the
|
|
// e_shstrndx entry in the ELF header.
|
|
fixhalf(SectionList.size()-1, ELFHeader_e_shstrndx_Offset);
|
|
|
|
// Set the NameIdx of each section in the string table and emit the bytes for
|
|
// the string table.
|
|
unsigned Index = 0;
|
|
|
|
for (unsigned i = 0, e = SectionList.size(); i != e; ++i) {
|
|
// Set the index into the table. Note if we have lots of entries with
|
|
// common suffixes, we could memoize them here if we cared.
|
|
SectionList[i].NameIdx = Index;
|
|
|
|
// Add the name to the output buffer, including the null terminator.
|
|
OutputBuffer.insert(OutputBuffer.end(), SectionList[i].Name.begin(),
|
|
SectionList[i].Name.end());
|
|
// Add a null terminator.
|
|
OutputBuffer.push_back(0);
|
|
|
|
// Keep track of the number of bytes emitted to this section.
|
|
Index += SectionList[i].Name.size()+1;
|
|
}
|
|
|
|
// Set the size of .shstrtab now that we know what it is.
|
|
SectionList.back().Size = Index;
|
|
}
|
|
|
|
/// EmitSectionTable - Now that we have emitted the entire contents of the file
|
|
/// (all of the sections), emit the section table which informs the reader where
|
|
/// the boundaries are.
|
|
void ELFWriter::EmitSectionTable() {
|
|
// Now that all of the sections have been emitted, set the e_shnum entry in
|
|
// the ELF header.
|
|
fixhalf(SectionList.size(), ELFHeader_e_shnum_Offset);
|
|
|
|
// Now that we know the offset in the file of the section table (which we emit
|
|
// next), update the e_shoff address in the ELF header.
|
|
fixaddr(OutputBuffer.size(), ELFHeader_e_shoff_Offset);
|
|
|
|
// Emit all of the section table entries.
|
|
for (unsigned i = 0, e = SectionList.size(); i != e; ++i) {
|
|
const ELFSection &S = SectionList[i];
|
|
outword(S.NameIdx); // sh_name - Symbol table name idx
|
|
outword(S.Type); // sh_type - Section contents & semantics
|
|
outword(S.Flags); // sh_flags - Section flags.
|
|
outaddr(S.Addr); // sh_addr - The mem address this section appears in.
|
|
outaddr(S.Offset); // sh_offset - The offset from the start of the file.
|
|
outword(S.Size); // sh_size - The section size.
|
|
outword(S.Link); // sh_link - Section header table index link.
|
|
outword(S.Info); // sh_info - Auxillary information.
|
|
outword(S.Align); // sh_addralign - Alignment of section.
|
|
outword(S.EntSize); // sh_entsize - Size of each entry in the section.
|
|
}
|
|
|
|
// Release the memory allocated for the section list.
|
|
std::vector<ELFSection>().swap(SectionList);
|
|
}
|