--- /dev/null
+//===-- 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);
+}
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