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-rw-r--r--lib/CodeGen/ELFWriter.cpp362
1 files changed, 231 insertions, 131 deletions
diff --git a/lib/CodeGen/ELFWriter.cpp b/lib/CodeGen/ELFWriter.cpp
index aeccefbd3e80..03db65699a2a 100644
--- a/lib/CodeGen/ELFWriter.cpp
+++ b/lib/CodeGen/ELFWriter.cpp
@@ -136,104 +136,40 @@ bool ELFWriter::doInitialization(Module &M) {
ElfHdr.emitWord16(0); // Placeholder
// Add the null section, which is required to be first in the file.
- getSection("", ELFSection::SHT_NULL, 0);
-
- // Start up the symbol table. The first entry in the symtab is the null
- // entry.
- SymbolList.push_back(ELFSym(0));
+ getNullSection();
return false;
}
-void ELFWriter::EmitGlobal(GlobalVariable *GV) {
+unsigned ELFWriter::getGlobalELFLinkage(const GlobalVariable *GV) {
+ if (GV->hasInternalLinkage())
+ return ELFSym::STB_LOCAL;
+
+ if (GV->hasWeakLinkage())
+ return ELFSym::STB_WEAK;
- // XXX: put local symbols *before* global ones!
+ return ELFSym::STB_GLOBAL;
+}
+
+// For global symbols without a section, return the Null section as a
+// placeholder
+ELFSection &ELFWriter::getGlobalSymELFSection(const GlobalVariable *GV,
+ ELFSym &Sym) {
const Section *S = TAI->SectionForGlobal(GV);
+ unsigned Flags = S->getFlags();
+ unsigned SectionType = ELFSection::SHT_PROGBITS;
+ unsigned SHdrFlags = ELFSection::SHF_ALLOC;
DOUT << "Section " << S->getName() << " for global " << GV->getName() << "\n";
- // If this is an external global, emit it now. TODO: Note that it would be
- // better to ignore the symbol here and only add it to the symbol table if
- // referenced.
+ // If this is an external global, the symbol does not have a section.
if (!GV->hasInitializer()) {
- ELFSym ExternalSym(GV);
- ExternalSym.SetBind(ELFSym::STB_GLOBAL);
- ExternalSym.SetType(ELFSym::STT_NOTYPE);
- ExternalSym.SectionIdx = ELFSection::SHN_UNDEF;
- SymbolList.push_back(ExternalSym);
- return;
+ Sym.SectionIdx = ELFSection::SHN_UNDEF;
+ return getNullSection();
}
const TargetData *TD = TM.getTargetData();
unsigned Align = TD->getPreferredAlignment(GV);
Constant *CV = GV->getInitializer();
- unsigned Size = TD->getTypeAllocSize(CV->getType());
-
- // If this global has a zero initializer, go to .bss or common section.
- if (CV->isNullValue() || isa<UndefValue>(CV)) {
- // If this global is part of the common block, add it now. Variables are
- // part of the common block if they are zero initialized and allowed to be
- // merged with other symbols.
- if (GV->hasLinkOnceLinkage() || GV->hasWeakLinkage() ||
- GV->hasCommonLinkage()) {
- ELFSym CommonSym(GV);
- // Value for common symbols is the alignment required.
- CommonSym.Value = Align;
- CommonSym.Size = Size;
- CommonSym.SetBind(ELFSym::STB_GLOBAL);
- CommonSym.SetType(ELFSym::STT_OBJECT);
- CommonSym.SectionIdx = ELFSection::SHN_COMMON;
- SymbolList.push_back(CommonSym);
- getSection(S->getName(), ELFSection::SHT_NOBITS,
- ELFSection::SHF_WRITE | ELFSection::SHF_ALLOC, 1);
- return;
- }
-
- // Otherwise, this symbol is part of the .bss section. Emit it now.
- // Handle alignment. Ensure section is aligned at least as much as required
- // by this symbol.
- ELFSection &BSSSection = getBSSSection();
- BSSSection.Align = std::max(BSSSection.Align, Align);
-
- // Within the section, emit enough virtual padding to get us to an alignment
- // boundary.
- if (Align)
- BSSSection.Size = (BSSSection.Size + Align - 1) & ~(Align-1);
-
- ELFSym BSSSym(GV);
- BSSSym.Value = BSSSection.Size;
- BSSSym.Size = Size;
- BSSSym.SetType(ELFSym::STT_OBJECT);
-
- switch (GV->getLinkage()) {
- default: // weak/linkonce/common handled above
- assert(0 && "Unexpected linkage type!");
- case GlobalValue::AppendingLinkage: // FIXME: This should be improved!
- case GlobalValue::ExternalLinkage:
- BSSSym.SetBind(ELFSym::STB_GLOBAL);
- break;
- case GlobalValue::InternalLinkage:
- BSSSym.SetBind(ELFSym::STB_LOCAL);
- break;
- }
-
- // Set the idx of the .bss section
- BSSSym.SectionIdx = BSSSection.SectionIdx;
- if (!GV->hasPrivateLinkage())
- SymbolList.push_back(BSSSym);
-
- // Reserve space in the .bss section for this symbol.
- BSSSection.Size += Size;
- return;
- }
-
- /// Emit the Global symbol to the right ELF section
- ELFSym GblSym(GV);
- GblSym.Size = Size;
- GblSym.SetType(ELFSym::STT_OBJECT);
- GblSym.SetBind(ELFSym::STB_GLOBAL);
- unsigned Flags = S->getFlags();
- unsigned SectType = ELFSection::SHT_PROGBITS;
- unsigned SHdrFlags = ELFSection::SHF_ALLOC;
if (Flags & SectionFlags::Code)
SHdrFlags |= ELFSection::SHF_EXECINSTR;
@@ -246,29 +182,81 @@ void ELFWriter::EmitGlobal(GlobalVariable *GV) {
if (Flags & SectionFlags::Strings)
SHdrFlags |= ELFSection::SHF_STRINGS;
- // Remove tab from section name prefix
- std::string SectionName(S->getName());
- size_t Pos = SectionName.find("\t");
- if (Pos != std::string::npos)
- SectionName.erase(Pos, 1);
-
- // The section alignment should be bound to the element with
- // the largest alignment
- ELFSection &ElfS = getSection(SectionName, SectType, SHdrFlags);
- GblSym.SectionIdx = ElfS.SectionIdx;
- if (Align > ElfS.Align)
- ElfS.Align = Align;
-
- // S.Value should contain the symbol index inside the section,
- // and all symbols should start on their required alignment boundary
- GblSym.Value = (ElfS.size() + (Align-1)) & (-Align);
- ElfS.emitAlignment(Align);
-
- // Emit the constant symbol to its section
- EmitGlobalConstant(CV, ElfS);
+ // If this global has a zero initializer, go to .bss or common section.
+ // Variables are part of the common block if they are zero initialized
+ // and allowed to be merged with other symbols.
+ if (CV->isNullValue() || isa<UndefValue>(CV)) {
+ SectionType = ELFSection::SHT_NOBITS;
+ ELFSection &ElfS = getSection(S->getName(), SectionType, SHdrFlags);
+ if (GV->hasLinkOnceLinkage() || GV->hasWeakLinkage() ||
+ GV->hasCommonLinkage()) {
+ Sym.SectionIdx = ELFSection::SHN_COMMON;
+ Sym.IsCommon = true;
+ ElfS.Align = 1;
+ return ElfS;
+ }
+ Sym.IsBss = true;
+ Sym.SectionIdx = ElfS.SectionIdx;
+ if (Align) ElfS.Size = (ElfS.Size + Align-1) & ~(Align-1);
+ ElfS.Align = std::max(ElfS.Align, Align);
+ return ElfS;
+ }
+
+ Sym.IsConstant = true;
+ ELFSection &ElfS = getSection(S->getName(), SectionType, SHdrFlags);
+ Sym.SectionIdx = ElfS.SectionIdx;
+ ElfS.Align = std::max(ElfS.Align, Align);
+ return ElfS;
+}
+
+void ELFWriter::EmitFunctionDeclaration(const Function *F) {
+ ELFSym GblSym(F);
+ GblSym.setBind(ELFSym::STB_GLOBAL);
+ GblSym.setType(ELFSym::STT_NOTYPE);
+ GblSym.SectionIdx = ELFSection::SHN_UNDEF;
SymbolList.push_back(GblSym);
}
+void ELFWriter::EmitGlobalVar(const GlobalVariable *GV) {
+ unsigned SymBind = getGlobalELFLinkage(GV);
+ unsigned Align=0, Size=0;
+ ELFSym GblSym(GV);
+ GblSym.setBind(SymBind);
+
+ if (GV->hasInitializer()) {
+ GblSym.setType(ELFSym::STT_OBJECT);
+ const TargetData *TD = TM.getTargetData();
+ Align = TD->getPreferredAlignment(GV);
+ Size = TD->getTypeAllocSize(GV->getInitializer()->getType());
+ GblSym.Size = Size;
+ } else {
+ GblSym.setType(ELFSym::STT_NOTYPE);
+ }
+
+ ELFSection &GblSection = getGlobalSymELFSection(GV, GblSym);
+
+ if (GblSym.IsCommon) {
+ GblSym.Value = Align;
+ } else if (GblSym.IsBss) {
+ GblSym.Value = GblSection.Size;
+ GblSection.Size += Size;
+ } else if (GblSym.IsConstant){
+ // GblSym.Value should contain the symbol index inside the section,
+ // and all symbols should start on their required alignment boundary
+ GblSym.Value = (GblSection.size() + (Align-1)) & (-Align);
+ GblSection.emitAlignment(Align);
+ EmitGlobalConstant(GV->getInitializer(), GblSection);
+ }
+
+ // Local symbols should come first on the symbol table.
+ if (!GV->hasPrivateLinkage()) {
+ if (SymBind == ELFSym::STB_LOCAL)
+ SymbolList.push_front(GblSym);
+ else
+ SymbolList.push_back(GblSym);
+ }
+}
+
void ELFWriter::EmitGlobalConstantStruct(const ConstantStruct *CVS,
ELFSection &GblS) {
@@ -306,6 +294,7 @@ void ELFWriter::EmitGlobalConstant(const Constant *CV, ELFSection &GblS) {
if (const ConstantArray *CVA = dyn_cast<ConstantArray>(CV)) {
if (CVA->isString()) {
std::string GblStr = CVA->getAsString();
+ GblStr.resize(GblStr.size()-1);
GblS.emitString(GblStr);
} else { // Not a string. Print the values in successive locations
for (unsigned i = 0, e = CVA->getNumOperands(); i != e; ++i)
@@ -370,13 +359,39 @@ bool ELFWriter::doFinalization(Module &M) {
// Build and emit data, bss and "common" sections.
for (Module::global_iterator I = M.global_begin(), E = M.global_end();
- I != E; ++I)
- EmitGlobal(I);
+ I != E; ++I) {
+ EmitGlobalVar(I);
+ GblSymLookup[I] = 0;
+ }
+
+ // Emit all pending globals
+ // TODO: this should be done only for referenced symbols
+ for (SetVector<GlobalValue*>::const_iterator I = PendingGlobals.begin(),
+ E = PendingGlobals.end(); I != E; ++I) {
+
+ // No need to emit the symbol again
+ if (GblSymLookup.find(*I) != GblSymLookup.end())
+ continue;
+
+ if (GlobalVariable *GV = dyn_cast<GlobalVariable>(*I)) {
+ EmitGlobalVar(GV);
+ } else if (Function *F = dyn_cast<Function>(*I)) {
+ // If function is not in GblSymLookup, it doesn't have a body,
+ // so emit the symbol as a function declaration (no section associated)
+ EmitFunctionDeclaration(F);
+ } else {
+ assert("unknown howto handle pending global");
+ }
+ GblSymLookup[*I] = 0;
+ }
// Emit non-executable stack note
if (TAI->getNonexecutableStackDirective())
getNonExecStackSection();
+ // Emit string table
+ EmitStringTable();
+
// Emit the symbol table now, if non-empty.
EmitSymbolTable();
@@ -400,6 +415,67 @@ bool ELFWriter::doFinalization(Module &M) {
/// EmitRelocations - Emit relocations
void ELFWriter::EmitRelocations() {
+
+ // Create Relocation sections for each section which needs it.
+ for (std::list<ELFSection>::iterator I = SectionList.begin(),
+ E = SectionList.end(); I != E; ++I) {
+
+ // This section does not have relocations
+ if (!I->hasRelocations()) continue;
+
+ // Get the relocation section for section 'I'
+ bool HasRelA = TEW->hasRelocationAddend();
+ ELFSection &RelSec = getRelocSection(I->getName(), HasRelA);
+
+ // 'Link' - Section hdr idx of the associated symbol table
+ // 'Info' - Section hdr idx of the section to which the relocation applies
+ ELFSection &SymTab = getSymbolTableSection();
+ RelSec.Link = SymTab.SectionIdx;
+ RelSec.Info = I->SectionIdx;
+ RelSec.EntSize = TEW->getRelocationEntrySize();
+
+ // Get the relocations from Section
+ std::vector<MachineRelocation> Relos = I->getRelocations();
+ for (std::vector<MachineRelocation>::iterator MRI = Relos.begin(),
+ MRE = Relos.end(); MRI != MRE; ++MRI) {
+ MachineRelocation &MR = *MRI;
+
+ // Offset from the start of the section containing the symbol
+ unsigned Offset = MR.getMachineCodeOffset();
+
+ // Symbol index in the symbol table
+ unsigned SymIdx = 0;
+
+ // Target specific ELF relocation type
+ unsigned RelType = TEW->getRelocationType(MR.getRelocationType());
+
+ // Constant addend used to compute the value to be stored
+ // into the relocatable field
+ int64_t Addend = TEW->getAddendForRelTy(RelType);
+
+ // There are several machine relocations types, and each one of
+ // them needs a different approach to retrieve the symbol table index.
+ if (MR.isGlobalValue()) {
+ const GlobalValue *G = MR.getGlobalValue();
+ SymIdx = GblSymLookup[G];
+ } else {
+ assert(0 && "dunno how to handle other relocation types");
+ }
+
+ // Get the relocation entry and emit to the relocation section
+ ELFRelocation Rel(Offset, SymIdx, RelType, HasRelA, Addend);
+ EmitRelocation(RelSec, Rel, HasRelA);
+ }
+ }
+}
+
+/// EmitRelocation - Write relocation 'Rel' to the relocation section 'Rel'
+void ELFWriter::EmitRelocation(BinaryObject &RelSec, ELFRelocation &Rel,
+ bool HasRelA) {
+ RelSec.emitWord(Rel.getOffset());
+ RelSec.emitWord(Rel.getInfo(is64Bit));
+ if (HasRelA)
+ RelSec.emitWord(Rel.getAddend());
}
/// EmitSymbol - Write symbol 'Sym' to the symbol table 'SymbolTable'
@@ -448,28 +524,28 @@ void ELFWriter::EmitSectionHeader(BinaryObject &SHdrTab,
}
}
-/// EmitSymbolTable - If the current symbol table is non-empty, emit the string
-/// table for it and then the symbol table itself.
-void ELFWriter::EmitSymbolTable() {
- if (SymbolList.size() == 1) return; // Only the null entry.
-
- // FIXME: compact all local symbols to the start of the symtab.
- unsigned FirstNonLocalSymbol = 1;
-
+/// EmitStringTable - If the current symbol table is non-empty, emit the string
+/// table for it
+void ELFWriter::EmitStringTable() {
+ if (!SymbolList.size()) return; // Empty symbol table.
ELFSection &StrTab = getStringTableSection();
// Set the zero'th symbol to a null byte, as required.
StrTab.emitByte(0);
+ // Walk on the symbol list and write symbol names into the
+ // string table.
unsigned Index = 1;
- for (unsigned i = 1, e = SymbolList.size(); i != e; ++i) {
+ for (std::list<ELFSym>::iterator I = SymbolList.begin(),
+ E = SymbolList.end(); I != E; ++I) {
+
// Use the name mangler to uniquify the LLVM symbol.
- std::string Name = Mang->getValueName(SymbolList[i].GV);
+ std::string Name = Mang->getValueName(I->GV);
if (Name.empty()) {
- SymbolList[i].NameIdx = 0;
+ I->NameIdx = 0;
} else {
- SymbolList[i].NameIdx = Index;
+ I->NameIdx = Index;
StrTab.emitString(Name);
// Keep track of the number of bytes emitted to this section.
@@ -478,20 +554,45 @@ void ELFWriter::EmitSymbolTable() {
}
assert(Index == StrTab.size());
StrTab.Size = Index;
+}
+
+/// EmitSymbolTable - Emit the symbol table itself.
+void ELFWriter::EmitSymbolTable() {
+ if (!SymbolList.size()) return; // Empty symbol table.
+ unsigned FirstNonLocalSymbol = 1;
// Now that we have emitted the string table and know the offset into the
// string table of each symbol, emit the symbol table itself.
ELFSection &SymTab = getSymbolTableSection();
- SymTab.Align = TEW->getSymTabAlignment();
- SymTab.Link = StrTab.SectionIdx; // Section Index of .strtab.
- SymTab.Info = FirstNonLocalSymbol; // First non-STB_LOCAL symbol.
+ SymTab.Align = TEW->getPrefELFAlignment();
+
+ // Section Index of .strtab.
+ SymTab.Link = getStringTableSection().SectionIdx;
// Size of each symtab entry.
SymTab.EntSize = TEW->getSymTabEntrySize();
- for (unsigned i = 0, e = SymbolList.size(); i != e; ++i)
- EmitSymbol(SymTab, SymbolList[i]);
+ // The first entry in the symtab is the null symbol
+ ELFSym NullSym = ELFSym(0);
+ EmitSymbol(SymTab, NullSym);
+
+ // Emit all the symbols to the symbol table. Skip the null
+ // symbol, cause it's emitted already
+ unsigned Index = 1;
+ for (std::list<ELFSym>::iterator I = SymbolList.begin(),
+ E = SymbolList.end(); I != E; ++I, ++Index) {
+ // Keep track of the first non-local symbol
+ if (I->getBind() == ELFSym::STB_LOCAL)
+ FirstNonLocalSymbol++;
+
+ // Emit symbol to the symbol table
+ EmitSymbol(SymTab, *I);
+ // Record the symbol table index for each global value
+ GblSymLookup[I->GV] = Index;
+ }
+
+ SymTab.Info = FirstNonLocalSymbol;
SymTab.Size = SymTab.size();
}
@@ -500,7 +601,7 @@ void ELFWriter::EmitSymbolTable() {
/// section names.
void ELFWriter::EmitSectionTableStringTable() {
// First step: add the section for the string table to the list of sections:
- ELFSection &SHStrTab = getSection(".shstrtab", ELFSection::SHT_STRTAB, 0);
+ ELFSection &SHStrTab = getSectionHeaderStringTableSection();
// Now that we know which section number is the .shstrtab section, update the
// e_shstrndx entry in the ELF header.
@@ -559,7 +660,7 @@ void ELFWriter::OutputSectionsAndSectionTable() {
}
// Align Section Header.
- unsigned TableAlign = is64Bit ? 8 : 4;
+ unsigned TableAlign = TEW->getPrefELFAlignment();
FileOff = (FileOff+TableAlign-1) & ~(TableAlign-1);
// Now that we know where all of the sections will be emitted, set the e_shnum
@@ -586,13 +687,12 @@ void ELFWriter::OutputSectionsAndSectionTable() {
<< ", SectionData Size: " << S.size() << "\n";
// Align FileOff to whatever the alignment restrictions of the section are.
- if (S.Align) {
- for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
- FileOff != NewFileOff; ++FileOff)
- O << (char)0xAB;
- }
-
if (S.size()) {
+ if (S.Align) {
+ for (size_t NewFileOff = (FileOff+S.Align-1) & ~(S.Align-1);
+ FileOff != NewFileOff; ++FileOff)
+ O << (char)0xAB;
+ }
O.write((char *)&S.getData()[0], S.Size);
FileOff += S.Size;
}
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