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[BOLT] Update local symbol count in symbol table
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Summary:
Fix sh_info entry for symbol table section to reflect updated number of
local symbols.

(cherry picked from FBD10503216)
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@maksfb
maksfb committed Oct 23, 2018
1 parent a76b13d commit 30fd960
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Showing 2 changed files with 27 additions and 22 deletions.
46 changes: 24 additions & 22 deletions bolt/src/RewriteInstance.cpp
View file
Expand Up @@ -3873,6 +3873,10 @@ std::vector<uint32_t> RewriteInstance::getOutputSections(
NewSection.sh_size = BSec->getOutputSize();
NewSection.sh_name = SHStrTab.getOffset(SectionName);

if (NewSection.sh_type == ELF::SHT_SYMTAB) {
NewSection.sh_info = NumLocalSymbols;
}

OutputSections->emplace_back(NewSection);

LastFileOffset = BSec->getFileOffset();
Expand Down Expand Up @@ -4005,8 +4009,7 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
auto updateSymbolTable =
[&](bool PatchExisting,
const Elf_Shdr *Section,
std::function<void(size_t, const char *, size_t)>
Write,
std::function<void(size_t, const Elf_Sym &)> Write,
std::function<size_t(StringRef)> AddToStrTab) {
auto StringSection = cantFail(Obj->getStringTableForSymtab(*Section));
unsigned IsHotTextUpdated = 0;
Expand All @@ -4029,7 +4032,7 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
NewSymbol.st_size = Function->getOutputSize();
NewSymbol.st_other = 0;
NewSymbol.setBindingAndType(ELF::STB_LOCAL, ELF::STT_FUNC);
Write(0, reinterpret_cast<const char *>(&NewSymbol), sizeof(NewSymbol));
Write(0, NewSymbol);

if (Function->isSplit()) {
auto NewColdSym = NewSymbol;
Expand All @@ -4039,8 +4042,7 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
Twine(Function->getPrintName()).concat(".cold.0").toStringRef(Buf));
NewColdSym.st_value = Function->cold().getAddress();
NewColdSym.st_size = Function->cold().getImageSize();
Write(0, reinterpret_cast<const char *>(&NewColdSym),
sizeof(NewColdSym));
Write(0, NewColdSym);
}
}

Expand All @@ -4067,8 +4069,7 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
.toStringRef(Buf));
NewColdSym.st_value = Function->cold().getAddress();
NewColdSym.st_size = Function->cold().getImageSize();
Write(0, reinterpret_cast<const char *>(&NewColdSym),
sizeof(NewColdSym));
Write(0, NewColdSym);
}
if (!PatchExisting && Function->hasConstantIsland()) {
auto DataMark = Function->getOutputDataAddress();
Expand All @@ -4083,10 +4084,8 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
auto CodeMarkSym = DataMarkSym;
CodeMarkSym.st_name = AddToStrTab("$x");
CodeMarkSym.st_value = CodeMark;
Write(0, reinterpret_cast<const char *>(&DataMarkSym),
sizeof(DataMarkSym));
Write(0, reinterpret_cast<const char *>(&CodeMarkSym),
sizeof(CodeMarkSym));
Write(0, DataMarkSym);
Write(0, CodeMarkSym);
}
if (!PatchExisting && Function->hasConstantIsland() &&
Function->isSplit()) {
Expand All @@ -4102,10 +4101,8 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
auto CodeMarkSym = DataMarkSym;
CodeMarkSym.st_name = AddToStrTab("$x");
CodeMarkSym.st_value = CodeMark;
Write(0, reinterpret_cast<const char *>(&DataMarkSym),
sizeof(DataMarkSym));
Write(0, reinterpret_cast<const char *>(&CodeMarkSym),
sizeof(CodeMarkSym));
Write(0, DataMarkSym);
Write(0, CodeMarkSym);
}
} else {
uint32_t OldSectionIndex = NewSymbol.st_shndx;
Expand Down Expand Up @@ -4190,7 +4187,7 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {

Write((&Symbol - cantFail(Obj->symbols(Section)).begin()) *
sizeof(Elf_Sym),
reinterpret_cast<const char *>(&NewSymbol), sizeof(NewSymbol));
NewSymbol);
}

assert((!IsHotTextUpdated || IsHotTextUpdated == 2) &&
Expand All @@ -4210,7 +4207,7 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
outs() << "BOLT-INFO: setting " << Name << " to 0x"
<< Twine::utohexstr(Symbol.st_value) << '\n';

Write(0, reinterpret_cast<const char *>(&Symbol), sizeof(Symbol));
Write(0, Symbol);
};

if (opts::HotText && !IsHotTextUpdated && !PatchExisting) {
Expand All @@ -4226,7 +4223,7 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {

// Update dynamic symbol table.
const Elf_Shdr *DynSymSection = nullptr;
for (const Elf_Shdr &Section : cantFail(Obj->sections())) {
for (const auto &Section : cantFail(Obj->sections())) {
if (Section.sh_type == ELF::SHT_DYNSYM) {
DynSymSection = &Section;
break;
Expand All @@ -4235,8 +4232,9 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
assert(DynSymSection && "no dynamic symbol table found");
updateSymbolTable(/*patch existing table?*/ true,
DynSymSection,
[&](size_t Offset, const char *Buf, size_t Size) {
Out->os().pwrite(Buf, Size,
[&](size_t Offset, const Elf_Sym &Sym) {
Out->os().pwrite(reinterpret_cast<const char *>(&Sym),
sizeof(Elf_Sym),
DynSymSection->sh_offset + Offset);
},
[](StringRef) -> size_t { return 0; });
Expand All @@ -4262,10 +4260,14 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
auto SecName = cantFail(Obj->getSectionName(SymTabSection));
auto StrSecName = cantFail(Obj->getSectionName(StrTabSection));

NumLocalSymbols = 0;
updateSymbolTable(/*patch existing table?*/ false,
SymTabSection,
[&](size_t Offset, const char *Buf, size_t Size) {
NewContents.append(Buf, Size);
[&](size_t Offset, const Elf_Sym &Sym) {
if (Sym.getBinding() == ELF::STB_LOCAL)
++NumLocalSymbols;
NewContents.append(reinterpret_cast<const char *>(&Sym),
sizeof(Elf_Sym));
},
[&](StringRef Str) {
size_t Idx = NewStrTab.size();
Expand Down
3 changes: 3 additions & 0 deletions bolt/src/RewriteInstance.h
View file
Expand Up @@ -478,6 +478,9 @@ class RewriteInstance {

uint64_t NewTextSectionIndex{0};

/// Number of local symbols in newly written symbol table.
uint64_t NumLocalSymbols{0};

/// Exception handling and stack unwinding information in this binary.
ErrorOr<BinarySection &> LSDASection{std::errc::bad_address};
const llvm::DWARFDebugFrame *EHFrame{nullptr};
Expand Down

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