maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[BOLT] Use local binding for cold fragment symbols 

Summary:
We used to use existing symbol binding while duplicating and renaming
cold fragment symbols. As a result, some of those were emitted with
global binding. This confuses gdb, and it starts treating those symbols
as additional entry points.

The fix is to always emit such symbols with a local binding. This also
means that we have to sort static symbol table before emission to make
sure local symbols precede all others.

(cherry picked from FBD14529265)
This commit is contained in:
Maksim Panchenko 2019-03-19 13:46:21 -07:00
parent 6bcb3389dd
commit b8d3dc40ea
1 changed files with 38 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
bolt/src/RewriteInstance.cpp
View File

@ -3938,6 +3938,8 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
unsigned IsHotTextUpdated = 0;
unsigned IsHotDataUpdated = 0;
std::vector<Elf_Sym> Symbols;
std::map<const BinaryFunction *, uint64_t> IslandSizes;
auto getConstantIslandSize = [&IslandSizes](const BinaryFunction *BF) {
auto Itr = IslandSizes.find(BF);
@ -3955,7 +3957,7 @@ 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, NewSymbol);
Symbols.emplace_back(NewSymbol);
if (Function->isSplit()) {
auto NewColdSym = NewSymbol;
@ -3965,7 +3967,7 @@ 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, NewColdSym);
Symbols.emplace_back(NewColdSym);
}
}
@ -3990,7 +3992,8 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
NewColdSym.st_shndx = Function->getColdCodeSection()->getIndex();
NewColdSym.st_value = Function->cold().getAddress();
NewColdSym.st_size = Function->cold().getImageSize();
Write(0, NewColdSym);
NewColdSym.setBindingAndType(ELF::STB_LOCAL, ELF::STT_FUNC);
Symbols.emplace_back(NewColdSym);
}
if (!PatchExisting && Function->hasConstantIsland()) {
auto DataMark = Function->getOutputDataAddress();
@ -4005,8 +4008,8 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
auto CodeMarkSym = DataMarkSym;
CodeMarkSym.st_name = AddToStrTab("$x");
CodeMarkSym.st_value = CodeMark;
Write(0, DataMarkSym);
Write(0, CodeMarkSym);
Symbols.emplace_back(DataMarkSym);
Symbols.emplace_back(CodeMarkSym);
}
if (!PatchExisting && Function->hasConstantIsland() &&
Function->isSplit()) {
@ -4022,8 +4025,8 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
auto CodeMarkSym = DataMarkSym;
CodeMarkSym.st_name = AddToStrTab("$x");
CodeMarkSym.st_value = CodeMark;
Write(0, DataMarkSym);
Write(0, CodeMarkSym);
Symbols.emplace_back(DataMarkSym);
Symbols.emplace_back(CodeMarkSym);
}
} else {
uint32_t OldSectionIndex = NewSymbol.st_shndx;
@ -4106,15 +4109,23 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
<< Twine::utohexstr(NewSymbol.st_value) << '\n';
}
Write((&Symbol - cantFail(Obj->symbols(Section)).begin()) *
sizeof(Elf_Sym),
NewSymbol);
if (PatchExisting) {
Write((&Symbol - cantFail(Obj->symbols(Section)).begin()) *
sizeof(Elf_Sym),
NewSymbol);
} else {
Symbols.emplace_back(NewSymbol);
}
}
if (PatchExisting)
return;
assert((!IsHotTextUpdated || IsHotTextUpdated == 2) &&
"either none or both __hot_start/__hot_end symbols were expected");
assert((!IsHotDataUpdated || IsHotDataUpdated == 2) &&
"either none or both __hot_data_start/__hot_data_end symbols were expected");
"either none or both __hot_data_start/__hot_data_end symbols were "
"expected");
auto addSymbol = [&](const std::string &Name) {
Elf_Sym Symbol;
@ -4128,18 +4139,31 @@ void RewriteInstance::patchELFSymTabs(ELFObjectFile<ELFT> *File) {
outs() << "BOLT-INFO: setting " << Name << " to 0x"
<< Twine::utohexstr(Symbol.st_value) << '\n';
Write(0, Symbol);
Symbols.emplace_back(Symbol);
};
if (opts::HotText && !IsHotTextUpdated && !PatchExisting) {
if (opts::HotText && !IsHotTextUpdated) {
addSymbol("__hot_start");
addSymbol("__hot_end");
}
if (opts::HotData && !IsHotDataUpdated && !PatchExisting) {
if (opts::HotData && !IsHotDataUpdated) {
addSymbol("__hot_data_start");
addSymbol("__hot_data_end");
}
// Put local symbols at the beginning.
std::stable_sort(Symbols.begin(), Symbols.end(),
[](const Elf_Sym &A, const Elf_Sym &B) {
if (A.getBinding() == ELF::STB_LOCAL &&
B.getBinding() != ELF::STB_LOCAL)
return true;
return false;
});
for (const auto &Symbol : Symbols) {
Write(0, Symbol);
}
};
// Update dynamic symbol table.