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Remove `Ignore` flag from SymbolAssignment class. 

Previously, Ignore flag is set if we don't want to assign
a value to symbols. It happens if a symbol assingment is in
PROVIDE() and there's already a symbol with the same name.

The previous code had a subtle but that we assume that the
existing symbol is an absolute symbol even if it is not.
This patch fixes the issue by always overwriting an absolute
symbol.

llvm-svn: 277115
This commit is contained in:
Rui Ueyama 2016-07-29 05:48:39 +00:00
parent 130b9f99d6
commit 8d083e6a0a
2 changed files with 19 additions and 23 deletions
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38
lld/ELF/LinkerScript.cpp
View File

@ -194,17 +194,6 @@ LinkerScript<ELFT>::filter(std::vector<OutputSectionBase<ELFT> *> &Sections) {
return Sections;
}
template <class ELFT>
void LinkerScript<ELFT>::dispatchAssignment(SymbolAssignment *Cmd) {
uint64_t Val = Cmd->Expression(Dot);
if (Cmd->Name == ".") {
Dot = Val;
} else if (!Cmd->Ignore) {
auto *D = cast<DefinedRegular<ELFT>>(Symtab<ELFT>::X->find(Cmd->Name));
D->Value = Val;
}
}
template <class ELFT>
void LinkerScript<ELFT>::assignAddresses(
ArrayRef<OutputSectionBase<ELFT> *> Sections) {
@ -226,7 +215,11 @@ void LinkerScript<ELFT>::assignAddresses(
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
if (auto *Cmd = dyn_cast<SymbolAssignment>(Base.get())) {
dispatchAssignment(Cmd);
if (Cmd->Name == ".") {
Dot = Cmd->Expression(Dot);
} else if (Cmd->Sym) {
cast<DefinedRegular<ELFT>>(Cmd->Sym)->Value = Cmd->Expression(Dot);
}
continue;
}
@ -368,22 +361,25 @@ int LinkerScript<ELFT>::compareSections(StringRef A, StringRef B) {
return I < J ? -1 : 1;
}
// Add symbols defined by linker scripts.
template <class ELFT> void LinkerScript<ELFT>::addScriptedSymbols() {
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
auto *Cmd = dyn_cast<SymbolAssignment>(Base.get());
if (!Cmd || Cmd->Name == ".")
continue;
// If a symbol was in PROVIDE(), define it only when it is an
// undefined symbol.
SymbolBody *B = Symtab<ELFT>::X->find(Cmd->Name);
// The semantic of PROVIDE is that of introducing a symbol only if
// it's not defined and there's at least a reference to it.
if ((!B && !Cmd->Provide) || (B && B->isUndefined()))
Symtab<ELFT>::X->addAbsolute(Cmd->Name,
Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT);
else
// Symbol already exists in symbol table. If it is provided
// then we can't override its value.
Cmd->Ignore = Cmd->Provide;
if (Cmd->Provide && !(B && B->isUndefined()))
continue;
// Define an absolute symbol. The symbol value will be assigned later.
// (At this point, we don't know the final address yet.)
Symbol *Sym = Symtab<ELFT>::X->addUndefined(Cmd->Name);
replaceBody<DefinedRegular<ELFT>>(Sym, Cmd->Name, STV_DEFAULT);
Sym->Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
Cmd->Sym = Sym->body();
}
}

4
lld/ELF/LinkerScript.h
View File

@ -20,6 +20,7 @@
namespace lld {
namespace elf {
class SymbolBody;
template <class ELFT> class InputSectionBase;
template <class ELFT> class OutputSectionBase;
template <class ELFT> class OutputSectionFactory;
@ -56,9 +57,8 @@ struct SymbolAssignment : BaseCommand {
StringRef Name;
Expr Expression;
bool Provide = false;
// Hidden and Ignore can be true, only if Provide is true
bool Hidden = false;
bool Ignore = false;
SymbolBody *Sym = nullptr;
};
// Linker scripts allow additional constraints to be put on ouput sections.