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-rw-r--r--lld/ELF/LinkerScript.cpp90
-rw-r--r--lld/ELF/LinkerScript.h4
2 files changed, 52 insertions, 42 deletions
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 4e8ee8bffda..14861d9bb68 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -79,25 +79,6 @@ uint64_t ExprValue::getSectionOffset() const {
return getValue() - getSecAddr();
}
-static SymbolBody *addRegular(SymbolAssignment *Cmd) {
- Symbol *Sym;
- uint8_t Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
- std::tie(Sym, std::ignore) = Symtab->insert(Cmd->Name, /*Type*/ 0, Visibility,
- /*CanOmitFromDynSym*/ false,
- /*File*/ nullptr);
- Sym->Binding = STB_GLOBAL;
- ExprValue Value = Cmd->Expression();
- SectionBase *Sec = Value.isAbsolute() ? nullptr : Value.Sec;
-
- // We want to set symbol values early if we can. This allows us to use symbols
- // as variables in linker scripts. Doing so allows us to write expressions
- // like this: `alignment = 16; . = ALIGN(., alignment)`
- uint64_t SymValue = Value.Sec ? 0 : Value.getValue();
- replaceBody<DefinedRegular>(Sym, nullptr, Cmd->Name, /*IsLocal=*/false,
- Visibility, STT_NOTYPE, SymValue, 0, Sec);
- return Sym->body();
-}
-
OutputSection *LinkerScript::createOutputSection(StringRef Name,
StringRef Location) {
OutputSection *&SecRef = NameToOutputSection[Name];
@@ -127,14 +108,55 @@ void LinkerScript::setDot(Expr E, const Twine &Loc, bool InSec) {
error(Loc + ": unable to move location counter backward for: " +
CurAddressState->OutSec->Name);
Dot = Val;
+
// Update to location counter means update to section size.
if (InSec)
CurAddressState->OutSec->Size = Dot - CurAddressState->OutSec->Addr;
}
-// Sets value of a symbol. Two kinds of symbols are processed: synthetic
-// symbols, whose value is an offset from beginning of section and regular
-// symbols whose value is absolute.
+// This function is called from processCommands, while we are
+// fixing the output section layout.
+void LinkerScript::addSymbol(SymbolAssignment *Cmd) {
+ if (Cmd->Name == ".")
+ return;
+
+ // If a symbol was in PROVIDE(), we need to define it only when
+ // it is a referenced undefined symbol.
+ SymbolBody *B = Symtab->find(Cmd->Name);
+ if (Cmd->Provide && (!B || B->isDefined()))
+ return;
+
+ // Define a symbol.
+ Symbol *Sym;
+ uint8_t Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
+ std::tie(Sym, std::ignore) = Symtab->insert(Cmd->Name, /*Type*/ 0, Visibility,
+ /*CanOmitFromDynSym*/ false,
+ /*File*/ nullptr);
+ Sym->Binding = STB_GLOBAL;
+ ExprValue Value = Cmd->Expression();
+ SectionBase *Sec = Value.isAbsolute() ? nullptr : Value.Sec;
+
+ // When this function is called, section addresses have not been
+ // fixed yet. So, we may or may not know the value of the RHS
+ // expression.
+ //
+ // For example, if an expression is `x = 42`, we know x is always 42.
+ // However, if an expression is `x = .`, there's no way to know its
+ // value at the moment.
+ //
+ // We want to set symbol values early if we can. This allows us to
+ // use symbols as variables in linker scripts. Doing so allows us to
+ // write expressions like this: `alignment = 16; . = ALIGN(., alignment)`.
+ uint64_t SymValue = Value.Sec ? 0 : Value.getValue();
+
+ replaceBody<DefinedRegular>(Sym, nullptr, Cmd->Name, /*IsLocal=*/false,
+ Visibility, STT_NOTYPE, SymValue, 0, Sec);
+ Cmd->Sym = cast<DefinedRegular>(Sym->body());
+}
+
+// This function is called from assignAddresses, while we are
+// fixing the output section addresses. This function is supposed
+// to set the final value for a given symbol assignment.
void LinkerScript::assignSymbol(SymbolAssignment *Cmd, bool InSec) {
if (Cmd->Name == ".") {
setDot(Cmd->Expression, Cmd->Location, InSec);
@@ -144,30 +166,16 @@ void LinkerScript::assignSymbol(SymbolAssignment *Cmd, bool InSec) {
if (!Cmd->Sym)
return;
- auto *Sym = cast<DefinedRegular>(Cmd->Sym);
ExprValue V = Cmd->Expression();
if (V.isAbsolute()) {
- Sym->Value = V.getValue();
- Sym->Section = nullptr;
+ Cmd->Sym->Section = nullptr;
+ Cmd->Sym->Value = V.getValue();
} else {
- Sym->Section = V.Sec;
- Sym->Value = V.getSectionOffset();
+ Cmd->Sym->Section = V.Sec;
+ Cmd->Sym->Value = V.getSectionOffset();
}
}
-void LinkerScript::addSymbol(SymbolAssignment *Cmd) {
- if (Cmd->Name == ".")
- return;
-
- // If a symbol was in PROVIDE(), we need to define it only when
- // it is a referenced undefined symbol.
- SymbolBody *B = Symtab->find(Cmd->Name);
- if (Cmd->Provide && (!B || B->isDefined()))
- return;
-
- Cmd->Sym = addRegular(Cmd);
-}
-
bool SymbolAssignment::classof(const BaseCommand *C) {
return C->Kind == AssignmentKind;
}
@@ -359,6 +367,7 @@ void LinkerScript::processCommands(OutputSectionFactory &Factory) {
Aether = make<OutputSection>("", 0, SHF_ALLOC);
Aether->SectionIndex = 1;
auto State = make_unique<AddressState>(Opt);
+
// CurAddressState captures the local AddressState and makes it accessible
// deliberately. This is needed as there are some cases where we cannot just
// thread the current state through to a lambda function created by the
@@ -785,6 +794,7 @@ void LinkerScript::assignAddresses() {
// -image-base if set.
Dot = Config->ImageBase ? *Config->ImageBase : 0;
auto State = make_unique<AddressState>(Opt);
+
// CurAddressState captures the local AddressState and makes it accessible
// deliberately. This is needed as there are some cases where we cannot just
// thread the current state through to a lambda function created by the
diff --git a/lld/ELF/LinkerScript.h b/lld/ELF/LinkerScript.h
index 6aa80c82e46..26c9b20e137 100644
--- a/lld/ELF/LinkerScript.h
+++ b/lld/ELF/LinkerScript.h
@@ -28,7 +28,7 @@
namespace lld {
namespace elf {
-class DefinedCommon;
+class DefinedRegular;
class SymbolBody;
class InputSectionBase;
class InputSection;
@@ -93,7 +93,7 @@ struct SymbolAssignment : BaseCommand {
// The LHS of an expression. Name is either a symbol name or ".".
StringRef Name;
- SymbolBody *Sym = nullptr;
+ DefinedRegular *Sym = nullptr;
// The RHS of an expression.
Expr Expression;
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