Recommitted 266457 with fix:
* Do script driven layout only if SECTIONS section exist.
Initial commit message:
[ELF] - Implemented basic location counter support.
This patch implements location counter support.
It also separates assign addresses for sections to assignAddressesScript() if it scipt exists.
Main testcase is test/ELF/linkerscript-locationcounter.s, It contains some work with location counter. It is basic now.
Implemented location counter assignment and '+' operations.
Patch by myself with LOTS of comments and design suggestions from Rui Ueyama.
Differential revision: http://reviews.llvm.org/D18499
llvm-svn: 266526
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 96afdb9..fec2e19 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -17,20 +17,55 @@
#include "Config.h"
#include "Driver.h"
#include "InputSection.h"
+#include "OutputSections.h"
#include "ScriptParser.h"
#include "SymbolTable.h"
+#include "llvm/Support/ELF.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/StringSaver.h"
using namespace llvm;
+using namespace llvm::ELF;
using namespace llvm::object;
using namespace lld;
using namespace lld::elf;
LinkerScript *elf::Script;
+static uint64_t getInteger(StringRef S) {
+ uint64_t V;
+ if (S.getAsInteger(0, V)) {
+ error("malformed number: " + S);
+ return 0;
+ }
+ return V;
+}
+
+// Evaluates the expression given by list of tokens.
+uint64_t LinkerScript::evaluate(std::vector<StringRef> &Tokens,
+ uint64_t LocCounter) {
+ uint64_t Result = 0;
+ for (size_t I = 0, E = Tokens.size(); I < E; ++I) {
+ // Each second token should be '+' as this is the
+ // only operator we support now.
+ if (I % 2 == 1) {
+ if (Tokens[I] == "+")
+ continue;
+ error("error in location counter expression");
+ return 0;
+ }
+
+ StringRef Tok = Tokens[I];
+ if (Tok == ".")
+ Result += LocCounter;
+ else
+ Result += getInteger(Tok);
+ }
+ return Result;
+}
+
template <class ELFT>
SectionRule *LinkerScript::find(InputSectionBase<ELFT> *S) {
for (SectionRule &R : Sections)
@@ -55,6 +90,66 @@
return R && R->Keep;
}
+// This method finalizes the Locations list. Adds neccesary locations for
+// orphan sections, what prepares it for futher use without
+// changes in LinkerScript::assignAddresses().
+template <class ELFT>
+void LinkerScript::fixupLocations(std::vector<OutputSectionBase<ELFT> *> &S) {
+ // Orphan sections are sections present in the input files which
+ // are not explicitly placed into the output file by the linker
+ // script. We place orphan sections at end of file. Other linkers places
+ // them using some heuristics as described in
+ // https://sourceware.org/binutils/docs/ld/Orphan-Sections.html#Orphan-Sections.
+ for (OutputSectionBase<ELFT> *Sec : S) {
+ StringRef Name = Sec->getName();
+ auto I = std::find(SectionOrder.begin(), SectionOrder.end(), Name);
+ if (I == SectionOrder.end())
+ Locations.push_back({Command::Section, {}, {Name}});
+ }
+}
+
+template <class ELFT>
+void LinkerScript::assignAddresses(std::vector<OutputSectionBase<ELFT> *> &S) {
+ typedef typename ELFT::uint uintX_t;
+
+ Script->fixupLocations(S);
+
+ uintX_t ThreadBssOffset = 0;
+ uintX_t VA =
+ Out<ELFT>::ElfHeader->getSize() + Out<ELFT>::ProgramHeaders->getSize();
+
+ for (LocationNode &Node : Locations) {
+ if (Node.Type == Command::Expr) {
+ VA = evaluate(Node.Expr, VA);
+ continue;
+ }
+
+ auto I =
+ std::find_if(S.begin(), S.end(), [&](OutputSectionBase<ELFT> *Sec) {
+ return Sec->getName() == Node.SectionName;
+ });
+ if (I == S.end())
+ continue;
+
+ OutputSectionBase<ELFT> *Sec = *I;
+ uintX_t Align = Sec->getAlign();
+ if ((Sec->getFlags() & SHF_TLS) && Sec->getType() == SHT_NOBITS) {
+ uintX_t TVA = VA + ThreadBssOffset;
+ TVA = alignTo(TVA, Align);
+ Sec->setVA(TVA);
+ ThreadBssOffset = TVA - VA + Sec->getSize();
+ continue;
+ }
+
+ if (Sec->getFlags() & SHF_ALLOC) {
+ VA = alignTo(VA, Align);
+ Sec->setVA(VA);
+ VA += Sec->getSize();
+ continue;
+ }
+ }
+}
+
ArrayRef<uint8_t> LinkerScript::getFiller(StringRef Name) {
auto I = Filler.find(Name);
if (I == Filler.end())
@@ -126,6 +221,7 @@
void readSearchDir();
void readSections();
+ void readLocationCounterValue();
void readOutputSectionDescription();
void readSectionPatterns(StringRef OutSec, bool Keep);
@@ -286,9 +382,15 @@
}
void ScriptParser::readSections() {
+ Script->DoLayout = true;
expect("{");
- while (!Error && !skip("}"))
- readOutputSectionDescription();
+ while (!Error && !skip("}")) {
+ StringRef Tok = peek();
+ if (Tok == ".")
+ readLocationCounterValue();
+ else
+ readOutputSectionDescription();
+ }
}
void ScriptParser::readSectionPatterns(StringRef OutSec, bool Keep) {
@@ -297,9 +399,25 @@
Script->Sections.emplace_back(OutSec, next(), Keep);
}
+void ScriptParser::readLocationCounterValue() {
+ expect(".");
+ expect("=");
+ Script->Locations.push_back({Command::Expr, {}, {}});
+ LocationNode &Node = Script->Locations.back();
+ while (!Error) {
+ StringRef Tok = next();
+ if (Tok == ";")
+ break;
+ Node.Expr.push_back(Tok);
+ }
+ if (Node.Expr.empty())
+ error("error in location counter expression");
+}
+
void ScriptParser::readOutputSectionDescription() {
StringRef OutSec = next();
Script->SectionOrder.push_back(OutSec);
+ Script->Locations.push_back({Command::Section, {}, {OutSec}});
expect(":");
expect("{");
while (!Error && !skip("}")) {
@@ -356,3 +474,12 @@
template bool LinkerScript::shouldKeep(InputSectionBase<ELF32BE> *);
template bool LinkerScript::shouldKeep(InputSectionBase<ELF64LE> *);
template bool LinkerScript::shouldKeep(InputSectionBase<ELF64BE> *);
+
+template void
+LinkerScript::assignAddresses(std::vector<OutputSectionBase<ELF32LE> *> &);
+template void
+LinkerScript::assignAddresses(std::vector<OutputSectionBase<ELF32BE> *> &);
+template void
+LinkerScript::assignAddresses(std::vector<OutputSectionBase<ELF64LE> *> &);
+template void
+LinkerScript::assignAddresses(std::vector<OutputSectionBase<ELF64BE> *> &);