[ELF2] SECTIONS command basic support
* determine output section by input section name
* discard input sections
* order output sections accordingly
Differential Revision: http://reviews.llvm.org/D14140
llvm-svn: 252868
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index edc47ab..7d0f49b 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -13,6 +13,7 @@
#include "SymbolTable.h"
#include "Target.h"
+#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Support/FileOutputBuffer.h"
#include "llvm/Support/StringSaver.h"
@@ -47,9 +48,12 @@
void scanRelocs(InputSection<ELFT> &C);
void scanRelocs(InputSectionBase<ELFT> &S, const Elf_Shdr &RelSec);
void assignAddresses();
+ void buildSectionMap();
void openFile(StringRef OutputPath);
void writeHeader();
void writeSections();
+ bool isDiscarded(InputSectionBase<ELFT> *IS) const;
+ StringRef getOutputSectionName(StringRef S) const;
bool needsInterpSection() const {
return !Symtab.getSharedFiles().empty() && !Config->DynamicLinker.empty();
}
@@ -82,6 +86,8 @@
uintX_t FileSize;
uintX_t SectionHeaderOff;
+
+ llvm::StringMap<llvm::StringRef> InputToOutputSection;
};
} // anonymous namespace
@@ -131,6 +137,7 @@
// The main function of the writer.
template <class ELFT> void Writer<ELFT>::run() {
+ buildSectionMap();
if (!Config->DiscardAll)
copyLocalSymbols();
createSections();
@@ -461,7 +468,12 @@
Out<ELFT>::Bss->setSize(Off);
}
-static StringRef getOutputName(StringRef S) {
+template <class ELFT>
+StringRef Writer<ELFT>::getOutputSectionName(StringRef S) const {
+ auto It = InputToOutputSection.find(S);
+ if (It != std::end(InputToOutputSection))
+ return It->second;
+
if (S.startswith(".text."))
return ".text";
if (S.startswith(".rodata."))
@@ -473,6 +485,27 @@
return S;
}
+template <class ELFT>
+bool Writer<ELFT>::isDiscarded(InputSectionBase<ELFT> *IS) const {
+ if (!IS || !IS->isLive() || IS == &InputSection<ELFT>::Discarded)
+ return true;
+ return InputToOutputSection.lookup(IS->getSectionName()) == "/DISCARD/";
+}
+
+template <class ELFT>
+static bool compareSections(OutputSectionBase<ELFT> *A,
+ OutputSectionBase<ELFT> *B) {
+ auto ItA = Config->OutputSections.find(A->getName());
+ auto ItEnd = std::end(Config->OutputSections);
+ if (ItA == ItEnd)
+ return compareOutputSections(A, B);
+ auto ItB = Config->OutputSections.find(B->getName());
+ if (ItB == ItEnd)
+ return compareOutputSections(A, B);
+
+ return std::distance(ItA, ItB) > 0;
+}
+
// Create output section objects and add them to OutputSections.
template <class ELFT> void Writer<ELFT>::createSections() {
// .interp needs to be on the first page in the output file.
@@ -485,7 +518,7 @@
for (const std::unique_ptr<ObjectFile<ELFT>> &F : Symtab.getObjectFiles()) {
for (InputSectionBase<ELFT> *C : F->getSections()) {
- if (!C || !C->isLive() || C == &InputSection<ELFT>::Discarded)
+ if (isDiscarded(C))
continue;
const Elf_Shdr *H = C->getSectionHdr();
uintX_t OutFlags = H->sh_flags & ~SHF_GROUP;
@@ -498,7 +531,7 @@
if (OutType == SHT_PROGBITS && C->getSectionName() == ".eh_frame" &&
Config->EMachine == EM_X86_64)
OutType = SHT_X86_64_UNWIND;
- SectionKey<ELFT::Is64Bits> Key{getOutputName(C->getSectionName()),
+ SectionKey<ELFT::Is64Bits> Key{getOutputSectionName(C->getSectionName()),
OutType, OutFlags, EntSize};
OutputSectionBase<ELFT> *&Sec = Map[Key];
if (!Sec) {
@@ -577,14 +610,14 @@
// Scan relocations. This must be done after every symbol is declared so that
// we can correctly decide if a dynamic relocation is needed.
for (const std::unique_ptr<ObjectFile<ELFT>> &F : Symtab.getObjectFiles()) {
- for (InputSectionBase<ELFT> *B : F->getSections()) {
- if (auto *S = dyn_cast_or_null<InputSection<ELFT>>(B)) {
- if (S != &InputSection<ELFT>::Discarded && S->isLive())
- scanRelocs(*S);
- } else if (auto *S = dyn_cast_or_null<EHInputSection<ELFT>>(B)) {
+ for (InputSectionBase<ELFT> *C : F->getSections()) {
+ if (isDiscarded(C))
+ continue;
+ if (auto *S = dyn_cast<InputSection<ELFT>>(C))
+ scanRelocs(*S);
+ else if (auto *S = dyn_cast<EHInputSection<ELFT>>(C))
if (S->RelocSection)
scanRelocs(*S, *S->RelocSection);
- }
}
}
@@ -656,7 +689,7 @@
OutputSections.push_back(Out<ELFT>::Plt);
std::stable_sort(OutputSections.begin(), OutputSections.end(),
- compareOutputSections<ELFT>);
+ compareSections<ELFT>);
for (unsigned I = 0, N = OutputSections.size(); I < N; ++I)
OutputSections[I]->SectionIndex = I + 1;
@@ -952,6 +985,13 @@
PH->p_align = From->getAlign();
}
+template <class ELFT> void Writer<ELFT>::buildSectionMap() {
+ for (const std::pair<StringRef, std::vector<StringRef>> &OutSec :
+ Config->OutputSections)
+ for (StringRef Name : OutSec.second)
+ InputToOutputSection[Name] = OutSec.first;
+}
+
template void lld::elf2::writeResult<ELF32LE>(SymbolTable<ELF32LE> *Symtab);
template void lld::elf2::writeResult<ELF32BE>(SymbolTable<ELF32BE> *Symtab);
template void lld::elf2::writeResult<ELF64LE>(SymbolTable<ELF64LE> *Symtab);