[PATCH] [ELF] Add support for -z {now, origin}

[Davide Italiano]

Hi ruiu, atanasyan, Bigcheese,

Note: Needs to wait until D9958 lands for a testcase/commit.

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D9963

Files:
  include/lld/ReaderWriter/ELFLinkingContext.h
  lib/Driver/GnuLdDriver.cpp
  lib/ReaderWriter/ELF/OutputELFWriter.cpp

Index: include/lld/ReaderWriter/ELFLinkingContext.h
===================================================================
--- include/lld/ReaderWriter/ELFLinkingContext.h
+++ include/lld/ReaderWriter/ELFLinkingContext.h
@@ -97,6 +97,12 @@
     OMAGIC,
   };
 
+  /// \brief ELF DT_FLAGS.
+  enum DTFlag : uint32_t {
+    DT_NOW = 1 << 1,
+    DT_ORIGIN = 1 << 2,
+  };
+
   llvm::Triple getTriple() const { return _triple; }
 
   uint64_t getPageSize() const { return _maxPageSize; }
@@ -329,6 +335,10 @@
   // --wrap option.
   void addWrapForSymbol(StringRef sym) { _wrapCalls.insert(sym); }
 
+  // \brief Set DT_FLAGS flag.
+  void setDTFlag(DTFlag f) { _dtFlags |= f; };
+  bool getDTFlag(DTFlag f) { return (_dtFlags & f); };
+
   const llvm::StringSet<> &wrapCalls() const { return _wrapCalls; }
 
   void setUndefinesResolver(std::unique_ptr<File> resolver);
@@ -383,6 +393,7 @@
   bool _armTarget1Rel = false;
   bool _mipsPcRelEhRel = false;
   uint64_t _maxPageSize = 0x1000;
+  uint32_t _dtFlags = 0;
 
   OutputMagic _outputMagic = OutputMagic::DEFAULT;
   StringRefVector _inputSearchPaths;
Index: lib/Driver/GnuLdDriver.cpp
===================================================================
--- lib/Driver/GnuLdDriver.cpp
+++ lib/Driver/GnuLdDriver.cpp
@@ -584,9 +584,13 @@
 
   for (auto *arg : parsedArgs->filtered(OPT_z)) {
     StringRef opt = arg->getValue();
-    if (opt == "muldefs") {
+    if (opt == "muldefs")
       ctx->setAllowDuplicates(true);
-    } else if (opt.startswith("max-page-size")) {
+    else if (opt == "now")
+      ctx->setDTFlag(ELFLinkingContext::DTFlag::DT_NOW);
+    else if (opt == "origin")
+      ctx->setDTFlag(ELFLinkingContext::DTFlag::DT_ORIGIN);
+    else if (opt.startswith("max-page-size")) {
       // Parse -z max-page-size option.
       // The default page size is considered the minimum page size the user
       // can set, check the user input if its atleast the minimum page size
Index: lib/ReaderWriter/ELF/OutputELFWriter.cpp
===================================================================
--- lib/ReaderWriter/ELF/OutputELFWriter.cpp
+++ lib/ReaderWriter/ELF/OutputELFWriter.cpp
@@ -140,6 +140,21 @@
   if (!soname.empty() && _ctx.getOutputELFType() == llvm::ELF::ET_DYN)
     _dynamicTable->addEntry(DT_SONAME, _dynamicStringTable->addString(soname));
 
+  // Add DT_FLAGS/DT_FLAGS_1 entries if necessary.
+  uint32_t dtflags = 0, dt1flags = 0;
+  if (_ctx.getDTFlag(ELFLinkingContext::DTFlag::DT_NOW)) {
+    dtflags |= DF_BIND_NOW;
+    dt1flags |= DF_1_NOW;
+  }
+  if (_ctx.getDTFlag(ELFLinkingContext::DTFlag::DT_ORIGIN)) {
+    dtflags |= DF_ORIGIN;
+    dt1flags |= DF_1_ORIGIN;
+  }
+  if (dtflags != 0)
+    _dynamicTable->addEntry(DT_FLAGS, dtflags);
+  if (dt1flags != 0)
+    _dynamicTable->addEntry(DT_FLAGS_1, dt1flags);
+
   // The dynamic symbol table need to be sorted earlier because the hash
   // table needs to be built using the dynamic symbol table. It would be
   // late to sort the symbols due to that in finalize. In the dynamic symbol

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