Add an option to MCJIT to have it forward all sections to the

RTDyldMemoryManager, regardless of whether it thinks they're "required for
execution".

Currently, RuntimeDyld only passes sections that are "required for execution"
to the RTDyldMemoryManager, and takes "required for execution" to mean exactly
"contains symbols or relocations". There are two problems with this:
(1) It can drop sections with anonymous data that is referenced by code.
(2) It leaves the JIT client no way to inspect interesting sections that aren't
    actually required to run the program (e.g dwarf sections).

A test case is still in the works.

Future work: We may want to replace this with a generic section filtering
mechanism, but that will require more consideration. For now, this flag at least
allows clients to volunteer to do the filtering themselves.

Fixes <rdar://problem/15177691>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204398 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/ExecutionEngine/ExecutionEngine.h b/include/llvm/ExecutionEngine/ExecutionEngine.h
index e4f276d0fad5c25ecb8de8f7a74f58cda79f0dfc..4dca870bec7f120105259d83bad4556691e1fdba 100644 (file)
--- a/include/llvm/ExecutionEngine/ExecutionEngine.h
+++ b/include/llvm/ExecutionEngine/ExecutionEngine.h
@@ -462,6 +462,21 @@ public:
     llvm_unreachable("No support for an object cache");
   }
 
+  /// setProcessAllSections (MCJIT Only): By default, only sections that are
+  /// "required for execution" are passed to the RTDyldMemoryManager, and other
+  /// sections are discarded. Passing 'true' to this method will cause
+  /// RuntimeDyld to pass all sections to its RTDyldMemoryManager regardless
+  /// of whether they are "required to execute" in the usual sense.
+  ///
+  /// Rationale: Some MCJIT clients want to be able to inspect metadata
+  /// sections (e.g. Dwarf, Stack-maps) to enable functionality or analyze
+  /// performance. Passing these sections to the memory manager allows the
+  /// client to make policy about the relevant sections, rather than having
+  /// MCJIT do it.
+  virtual void setProcessAllSections(bool ProcessAllSections) {
+    llvm_unreachable("No support for ProcessAllSections option");
+  }
+
   /// Return the target machine (if available).
   virtual TargetMachine *getTargetMachine() { return NULL; }
 

diff --git a/include/llvm/ExecutionEngine/RuntimeDyld.h b/include/llvm/ExecutionEngine/RuntimeDyld.h
index fd9f338669f22f19fcee34a9d70d11bd6c68add7..0b6b75be48b37275e2020344052c5dd04c02034b 100644 (file)
--- a/include/llvm/ExecutionEngine/RuntimeDyld.h
+++ b/include/llvm/ExecutionEngine/RuntimeDyld.h
@@ -36,6 +36,7 @@ class RuntimeDyld {
   // interface.
   RuntimeDyldImpl *Dyld;
   RTDyldMemoryManager *MM;
+  bool ProcessAllSections;
 protected:
   // Change the address associated with a section when resolving relocations.
   // Any relocations already associated with the symbol will be re-resolved.
@@ -84,6 +85,19 @@ public:
   void deregisterEHFrames();
 
   StringRef getErrorString();
+
+  /// By default, only sections that are "required for execution" are passed to
+  /// the RTDyldMemoryManager, and other sections are discarded. Passing 'true'
+  /// to this method will cause RuntimeDyld to pass all sections to its
+  /// memory manager regardless of whether they are "required to execute" in the
+  /// usual sense. This is useful for inspecting metadata sections that may not
+  /// contain relocations, E.g. Debug info, stackmaps.
+  ///
+  /// Must be called before the first object file is loaded.
+  void setProcessAllSections(bool ProcessAllSections) {
+    assert(!Dyld && "setProcessAllSections must be called before loadObject.");
+    this->ProcessAllSections = ProcessAllSections;
+  }
 };
 
 } // end namespace llvm

diff --git a/lib/ExecutionEngine/MCJIT/MCJIT.h b/lib/ExecutionEngine/MCJIT/MCJIT.h
index 16a9f3710b766005be66f7f0ab07391d4620cb40..066ecebaa259326d2356a9d80f706c927bee2117 100644 (file)
--- a/lib/ExecutionEngine/MCJIT/MCJIT.h
+++ b/lib/ExecutionEngine/MCJIT/MCJIT.h
@@ -251,6 +251,10 @@ public:
   /// Sets the object manager that MCJIT should use to avoid compilation.
   void setObjectCache(ObjectCache *manager) override;
 
+  void setProcessAllSections(bool ProcessAllSections) override {
+    Dyld.setProcessAllSections(ProcessAllSections);
+  }
+
   void generateCodeForModule(Module *M) override;
 
   /// finalizeObject - ensure the module is fully processed and is usable.

diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
index 5d6a2c0f1235955a69087d52dfdac308a3dfd53b..310b206a067c1069798fa99829fc294633e531ae 100644 (file)
--- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
@@ -161,25 +161,22 @@ ObjectImage* RuntimeDyldImpl::loadObject(ObjectImage *InputObject) {
   DEBUG(dbgs() << "Parse relocations:\n");
   for (section_iterator SI = Obj->begin_sections(), SE = Obj->end_sections();
        SI != SE; ++SI) {
-    bool IsFirstRelocation = true;
     unsigned SectionID = 0;
     StubMap Stubs;
     section_iterator RelocatedSection = SI->getRelocatedSection();
 
-    for (const RelocationRef &Reloc : SI->relocations()) {
-      // If it's the first relocation in this section, find its SectionID
-      if (IsFirstRelocation) {
-        bool IsCode = false;
-        Check(RelocatedSection->isText(IsCode));
-        SectionID =
-            findOrEmitSection(*Obj, *RelocatedSection, IsCode, LocalSections);
-        DEBUG(dbgs() << "\tSectionID: " << SectionID << "\n");
-        IsFirstRelocation = false;
-      }
+    if ((SI->relocation_begin() != SI->relocation_end()) ||
+        ProcessAllSections) {
+      bool IsCode = false;
+      Check(RelocatedSection->isText(IsCode));
+      SectionID =
+        findOrEmitSection(*Obj, *RelocatedSection, IsCode, LocalSections);
+      DEBUG(dbgs() << "\tSectionID: " << SectionID << "\n");
+    }
 
+    for (const RelocationRef &Reloc : SI->relocations())
       processRelocationRef(SectionID, Reloc, *Obj, LocalSections, LocalSymbols,
                            Stubs);
-    }
   }
 
   // Give the subclasses a chance to tie-up any loose ends.
@@ -665,23 +662,40 @@ RuntimeDyld::RuntimeDyld(RTDyldMemoryManager *mm) {
   // permissions are applied.
   Dyld = 0;
   MM = mm;
+  ProcessAllSections = false;
 }
 
 RuntimeDyld::~RuntimeDyld() {
   delete Dyld;
 }
 
+static std::unique_ptr<RuntimeDyldELF> createRuntimeDyldELF(
+                                                   RTDyldMemoryManager *MM,
+                                                   bool ProcessAllSections) {
+  std::unique_ptr<RuntimeDyldELF> Dyld(new RuntimeDyldELF(MM));
+  Dyld->setProcessAllSections(ProcessAllSections);
+  return Dyld;
+}
+
+static std::unique_ptr<RuntimeDyldMachO> createRuntimeDyldMachO(
+                                                   RTDyldMemoryManager *MM,
+                                                   bool ProcessAllSections) {
+  std::unique_ptr<RuntimeDyldMachO> Dyld(new RuntimeDyldMachO(MM));
+  Dyld->setProcessAllSections(ProcessAllSections);
+  return Dyld;
+}
+
 ObjectImage *RuntimeDyld::loadObject(ObjectFile *InputObject) {
   std::unique_ptr<ObjectImage> InputImage;
 
   if (InputObject->isELF()) {
     InputImage.reset(RuntimeDyldELF::createObjectImageFromFile(InputObject));
     if (!Dyld)
-      Dyld = new RuntimeDyldELF(MM);
+      Dyld = createRuntimeDyldELF(MM, ProcessAllSections).release();
   } else if (InputObject->isMachO()) {
     InputImage.reset(RuntimeDyldMachO::createObjectImageFromFile(InputObject));
     if (!Dyld)
-      Dyld = new RuntimeDyldMachO(MM);
+      Dyld = createRuntimeDyldMachO(MM, ProcessAllSections).release();
   } else
     report_fatal_error("Incompatible object format!");
 
@@ -704,7 +718,7 @@ ObjectImage *RuntimeDyld::loadObject(ObjectBuffer *InputBuffer) {
   case sys::fs::file_magic::elf_core:
     InputImage.reset(RuntimeDyldELF::createObjectImage(InputBuffer));
     if (!Dyld)
-      Dyld = new RuntimeDyldELF(MM);
+      Dyld = createRuntimeDyldELF(MM, ProcessAllSections).release();
     break;
   case sys::fs::file_magic::macho_object:
   case sys::fs::file_magic::macho_executable:
@@ -718,7 +732,7 @@ ObjectImage *RuntimeDyld::loadObject(ObjectBuffer *InputBuffer) {
   case sys::fs::file_magic::macho_dsym_companion:
     InputImage.reset(RuntimeDyldMachO::createObjectImage(InputBuffer));
     if (!Dyld)
-      Dyld = new RuntimeDyldMachO(MM);
+      Dyld = createRuntimeDyldMachO(MM, ProcessAllSections).release();
     break;
   case sys::fs::file_magic::unknown:
   case sys::fs::file_magic::bitcode:

diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
index 8fd55920f2e532fd964a32569d694005a50b8088..0b7de17a6e985dc32239988bfd7bdabd2ed69661 100644 (file)
--- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
@@ -187,6 +187,10 @@ protected:
   Triple::ArchType Arch;
   bool IsTargetLittleEndian;
 
+  // True if all sections should be passed to the memory manager, false if only
+  // sections containing relocations should be. Defaults to 'false'.
+  bool ProcessAllSections;
+
   // This mutex prevents simultaneously loading objects from two different
   // threads.  This keeps us from having to protect individual data structures
   // and guarantees that section allocation requests to the memory manager
@@ -320,10 +324,15 @@ protected:
   unsigned computeSectionStubBufSize(ObjectImage &Obj, const SectionRef &Section); 
 
 public:
-  RuntimeDyldImpl(RTDyldMemoryManager *mm) : MemMgr(mm), HasError(false) {}
+  RuntimeDyldImpl(RTDyldMemoryManager *mm)
+    : MemMgr(mm), ProcessAllSections(false), HasError(false) {}
 
   virtual ~RuntimeDyldImpl();
 
+  void setProcessAllSections(bool ProcessAllSections) {
+    this->ProcessAllSections = ProcessAllSections;
+  }
+
   ObjectImage* loadObject(ObjectImage* InputObject);
 
   void *getSymbolAddress(StringRef Name) {