[mach-o] Add support for interposing tuples section

Darwin uses two-level-namespace lookup for symbols which means the static
linker records where each symbol must be found at runtime.  Thus defining a
symbol in a dylib loaded earlier will not effect where symbols needed by
later dylibs will be found.  Instead overriding is done through a section
of type S_INTERPOSING which contains tuples of <interposer, interposee>.

llvm-svn: 221421

5 files changed, 7 insertions, 0 deletions

diff --git a/lld/include/lld/Core/DefinedAtom.h b/lld/include/lld/Core/DefinedAtom.h
index 65c0481e616..38e58382eed 100644
--- a/lld/include/lld/Core/DefinedAtom.h
+++ b/lld/include/lld/Core/DefinedAtom.h
@@ -135,6 +135,7 @@ public:
     typeObjCClassPtr,       // pointer to ObjC class [Darwin]
     typeObjC2CategoryList,  // pointers to ObjC category [Darwin]
     typeDTraceDOF,          // runtime data for Dtrace [Darwin]
+    typeInterposingTuples,  // tuples of interposing info for dyld [Darwin]
     typeTempLTO,            // temporary atom for bitcode reader
     typeCompactUnwindInfo,  // runtime data for unwinder [Darwin]
     typeProcessedUnwindInfo,// compressed compact unwind info [Darwin]
diff --git a/lld/lib/Core/DefinedAtom.cpp b/lld/lib/Core/DefinedAtom.cpp
index 6b9a08a161f..fa2fa45f695 100644
--- a/lld/lib/Core/DefinedAtom.cpp
+++ b/lld/lib/Core/DefinedAtom.cpp
@@ -64,6 +64,7 @@ DefinedAtom::ContentPermissions DefinedAtom::permissions(ContentType type) {
   case typeCStringPtr:
   case typeObjCClassPtr:
   case typeObjC2CategoryList:
+  case typeInterposingTuples:
   case typeTLVInitialData:
   case typeTLVInitialZeroFill:
   case typeTLVInitializerPtr:
diff --git a/lld/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp b/lld/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp
index dc015c5f296..abde41a9dd0 100644
--- a/lld/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp
+++ b/lld/lib/ReaderWriter/MachO/MachONormalizedFileFromAtoms.cpp
@@ -231,6 +231,7 @@ const MachOFinalSectionFromAtomType sectsToAtomType[] = {
   ENTRY("__DATA", "___got",           S_NON_LAZY_SYMBOL_POINTERS,
                                                           typeGOT),
   ENTRY("__DATA", "___bss",           S_ZEROFILL,         typeZeroFill),
+  ENTRY("__DATA", "__interposing",    S_INTERPOSING,      typeInterposingTuples),
 };
 #undef ENTRY
 
diff --git a/lld/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp b/lld/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp
index 54899b00a0f..ec66d480833 100644
--- a/lld/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp
+++ b/lld/lib/ReaderWriter/MachO/MachONormalizedFileToAtoms.cpp
@@ -77,6 +77,8 @@ const MachORelocatableSectionToAtomType sectsToAtomType[] = {
   ENTRY("__DATA", "___bss",           S_ZEROFILL,         typeZeroFill),
   ENTRY("",       "",                 S_NON_LAZY_SYMBOL_POINTERS,
                                                           typeGOT),
+  ENTRY("__DATA", "__interposing",    S_INTERPOSING,      typeInterposingTuples),
+  ENTRY("",       "",                 S_INTERPOSING,      typeInterposingTuples),
   ENTRY("__LD",   "__compact_unwind", S_REGULAR,
                                                          typeCompactUnwindInfo),
   ENTRY("",       "",                 S_REGULAR,          typeUnknown)
diff --git a/lld/lib/ReaderWriter/YAML/ReaderWriterYAML.cpp b/lld/lib/ReaderWriter/YAML/ReaderWriterYAML.cpp
index 31fd4dbd235..72537b94cd3 100644
--- a/lld/lib/ReaderWriter/YAML/ReaderWriterYAML.cpp
+++ b/lld/lib/ReaderWriter/YAML/ReaderWriterYAML.cpp
@@ -437,6 +437,8 @@ template <> struct ScalarEnumerationTraits<lld::DefinedAtom::ContentType> {
                                           DefinedAtom::typeObjC2CategoryList);
     io.enumCase(value, "objc-class1",     DefinedAtom::typeObjC1Class);
     io.enumCase(value, "dtraceDOF",       DefinedAtom::typeDTraceDOF);
+    io.enumCase(value, "interposing-tuples",
+                                          DefinedAtom::typeInterposingTuples);
     io.enumCase(value, "lto-temp",        DefinedAtom::typeTempLTO);
     io.enumCase(value, "compact-unwind",  DefinedAtom::typeCompactUnwindInfo);
     io.enumCase(value, "unwind-info",     DefinedAtom::typeProcessedUnwindInfo);