Change how we iterate over relocations on ELF.

For COFF and MachO, sections semantically have relocations that apply to them.
That is not the case on ELF.

In relocatable objects (.o), a section with relocations in ELF has offsets to
another section where the relocations should be applied.

In dynamic objects and executables, relocations don't have an offset, they have
a virtual address. The section sh_info may or may not point to another section,
but that is not actually used for resolving the relocations.

This patch exposes that in the ObjectFile API. It has the following advantages:

* Most (all?) clients can handle this more efficiently. They will normally walk
all relocations, so doing an effort to iterate in a particular order doesn't
save time.

* llvm-readobj now prints relocations in the same way the native readelf does.

* probably most important, relocations that don't point to any section are now
visible. This is the case of relocations in the rela.dyn section. See the
updated relocation-executable.test for example.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182908 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 8 deletions

diff --git a/include/llvm/Object/ObjectFile.h b/include/llvm/Object/ObjectFile.h
index c73a568..ba1bb69 100644
--- a/include/llvm/Object/ObjectFile.h
+++ b/include/llvm/Object/ObjectFile.h
@@ -28,12 +28,8 @@ namespace object {
 class ObjectFile;
 
 union DataRefImpl {
-  struct {
-    // ELF needs this for relocations. This entire union should probably be a
-    // char[max(8, sizeof(uintptr_t))] and require the impl to cast.
-    uint16_t a, b;
-    uint32_t c;
-  } w;
+  // This entire union should probably be a
+  // char[max(8, sizeof(uintptr_t))] and require the impl to cast.
   struct {
     uint32_t a, b;
   } d;
@@ -133,6 +129,8 @@ typedef content_iterator<RelocationRef> relocation_iterator;
 
 /// SectionRef - This is a value type class that represents a single section in
 /// the list of sections in the object file.
+class SectionRef;
+typedef content_iterator<SectionRef> section_iterator;
 class SectionRef {
   friend class SymbolRef;
   DataRefImpl SectionPimpl;
@@ -169,10 +167,10 @@ public:
 
   relocation_iterator begin_relocations() const;
   relocation_iterator end_relocations() const;
+  section_iterator getRelocatedSection() const;
 
   DataRefImpl getRawDataRefImpl() const;
 };
-typedef content_iterator<SectionRef> section_iterator;
 
 /// SymbolRef - This is a value type class that represents a single symbol in
 /// the list of symbols in the object file.
@@ -326,7 +324,7 @@ protected:
                                            bool &Result) const = 0;
   virtual relocation_iterator getSectionRelBegin(DataRefImpl Sec) const = 0;
   virtual relocation_iterator getSectionRelEnd(DataRefImpl Sec) const = 0;
-
+  virtual section_iterator getRelocatedSection(DataRefImpl Sec) const;
 
   // Same as above for RelocationRef.
   friend class RelocationRef;
@@ -538,6 +536,10 @@ inline relocation_iterator SectionRef::end_relocations() const {
   return OwningObject->getSectionRelEnd(SectionPimpl);
 }
 
+inline section_iterator SectionRef::getRelocatedSection() const {
+  return OwningObject->getRelocatedSection(SectionPimpl);
+}
+
 inline DataRefImpl SectionRef::getRawDataRefImpl() const {
   return SectionPimpl;
 }