[llvm] r188697 - Adding comments to document RuntimeDyld relocation handling

[Andrew Kaylor]

Author: akaylor
Date: Mon Aug 19 14:38:06 2013
New Revision: 188697

URL: http://llvm.org/viewvc/llvm-project?rev=188697&view=rev
Log:
Adding comments to document RuntimeDyld relocation handling

Modified:
    llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
    llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
    llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp

Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp?rev=188697&r1=188696&r2=188697&view=diff
==============================================================================
--- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp (original)
+++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp Mon Aug 19 14:38:06 2013
@@ -41,6 +41,9 @@ void RuntimeDyldImpl::resolveRelocations
   // Just iterate over the sections we have and resolve all the relocations
   // in them. Gross overkill, but it gets the job done.
   for (int i = 0, e = Sections.size(); i != e; ++i) {
+    // The Section here (Sections[i]) refers to the section in which the
+    // symbol for the relocation is located.  The SectionID in the relocation
+    // entry provides the section to which the relocation will be applied.
     uint64_t Addr = Sections[i].LoadAddress;
     DEBUG(dbgs() << "Resolving relocations Section #" << i
             << "\t" << format("%p", (uint8_t *)Addr)

Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp?rev=188697&r1=188696&r2=188697&view=diff
==============================================================================
--- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp (original)
+++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp Mon Aug 19 14:38:06 2013
@@ -734,8 +734,28 @@ void RuntimeDyldELF::resolveSystemZReloc
   }
 }
 
+// The target location for the relocation is described by RE.SectionID and
+// RE.Offset.  RE.SectionID can be used to find the SectionEntry.  Each
+// SectionEntry has three members describing its location.
+// SectionEntry::Address is the address at which the section has been loaded
+// into memory in the current (host) process.  SectionEntry::LoadAddress is the
+// address that the section will have in the target process.
+// SectionEntry::ObjAddress is the address of the bits for this section in the
+// original emitted object image (also in the current address space).
+//
+// Relocations will be applied as if the section were loaded at
+// SectionEntry::LoadAddress, but they will be applied at an address based
+// on SectionEntry::Address.  SectionEntry::ObjAddress will be used to refer to
+// Target memory contents if they are required for value calculations.
+//
+// The Value parameter here is the load address of the symbol for the
+// relocation to be applied.  For relocations which refer to symbols in the
+// current object Value will be the LoadAddress of the section in which
+// the symbol resides (RE.Addend provides additional information about the
+// symbol location).  For external symbols, Value will be the address of the
+// symbol in the target address space.
 void RuntimeDyldELF::resolveRelocation(const RelocationEntry &RE,
-				       uint64_t Value) {
+                                       uint64_t Value) {
   const SectionEntry &Section = Sections[RE.SectionID];
   return resolveRelocation(Section, RE.Offset, Value, RE.RelType, RE.Addend);
 }

Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp?rev=188697&r1=188696&r2=188697&view=diff
==============================================================================
--- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp (original)
+++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp Mon Aug 19 14:38:06 2013
@@ -84,6 +84,26 @@ StringRef RuntimeDyldMachO::getEHFrameSe
   return StringRef((char*)EHFrame->Address, EHFrame->Size);
 }
 
+// The target location for the relocation is described by RE.SectionID and
+// RE.Offset.  RE.SectionID can be used to find the SectionEntry.  Each
+// SectionEntry has three members describing its location.
+// SectionEntry::Address is the address at which the section has been loaded
+// into memory in the current (host) process.  SectionEntry::LoadAddress is the
+// address that the section will have in the target process.
+// SectionEntry::ObjAddress is the address of the bits for this section in the
+// original emitted object image (also in the current address space).
+//
+// Relocations will be applied as if the section were loaded at
+// SectionEntry::LoadAddress, but they will be applied at an address based
+// on SectionEntry::Address.  SectionEntry::ObjAddress will be used to refer to
+// Target memory contents if they are required for value calculations.
+//
+// The Value parameter here is the load address of the symbol for the
+// relocation to be applied.  For relocations which refer to symbols in the
+// current object Value will be the LoadAddress of the section in which
+// the symbol resides (RE.Addend provides additional information about the
+// symbol location).  For external symbols, Value will be the address of the
+// symbol in the target address space.
 void RuntimeDyldMachO::resolveRelocation(const RelocationEntry &RE,
                                          uint64_t Value) {
   const SectionEntry &Section = Sections[RE.SectionID];