[llvm] r279182 - [RuntimeDyld] Add support for ELF R_ARM_REL32 and R_ARM_GOT_PREL.

[Lang Hames via llvm-commits]

Author: lhames
Date: Thu Aug 18 20:15:39 2016
New Revision: 279182

URL: http://llvm.org/viewvc/llvm-project?rev=279182&view=rev
Log:
[RuntimeDyld] Add support for ELF R_ARM_REL32 and R_ARM_GOT_PREL.

Patch by William Dillon. Thanks William!

This patch adds support for the R_ARM_REL32 and R_ARM_GOT_PREL ELF ARM
relocations to RuntimeDyld, which should allow JITing of code that
produces these relocations.

No test case: Unfortunately RuntimeDyldELF's GOT building mechanism (which
uses a separate section for GOT entries) isn't compatible with
RuntimeDyldChecker. The correct fix for this is to fix RuntimeDyldELF's GOT
support (it's fundamentally broken at the moment: separate sections aren't
guaranteed to be in range of a GOT entry load), but that's a non-trivial job.


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

Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp?rev=279182&r1=279181&r2=279182&view=diff
==============================================================================
--- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp (original)
+++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp Thu Aug 18 20:15:39 2016
@@ -480,6 +480,9 @@ void RuntimeDyldELF::resolveARMRelocatio
     *TargetPtr |= Value & 0xFFF;
     *TargetPtr |= ((Value >> 12) & 0xF) << 16;
     break;
+  case ELF::R_ARM_REL32:
+    *TargetPtr += Value - FinalAddress;
+    break;
     // Write 24 bit relative value to the branch instruction.
   case ELF::R_ARM_PC24: // Fall through.
   case ELF::R_ARM_CALL: // Fall through.
@@ -1365,6 +1368,19 @@ RuntimeDyldELF::processRelocationRef(
                           RelType, 0);
         Section.advanceStubOffset(getMaxStubSize());
       }
+    } else if (RelType == ELF::R_ARM_GOT_PREL) {
+      uint32_t GOTOffset = allocateGOTEntries(SectionID, 1);
+
+      RelocationEntry GOTRE(SectionID, Offset, ELF::R_ARM_REL32, GOTOffset);
+      addRelocationForSection(GOTRE, GOTSectionID);
+
+      // Fill in the value of the symbol we're targeting into the GOT
+      RelocationEntry RE = computeGOTOffsetRE(SectionID, GOTOffset,
+                                              Value.Offset, ELF::R_ARM_ABS32);
+      if (Value.SymbolName)
+        addRelocationForSymbol(RE, Value.SymbolName);
+      else
+        addRelocationForSection(RE, Value.SectionID);
     } else {
       uint32_t *Placeholder =
         reinterpret_cast<uint32_t*>(computePlaceholderAddress(SectionID, Offset));