[llvm] r211384 - [RuntimeDyld] Fix ppc64 stub relocations on little-endian

[Ulrich Weigand]

Author: uweigand
Date: Fri Jun 20 13:17:56 2014
New Revision: 211384

URL: http://llvm.org/viewvc/llvm-project?rev=211384&view=rev
Log:
[RuntimeDyld] Fix ppc64 stub relocations on little-endian

When RuntimeDyldELF creates stub functions, it needs to install
relocations that will resolve to the final address of the target
routine. Since those are 16-bit relocs, they need to be applied to the
least-significant halfword of the instruction.  On big-endian ppc64,
this means that addresses have to be adjusted by 2, which is what the
code currently does.

However, on a little-endian system, the address must *not* be adjusted;
the least-significant halfword is the first one.  This patch updates the
RuntimeDyldELF code to take the target byte order into account.


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=211384&r1=211383&r2=211384&view=diff
==============================================================================
--- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp (original)
+++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp Fri Jun 20 13:17:56 2014
@@ -1205,14 +1205,20 @@ relocation_iterator RuntimeDyldELF::proc
                              ELF::R_PPC64_ADDR64, Value.Addend);
 
           // Generates the 64-bits address loads as exemplified in section
-          // 4.5.1 in PPC64 ELF ABI.
-          RelocationEntry REhst(SectionID, StubTargetAddr - Section.Address + 2,
+          // 4.5.1 in PPC64 ELF ABI.  Note that the relocations need to
+          // apply to the low part of the instructions, so we have to update
+          // the offset according to the target endianness.
+          uint64_t StubRelocOffset = StubTargetAddr - Section.Address;
+          if (!IsTargetLittleEndian)
+            StubRelocOffset += 2;
+
+          RelocationEntry REhst(SectionID, StubRelocOffset + 0,
                                 ELF::R_PPC64_ADDR16_HIGHEST, Value.Addend);
-          RelocationEntry REhr(SectionID, StubTargetAddr - Section.Address + 6,
+          RelocationEntry REhr(SectionID, StubRelocOffset + 4,
                                ELF::R_PPC64_ADDR16_HIGHER, Value.Addend);
-          RelocationEntry REh(SectionID, StubTargetAddr - Section.Address + 14,
+          RelocationEntry REh(SectionID, StubRelocOffset + 12,
                               ELF::R_PPC64_ADDR16_HI, Value.Addend);
-          RelocationEntry REl(SectionID, StubTargetAddr - Section.Address + 18,
+          RelocationEntry REl(SectionID, StubRelocOffset + 16,
                               ELF::R_PPC64_ADDR16_LO, Value.Addend);
 
           if (Value.SymbolName) {