Produce an error on non-encodable offsets for darwin ARM scattered relocations.

Scattered ARM relocations for Mach-O's only have 24 bits available to
encode the offset. This is not checked but just truncated and can result
in corrupt binaries after linking because the relocations are applied to
the wrong offset. This patch will check and error out in those
situations instead of emitting a wrong relocation.

Patch by: Sander Bogaert (dzn)

Differential revision: https://reviews.llvm.org/D54776

llvm-svn: 347922

1 files changed, 20 insertions, 0 deletions

diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
index 4b4956e914f..0ced8195790 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
@@ -22,6 +22,8 @@
 #include "llvm/MC/MCSection.h"
 #include "llvm/MC/MCValue.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/ScopedPrinter.h"
+
 using namespace llvm;
 
 namespace {
@@ -144,6 +146,15 @@ RecordARMScatteredHalfRelocation(MachObjectWriter *Writer,
                                  MCValue Target,
                                  uint64_t &FixedValue) {
   uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
+
+  if (FixupOffset & 0xff000000) {
+    Asm.getContext().reportError(Fixup.getLoc(),
+                                 "can not encode offset '0x" +
+                                     to_hexString(FixupOffset) +
+                                     "' in resulting scattered relocation.");
+    return;
+  }
+
   unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
   unsigned Type = MachO::ARM_RELOC_HALF;
 
@@ -250,6 +261,15 @@ void ARMMachObjectWriter::RecordARMScatteredRelocation(MachObjectWriter *Writer,
                                                     unsigned Log2Size,
                                                     uint64_t &FixedValue) {
   uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
+
+  if (FixupOffset & 0xff000000) {
+    Asm.getContext().reportError(Fixup.getLoc(),
+                                 "can not encode offset '0x" +
+                                     to_hexString(FixupOffset) +
+                                     "' in resulting scattered relocation.");
+    return;
+  }
+
   unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
 
   // See <reloc.h>.