[BOLT][RelVTable] Skip special handling on non virtual function pointer relocations (#137406)

Besides virtual function pointers vtable could contain other kinds of
entries like those for RTTI data that also require relocations. We need
to skip special handling on relocations for non virtual function pointers
in relative vtable.

Co-authored-by: Maksim Panchenko <[email protected]>

Author: yozhu

bolt/lib/Rewrite/RewriteInstance.cpp

@@ -2697,20 +2697,19 @@ void RewriteInstance::handleRelocation(const SectionRef &RelocatedSection,
                BD->nameStartsWith("_ZTCN"))) { // construction vtable
       BinaryFunction *BF = BC->getBinaryFunctionContainingAddress(
           SymbolAddress, /*CheckPastEnd*/ false, /*UseMaxSize*/ true);
-      if (!BF || BF->getAddress() != SymbolAddress) {
-        BC->errs()
-            << "BOLT-ERROR: the virtual function table entry at offset 0x"
-            << Twine::utohexstr(Rel.getOffset());
-        if (BF)
-          BC->errs() << " points to the middle of a function @ 0x"
-                     << Twine::utohexstr(BF->getAddress()) << "\n";
-        else
-          BC->errs() << " does not point to any function\n";
-        exit(1);
+      if (BF) {
+        if (BF->getAddress() != SymbolAddress) {
+          BC->errs()
+              << "BOLT-ERROR: the virtual function table entry at offset 0x"
+              << Twine::utohexstr(Rel.getOffset())
+              << " points to the middle of a function @ 0x"
+              << Twine::utohexstr(BF->getAddress()) << "\n";
+          exit(1);
+        }
+        BC->addRelocation(Rel.getOffset(), BF->getSymbol(), RType, Addend,
+                          ExtractedValue);
+        return;
       }
-      BC->addRelocation(Rel.getOffset(), BF->getSymbol(), RType, Addend,
-                        ExtractedValue);
-      return;
     }
   }
 

bolt/test/AArch64/skip-non-vfuncptr-reloc-in-relative-vtable.s

@@ -0,0 +1,35 @@
+// Test the fix that BOLT should skip special handling of any non-virtual
+// function pointer relocations in relative vtable.
+
+// RUN: llvm-mc -filetype=obj -triple aarch64-unknown-gnu %s -o %t.o
+// RUN: %clang %cxxflags -fuse-ld=lld %t.o -o %t.so -Wl,-q
+// RUN: llvm-bolt %t.so -o %t.bolted.so
+
+	.text
+	.p2align	2
+	.type	foo,@function
+foo:
+	.cfi_startproc
+	adrp	x8, _ZTV3gooE
+	add	x8, x8, :lo12:_ZTV3gooE
+	ldr	x0, [x8]
+	ret
+.Lfunc_end0:
+	.size	foo, .Lfunc_end0-foo
+	.cfi_endproc
+
+	.type	_fake_rtti_data,@object
+	.section	.rodata.cst16._fake_rtti_data,"aMG",@progbits,16,_fake_rtti_data,comdat
+	.p2align	3, 0x0
+_fake_rtti_data:
+	.ascii	"_FAKE_RTTI_DATA_"
+	.size	_fake_rtti_data, 16
+
+	.type	_ZTV3gooE,@object
+	.section	.rodata,"a",@progbits
+	.p2align	2, 0x0
+_ZTV3gooE:
+	.word	0
+	.word	_fake_rtti_data-_ZTV3gooE-8
+	.word	foo@PLT-_ZTV3gooE-8
+	.size	_ZTV3gooE, 12