From 56c940ba496967e14a5ca87e67fac3128b2376d7 Mon Sep 17 00:00:00 2001
From: Ed Maste <emaste@FreeBSD.org>
Date: Tue, 13 Jun 2017 00:31:16 +0000
Subject: [PATCH] lld: ELF: Fix ICF crash on absolute symbol relocations.

If two sections contained relocations to absolute symbols with the same
value we would crash when trying to access their sections. Add a check that
both symbols point to sections before accessing their sections, and treat
absolute symbols as equal if their values are equal.

Obtained from:	LLD commit r292578
MFC after:	3 days
---
 contrib/llvm/tools/lld/ELF/ICF.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/contrib/llvm/tools/lld/ELF/ICF.cpp b/contrib/llvm/tools/lld/ELF/ICF.cpp
index 32cd0f8a185c..838b3d8b4930 100644
--- a/contrib/llvm/tools/lld/ELF/ICF.cpp
+++ b/contrib/llvm/tools/lld/ELF/ICF.cpp
@@ -245,7 +245,6 @@ bool ICF<ELFT>::variableEq(const InputSection<ELFT> *A, ArrayRef<RelTy> RelsA,
     if (&SA == &SB)
       return true;
 
-    // Or, the two sections must be in the same equivalence class.
     auto *DA = dyn_cast<DefinedRegular<ELFT>>(&SA);
     auto *DB = dyn_cast<DefinedRegular<ELFT>>(&SB);
     if (!DA || !DB)
@@ -253,6 +252,11 @@ bool ICF<ELFT>::variableEq(const InputSection<ELFT> *A, ArrayRef<RelTy> RelsA,
     if (DA->Value != DB->Value)
       return false;
 
+    // Either both symbols must be absolute...
+    if (!DA->Section || !DB->Section)
+      return !DA->Section && !DB->Section;
+
+    // Or the two sections must be in the same equivalence class.
     auto *X = dyn_cast<InputSection<ELFT>>(DA->Section);
     auto *Y = dyn_cast<InputSection<ELFT>>(DB->Section);
     if (!X || !Y)