From c958d8d621c3eccd9d0b7799471b8d060fed66df Mon Sep 17 00:00:00 2001
From: Eugene Leviant <evgeny.leviant@gmail.com>
Date: Wed, 12 Oct 2016 08:19:30 +0000
Subject: [PATCH] Don't crash if reloc targets discarded section

Differential revision: https://reviews.llvm.org/D25433

llvm-svn: 283984
---
 lld/ELF/Symbols.cpp                         | 12 ++++++++++++
 lld/test/ELF/linkerscript/discard-section.s |  9 +++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/lld/ELF/Symbols.cpp b/lld/ELF/Symbols.cpp
index 7457224..1dcb8cb 100644
--- a/lld/ELF/Symbols.cpp
+++ b/lld/ELF/Symbols.cpp
@@ -15,6 +15,7 @@
 #include "Target.h"
 
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/Path.h"
 
 using namespace llvm;
 using namespace llvm::object;
@@ -24,6 +25,12 @@ using namespace lld;
 using namespace lld::elf;
 
 template <class ELFT>
+static std::string getSectionName(InputSectionBase<ELFT> *S) {
+  StringRef Filename = S->getFile()->getName();
+  return (sys::path::filename(Filename) + "(" + S->Name + ")").str();
+}
+
+template <class ELFT>
 static typename ELFT::uint getSymVA(const SymbolBody &Body,
                                     typename ELFT::uint &Addend) {
   typedef typename ELFT::uint uintX_t;
@@ -53,6 +60,11 @@ static typename ELFT::uint getSymVA(const SymbolBody &Body,
     if (!SC)
       return D.Value;
 
+    if (!SC->Live) {
+      warn("relocation refers to discarded section '" + getSectionName(SC) + "'");
+      return 0;
+    }
+
     uintX_t Offset = D.Value;
     if (D.isSection()) {
       Offset += Addend;
diff --git a/lld/test/ELF/linkerscript/discard-section.s b/lld/test/ELF/linkerscript/discard-section.s
index d7d2acf..edeeee4 100644
--- a/lld/test/ELF/linkerscript/discard-section.s
+++ b/lld/test/ELF/linkerscript/discard-section.s
@@ -1,10 +1,15 @@
 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 # RUN: echo "SECTIONS { /DISCARD/ : { *(.aaa*) } }" > %t.script
-# RUN: ld.lld -o %t1 --script %t.script %t
+# RUN: ld.lld -o %t1 --script %t.script %t 2>&1 | FileCheck --check-prefix=WARN %s
 # RUN: llvm-objdump -section-headers %t1 | FileCheck %s
+
+# WARN: relocation refers to discarded section {{.+}}(.aaa)
 # CHECK-NOT: .aaa
 
 .section .aaa,"a"
-aaa:
+aab:
   .quad 0
+
+.section .zzz,"a"
+  .quad aab
-- 
2.7.4