From 6ab275c0c803b1d825dccd0b418f918e97cc01bc Mon Sep 17 00:00:00 2001
From: George Rimar <grimar@accesssoftek.com>
Date: Fri, 25 Dec 2015 09:51:42 +0000
Subject: [PATCH] [ELF] - Fixed handling relocations against zero sized
 .eh_frame section.

The file crtbeginT.o has relocations pointing to the start of an empty
.eh_frame that is known to be the first in the link. It does that to
identify the start of the output .eh_frame. Handle this special case.

Differential revision: http://reviews.llvm.org/D15610

llvm-svn: 256414
---
 lld/ELF/InputSection.cpp          |  5 +++++
 lld/test/ELF/ehframe-relocation.s | 29 +++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+)
 create mode 100644 lld/test/ELF/ehframe-relocation.s

diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index a2ee588f4e1e..1b45ec7a5592 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -268,6 +268,11 @@ bool EHInputSection<ELFT>::classof(const InputSectionBase<ELFT> *S) {
 template <class ELFT>
 typename EHInputSection<ELFT>::uintX_t
 EHInputSection<ELFT>::getOffset(uintX_t Offset) {
+  // The file crtbeginT.o has relocations pointing to the start of an empty
+  // .eh_frame that is known to be the first in the link. It does that to
+  // identify the start of the output .eh_frame. Handle this special case.
+  if (this->getSectionHdr()->sh_size == 0)
+    return Offset;
   std::pair<uintX_t, uintX_t> *I = this->getRangeAndSize(Offset).first;
   uintX_t Base = I->second;
   if (Base == uintX_t(-1))
diff --git a/lld/test/ELF/ehframe-relocation.s b/lld/test/ELF/ehframe-relocation.s
new file mode 100644
index 000000000000..f952ebc60865
--- /dev/null
+++ b/lld/test/ELF/ehframe-relocation.s
@@ -0,0 +1,29 @@
+// REQUIRES: x86
+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+// RUN: ld.lld %t.o -o %t
+// RUN: llvm-readobj -s %t | FileCheck %s
+// RUN: llvm-objdump -d %t | FileCheck --check-prefix=DISASM %s
+
+// CHECK:      Name: .eh_frame
+// CHECK-NEXT: Type: SHT_X86_64_UNWIND
+// CHECK-NEXT: Flags [
+// CHECK-NEXT:   SHF_ALLOC
+// CHECK-NEXT: ]
+// CHECK-NEXT: Address: 0x10120
+// CHECK-NEXT: Offset:
+// CHECK-NEXT: Size: 0
+
+// 0x10120 = 65824
+// 0x10120 + 5 = 65829
+// DISASM:      Disassembly of section .text:
+// DISASM-NEXT: _start:
+// DISASM-NEXT:    11000: {{.*}} movq 65824, %rax
+// DISASM-NEXT:    11008: {{.*}} movq 65829, %rax
+
+.section .eh_frame,"ax",@unwind
+
+.section .text
+.globl _start
+_start:
+ movq .eh_frame, %rax
+ movq .eh_frame + 5, %rax