[lld] r297638 - ELF: Resolve _end symbols correctly.

[Peter Collingbourne via llvm-commits]

Author: pcc
Date: Mon Mar 13 11:40:20 2017
New Revision: 297638

URL: http://llvm.org/viewvc/llvm-project?rev=297638&view=rev
Log:
ELF: Resolve _end symbols correctly.

Fix a bug introduced in r297313 which caused them to resolve to the end
of the ELF header in PIEs and DSOs.

Differential Revision: https://reviews.llvm.org/D30843

Modified:
    lld/trunk/ELF/Writer.cpp
    lld/trunk/test/ELF/pre_init_fini_array_missing.s

Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=297638&r1=297637&r2=297638&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Mon Mar 13 11:40:20 2017
@@ -1228,10 +1228,15 @@ template <class ELFT> void Writer<ELFT>:
   auto Define = [&](StringRef Start, StringRef End, OutputSection *OS) {
     // These symbols resolve to the image base if the section does not exist.
     // A special value -1 indicates end of the section.
-    if (!OS && Config->pic())
-      OS = Out::ElfHeader;
-    addOptionalRegular<ELFT>(Start, OS, 0);
-    addOptionalRegular<ELFT>(End, OS, OS ? -1 : 0);
+    if (OS) {
+      addOptionalRegular<ELFT>(Start, OS, 0);
+      addOptionalRegular<ELFT>(End, OS, -1);
+    } else {
+      if (Config->pic())
+        OS = Out::ElfHeader;
+      addOptionalRegular<ELFT>(Start, OS, 0);
+      addOptionalRegular<ELFT>(End, OS, 0);
+    }
   };
 
   Define("__preinit_array_start", "__preinit_array_end", Out::PreinitArray);

Modified: lld/trunk/test/ELF/pre_init_fini_array_missing.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/pre_init_fini_array_missing.s?rev=297638&r1=297637&r2=297638&view=diff
==============================================================================
--- lld/trunk/test/ELF/pre_init_fini_array_missing.s (original)
+++ lld/trunk/test/ELF/pre_init_fini_array_missing.s Mon Mar 13 11:40:20 2017
@@ -1,6 +1,8 @@
 // RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
 // RUN: ld.lld %t -o %t2
 // RUN: llvm-objdump -d %t2 | FileCheck %s
+// RUN: ld.lld -pie %t -o %t3
+// RUN: llvm-objdump -d %t3 | FileCheck --check-prefix=PIE %s
 // REQUIRES: x86
 
 .globl _start
@@ -28,3 +30,14 @@ _start:
 // CHECK-NEXT:   20100f:    e8 ec ef df ff     callq    -2101268
 // CHECK-NEXT:   201014:    e8 e7 ef df ff     callq    -2101273
 // CHECK-NEXT:   201019:    e8 e2 ef df ff     callq    -2101278
+
+// In position-independent binaries, they resolve to the image base.
+
+// PIE:      Disassembly of section .text:
+// PIE-NEXT: _start:
+// PIE-NEXT:     1000:	e8 fb ef ff ff 	callq	-4101
+// PIE-NEXT:     1005:	e8 f6 ef ff ff 	callq	-4106
+// PIE-NEXT:     100a:	e8 f1 ef ff ff 	callq	-4111
+// PIE-NEXT:     100f:	e8 ec ef ff ff 	callq	-4116
+// PIE-NEXT:     1014:	e8 e7 ef ff ff 	callq	-4121
+// PIE-NEXT:     1019:	e8 e2 ef ff ff 	callq	-4126