From 28ac19c9ee0c486870b98ac00f074ceff5bbbe2a Mon Sep 17 00:00:00 2001
From: George Rimar <grimar@accesssoftek.com>
Date: Mon, 8 Aug 2016 08:42:48 +0000
Subject: [PATCH] [ELF] - Linkerscript: do not define _edata,_end,_etext if
 SECTIONS is used.

I faced that when tried to link FreeBSD kernel.
It was "duplicate symbol: _edata in (internal) and (internal)" error.
_data was a shared symbol that came from hack.so. At first it was replaced with DefinedRegular by the code
disabled in this patch and later when script tried to define the same symbol - the error was shown.

In the same situation (as given in testcase) ld defines them as UND. gold defines as ABS with zero value.
Patch just disables any operations of creating these symbols if script do layout.

Differential revision: https://reviews.llvm.org/D23206

llvm-svn: 277986
---
 lld/ELF/Writer.cpp                                 |  4 ++
 lld/test/ELF/end.s                                 | 46 ----------------------
 .../ELF/linkerscript/linkerscript-edata-etext.s    | 20 ++++++++++
 3 files changed, 24 insertions(+), 46 deletions(-)
 create mode 100644 lld/test/ELF/linkerscript/linkerscript-edata-etext.s

diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index f98530b..8ab906d 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -578,6 +578,10 @@ template <class ELFT> void Writer<ELFT>::addReservedSymbols() {
   if (!isOutputDynamic<ELFT>())
     Symtab.addIgnored("__tls_get_addr");
 
+  // If linker script do layout we do not need to create any standart symbols.
+  if (ScriptConfig->HasContents)
+    return;
+
   auto Define = [this](StringRef S, DefinedRegular<ELFT> *&Sym1,
                        DefinedRegular<ELFT> *&Sym2) {
     Sym1 = Symtab.addIgnored(S, STV_DEFAULT);
diff --git a/lld/test/ELF/end.s b/lld/test/ELF/end.s
index 689157f..18c77a3 100644
--- a/lld/test/ELF/end.s
+++ b/lld/test/ELF/end.s
@@ -23,52 +23,6 @@
 // DEFAULT-NEXT:     Value: 0x12008
 // DEFAULT: ]
 
-// If there is no .bss section, "_end" should point to the end of the .data section.
-// RUN: echo "SECTIONS { \
-// RUN:          /DISCARD/ : { *(.bss) } }" > %t.script
-// RUN: ld.lld %t.o --script %t.script -o %t
-// RUN: llvm-readobj -sections -symbols %t | FileCheck %s --check-prefix=NOBSS
-
-// NOBSS: Sections [
-// NOBSS:     Name: .data
-// NOBSS-NEXT:     Type:
-// NOBSS-NEXT:     Flags [
-// NOBSS-NEXT:       SHF_ALLOC
-// NOBSS-NEXT:       SHF_WRITE
-// NOBSS-NEXT:     ]
-// NOBSS-NEXT:     Address: 0x159
-// NOBSS-NEXT:     Offset:
-// NOBSS-NEXT:     Size: 2
-// NOBSS: ]
-// NOBSS: Symbols [
-// NOBSS:     Name: _end
-// NOBSS-NEXT:     Value: 0x15B
-// NOBSS: ]
-
-// If the layout of the sections is changed, "_end" should point to the end of allocated address space.
-// RUN: echo "SECTIONS { \
-// RUN:          .bss : { *(.bss) } \
-// RUN:          .data : { *(.data) } \
-// RUN:          .text : { *(.text) } }" > %t.script
-// RUN: ld.lld %t.o --script %t.script -o %t
-// RUN: llvm-readobj -sections -symbols %t | FileCheck %s --check-prefix=TEXTATEND
-
-// TEXTATEND: Sections [
-// TEXTATEND:     Name: .text
-// TEXTATEND-NEXT:     Type:
-// TEXTATEND-NEXT:     Flags [
-// TEXTATEND-NEXT:       SHF_ALLOC
-// TEXTATEND-NEXT:       SHF_EXECINSTR
-// TEXTATEND-NEXT:     ]
-// TEXTATEND-NEXT:     Address: 0x160
-// TEXTATEND-NEXT:     Offset:
-// TEXTATEND-NEXT:     Size: 1
-// TEXTATEND: ]
-// TEXTATEND: Symbols [
-// TEXTATEND:     Name: _end
-// TEXTATEND-NEXT:     Value: 0x161
-// TEXTATEND: ]
-
 .global _start,_end
 .text
 _start:
diff --git a/lld/test/ELF/linkerscript/linkerscript-edata-etext.s b/lld/test/ELF/linkerscript/linkerscript-edata-etext.s
new file mode 100644
index 0000000..d5891ee
--- /dev/null
+++ b/lld/test/ELF/linkerscript/linkerscript-edata-etext.s
@@ -0,0 +1,20 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+# RUN: echo "SECTIONS { }" > %t.script
+# RUN: not ld.lld %t.o -script %t.script -o %t 2>&1 | FileCheck %s
+# CHECK: undefined symbol: _edata
+# CHECK: undefined symbol: _end
+# CHECK: undefined symbol: _etext
+
+.global _start,_end,_etext,_edata
+.text
+_start:
+ .quad _edata + 0x1
+ .quad _etext + 0x1
+ .quad _end + 0x1
+
+.data
+  .word 1
+.bss
+  .align 4
+  .space 6
-- 
2.7.4