[lld] r319755 - [ELF] InX::BssRelRo should check section contents before marking relro

[Peter Smith via llvm-commits]

Author: psmith
Date: Tue Dec  5 03:15:58 2017
New Revision: 319755

URL: http://llvm.org/viewvc/llvm-project?rev=319755&view=rev
Log:
[ELF] InX::BssRelRo should check section contents before marking relro

When a linker script is used with a pattern like { *(.bss .bss.*) } the
InX::BssRelRo section will match against .bss.*. By matching on the name
only, in the same way that .data.rel.ro works we prevent this
from happening, but permit scripts that want to explicitly provide
a .bss.rel.ro OutputSection.
    
Differential Revision: https://reviews.llvm.org/D40735

Added:
    lld/trunk/test/ELF/relro-copyrel-bss-script.s
Modified:
    lld/trunk/ELF/Writer.cpp

Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=319755&r1=319754&r2=319755&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Tue Dec  5 03:15:58 2017
@@ -576,20 +576,14 @@ static bool isRelroSection(const OutputS
   if (Sec == InX::Dynamic->getParent())
     return true;
 
-  // .bss.rel.ro is used for copy relocations for read-only symbols.
-  // Since the dynamic linker needs to process copy relocations, the
-  // section cannot be read-only, but once initialized, they shouldn't
-  // change.
-  if (Sec == InX::BssRelRo->getParent())
-    return true;
-
   // Sections with some special names are put into RELRO. This is a
   // bit unfortunate because section names shouldn't be significant in
   // ELF in spirit. But in reality many linker features depend on
   // magic section names.
   StringRef S = Sec->Name;
-  return S == ".data.rel.ro" || S == ".ctors" || S == ".dtors" || S == ".jcr" ||
-         S == ".eh_frame" || S == ".openbsd.randomdata";
+  return S == ".data.rel.ro" || S == ".bss.rel.ro" || S == ".ctors" ||
+         S == ".dtors" || S == ".jcr" || S == ".eh_frame" ||
+         S == ".openbsd.randomdata";
 }
 
 // We compute a rank for each section. The rank indicates where the

Added: lld/trunk/test/ELF/relro-copyrel-bss-script.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/relro-copyrel-bss-script.s?rev=319755&view=auto
==============================================================================
--- lld/trunk/test/ELF/relro-copyrel-bss-script.s (added)
+++ lld/trunk/test/ELF/relro-copyrel-bss-script.s Tue Dec  5 03:15:58 2017
@@ -0,0 +1,40 @@
+// REQUIRES: x86
+// RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/shared.s -o %t.o
+// RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/copy-in-shared.s -o %t2.o
+// RUN: ld.lld -shared %t.o %t2.o -o %t.so
+
+// A linker script that will map .bss.rel.ro into .bss.
+// RUN: echo "SECTIONS { \
+// RUN: .bss : { *(.bss) *(.bss.*) } \
+// RUN: } " > %t.script
+
+// RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t3.o
+// RUN: ld.lld %t3.o %t.so -z relro -o %t --script=%t.script 2>&1
+// RUN: llvm-readobj --program-headers %t | FileCheck %s
+        .section .text, "ax", @progbits
+        .global bar
+        .global foo
+        .global _start
+_start:
+        callq bar
+        // Will produce .bss.rel.ro that will match in .bss, this will lose
+        // the relro property of the copy relocation.
+        .quad foo
+
+        // Non relro bss
+        .bss
+        // make large enough to affect PT_GNU_RELRO MemSize if this was marked
+        // as relro.
+        .space 0x2000
+
+// CHECK:     Type: PT_GNU_RELRO (0x6474E552)
+// CHECK-NEXT:     Offset:
+// CHECK-NEXT:     VirtualAddress:
+// CHECK-NEXT:     PhysicalAddress:
+// CHECK-NEXT:     FileSize:
+// CHECK-NEXT:     MemSize: 4096
+// CHECK-NEXT:     Flags [ (0x4)
+// CHECK-NEXT:       PF_R (0x4)
+// CHECK-NEXT:     ]
+// CHECK-NEXT:     Alignment: 1
+// CHECK-NEXT:   }