[lld] r315054 - [ELF] - Do not produce broken .dynamic section with --no-rosegment

[George Rimar via llvm-commits]

Author: grimar
Date: Fri Oct  6 03:06:13 2017
New Revision: 315054

URL: http://llvm.org/viewvc/llvm-project?rev=315054&view=rev
Log:
[ELF] - Do not produce broken .dynamic section with --no-rosegment

LLD produces broken .dynamic section when --no-rosegment and at least
one of following options is present:
  1) -z rodynamic is given.
  2) MIPS target.

That happens because code that writes .dynamic assumes target buffer
is zero-filled, what can be not true after LLD fills it with trap
instructions. With one of two options above, .dynamic becomes
SHF_ALLOC section, so can be affected.

Differential revision: https://reviews.llvm.org/D38580

Added:
    lld/trunk/test/ELF/dynamic-no-rosegment.s
Modified:
    lld/trunk/ELF/SyntheticSections.cpp

Modified: lld/trunk/ELF/SyntheticSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.cpp?rev=315054&r1=315053&r2=315054&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.cpp (original)
+++ lld/trunk/ELF/SyntheticSections.cpp Fri Oct  6 03:06:13 2017
@@ -1171,10 +1171,10 @@ template <class ELFT> void DynamicSectio
       add({DT_MIPS_RLD_MAP, InX::MipsRldMap});
   }
 
-  getParent()->Link = this->Link;
+  add({DT_NULL, (uint64_t)0});
 
-  // +1 for DT_NULL
-  this->Size = (Entries.size() + 1) * this->Entsize;
+  getParent()->Link = this->Link;
+  this->Size = Entries.size() * this->Entsize;
 }
 
 template <class ELFT> void DynamicSection<ELFT>::writeTo(uint8_t *Buf) {

Added: lld/trunk/test/ELF/dynamic-no-rosegment.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/dynamic-no-rosegment.s?rev=315054&view=auto
==============================================================================
--- lld/trunk/test/ELF/dynamic-no-rosegment.s (added)
+++ lld/trunk/test/ELF/dynamic-no-rosegment.s Fri Oct  6 03:06:13 2017
@@ -0,0 +1,15 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+# RUN: ld.lld -shared --no-rosegment -z rodynamic -o %t %t.o
+# RUN: llvm-readobj -dynamic-table -s %t | FileCheck %s
+
+# CHECK:      DynamicSection [ (7 entries)
+# CHECK-NEXT:   Tag                Type                 Name/Value
+# CHECK-NEXT:   0x0000000000000006 SYMTAB               0x120
+# CHECK-NEXT:   0x000000000000000B SYMENT               24 (bytes)
+# CHECK-NEXT:   0x0000000000000005 STRTAB               0x1D0
+# CHECK-NEXT:   0x000000000000000A STRSZ                1 (bytes)
+# CHECK-NEXT:   0x000000006FFFFEF5 GNU_HASH             0x138
+# CHECK-NEXT:   0x0000000000000004 HASH                 0x150
+# CHECK-NEXT:   0x0000000000000000 NULL                 0x0
+# CHECK-NEXT: ]