[lld] r270910 - [ELF][MIPS] Handle section symbol points to the .MIPS.options / .reginfo section

[Simon Atanasyan via llvm-commits]

Author: atanasyan
Date: Thu May 26 15:46:01 2016
New Revision: 270910

URL: http://llvm.org/viewvc/llvm-project?rev=270910&view=rev
Log:
[ELF][MIPS] Handle section symbol points to the .MIPS.options / .reginfo section

MIPS .reginfo and .MIPS.options sections are consumed by the linker, and
the linker produces a single output section. But it is possible that
input files contain section symbol points to the corresponding input
section. In case of generation a relocatable output we need to write
such symbols to the output file.

Fixes bug 27878.

Differential Revision: http://reviews.llvm.org/D20688

Added:
    lld/trunk/test/ELF/Inputs/mips-options.o
    lld/trunk/test/ELF/mips-options-r.test
Modified:
    lld/trunk/ELF/InputSection.cpp
    lld/trunk/ELF/OutputSections.cpp

Modified: lld/trunk/ELF/InputSection.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputSection.cpp?rev=270910&r1=270909&r2=270910&view=diff
==============================================================================
--- lld/trunk/ELF/InputSection.cpp (original)
+++ lld/trunk/ELF/InputSection.cpp Thu May 26 15:46:01 2016
@@ -67,8 +67,13 @@ typename ELFT::uint InputSectionBase<ELF
   case MipsReginfo:
   case MipsOptions:
     // MIPS .reginfo and .MIPS.options sections are consumed by the linker,
-    // so they should never be copied to output.
-    llvm_unreachable("MIPS reginfo/options section reached writeTo().");
+    // and the linker produces a single output section. It is possible that
+    // input files contain section symbol points to the corresponding input
+    // section. Redirect it to the produced output section.
+    if (Offset != 0)
+      fatal("Unsupported reference to the middle of '" + getSectionName() +
+            "' section");
+    return this->OutSec->getVA();
   }
   llvm_unreachable("invalid section kind");
 }

Modified: lld/trunk/ELF/OutputSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.cpp?rev=270910&r1=270909&r2=270910&view=diff
==============================================================================
--- lld/trunk/ELF/OutputSections.cpp (original)
+++ lld/trunk/ELF/OutputSections.cpp Thu May 26 15:46:01 2016
@@ -1582,6 +1582,7 @@ void MipsReginfoOutputSection<ELFT>::add
   // Copy input object file's .reginfo gprmask to output.
   auto *S = cast<MipsReginfoInputSection<ELFT>>(C);
   GprMask |= S->Reginfo->ri_gprmask;
+  S->OutSec = this;
 }
 
 template <class ELFT>
@@ -1610,6 +1611,7 @@ void MipsOptionsOutputSection<ELFT>::add
   auto *S = cast<MipsOptionsInputSection<ELFT>>(C);
   if (S->Reginfo)
     GprMask |= S->Reginfo->ri_gprmask;
+  S->OutSec = this;
 }
 
 namespace lld {

Added: lld/trunk/test/ELF/Inputs/mips-options.o
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/Inputs/mips-options.o?rev=270910&view=auto
==============================================================================
Binary files lld/trunk/test/ELF/Inputs/mips-options.o (added) and lld/trunk/test/ELF/Inputs/mips-options.o Thu May 26 15:46:01 2016 differ

Added: lld/trunk/test/ELF/mips-options-r.test
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/mips-options-r.test?rev=270910&view=auto
==============================================================================
--- lld/trunk/test/ELF/mips-options-r.test (added)
+++ lld/trunk/test/ELF/mips-options-r.test Thu May 26 15:46:01 2016
@@ -0,0 +1,19 @@
+# Check that if input file contains .MIPS.options section and symbol
+# points to the section and the linker generates a relocatable output,
+# LLD does not crash and write section symbols point to the output
+# .MIPS.options section.
+#
+# PR 27878
+#
+# Input object file created using the following script:
+# % cat t.s
+#   .text
+#   nop
+# % as -mabi=64 -mips64r2 t.s
+
+# RUN: ld.lld -r %p/Inputs/mips-options.o -o %t.o
+# RUN: llvm-readobj -t %t.o | FileCheck %s
+
+# REQUIRES: mips
+
+# CHECK: Section: .MIPS.options