[lld] r315292 - [LLD] Fix findOrphanPos to consistently ignore "dead" OutputSection's

[Andrew Ng via llvm-commits]

Author: anng
Date: Tue Oct 10 03:05:52 2017
New Revision: 315292

URL: http://llvm.org/viewvc/llvm-project?rev=315292&view=rev
Log:
[LLD] Fix findOrphanPos to consistently ignore "dead" OutputSection's

When findOrphanPos does the reverse search to find the OutputSection
preceding the orphan's insertion point, look for a live OutputSection
and ignore "dead" OutputSection's. This matches the behaviour of the
forward search performed earlier in this function.

Added test which without the above fix fails as a result of an orphan
executable section being incorrectly placed in a non-executable segment.

Differential Review: https://reviews.llvm.org/D38690

Added:
    lld/trunk/test/ELF/linkerscript/orphan-phdrs.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=315292&r1=315291&r2=315292&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Tue Oct 10 03:05:52 2017
@@ -1031,9 +1031,11 @@ findOrphanPos(std::vector<BaseCommand *>
         Sec->SortRank < CurSec->SortRank)
       break;
   }
-  auto J = std::find_if(
-      llvm::make_reverse_iterator(I), llvm::make_reverse_iterator(B),
-      [](BaseCommand *Cmd) { return isa<OutputSection>(Cmd); });
+  auto J = std::find_if(llvm::make_reverse_iterator(I),
+                        llvm::make_reverse_iterator(B), [](BaseCommand *Cmd) {
+                          auto *OS = dyn_cast<OutputSection>(Cmd);
+                          return OS && OS->Live;
+                        });
   I = J.base();
 
   // As a special case, if the orphan section is the last section, put

Added: lld/trunk/test/ELF/linkerscript/orphan-phdrs.s
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/linkerscript/orphan-phdrs.s?rev=315292&view=auto
==============================================================================
--- lld/trunk/test/ELF/linkerscript/orphan-phdrs.s (added)
+++ lld/trunk/test/ELF/linkerscript/orphan-phdrs.s Tue Oct 10 03:05:52 2017
@@ -0,0 +1,34 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
+# RUN: echo "PHDRS { \
+# RUN:   exec PT_LOAD FLAGS(0x4 | 0x1); \
+# RUN:   rw   PT_LOAD FLAGS(0x4 | 0x2); \
+# RUN: } \
+# RUN: SECTIONS { \
+# RUN:  .text : { *(.text) } :exec \
+# RUN:  .empty : { *(.empty) } :rw \
+# RUN:  .rw : { *(.rw) } \
+# RUN: }" > %t.script
+# RUN: ld.lld -o %t --script %t.script %t.o
+# RUN: llvm-readobj -elf-output-style=GNU -s -l %t | FileCheck %s
+
+## Check that the orphan section is placed correctly and belongs to
+## the correct segment.
+
+# CHECK: Section Headers
+# CHECK: .text
+# CHECK-NEXT: .orphan
+# CHECK-NEXT: .rw
+
+# CHECK: Segment Sections
+# CHECK-NEXT: .text .orphan
+# CHECK-NEXT: .rw
+
+.section .text, "ax"
+ ret
+
+.section .rw, "aw"
+ .quad 0
+
+.section .orphan, "ax"
+ ret