[lld] r295938 - Update a comment about .note.GNU-stack.

[Rui Ueyama via llvm-commits]

Author: ruiu
Date: Thu Feb 23 01:06:43 2017
New Revision: 295938

URL: http://llvm.org/viewvc/llvm-project?rev=295938&view=rev
Log:
Update a comment about .note.GNU-stack.

Modified:
    lld/trunk/ELF/InputFiles.cpp

Modified: lld/trunk/ELF/InputFiles.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputFiles.cpp?rev=295938&r1=295937&r2=295938&view=diff
==============================================================================
--- lld/trunk/ELF/InputFiles.cpp (original)
+++ lld/trunk/ELF/InputFiles.cpp Thu Feb 23 01:06:43 2017
@@ -414,10 +414,18 @@ elf::ObjectFile<ELFT>::createInputSectio
   }
   }
 
-  // .note.GNU-stack is a marker section to control the presence of
-  // PT_GNU_STACK segment in outputs. Since the presence of the segment
-  // is controlled only by the command line option (-z execstack) in LLD,
-  // .note.GNU-stack is ignored.
+  // The GNU linker uses .note.GNU-stack section as a marker indicating
+  // that the code in the object file does not expect that the stack is
+  // executable (in terms of NX bit). If all input files have the marker,
+  // the GNU linker adds a PT_GNU_STACK segment to tells the loader to
+  // make the stack non-executable.
+  //
+  // But making the stack non-executable is a norm today for security
+  // reasons (as of 2017). Failure to do so may result in a serious
+  // security issue. Therefore, LLD always adds PT_GNU_STACK unless it is
+  // explicitly told to do otherwise (by -z execstack). Because the stack
+  // executable-ness is controlled solely by command line options,
+  // .note.GNU-stack sections are simply ignored.
   if (Name == ".note.GNU-stack")
     return &InputSection<ELFT>::Discarded;