r333401 | emaste | 2018-05-09 13:17:01 +0200 (Wed, 09 May 2018) | 19 lines

lld: Omit PT_NOTE for SHT_NOTE without SHF_ALLOC

A non-alloc note section should not have a PT_NOTE program header.

Found while linking ghc (Haskell compiler) with lld on FreeBSD.  Haskell
emits a .debug-ghc-link-info note section (as the name suggests, it
contains link info) as a SHT_NOTE section without SHF_ALLOC set.

For this case ld.bfd does not emit a PT_NOTE segment for
.debug-ghc-link-info.  lld previously emitted a PT_NOTE with p_vaddr = 0
and FreeBSD's rtld segfaulted when trying to parse a note at address 0.

LLVM PR:	https://llvm.org/pr37361
LLVM review:	https://reviews.llvm.org/D46623

PR:		226872
Reviewed by:	dim
Sponsored by:	The FreeBSD Foundation

Index: tools/lld/ELF/Writer.cpp
===================================================================
--- tools/lld/ELF/Writer.cpp	(revision 333400)
+++ tools/lld/ELF/Writer.cpp	(revision 333401)
@@ -1708,7 +1708,7 @@ template <class ELFT> std::vector<PhdrEntry *> Wri
   // Create one PT_NOTE per a group of contiguous .note sections.
   PhdrEntry *Note = nullptr;
   for (OutputSection *Sec : OutputSections) {
-    if (Sec->Type == SHT_NOTE) {
+    if (Sec->Type == SHT_NOTE && (Sec->Flags & SHF_ALLOC)) {
       if (!Note || Sec->LMAExpr)
         Note = AddHdr(PT_NOTE, PF_R);
       Note->add(Sec);