diff -rup binutils.orig/bfd/elf64-ppc.c binutils-2.29/bfd/elf64-ppc.c

--- binutils.orig/bfd/elf64-ppc.c	2017-07-31 10:48:13.642980052 +0100

+++ binutils-2.29/bfd/elf64-ppc.c	2017-07-31 10:48:37.386711582 +0100

@@ -4010,6 +4010,10 @@ struct ppc_link_hash_entry

      with non-standard calling convention.  */

   unsigned int save_res:1;

+  /* Set if a duplicate symbol with non-zero localentry is detected,

+     even when the duplicate symbol does not provide a definition.  */

+  unsigned int non_zero_localentry:1;

+

   /* Contexts in which symbol is used in the GOT (or TOC).

      TLS_GD .. TLS_EXPLICIT bits are or'd into the mask as the

      corresponding relocs are encountered during check_relocs.

@@ -5018,7 +5022,7 @@ ppc64_elf_merge_symbol_attribute (struct

 static bfd_boolean

 ppc64_elf_merge_symbol (struct elf_link_hash_entry *h,

-			const Elf_Internal_Sym *isym ATTRIBUTE_UNUSED,

+			const Elf_Internal_Sym *isym,

 			asection **psec ATTRIBUTE_UNUSED,

 			bfd_boolean newdef ATTRIBUTE_UNUSED,

 			bfd_boolean olddef ATTRIBUTE_UNUSED,

@@ -5026,6 +5030,8 @@ ppc64_elf_merge_symbol (struct elf_link_

 			const asection *oldsec ATTRIBUTE_UNUSED)

 {

   ((struct ppc_link_hash_entry *) h)->fake = 0;

+  if ((STO_PPC64_LOCAL_MASK & isym->st_other) != 0)

+    ((struct ppc_link_hash_entry *) h)->non_zero_localentry = 1;

   return TRUE;

 }

@@ -6332,6 +6338,7 @@ is_elfv2_localentry0 (struct elf_link_ha

 	  && h->type == STT_FUNC

 	  && h->root.type == bfd_link_hash_defined

 	  && (STO_PPC64_LOCAL_MASK & h->other) == 0

+	  && !((struct ppc_link_hash_entry *) h)->non_zero_localentry

 	  && is_ppc64_elf (h->root.u.def.section->owner)

 	  && abiversion (h->root.u.def.section->owner) >= 2);

 }

@@ -8346,10 +8353,28 @@ ppc64_elf_tls_setup (struct bfd_link_inf

   else if (!htab->do_multi_toc)

     htab->params->no_multi_toc = 1;

+  /* Default to --no-plt-localentry, as this option can cause problems

+     with symbol interposition.  For example, glibc libpthread.so and

+     libc.so duplicate many pthread symbols, with a fallback

+     implementation in libc.so.  In some cases the fallback does more

+     work than the pthread implementation.  __pthread_condattr_destroy

+     is one such symbol: the libpthread.so implementation is

+     localentry:0 while the libc.so implementation is localentry:8.

+     An app that "cleverly" uses dlopen to only load necessary

+     libraries at runtime may omit loading libpthread.so when not

+     running multi-threaded, which then results in the libc.so

+     fallback symbols being used and ld.so complaining.  Now there

+     are workarounds in ld (see non_zero_localentry) to detect the

+     pthread situation, but that may not be the only case where

+     --plt-localentry can cause trouble.  */

   if (htab->params->plt_localentry0 < 0)

-    htab->params->plt_localentry0

-      = elf_link_hash_lookup (&htab->elf, "GLIBC_2.26",

-			      FALSE, FALSE, FALSE) != NULL;

+    htab->params->plt_localentry0 = 0;

+  if (htab->params->plt_localentry0

+      && elf_link_hash_lookup (&htab->elf, "GLIBC_2.26",

+			       FALSE, FALSE, FALSE) == NULL)

+    info->callbacks->einfo

+      (_("%P: warning: --plt-localentry is especially dangerous without "

+	 "ld.so support to detect ABI violations.\n"));

   htab->tls_get_addr = ((struct ppc_link_hash_entry *)

 			elf_link_hash_lookup (&htab->elf, ".__tls_get_addr",

diff -rup binutils.orig/gold/powerpc.cc binutils-2.29/gold/powerpc.cc

--- binutils.orig/gold/powerpc.cc	2017-07-31 10:48:13.621980289 +0100

+++ binutils-2.29/gold/powerpc.cc	2017-07-31 10:48:37.387711571 +0100

@@ -7660,8 +7660,10 @@ Target_powerpc<size, big_endian>::scan_r

 	{

 	  if (parameters->options().user_set_plt_localentry())

 	    plt_localentry0 = parameters->options().plt_localentry();

-	  else

-	    plt_localentry0 = symtab->lookup("GLIBC_2.26", NULL) != NULL;

+	  if (plt_localentry0

+	      && symtab->lookup("GLIBC_2.26", NULL) == NULL)

+	    gold_warning(_("--plt-localentry is especially dangerous without "

+			   "ld.so support to detect ABI violations"));

 	}

       this->plt_localentry0_ = plt_localentry0;

       this->plt_localentry0_init_ = true;

diff -rup binutils.orig/ld/ld.texinfo binutils-2.29/ld/ld.texinfo

--- binutils.orig/ld/ld.texinfo	2017-07-31 10:48:13.601980515 +0100

+++ binutils-2.29/ld/ld.texinfo	2017-07-31 10:48:37.388711559 +0100

@@ -7600,6 +7600,24 @@ barrier in the call stub, or use LD_BIND

 looks for calls to commonly used functions that create threads, and if

 seen, adds the necessary barriers.  Use these options to change the

 default behaviour.

+

+@cindex PowerPC64 ELFv2 PLT localentry optimization

+@kindex --plt-localentry

+@kindex --no-plt-localentry

+@item --plt-localentry

+@itemx --no-localentry

+ELFv2 functions with localentry:0 are those with a single entry point,

+ie. global entry == local entry, and that have no requirement on r2

+(the TOC/GOT pointer) or r12, and guarantee r2 is unchanged on return.

+Such an external function can be called via the PLT without saving r2

+or restoring it on return, avoiding a common load-hit-store for small

+functions.   The optimization is attractive, with up to 40% reduction

+in execution time for a small function, but can result in symbol

+interposition failures.  Also, minor changes in a shared library,

+including system libraries, can cause a function that was localentry:0

+to become localentry:8.  This will result in a dynamic loader

+complaint and failure to run.  The option is experimental, use with

+care.  @option{--no-plt-localentry} is the default.

 @end table

 @ifclear GENERIC