powerpc __tls_get_addr call optimization

This patch is glibc support for a PowerPC TLS optimization, inspired
by Alexandre Oliva's TLS optimization for other processors,
http://www.lsd.ic.unicamp.br/~oliva/writeups/TLS/RFC-TLSDESC-x86.txt

In essence, this optimization uses a zero module id in the tls_index
GOT entry to indicate that a TLS variable is allocated space in the
static TLS area.  A special plt call linker stub for __tls_get_addr
checks for such a tls_index and if found, returns the offset
immediately.  The linker communicates the fact that the special
__tls_get_addr stub is used by setting a bit in the dynamic tag
DT_PPC64_OPT/DT_PPC_OPT.  glibc communicates to the linker that this
optimization is available by the presence of __tls_get_addr_opt.

tst-tlsmod2.so is built with -Wl,--no-tls-get-addr-optimize for
tst-tls-dlinfo, which otherwise would fail since it tests that no
static tls is allocated.  The ld option --no-tls-get-addr-optimize has
been available since binutils-2.20 so doesn't need a configure test.

	* NEWS: Advertise TLS optimization.
	* elf/elf.h (R_PPC_TLSGD, R_PPC_TLSLD, DT_PPC_OPT, PPC_OPT_TLS): Define.
	(DT_PPC_NUM): Increment.
	* elf/dynamic-link.h (HAVE_STATIC_TLS): Define.
	(CHECK_STATIC_TLS): Use here.
	* sysdeps/powerpc/powerpc32/dl-machine.h (elf_machine_rela): Optimize
	TLS descriptors.
	* sysdeps/powerpc/powerpc64/dl-machine.h (elf_machine_rela): Likewise.
	* sysdeps/powerpc/dl-tls.c: New file.
	* sysdeps/powerpc/Versions: Add __tls_get_addr_opt.
	* sysdeps/powerpc/tst-tlsopt-powerpc.c: New tls test.
	* sysdeps/unix/sysv/linux/powerpc/Makefile: Add new test.
	Build tst-tlsmod2.so with --no-tls-get-addr-optimize.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/ld.abilist: Update.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/ld.abilist: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/ld-le.abilist: Likewise.

6 files changed, 181 insertions, 0 deletions

diff --git a/sysdeps/powerpc/Makefile b/sysdeps/powerpc/Makefile
index b11edd7..533d763 100644
--- a/sysdeps/powerpc/Makefile
+++ b/sysdeps/powerpc/Makefile
@@ -8,6 +8,9 @@ sysdep-dl-routines += dl-machine
 sysdep_routines += dl-machine
 # extra shared linker files to link only into dl-allobjs.so
 sysdep-rtld-routines += dl-machine
+# Don't optimize GD tls sequence to LE.
+LDFLAGS-tst-tlsopt-powerpc += -Wl,--no-tls-optimize
+tests += tst-tlsopt-powerpc
 endif
 
 ifeq ($(subdir),setjmp)
diff --git a/sysdeps/powerpc/Versions b/sysdeps/powerpc/Versions
index 47c2c3e..2aebf7c 100644
--- a/sysdeps/powerpc/Versions
+++ b/sysdeps/powerpc/Versions
@@ -15,3 +15,9 @@ libc {
     __vmx__libc_longjmp; __vmx__libc_siglongjmp;
   }
 }
+
+ld {
+  GLIBC_2.22 {
+    __tls_get_addr_opt;
+  }
+}
diff --git a/sysdeps/powerpc/dl-tls.c b/sysdeps/powerpc/dl-tls.c
new file mode 100644
index 0000000..a18b23e
--- /dev/null
+++ b/sysdeps/powerpc/dl-tls.c
@@ -0,0 +1,24 @@
+/* Thread-local storage handling in the ELF dynamic linker.  PowerPC version.
+   Copyright (C) 2009-2015 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include "elf/dl-tls.c"
+
+#ifdef SHARED
+strong_alias(__tls_get_addr, __tls_get_addr_opt)
+#endif
diff --git a/sysdeps/powerpc/powerpc32/dl-machine.h b/sysdeps/powerpc/powerpc32/dl-machine.h
index c94674f..8b0c067 100644
--- a/sysdeps/powerpc/powerpc32/dl-machine.h
+++ b/sysdeps/powerpc/powerpc32/dl-machine.h
@@ -333,6 +333,32 @@ elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
 # endif
 
     case R_PPC_DTPMOD32:
+      if (map->l_info[DT_PPC(OPT)]
+	  && (map->l_info[DT_PPC(OPT)]->d_un.d_val & PPC_OPT_TLS))
+	{
+	  if (!NOT_BOOTSTRAP)
+	    {
+	      reloc_addr[0] = 0;
+	      reloc_addr[1] = (sym_map->l_tls_offset - TLS_TP_OFFSET
+			       + TLS_DTV_OFFSET);
+	      break;
+	    }
+	  else if (sym_map != NULL)
+	    {
+# ifndef SHARED
+	      CHECK_STATIC_TLS (map, sym_map);
+# else
+	      if (TRY_STATIC_TLS (map, sym_map))
+# endif
+		{
+		  reloc_addr[0] = 0;
+		  /* Set up for local dynamic.  */
+		  reloc_addr[1] = (sym_map->l_tls_offset - TLS_TP_OFFSET
+				   + TLS_DTV_OFFSET);
+		  break;
+		}
+	    }
+	}
       if (!NOT_BOOTSTRAP)
 	/* During startup the dynamic linker is always index 1.  */
 	*reloc_addr = 1;
@@ -342,6 +368,28 @@ elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
 	*reloc_addr = sym_map->l_tls_modid;
       break;
     case R_PPC_DTPREL32:
+      if (map->l_info[DT_PPC(OPT)]
+	  && (map->l_info[DT_PPC(OPT)]->d_un.d_val & PPC_OPT_TLS))
+	{
+	  if (!NOT_BOOTSTRAP)
+	    {
+	      *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
+	      break;
+	    }
+	  else if (sym_map != NULL)
+	    {
+	      /* This reloc is always preceded by R_PPC_DTPMOD32.  */
+# ifndef SHARED
+	      assert (HAVE_STATIC_TLS (map, sym_map));
+# else
+	      if (HAVE_STATIC_TLS (map, sym_map))
+# endif
+		{
+		  *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
+		  break;
+		}
+	    }
+	}
       /* During relocation all TLS symbols are defined and used.
 	 Therefore the offset is already correct.  */
       if (NOT_BOOTSTRAP && sym_map != NULL)
diff --git a/sysdeps/powerpc/powerpc64/dl-machine.h b/sysdeps/powerpc/powerpc64/dl-machine.h
index 5cb0087..55ac736 100644
--- a/sysdeps/powerpc/powerpc64/dl-machine.h
+++ b/sysdeps/powerpc/powerpc64/dl-machine.h
@@ -701,6 +701,32 @@ elf_machine_rela (struct link_map *map,
       return;
 
     case R_PPC64_DTPMOD64:
+      if (map->l_info[DT_PPC64(OPT)]
+	  && (map->l_info[DT_PPC64(OPT)]->d_un.d_val & PPC64_OPT_TLS))
+	{
+#ifdef RTLD_BOOTSTRAP
+	  reloc_addr[0] = 0;
+	  reloc_addr[1] = (sym_map->l_tls_offset - TLS_TP_OFFSET
+			   + TLS_DTV_OFFSET);
+	  return;
+#else
+	  if (sym_map != NULL)
+	    {
+# ifndef SHARED
+	      CHECK_STATIC_TLS (map, sym_map);
+# else
+	      if (TRY_STATIC_TLS (map, sym_map))
+# endif
+		{
+		  reloc_addr[0] = 0;
+		  /* Set up for local dynamic.  */
+		  reloc_addr[1] = (sym_map->l_tls_offset - TLS_TP_OFFSET
+				   + TLS_DTV_OFFSET);
+		  return;
+		}
+	    }
+#endif
+	}
 #ifdef RTLD_BOOTSTRAP
       /* During startup the dynamic linker is always index 1.  */
       *reloc_addr = 1;
@@ -713,6 +739,28 @@ elf_machine_rela (struct link_map *map,
       return;
 
     case R_PPC64_DTPREL64:
+      if (map->l_info[DT_PPC64(OPT)]
+	  && (map->l_info[DT_PPC64(OPT)]->d_un.d_val & PPC64_OPT_TLS))
+	{
+#ifdef RTLD_BOOTSTRAP
+	  *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
+	  return;
+#else
+	  if (sym_map != NULL)
+	    {
+	      /* This reloc is always preceded by R_PPC64_DTPMOD64.  */
+# ifndef SHARED
+	      assert (HAVE_STATIC_TLS (map, sym_map));
+# else
+	      if (HAVE_STATIC_TLS (map, sym_map))
+#  endif
+		{
+		  *reloc_addr = TLS_TPREL_VALUE (sym_map, sym, reloc);
+		  return;
+		}
+	    }
+#endif
+	}
       /* During relocation all TLS symbols are defined and used.
 	 Therefore the offset is already correct.  */
 #ifndef RTLD_BOOTSTRAP
diff --git a/sysdeps/powerpc/tst-tlsopt-powerpc.c b/sysdeps/powerpc/tst-tlsopt-powerpc.c
new file mode 100644
index 0000000..c9a14cb
--- /dev/null
+++ b/sysdeps/powerpc/tst-tlsopt-powerpc.c
@@ -0,0 +1,52 @@
+/* glibc test for __tls_get_addr optimization.  */
+#include <stdio.h>
+
+#include "../../elf/tls-macros.h"
+#include "dl-tls.h"
+
+/* common 'int' variable in TLS.  */
+COMMON_INT_DEF(foo);
+
+
+#define TEST_FUNCTION do_test ()
+static int
+do_test (void)
+{
+  int result = 0;
+
+  /* Get variable using general dynamic model.  */
+  int *ap = TLS_GD (foo);
+  if (*ap != 0)
+    {
+      printf ("foo = %d\n", *ap);
+      result = 1;
+    }
+
+  tls_index *tls_arg;
+#ifdef __powerpc64__
+  register unsigned long thread_pointer __asm__ ("r13");
+  asm ("addi %0,2,foo@got@tlsgd" : "=r" (tls_arg));
+#else
+  register unsigned long thread_pointer __asm__ ("r2");
+  asm ("bcl 20,31,1f\n1:\t"
+       "mflr %0\n\t"
+       "addis %0,%0,_GLOBAL_OFFSET_TABLE_-1b@ha\n\t"
+       "addi %0,%0,_GLOBAL_OFFSET_TABLE_-1b@l\n\t"
+       "addi %0,%0,foo@got@tlsgd" : "=b" (tls_arg));
+#endif
+
+  if (tls_arg->ti_module != 0)
+    {
+      printf ("tls_index not optimized, binutils too old?\n");
+      result = 1;
+    }
+  else if (tls_arg->ti_offset + thread_pointer != (unsigned long) ap)
+    {
+      printf ("tls_index->ti_offset wrong value\n");
+      result = 1;
+    }
+
+  return result;
+}
+
+#include "../../test-skeleton.c"