aarch64: Add split-stack TCB fieldazanella/aarch64-split-stack

This patch adds split-stack support pointer guard on glibc for aarch64.
Different from other architectures (powerpc, s390) where the memory is
placed on TCB, aarch64 one is placed before thread pointer initial
position.  It has an advantage over extending TCB because for aarch64
TLS variable placement take in consideration tcbhead_t size and by
changing its value would require to also update the static linker
(and it would also add incompatibility with glibc and older linkers).

For aarch64 tcb direct access is fastest for thread local variable on
all mode and related TLS access.  It requires just a direct load with
displacement of -8 (since thread pointer points to tcbhead_t).

It also adds a loader symbol (__tcb_private_ss) to signal the existence
of the split stack guard area.

Checked on aarch64-linux-gnu.

	* sysdeps/aarch64/Makefile [$(subdir) = elf] (sysdeps-dl-routines):
	Add tcb-version.
	* sysdeps/aarch64/Versions [ld] (GLIBC_2.26): Add
	__libc_tcb_private_ss.
	* sysdeps/aarch64/nptl/tls.h (tcbprehead_t): New struct.
	(TLS_PRE_TCB_SIZE): Take tcbprehead_t in consideration.
	(TLS_DEFINE_INIT_TP): Likewise.
	(THREAD_SELF): Likewise.
	(DB_THREAD_SELF): Likewise.
	* sysdeps/aarch64/tcb-version.c: New file.
	* sysdeps/unix/sysv/linux/aarch64/ld.abilist (GLIBC_2.26): Add.
	(__libc_tcb_private_ss): Likewise.
	* sysdeps/aarch64/nptl/tcb-offsets.sym (PTHREAD_SIZEOF): Rename to
	PTHREAD_PRE_TCB_SIZE.

7 files changed, 72 insertions, 7 deletions

diff --git a/ChangeLog b/ChangeLog
index 42f871e4fc..be9c051a13 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,20 @@
+2017-08-17  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
+
+	* sysdeps/aarch64/Makefile [$(subdir) = elf] (sysdeps-dl-routines):
+	Add tcb-version.
+	* sysdeps/aarch64/Versions [ld] (GLIBC_2.27): Add
+	__libc_tcb_private_ss.
+	* sysdeps/aarch64/nptl/tls.h (tcbprehead_t): New struct.
+	(TLS_PRE_TCB_SIZE): Take tcbprehead_t in consideration.
+	(TLS_DEFINE_INIT_TP): Likewise.
+	(THREAD_SELF): Likewise.
+	(DB_THREAD_SELF): Likewise.
+	* sysdeps/aarch64/tcb-version.c: New file.
+	* sysdeps/unix/sysv/linux/aarch64/ld.abilist (GLIBC_2.27): Add.
+	(__libc_tcb_private_ss): Likewise.
+	* sysdeps/aarch64/nptl/tcb-offsets.sym (PTHREAD_SIZEOF): Rename to
+	PTHREAD_PRE_TCB_SIZE.
+
 2018-01-16  Joseph Myers  <joseph@codesourcery.com>
 
 	* sysdeps/x86_64/backtrace.c: Include <gnu/lib-names.h>.
diff --git a/sysdeps/aarch64/Makefile b/sysdeps/aarch64/Makefile
index 5f3e20371a..141442a237 100644
--- a/sysdeps/aarch64/Makefile
+++ b/sysdeps/aarch64/Makefile
@@ -1,7 +1,7 @@
 long-double-fcts = yes
 
 ifeq ($(subdir),elf)
-sysdep-dl-routines += tlsdesc dl-tlsdesc
+sysdep-dl-routines += tlsdesc dl-tlsdesc tcb-version
 gen-as-const-headers += dl-link.sym
 endif
 
diff --git a/sysdeps/aarch64/Versions b/sysdeps/aarch64/Versions
index e1aa44f33d..04ad5ff537 100644
--- a/sysdeps/aarch64/Versions
+++ b/sysdeps/aarch64/Versions
@@ -3,3 +3,11 @@ libc {
     _mcount;
   }
 }
+
+ld {
+  GLIBC_2.27 {
+    # Symbol used to version control the private GLIBC TCB split-stack
+    # field.
+    __libc_tcb_private_ss;
+  }
+}
diff --git a/sysdeps/aarch64/nptl/tcb-offsets.sym b/sysdeps/aarch64/nptl/tcb-offsets.sym
index 238647dd47..600437980c 100644
--- a/sysdeps/aarch64/nptl/tcb-offsets.sym
+++ b/sysdeps/aarch64/nptl/tcb-offsets.sym
@@ -3,4 +3,4 @@
 
 PTHREAD_MULTIPLE_THREADS_OFFSET		offsetof (struct pthread, header.multiple_threads)
 PTHREAD_TID_OFFSET			offsetof (struct pthread, tid)
-PTHREAD_SIZEOF				sizeof (struct pthread)
+PTHREAD_PRE_TCB_SIZE			TLS_PRE_TCB_SIZE
diff --git a/sysdeps/aarch64/nptl/tls.h b/sysdeps/aarch64/nptl/tls.h
index ac39c24045..2d88310aca 100644
--- a/sysdeps/aarch64/nptl/tls.h
+++ b/sysdeps/aarch64/nptl/tls.h
@@ -26,6 +26,7 @@
 # include <stddef.h>
 # include <stdint.h>
 # include <dl-dtv.h>
+# include <libc-pointer-arith.h>
 
 #else /* __ASSEMBLER__ */
 # include <tcb-offsets.h>
@@ -49,6 +50,12 @@ typedef struct
   void *private;
 } tcbhead_t;
 
+typedef struct
+{
+  /* GCC split stack support.  */
+  void *__private_ss;
+} tcbprehead_t;
+
 /* This is the size of the initial TCB.  */
 # define TLS_INIT_TCB_SIZE	sizeof (tcbhead_t)
 
@@ -58,8 +65,14 @@ typedef struct
 /* This is the size of the TCB.  */
 # define TLS_TCB_SIZE		sizeof (tcbhead_t)
 
-/* This is the size we need before TCB.  */
-# define TLS_PRE_TCB_SIZE	sizeof (struct pthread)
+/* This is the size we need before TCB.  Check if there is room for
+   tcbprehead_t in struct pthread's final padding and if not add it on
+   required pre-tcb size.  */
+# define TLS_PRE_TCB_SIZE \
+  (sizeof (struct pthread)						\
+   + (PTHREAD_STRUCT_END_PADDING < sizeof (tcbprehead_t)		\
+      ? ALIGN_UP (sizeof (tcbprehead_t), __alignof__ (struct pthread))	\
+      : 0))
 
 /* Alignment requirements for the TCB.  */
 # define TLS_TCB_ALIGN		__alignof__ (struct pthread)
@@ -84,7 +97,8 @@ typedef struct
   ({ __asm __volatile ("msr tpidr_el0, %0" : : "r" (tcbp)); NULL; })
 
 /* Value passed to 'clone' for initialization of the thread register.  */
-# define TLS_DEFINE_INIT_TP(tp, pd) void *tp = (pd) + 1
+# define TLS_DEFINE_INIT_TP(tp, pd) \
+  void *tp = (void*)((uintptr_t) (pd) + TLS_PRE_TCB_SIZE)
 
 /* Return the address of the dtv for the current thread.  */
 # define THREAD_DTV() \
@@ -92,11 +106,12 @@ typedef struct
 
 /* Return the thread descriptor for the current thread.  */
 # define THREAD_SELF \
- ((struct pthread *)__builtin_thread_pointer () - 1)
+  ((struct pthread *)((uintptr_t) __builtin_thread_pointer () \
+		      - TLS_PRE_TCB_SIZE))
 
 /* Magic for libthread_db to know how to do THREAD_SELF.  */
 # define DB_THREAD_SELF \
-  CONST_THREAD_AREA (64, sizeof (struct pthread))
+  CONST_THREAD_AREA (64, TLS_PRE_TCB_SIZE)
 
 /* Access to data in the thread descriptor is easy.  */
 # define THREAD_GETMEM(descr, member) \
diff --git a/sysdeps/aarch64/tcb-version.c b/sysdeps/aarch64/tcb-version.c
new file mode 100644
index 0000000000..c94e5d3928
--- /dev/null
+++ b/sysdeps/aarch64/tcb-version.c
@@ -0,0 +1,23 @@
+/* TCB field abi advertise symbols.
+   Copyright (C) 2017 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, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <libc-internal.h>
+
+/* Symbol used to version control the private GLIBC TCB split-stack
+   field.  */
+long int attribute_relro __libc_tcb_private_ss;
diff --git a/sysdeps/unix/sysv/linux/aarch64/ld.abilist b/sysdeps/unix/sysv/linux/aarch64/ld.abilist
index ec7f6174c5..b69883ae18 100644
--- a/sysdeps/unix/sysv/linux/aarch64/ld.abilist
+++ b/sysdeps/unix/sysv/linux/aarch64/ld.abilist
@@ -8,3 +8,5 @@ GLIBC_2.17 calloc F
 GLIBC_2.17 free F
 GLIBC_2.17 malloc F
 GLIBC_2.17 realloc F
+GLIBC_2.27 GLIBC_2.27 A
+GLIBC_2.27 __libc_tcb_private_ss D 0x8