diff --git a/bits/types/__cancel_jmp_buf_tag.h b/bits/types/__cancel_jmp_buf_tag.h
new file mode 100644
index 0000000000..62f5c61f83
--- /dev/null
+++ b/bits/types/__cancel_jmp_buf_tag.h
@@ -0,0 +1,28 @@
+/* Define struct __cancel_jmp_buf_tag.
+   Copyright (C) 2017-2018 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/>.  */
+
+#ifndef ____cancel_jmp_buf_tag_defined
+#define ____cancel_jmp_buf_tag_defined 1
+
+struct __cancel_jmp_buf_tag
+  {
+    __jmp_buf __cancel_jmp_buf;
+    int __mask_was_saved;
+  };
+
+#endif
diff --git a/nptl/Makefile b/nptl/Makefile
index 6fc2c8bb6a..7940b3d26b 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -22,7 +22,8 @@ subdir	:= nptl
 
 include ../Makeconfig
 
-headers := pthread.h semaphore.h bits/semaphore.h
+headers := pthread.h semaphore.h bits/semaphore.h \
+	   bits/types/__cancel_jmp_buf_tag.h
 
 extra-libs := libpthread
 extra-libs-others := $(extra-libs)
diff --git a/nptl/descr.h b/nptl/descr.h
index 64ba29e1cb..1cc6b09d1e 100644
--- a/nptl/descr.h
+++ b/nptl/descr.h
@@ -65,6 +65,9 @@ struct pthread_unwind_buf
   {
     __jmp_buf jmp_buf;
     int mask_was_saved;
+#ifdef NEED_SAVED_MASK_IN_CANCEL_JMP_BUF
+    __sigset_t saved_mask;
+#endif
   } cancel_jmp_buf[1];
 
   union
diff --git a/sysdeps/i386/nptl/tcb-offsets.sym b/sysdeps/i386/nptl/tcb-offsets.sym
index 695a810386..250f1a6e13 100644
--- a/sysdeps/i386/nptl/tcb-offsets.sym
+++ b/sysdeps/i386/nptl/tcb-offsets.sym
@@ -15,3 +15,4 @@ POINTER_GUARD		offsetof (tcbhead_t, pointer_guard)
 #ifndef __ASSUME_PRIVATE_FUTEX
 PRIVATE_FUTEX		offsetof (tcbhead_t, private_futex)
 #endif
+FEATURE_1_OFFSET	offsetof (tcbhead_t, feature_1)
diff --git a/sysdeps/i386/nptl/tls.h b/sysdeps/i386/nptl/tls.h
index fcda135b7c..30643d452a 100644
--- a/sysdeps/i386/nptl/tls.h
+++ b/sysdeps/i386/nptl/tls.h
@@ -50,6 +50,10 @@ typedef struct
   void *__private_tm[4];
   /* GCC split stack support.  */
   void *__private_ss;
+  /* Bit 0: IBT.
+     Bit 1: SHSTK.
+   */
+  unsigned int feature_1;
 } tcbhead_t;
 
 # define TLS_MULTIPLE_THREADS_IN_TCB 1
diff --git a/sysdeps/nptl/pthread.h b/sysdeps/nptl/pthread.h
index df049abf74..c8ba5a75c5 100644
--- a/sysdeps/nptl/pthread.h
+++ b/sysdeps/nptl/pthread.h
@@ -27,6 +27,7 @@
 #include <bits/setjmp.h>
 #include <bits/wordsize.h>
 #include <bits/types/struct_timespec.h>
+#include <bits/types/__cancel_jmp_buf_tag.h>
 
 
 /* Detach state.  */
@@ -523,11 +524,7 @@ extern void pthread_testcancel (void);
 
 typedef struct
 {
-  struct
-  {
-    __jmp_buf __cancel_jmp_buf;
-    int __mask_was_saved;
-  } __cancel_jmp_buf[1];
+  struct __cancel_jmp_buf_tag __cancel_jmp_buf[1];
   void *__pad[4];
 } __pthread_unwind_buf_t __attribute__ ((__aligned__));
 
diff --git a/sysdeps/unix/sysv/linux/hppa/pthread.h b/sysdeps/unix/sysv/linux/hppa/pthread.h
index 11a024db59..3df5e7c2ac 100644
--- a/sysdeps/unix/sysv/linux/hppa/pthread.h
+++ b/sysdeps/unix/sysv/linux/hppa/pthread.h
@@ -27,6 +27,7 @@
 #include <bits/setjmp.h>
 #include <bits/wordsize.h>
 #include <bits/types/struct_timespec.h>
+#include <bits/types/__cancel_jmp_buf_tag.h>
 
 
 /* Detach state.  */
@@ -499,11 +500,7 @@ extern void pthread_testcancel (void);
 
 typedef struct
 {
-  struct
-  {
-    __jmp_buf __cancel_jmp_buf;
-    int __mask_was_saved;
-  } __cancel_jmp_buf[1];
+  struct __cancel_jmp_buf_tag __cancel_jmp_buf[1];
   void *__pad[4];
 } __pthread_unwind_buf_t __attribute__ ((__aligned__));
 
diff --git a/sysdeps/unix/sysv/linux/x86/bits/types/__cancel_jmp_buf_tag.h b/sysdeps/unix/sysv/linux/x86/bits/types/__cancel_jmp_buf_tag.h
new file mode 100644
index 0000000000..70efbb190c
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/bits/types/__cancel_jmp_buf_tag.h
@@ -0,0 +1,31 @@
+/* Define struct __cancel_jmp_buf_tag.
+   Copyright (C) 2017-2018 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/>.  */
+
+#ifndef ____cancel_jmp_buf_tag_defined
+#define ____cancel_jmp_buf_tag_defined 1
+
+#include <bits/types/__sigset_t.h>
+
+struct __cancel_jmp_buf_tag
+  {
+    __jmp_buf __cancel_jmp_buf;
+    int __mask_was_saved;
+    __sigset_t __saved_mask;
+  };
+
+#endif
diff --git a/sysdeps/unix/sysv/linux/x86/nptl/pthreadP.h b/sysdeps/unix/sysv/linux/x86/nptl/pthreadP.h
new file mode 100644
index 0000000000..247a62e9a0
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/nptl/pthreadP.h
@@ -0,0 +1,36 @@
+/* Internal pthread header.  Linux/x86 version.
+   Copyright (C) 2017-2018 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_next <nptl/pthreadP.h>
+
+#ifndef _PTHREADP_H_X86
+#define _PTHREADP_H_X86 1
+
+extern struct pthread_unwind_buf ____pthread_unwind_buf_private;
+
+_Static_assert (sizeof (____pthread_unwind_buf_private.cancel_jmp_buf)
+		>= sizeof (struct __jmp_buf_tag),
+		"size of cancel_jmp_buf < sizeof __jmp_buf_tag");
+
+extern __pthread_unwind_buf_t ____pthread_unwind_buf;
+
+_Static_assert (sizeof (____pthread_unwind_buf.__cancel_jmp_buf)
+		>= sizeof (struct __jmp_buf_tag),
+		"size of __cancel_jmp_buf < sizeof __jmp_buf_tag");
+
+#endif
diff --git a/sysdeps/unix/sysv/linux/x86/pthreaddef.h b/sysdeps/unix/sysv/linux/x86/pthreaddef.h
new file mode 100644
index 0000000000..a405a65666
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/pthreaddef.h
@@ -0,0 +1,22 @@
+/* Pthread macros.  Linux/x86 version.
+   Copyright (C) 2017-2018 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_next <pthreaddef.h>
+
+/* Need saved_mask in cancel_jmp_buf.  */
+#define NEED_SAVED_MASK_IN_CANCEL_JMP_BUF 1
diff --git a/sysdeps/x86_64/nptl/tcb-offsets.sym b/sysdeps/x86_64/nptl/tcb-offsets.sym
index 8a25c482cb..03b6dba5c3 100644
--- a/sysdeps/x86_64/nptl/tcb-offsets.sym
+++ b/sysdeps/x86_64/nptl/tcb-offsets.sym
@@ -15,6 +15,7 @@ VGETCPU_CACHE_OFFSET	offsetof (tcbhead_t, vgetcpu_cache)
 #ifndef __ASSUME_PRIVATE_FUTEX
 PRIVATE_FUTEX		offsetof (tcbhead_t, private_futex)
 #endif
+FEATURE_1_OFFSET	offsetof (tcbhead_t, feature_1)
 
 -- Not strictly offsets, but these values are also used in the TCB.
 TCB_CANCELSTATE_BITMASK	 CANCELSTATE_BITMASK
diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h
index bdd02376f9..7f0b292f42 100644
--- a/sysdeps/x86_64/nptl/tls.h
+++ b/sysdeps/x86_64/nptl/tls.h
@@ -56,7 +56,10 @@ typedef struct
 # else
   int __glibc_reserved1;
 # endif
-  int __glibc_unused1;
+  /* Bit 0: IBT.
+     Bit 1: SHSTK.
+   */
+  unsigned int feature_1;
   /* Reservation of some values for the TM ABI.  */
   void *__private_tm[4];
   /* GCC split stack support.  */
