Revert Intel CET changes to __jmp_buf_tag (Bug 22743)

In commit cba595c350e52194e10c0006732e1991e3d0803b and commit
f81ddabffd76ac9dd600b02adbf3e1dac4bb10ec, ABI compatibility with
applications was broken by increasing the size of the on-stack
allocated __pthread_unwind_buf_t beyond the oringal size.
Applications only have the origianl space available for
__pthread_unwind_register, and __pthread_unwind_next to use,
any increase in the size of __pthread_unwind_buf_t causes these
functions to write beyond the original structure into other
on-stack variables leading to segmentation faults in common
applications like vlc. The only workaround is to version those
functions which operate on the old sized objects, but this must
happen in glibc 2.28.

Thank you to Andrew Senkevich, H.J. Lu, and Aurelien Jarno, for
submitting reports and tracking the issue down.

The commit reverts the above mentioned commits and testing on
x86_64 shows that the ABI compatibility is restored. A tst-cleanup1
regression test linked with an older glibc now passes when run
with the newly built glibc. Previously a tst-cleanup1 linked with
an older glibc would segfault when run with an affected glibc build.

Tested on x86_64 with no regressions.

Signed-off-by: Carlos O'Donell <carlos@redhat.com>

9 files changed, 11 insertions, 103 deletions

diff --git a/sysdeps/i386/nptl/tcb-offsets.sym b/sysdeps/i386/nptl/tcb-offsets.sym
index 250f1a6e13..695a810386 100644
--- a/sysdeps/i386/nptl/tcb-offsets.sym
+++ b/sysdeps/i386/nptl/tcb-offsets.sym
@@ -15,4 +15,3 @@ 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 30643d452a..fcda135b7c 100644
--- a/sysdeps/i386/nptl/tls.h
+++ b/sysdeps/i386/nptl/tls.h
@@ -50,10 +50,6 @@ 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 c8ba5a75c5..df049abf74 100644
--- a/sysdeps/nptl/pthread.h
+++ b/sysdeps/nptl/pthread.h
@@ -27,7 +27,6 @@
 #include <bits/setjmp.h>
 #include <bits/wordsize.h>
 #include <bits/types/struct_timespec.h>
-#include <bits/types/__cancel_jmp_buf_tag.h>
 
 
 /* Detach state.  */
@@ -524,7 +523,11 @@ extern void pthread_testcancel (void);
 
 typedef struct
 {
-  struct __cancel_jmp_buf_tag __cancel_jmp_buf[1];
+  struct
+  {
+    __jmp_buf __cancel_jmp_buf;
+    int __mask_was_saved;
+  } __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 3df5e7c2ac..11a024db59 100644
--- a/sysdeps/unix/sysv/linux/hppa/pthread.h
+++ b/sysdeps/unix/sysv/linux/hppa/pthread.h
@@ -27,7 +27,6 @@
 #include <bits/setjmp.h>
 #include <bits/wordsize.h>
 #include <bits/types/struct_timespec.h>
-#include <bits/types/__cancel_jmp_buf_tag.h>
 
 
 /* Detach state.  */
@@ -500,7 +499,11 @@ extern void pthread_testcancel (void);
 
 typedef struct
 {
-  struct __cancel_jmp_buf_tag __cancel_jmp_buf[1];
+  struct
+  {
+    __jmp_buf __cancel_jmp_buf;
+    int __mask_was_saved;
+  } __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
deleted file mode 100644
index 70efbb190c..0000000000
--- a/sysdeps/unix/sysv/linux/x86/bits/types/__cancel_jmp_buf_tag.h
+++ /dev/null
@@ -1,31 +0,0 @@
-/* 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
deleted file mode 100644
index 247a62e9a0..0000000000
--- a/sysdeps/unix/sysv/linux/x86/nptl/pthreadP.h
+++ /dev/null
@@ -1,36 +0,0 @@
-/* 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
deleted file mode 100644
index a405a65666..0000000000
--- a/sysdeps/unix/sysv/linux/x86/pthreaddef.h
+++ /dev/null
@@ -1,22 +0,0 @@
-/* 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 03b6dba5c3..8a25c482cb 100644
--- a/sysdeps/x86_64/nptl/tcb-offsets.sym
+++ b/sysdeps/x86_64/nptl/tcb-offsets.sym
@@ -15,7 +15,6 @@ 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 7f0b292f42..bdd02376f9 100644
--- a/sysdeps/x86_64/nptl/tls.h
+++ b/sysdeps/x86_64/nptl/tls.h
@@ -56,10 +56,7 @@ typedef struct
 # else
   int __glibc_reserved1;
 # endif
-  /* Bit 0: IBT.
-     Bit 1: SHSTK.
-   */
-  unsigned int feature_1;
+  int __glibc_unused1;
   /* Reservation of some values for the TM ABI.  */
   void *__private_tm[4];
   /* GCC split stack support.  */