[PATCH v2 11/21] nptl: ia64: Fix Race conditions in pthread cancellation (BZ#12683)

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

This patch adds the s390 modifications required for the BZ#12683.
It basically adds the required ucontext_get_pc function. a workaround
for mismatched sigcontext::sa_flags defiition between kernel and
GLIBC (tracked by BZ#21634), and an arch specific syscall_cancel
implementation.

IA64 requires an arch-specific syscall_cancel implemetantion because
{INLINE,INTERNAL}_SYSCALL is implemented by branching to a gate
DSO (similar to i386) which renders the pointer comparison in
SIGCANCEL handler wrong.  This incurs in performance penalty due the
use of a break instruction insteaf of a eds one, however
cancellable syscalls should potentially incur in syscalls blocking.

Checked with a ia64-linux-gnu build with run-tests-built=no.

	[BZ #12683]
	* sysdeps/unix/sysv/linux/ia64/sigcontextinfo.h (ucontext_get_pc,
	ucontext_get_mask): New functions.
	* sysdeps/unix/sysv/linux/ia64/syscall_cancel.S: New file.
---
 ChangeLog                                     |  5 ++
 sysdeps/unix/sysv/linux/ia64/sigcontextinfo.h | 24 +++++++
 sysdeps/unix/sysv/linux/ia64/syscall_cancel.S | 94 +++++++++++++++++++++++++++
 3 files changed, 123 insertions(+)
 create mode 100644 sysdeps/unix/sysv/linux/ia64/syscall_cancel.S

diff --git a/sysdeps/unix/sysv/linux/ia64/sigcontextinfo.h b/sysdeps/unix/sysv/linux/ia64/sigcontextinfo.h
index 214292d..24cfb51 100644
--- a/sysdeps/unix/sysv/linux/ia64/sigcontextinfo.h
+++ b/sysdeps/unix/sysv/linux/ia64/sigcontextinfo.h
@@ -15,6 +15,11 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#ifndef _SIGCONTEXTINFO_H
+#define _SIGCONTEXTINFO_H
+
+#include <stdint.h>
+
 #define SIGCONTEXT siginfo_t *_si, struct sigcontext *
 #define SIGCONTEXT_EXTRA_ARGS _si,
 #define GET_PC(ctx)	((ctx)->sc_ip)
@@ -23,3 +28,22 @@
 
 #define CALL_SIGHANDLER(handler, signo, ctx) \
   (handler)((signo), SIGCONTEXT_EXTRA_ARGS (ctx))
+
+/* Different that other architectures, ia64 pass a sigcontext_t struct
+   in third argument for sa_sigaction handler with SA_SIGINFO.  */
+static inline uintptr_t
+ucontext_get_pc (const struct sigcontext *sigctx)
+{
+  return sigctx->sc_ip;
+}
+
+static inline sigset_t *
+ucontext_get_mask (const struct sigcontext *sigctx)
+{
+  /* IA64 sigcontext::sa_mask is a sigset_t since Linux 2.6.12 (initial
+     git repository build).  */
+  return (sigset_t *) &sigctx->sc_mask;
+}
+#define UCONTEXT_SIGMASK(ctx) ucontext_get_mask (ctx)
+
+#endif /* _SIGCONTEXTINFO_H  */
diff --git a/sysdeps/unix/sysv/linux/ia64/syscall_cancel.S b/sysdeps/unix/sysv/linux/ia64/syscall_cancel.S
new file mode 100644
index 0000000..9c6c9d3
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/ia64/syscall_cancel.S
@@ -0,0 +1,94 @@
+/* Cancellable syscall wrapper.  Linux/IA64 version.
+   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 <sysdep.h>
+#undef ret
+
+/* long int __syscall_cancel_arch (int *cancelhandling, long int nr,
+				   long int arg1, long int arg2, long int arg3,
+				   long int arg4, long int arg5, long int arg6)
+*/
+
+ENTRY (__syscall_cancel_arch)
+	.prologue 14, 40
+	.mmi
+	.save ar.pfs, r41
+	alloc r41 = ar.pfs, 8, 4, 8, 0
+	.vframe r42
+	mov r42 = r12
+	.save rp, r40
+	mov r40 = b0
+	.body
+	;;
+
+	.global __syscall_cancel_arch_start	
+	.type __syscall_cancel_arch_start,@function	
+__syscall_cancel_arch_start:
+
+	;;
+	.mmi
+	nop 0
+	ld4.acq r14 = [r32]
+	nop 0
+	;;
+	.mib
+	nop 0
+	tbit.z p6, p7 = r14, 2
+	.pred.safe_across_calls p1-p63
+	(p7) br.call.dpnt.many b0 = __syscall_do_cancel#
+	.pred.safe_across_calls p1-p5,p16-p63
+	;;
+	.mmi
+	mov r15 = r33
+	mov r49 = r39
+	mov r48 = r38
+	.mmi
+	mov r47 = r37
+	mov r46 = r36
+	mov r45 = r35
+	;;
+	.mmi
+	nop 0
+	mov r44 = r34
+	nop 0
+	;;
+	break 0x100000
+	;;
+
+	.global __syscall_cancel_arch_end	
+	.type __syscall_cancel_arch_end,@function	
+__syscall_cancel_arch_end:
+
+	;;
+	.mmi
+	cmp.ne p6, p7 = -1, r10
+	nop 0
+	mov ar.pfs = r41
+	;;
+	.mmi
+	nop 0
+	(p7) sub r8 = r0, r8
+	mov b0 = r40
+	.mmb
+	nop 0
+	.restore sp
+	mov r12 = r42
+	br.ret.sptk.many b0
+
+END (__syscall_cancel_arch)
+libc_hidden_def (__syscall_cancel_arch)
-- 
2.7.4