[glibc/azanella/bz12683] nptl: aarch64: Fix Race conditions in pthread cancellation (BZ#12683)

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=13d801afca6868738aa16c6ff8b118dd7a58a3f4

commit 13d801afca6868738aa16c6ff8b118dd7a58a3f4
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Mon Jan 7 16:03:04 2019 +0000

    nptl: aarch64: Fix Race conditions in pthread cancellation (BZ#12683)
    
    This patch adds the aarch64 modifications required for the BZ#12683 fix
    by adding the arch-specific cancellation syscall bridge.
    
    Checked on aarch64-linux-gnu.
    
    	[BZ #12683]
    	* sysdeps/unix/sysv/linux/aarch64/syscall_cancel.S: New file.

Diff:
---
 sysdeps/unix/sysv/linux/aarch64/syscall_cancel.S | 61 ++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/sysdeps/unix/sysv/linux/aarch64/syscall_cancel.S b/sysdeps/unix/sysv/linux/aarch64/syscall_cancel.S
new file mode 100644
index 0000000..e105480
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/aarch64/syscall_cancel.S
@@ -0,0 +1,61 @@
+/* Cancellable syscall wrapper.  Linux/AArch64 version.
+   Copyright (C) 2019 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>
+
+/* long int [r0] __syscall_cancel_arch (int *cancelhandling [r0],
+					long int nr   [r1],
+					long int arg1 [r2],
+					long int arg2 [r3],
+					long int arg3 [SP],
+					long int arg4 [SP+4],
+					long int arg5 [SP+8],
+					long int arg6 [SP+12])  */
+
+ENTRY (__syscall_cancel_arch)
+
+	.globl __syscall_cancel_arch_start
+	.type  __syscall_cancel_arch_start,%function
+__syscall_cancel_arch_start:
+
+	/* if (*cancelhandling & CANCELED_BITMASK)
+	     __syscall_do_cancel()  */
+	ldr	w0, [x0]
+	tbnz    w0, 2, 1f
+
+	/* Issue a 6 argument syscall, the nr [x1] being the syscall
+	   number.  */
+	mov	x8, x1
+	mov	x0, x2
+	mov	x1, x3
+	mov	x2, x4
+	mov	x3, x5
+	mov	x4, x6
+	mov	x5, x7
+	svc	0x0
+
+	.globl __syscall_cancel_arch_end
+	.type  __syscall_cancel_arch_end,%function
+__syscall_cancel_arch_end:
+	ret
+
+1:
+	b	__syscall_do_cancel
+
+END (__syscall_cancel_arch)
+libc_hidden_def (__syscall_cancel_arch)