[PATCH v4 20/21] nptl: csky: Fix Race conditions in pthread cancellation [BZ#12683]

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

This patch adds the csky modifications required for the BZ#12683 fix
by adding the arch-specific cancellation syscall bridge.

Checked against a build and make check run-built-tests=no for
csky-linux-gnuabiv2.
---
 sysdeps/csky/nptl/tcb-offsets.sym             |   3 +
 sysdeps/unix/sysv/linux/csky/syscall_cancel.S | 115 ++++++++++++++++++
 2 files changed, 118 insertions(+)
 create mode 100644 sysdeps/unix/sysv/linux/csky/syscall_cancel.S

diff --git a/sysdeps/csky/nptl/tcb-offsets.sym b/sysdeps/csky/nptl/tcb-offsets.sym
index f1105205c0..dab7518aa4 100644
--- a/sysdeps/csky/nptl/tcb-offsets.sym
+++ b/sysdeps/csky/nptl/tcb-offsets.sym
@@ -8,3 +8,6 @@
 
 MULTIPLE_THREADS_OFFSET		thread_offsetof (header.multiple_threads)
 TID_OFFSET			thread_offsetof (tid)
+
+-- Not strictly offsets, used on syscall_cancel.S
+TCB_CANCELED_BITMASK		CANCELED_BITMASK
diff --git a/sysdeps/unix/sysv/linux/csky/syscall_cancel.S b/sysdeps/unix/sysv/linux/csky/syscall_cancel.S
new file mode 100644
index 0000000000..a730225a22
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/csky/syscall_cancel.S
@@ -0,0 +1,115 @@
+/* Cancellable syscall wrapper.  Linux/csky version.
+   Copyright (C) 2020 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 __syscall_cancel_arch (int *cancelhandling,
+				   __syscall_arg_t nr,
+				   __syscall_arg_t arg1,
+				   __syscall_arg_t arg2,
+				   __syscall_arg_t arg3,
+				   __syscall_arg_t arg4,
+				   __syscall_arg_t arg5,
+				   __syscall_arg_t arg6)  */
+
+#ifdef SHARED
+# define STACK_ADJ 4
+#else
+# define STACK_ADJ 0
+#endif
+
+ENTRY (__syscall_cancel_arch)
+	subi	sp, sp, 16 + STACK_ADJ
+	cfi_def_cfa_offset (16 + STACK_ADJ)
+#ifdef SHARED
+	st.w	gb, (sp, 16)
+	lrw	t1, 1f@GOTPC
+	cfi_offset (gb, -4)
+	grs	gb, 1f
+1:
+#endif
+	st.w	lr, (sp, 12)
+	st.w	l3, (sp, 8)
+	st.w	l1, (sp, 4)
+	st.w	l0, (sp, 0)
+#ifdef SHARED
+	addu	gb, gb, t1
+#endif
+	subi	sp, sp, 16
+	cfi_def_cfa_offset (32 + STACK_ADJ)
+	cfi_offset (lr, -( 4 + STACK_ADJ))
+	cfi_offset (l3, -( 8 + STACK_ADJ))
+	cfi_offset (l1, -(12 + STACK_ADJ))
+	cfi_offset (l0, -(16 + STACK_ADJ))
+
+	mov	l3, a1
+	mov	a1, a3
+	ld.w	a3, (sp, 32 + STACK_ADJ)
+	st.w	a3, (sp, 0)
+	ld.w	a3, (sp, 36 + STACK_ADJ)
+	st.w	a3, (sp, 4)
+	ld.w	a3, (sp, 40 + STACK_ADJ)
+	st.w	a3, (sp, 8)
+	ld.w	a3, (sp, 44 + STACK_ADJ)
+	st.w	a3, (sp, 12)
+
+	.globl __syscall_cancel_arch_start
+__syscall_cancel_arch_start:
+	ld.w	t0, (a0, 0)
+	andi	t0, t0, TCB_CANCELED_BITMASK
+	jbnez	t0, 2f
+	mov	a0, a2
+	ld.w	a3, (sp, 4)
+	ld.w	a2, (sp, 0)
+	ld.w	l0, (sp, 8)
+	ld.w	l1, (sp, 12)
+	trap	0
+
+	.globl __syscall_cancel_arch_end
+	.type  __syscall_cancel_arch_end,@function
+__syscall_cancel_arch_end:
+	addi	sp, sp, 16
+	cfi_remember_state
+	cfi_def_cfa_offset (16 + STACK_ADJ)
+#ifdef SHARED
+	ld.w	gb, (sp, 16)
+	cfi_restore (gb)
+#endif
+	ld.w	lr, (sp, 12)
+	cfi_restore (lr)
+	ld.w	l3, (sp, 8)
+	cfi_restore (l3)
+	ld.w	l1, (sp, 4)
+	cfi_restore (l1)
+	ld.w	l0, (sp, 0)
+	cfi_restore (l0)
+	addi	sp, sp, 16
+	cfi_def_cfa_offset (0)
+	rts
+
+2:
+	cfi_restore_state
+#ifdef SHARED
+	lrw	a3, __syscall_do_cancel@GOTOFF
+	addu	a3, a3, gb
+	jsr	a3
+#else
+	jbsr	__syscall_do_cancel
+#endif
+END (__syscall_cancel_arch)
+libc_hidden_def (__syscall_cancel_arch)
-- 
2.17.1