x86_64: Fix Race conditions in pthread cancellation [BZ#12683]

By adding the required syscall_cancel.S.

Checked on x86_64-linux-gnu.

2 files changed, 57 insertions, 3 deletions

diff --git a/sysdeps/unix/sysv/linux/x86_64/syscall_cancel.S b/sysdeps/unix/sysv/linux/x86_64/syscall_cancel.S
new file mode 100644
index 0000000000..cda9d20a83
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/syscall_cancel.S
@@ -0,0 +1,57 @@
+/* Cancellable syscall wrapper.  Linux/x86_64 version.
+   Copyright (C) 2023 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>
+#include <descr-const.h>
+
+/* long int [rax] __syscall_cancel_arch (volatile int *cancelhandling [%rdi],
+					 __syscall_arg_t nr   [%rsi],
+					 __syscall_arg_t arg1 [%rdx],
+					 __syscall_arg_t arg2 [%rcx],
+					 __syscall_arg_t arg3 [%r8],
+					 __syscall_arg_t arg4 [%r9],
+					 __syscall_arg_t arg5 [SP+8],
+					 __syscall_arg_t arg6 [SP+16])  */
+
+ENTRY (__syscall_cancel_arch)
+	.globl __syscall_cancel_arch_start
+__syscall_cancel_arch_start:
+
+	/* if (*cancelhandling & CANCELED_BITMASK)
+	     __syscall_do_cancel()  */
+	mov    (%rdi),%eax
+	testb  $TCB_CANCELED_BITMASK, (%rdi)
+	jne    __syscall_do_cancel
+
+	/* Issue a 6 argument syscall, the nr [%rax] being the syscall
+	   number.  */
+	mov    %rdi,%r11
+	mov    %rsi,%rax
+	mov    %rdx,%rdi
+	mov    %rcx,%rsi
+	mov    %r8,%rdx
+	mov    %r9,%r10
+	mov    8(%rsp),%r8
+	mov    16(%rsp),%r9
+	mov    %r11,8(%rsp)
+	syscall
+
+	.globl __syscall_cancel_arch_end
+__syscall_cancel_arch_end:
+	ret
+END (__syscall_cancel_arch)
diff --git a/sysdeps/x86_64/nptl/tcb-offsets.sym b/sysdeps/x86_64/nptl/tcb-offsets.sym
index 2bbd563a6c..988a4b8593 100644
--- a/sysdeps/x86_64/nptl/tcb-offsets.sym
+++ b/sysdeps/x86_64/nptl/tcb-offsets.sym
@@ -13,6 +13,3 @@ MULTIPLE_THREADS_OFFSET	offsetof (tcbhead_t, multiple_threads)
 POINTER_GUARD		offsetof (tcbhead_t, pointer_guard)
 FEATURE_1_OFFSET	offsetof (tcbhead_t, feature_1)
 SSP_BASE_OFFSET		offsetof (tcbhead_t, ssp_base)
-
--- Not strictly offsets, but these values are also used in the TCB.
-TCB_CANCELED_BITMASK	 CANCELED_BITMASK