Refactor Linux ARCH_FORK implementation

This patch refactors the ARCH_FORK macro and the required architecture
specific header to simplify the required architecture definitions
to provide the fork syscall semantic and proper document current
Linux clone ABI variant.

Instead of require the reimplementation of arch-fork.h header, this
patch changes the ARCH_FORK to an inline function with clone ABI
defined by kernel-features.h define.  The generic kernel ABI meant
for newer ports is used as default and redefine if the architecture
requires.

Checked on x86_64-linux-gnu and i686-linux-gnu.  Also with a build
for all the afected ABIs.

	* sysdeps/nptl/fork.c (ARCH_FORK): Replace by auch_fork.
	* sysdeps/unix/sysv/linux/alpha/arch-fork.h: Remove file.
	* sysdeps/unix/sysv/linux/riscv/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/aarch64/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/arm/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/hppa/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/i386/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/ia64/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/m68k/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/microblaze/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/mips/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/nios2/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/s390/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/sh/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/sparc/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/tile/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/arch-fork.h: Likewise.
	* sysdeps/unix/sysv/linux/arch-fork.h (arch_fork): New function.
	* sysdeps/unix/sysv/linux/aarch64/kernel-features.h: New file.
	* sysdeps/unix/sysv/linux/riscv/kernel-features.h: Likewise.
	* sysdeps/unix/sysv/linux/arm/kernel-features.h
	(__ASSUME_CLONE_BACKWARDS): Define.
	* sysdeps/unix/sysv/linux/createthread.c (ARCH_CLONE): Define to
	__clone2 if __NR_clone2 is defined.
	* sysdeps/unix/sysv/linux/hppa/kernel-features.h
	(__ASSUME_CLONE_BACKWARDS): Likewise.
	* sysdeps/unix/sysv/linux/i386/kernel-features.h
	(__ASSUME_CLONE_BACKWARDS): Likewise.
	* sysdeps/unix/sysv/linux/ia64/kernel-features.h
	(__ASSUME_CLONE2): Likewise.
	* sysdeps/unix/sysv/linux/microblaze/kernel-features.h
	(__ASSUME_CLONE_BACKWARDS3): Likewise.
	* sysdeps/unix/sysv/linux/kernel-features.h: Document possible clone
	variants and the define architecture can use.
	(__ASSUME_CLONE_DEFAULT): Define as default.
	* sysdeps/unix/sysv/linux/mips/kernel-features.h
	(__ASSUME_CLONE_BACKWARDS): Likewise.
	* sysdeps/unix/sysv/linux/powerpc/kernel-features.h
	(__ASSUME_CLONE_BACKWARDS): Likewise.
	* sysdeps/unix/sysv/linux/s390/kernel-features.h
	(__ASSUME_CLONE_BACKWARDS2): Likewise.

28 files changed, 108 insertions, 406 deletions

diff --git a/sysdeps/unix/sysv/linux/riscv/arch-fork.h b/sysdeps/unix/sysv/linux/aarch64/kernel-features.h
index f6f5d73343..9cfa51471c 100644
--- a/sysdeps/unix/sysv/linux/riscv/arch-fork.h
+++ b/sysdeps/unix/sysv/linux/aarch64/kernel-features.h
@@ -1,5 +1,6 @@
-/* Internal definitions for thread-friendly fork implementation.  Linux/RISC-V.
-   Copyright (C) 2002-2018 Free Software Foundation, Inc.
+/* Set flags signalling availability of kernel features based on given
+   kernel version number.  AArch64 version.
+   Copyright (C) 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
@@ -16,11 +17,7 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <sched.h>
-#include <sysdep.h>
-#include <tls.h>
+#include_next <kernel-features.h>
 
-#define ARCH_FORK() \
-  INLINE_SYSCALL (clone, 5,						      \
-		  CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD, 0,     \
-		  NULL, NULL, &THREAD_SELF->tid)
+#undef __ASSUME_CLONE_DEFAULT
+#define __ASSUME_CLONE_BACKWARDS 1
diff --git a/sysdeps/unix/sysv/linux/alpha/arch-fork.h b/sysdeps/unix/sysv/linux/alpha/arch-fork.h
deleted file mode 100644
index 41897dc519..0000000000
--- a/sysdeps/unix/sysv/linux/alpha/arch-fork.h
+++ /dev/null
@@ -1,28 +0,0 @@
-/* ARCH_FORK definition for Linux fork implementation.  Alpha version.
-   Copyright (C) 2003-2018 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 <sched.h>
-#include <signal.h>
-#include <sysdep.h>
-#include <tls.h>
-
-
-#define ARCH_FORK()							\
-  INLINE_SYSCALL (clone, 5,						\
-		  CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD,	\
-		  NULL, NULL, &THREAD_SELF->tid, NULL)
diff --git a/sysdeps/unix/sysv/linux/arch-fork.h b/sysdeps/unix/sysv/linux/arch-fork.h
index d5f542924f..3daa9651e5 100644
--- a/sysdeps/unix/sysv/linux/arch-fork.h
+++ b/sysdeps/unix/sysv/linux/arch-fork.h
@@ -1,4 +1,4 @@
-/* ARCH_FORK definition for Linux fork implementation.  Stub version.
+/* arch_fork definition for Linux fork implementation.
    Copyright (C) 2014-2018 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
@@ -16,12 +16,37 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-/* This file should define the function-like macro of no arguments
-   ARCH_FORK to an INLINE_SYSCALL invocation of the clone-like system
-   call, passing the CLONE_CHILD_SETTID and CLONE_CHILD_CLEARTID flags
-   and &THREAD_SELF->tid as the TID address.
+#ifndef __ARCH_FORK_H
+#define __ARCH_FORK_H
 
-   Machines that lack an arch-fork.h header file will hit an #error in
-   fork.c; this stub file doesn't contain an #error itself mainly for
-   the transition period of migrating old machine-specific fork.c files
-   to machine-specific arch-fork.h instead.  */
+#include <unistd.h>
+
+/* Call the clone syscall with fork semantic.  The CTID address is used
+   to store the child thread ID at its locationm, to erase it in child memory
+   when the child exits, and do a wakeup on the futex at that address.
+
+   The architecture with non-default kernel abi semantic should correctlly
+   override it with one of the supported calling convention (check generic
+   kernel-features.h for the clone abi variants).  */
+static inline pid_t
+arch_fork (void *ctid)
+{
+  const int flags = CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD;
+  long int ret;
+#ifdef __ASSUME_CLONE_BACKWARDS
+  ret = INLINE_SYSCALL_CALL (clone, flags, 0, NULL, 0, ctid);
+#elif defined(__ASSUME_CLONE_BACKWARDS2)
+  ret = INLINE_SYSCALL_CALL (clone, 0, flags, NULL, ctid, 0);
+#elif defined(__ASSUME_CLONE_BACKWARDS3)
+  ret = INLINE_SYSCALL_CALL (clone, flags, 0, 0, NULL, ctid, 0);
+#elif defined(__ASSUME_CLONE2)
+  ret = INLINE_SYSCALL_CALL (clone2, flags, 0, 0, NULL, ctid, 0);
+#elif defined(__ASSUME_CLONE_DEFAULT)
+  ret = INLINE_SYSCALL_CALL (clone, flags, 0, NULL, ctid, 0);
+#else
+# error "Undefined clone variant"
+#endif
+  return ret;
+}
+
+#endif /* __ARCH_FORK_H  */
diff --git a/sysdeps/unix/sysv/linux/arm/arch-fork.h b/sysdeps/unix/sysv/linux/arm/arch-fork.h
deleted file mode 100644
index ff3bc90b15..0000000000
--- a/sysdeps/unix/sysv/linux/arm/arch-fork.h
+++ /dev/null
@@ -1,27 +0,0 @@
-/* ARCH_FORK definition for Linux fork implementation.  ARM version.
-   Copyright (C) 2014-2018 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 <sched.h>
-#include <sysdep.h>
-#include <tls.h>
-
-
-#define ARCH_FORK()                                                     \
-  INLINE_SYSCALL (clone, 5,                                             \
-                  CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD,  \
-                  NULL, NULL, NULL, &THREAD_SELF->tid)
diff --git a/sysdeps/unix/sysv/linux/arm/kernel-features.h b/sysdeps/unix/sysv/linux/arm/kernel-features.h
index f13632b9be..7831ab1e0f 100644
--- a/sysdeps/unix/sysv/linux/arm/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/arm/kernel-features.h
@@ -39,3 +39,6 @@
 
 #define __ASSUME_RECV_SYSCALL   1
 #define __ASSUME_SEND_SYSCALL	1
+
+#undef __ASSUME_CLONE_DEFAULT
+#define __ASSUME_CLONE_BACKWARDS	1
diff --git a/sysdeps/unix/sysv/linux/createthread.c b/sysdeps/unix/sysv/linux/createthread.c
index 5b5464a827..5879e51bd2 100644
--- a/sysdeps/unix/sysv/linux/createthread.c
+++ b/sysdeps/unix/sysv/linux/createthread.c
@@ -28,8 +28,9 @@
 
 #include <arch-fork.h>
 
-
-#ifndef ARCH_CLONE
+#ifdef __NR_clone2
+# define ARCH_CLONE __clone2
+#else
 # define ARCH_CLONE __clone
 #endif
 
diff --git a/sysdeps/unix/sysv/linux/hppa/arch-fork.h b/sysdeps/unix/sysv/linux/hppa/arch-fork.h
deleted file mode 100644
index 7d52994915..0000000000
--- a/sysdeps/unix/sysv/linux/hppa/arch-fork.h
+++ /dev/null
@@ -1,32 +0,0 @@
-/* ARCH_FORK definition for Linux fork implementation.  HPPA version.
-   Copyright (C) 2005-2018 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 <sched.h>
-#include <signal.h>
-#include <sysdep.h>
-#include <tls.h>
-
-/* Argument 1 - Clone flags.
-            2 - Child stack pointer.
-	    3 - Parent tid pointer.
-	    4 - New TLS area pointer.
-	    5 - Child tid pointer. */
-#define ARCH_FORK() \
-  INLINE_SYSCALL (clone, 5,						\
-		  CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD,	\
-                  NULL, NULL, NULL, &THREAD_SELF->tid)
diff --git a/sysdeps/unix/sysv/linux/hppa/kernel-features.h b/sysdeps/unix/sysv/linux/hppa/kernel-features.h
index 3f005a5f2e..ef3c4ddfd7 100644
--- a/sysdeps/unix/sysv/linux/hppa/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/hppa/kernel-features.h
@@ -32,3 +32,6 @@
 #if __LINUX_KERNEL_VERSION < 0x040000
 # undef __ASSUME_EXECVEAT
 #endif
+
+#undef __ASSUME_CLONE_DEFAULT
+#define __ASSUME_CLONE_BACKWARDS 1
diff --git a/sysdeps/unix/sysv/linux/i386/arch-fork.h b/sysdeps/unix/sysv/linux/i386/arch-fork.h
deleted file mode 100644
index 0c43e2fc5c..0000000000
--- a/sysdeps/unix/sysv/linux/i386/arch-fork.h
+++ /dev/null
@@ -1,27 +0,0 @@
-/* Internal definitions for thread-friendly fork implementation.  Linux/i386.
-   Copyright (C) 2002-2018 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
-
-   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 <sched.h>
-#include <sysdep.h>
-#include <tls.h>
-
-#define ARCH_FORK() \
-  INLINE_SYSCALL (clone, 5,						      \
-		  CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD, 0,     \
-		  NULL, NULL, &THREAD_SELF->tid)
diff --git a/sysdeps/unix/sysv/linux/i386/kernel-features.h b/sysdeps/unix/sysv/linux/i386/kernel-features.h
index 87087125e5..f3cfd48c44 100644
--- a/sysdeps/unix/sysv/linux/i386/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/i386/kernel-features.h
@@ -48,3 +48,6 @@
 
 /* i686 only supports ipc syscall.  */
 #undef __ASSUME_DIRECT_SYSVIPC_SYSCALLS
+
+#undef __ASSUME_CLONE_DEFAULT
+#define __ASSUME_CLONE_BACKWARDS	1
diff --git a/sysdeps/unix/sysv/linux/ia64/arch-fork.h b/sysdeps/unix/sysv/linux/ia64/arch-fork.h
deleted file mode 100644
index 522712ea15..0000000000
--- a/sysdeps/unix/sysv/linux/ia64/arch-fork.h
+++ /dev/null
@@ -1,31 +0,0 @@
-/* ARCH_FORK definition for Linux fork implementation.  IA64 version.
-   Copyright (C) 2003-2018 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Contributed by Jakub Jelinek <jakub@redhat.com>, 2003.
-
-   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 <sched.h>
-#include <signal.h>
-#include <sysdep.h>
-#include <tls.h>
-
-
-#define ARCH_FORK() \
-  INLINE_SYSCALL (clone2, 6,						      \
-		  CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD,	      \
-		  NULL, 0, NULL, &THREAD_SELF->tid, NULL)
-
-#define ARCH_CLONE __clone2
diff --git a/sysdeps/unix/sysv/linux/ia64/kernel-features.h b/sysdeps/unix/sysv/linux/ia64/kernel-features.h
index cc3fe92d42..04cdf43511 100644
--- a/sysdeps/unix/sysv/linux/ia64/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/ia64/kernel-features.h
@@ -26,4 +26,7 @@
 #define __ASSUME_SEND_SYSCALL		1
 #define __ASSUME_ACCEPT4_SYSCALL	1
 
+#undef __ASSUME_CLONE_DEFAULT
+#define __ASSUME_CLONE2
+
 #endif /* _KERNEL_FEATURES_H */
diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h
index 3aa2052c71..f65a262994 100644
--- a/sysdeps/unix/sysv/linux/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/kernel-features.h
@@ -115,3 +115,38 @@
 #if __LINUX_KERNEL_VERSION >= 0x040500
 # define __ASSUME_COPY_FILE_RANGE 1
 #endif
+
+/* Support for clone call used on fork.  The signature varies across the
+   architectures with current 4 different variants:
+
+   1. long int clone (unsigned long flags, unsigned long newsp,
+		      int *parent_tidptr, unsigned long tls,
+		      int *child_tidptr)
+
+   2. long int clone (unsigned long newsp, unsigned long clone_flags,
+		      int *parent_tidptr, int * child_tidptr,
+		      unsigned long tls)
+
+   3. long int clone (unsigned long flags, unsigned long newsp,
+		      int stack_size, int *parent_tidptr,
+		      int *child_tidptr, unsigned long tls)
+
+   4. long int clone (unsigned long flags, unsigned long newsp,
+		      int *parent_tidptr, int *child_tidptr,
+		      unsigned long tls)
+
+   The fourth variant is intended to be used as the default for newer ports,
+   Also IA64 uses the third variant but with __NR_clone2 instead of
+   __NR_clone.
+
+   The macros names to define the variant used for the architecture is
+   similar to kernel:
+
+   - __ASSUME_CLONE_BACKWARDS: for variant 1.
+   - __ASSUME_CLONE_BACKWARDS2: for variant 2 (s390).
+   - __ASSUME_CLONE_BACKWARDS3: for variant 3 (microblaze).
+   - __ASSUME_CLONE_DEFAULT: for variant 4.
+   - __ASSUME_CLONE2: for clone2 with variant 3 (ia64).
+   */
+
+#define __ASSUME_CLONE_DEFAULT 1
diff --git a/sysdeps/unix/sysv/linux/m68k/arch-fork.h b/sysdeps/unix/sysv/linux/m68k/arch-fork.h
deleted file mode 100644
index 20b6bab8e9..0000000000
--- a/sysdeps/unix/sysv/linux/m68k/arch-fork.h
+++ /dev/null
@@ -1,28 +0,0 @@
-/* ARCH_FORK definition for Linux fork implementation.  m68k version.
-   Copyright (C) 2010-2018 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Contributed by Maxim Kuvyrkov <maxim@codesourcery.com>, 2010.
-
-   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 <sched.h>
-#include <signal.h>
-#include <sysdep.h>
-#include <tls.h>
-
-#define ARCH_FORK() \
-  INLINE_SYSCALL (clone, 5,						      \
-		  CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD, 0,     \
-		  NULL, &THREAD_SELF->tid, NULL)
diff --git a/sysdeps/unix/sysv/linux/microblaze/arch-fork.h b/sysdeps/unix/sysv/linux/microblaze/arch-fork.h
deleted file mode 100644
index 05ed4fae5a..0000000000
--- a/sysdeps/unix/sysv/linux/microblaze/arch-fork.h
+++ /dev/null
@@ -1,27 +0,0 @@
-/* ARCH_FORK definition for Linux fork implementation.  MicroBlaze version.
-   Copyright (C) 2014-2018 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 <sched.h>
-#include <signal.h>
-#include <sysdep.h>
-#include <tls.h>
-
-#define ARCH_FORK()                                                           \
-  INLINE_SYSCALL (clone, 5,                                                   \
-                  CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD, 0,     \
-                  NULL, NULL, &THREAD_SELF->tid)
diff --git a/sysdeps/unix/sysv/linux/microblaze/kernel-features.h b/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
index 745f899911..b13b863f06 100644
--- a/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/microblaze/kernel-features.h
@@ -57,3 +57,6 @@
 #if __LINUX_KERNEL_VERSION < 0x040A00
 # undef __ASSUME_COPY_FILE_RANGE
 #endif
+
+#undef __ASSUME_CLONE_DEFAULT
+#define __ASSUME_CLONE_BACKWARDS3
diff --git a/sysdeps/unix/sysv/linux/mips/arch-fork.h b/sysdeps/unix/sysv/linux/mips/arch-fork.h
deleted file mode 100644
index 5f945378ee..0000000000
--- a/sysdeps/unix/sysv/linux/mips/arch-fork.h
+++ /dev/null
@@ -1 +0,0 @@
-#include <sysdeps/unix/sysv/linux/i386/arch-fork.h>
diff --git a/sysdeps/unix/sysv/linux/mips/kernel-features.h b/sysdeps/unix/sysv/linux/mips/kernel-features.h
index 7756a3495b..ce798ccffe 100644
--- a/sysdeps/unix/sysv/linux/mips/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/mips/kernel-features.h
@@ -47,3 +47,6 @@
 #if _MIPS_SIM == _ABIN32
 # define __ASSUME_WORDSIZE64_ILP32	1
 #endif
+
+#undef __ASSUME_CLONE_DEFAULT
+#define __ASSUME_CLONE_BACKWARDS	1
diff --git a/sysdeps/unix/sysv/linux/nios2/arch-fork.h b/sysdeps/unix/sysv/linux/nios2/arch-fork.h
deleted file mode 100644
index 6dacec2688..0000000000
--- a/sysdeps/unix/sysv/linux/nios2/arch-fork.h
+++ /dev/null
@@ -1,33 +0,0 @@
-/* ARCH_FORK definition for Linux fork implementation.  Nios II version.
-   Copyright (C) 2005-2018 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 <sched.h>
-#include <signal.h>
-#include <sysdep.h>
-#include <tls.h>
-
-/* Argument 1 - Clone flags.
-            2 - Child stack pointer.
-	    3 - Parent tid pointer.
-	    4 - Child tid pointer.
-	    5 - New TLS area pointer. */
-
-#define ARCH_FORK() \
-  INLINE_SYSCALL (clone, 5,						\
-		  CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD,	\
-                  NULL, NULL, &THREAD_SELF->tid, NULL)
diff --git a/sysdeps/unix/sysv/linux/powerpc/arch-fork.h b/sysdeps/unix/sysv/linux/powerpc/arch-fork.h
deleted file mode 100644
index 5f945378ee..0000000000
--- a/sysdeps/unix/sysv/linux/powerpc/arch-fork.h
+++ /dev/null
@@ -1 +0,0 @@
-#include <sysdeps/unix/sysv/linux/i386/arch-fork.h>
diff --git a/sysdeps/unix/sysv/linux/powerpc/kernel-features.h b/sysdeps/unix/sysv/linux/powerpc/kernel-features.h
index f3c02e6ec2..503f562d76 100644
--- a/sysdeps/unix/sysv/linux/powerpc/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/powerpc/kernel-features.h
@@ -49,3 +49,6 @@
 
 /* powerpc only supports ipc syscall.  */
 #undef __ASSUME_DIRECT_SYSVIPC_SYSCALLS
+
+#undef __ASSUME_CLONE_DEFAULT
+#define __ASSUME_CLONE_BACKWARDS	1
diff --git a/sysdeps/unix/sysv/linux/aarch64/arch-fork.h b/sysdeps/unix/sysv/linux/riscv/kernel-features.h
index cab797efe8..37f4d99a92 100644
--- a/sysdeps/unix/sysv/linux/aarch64/arch-fork.h
+++ b/sysdeps/unix/sysv/linux/riscv/kernel-features.h
@@ -1,5 +1,6 @@
-/* ARCH_FORK definition for Linux fork implementation.  AArch64 version.
-   Copyright (C) 2005-2018 Free Software Foundation, Inc.
+/* Set flags signalling availability of kernel features based on given
+   kernel version number.  RISC-V version.
+   Copyright (C) 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
@@ -16,13 +17,7 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <sched.h>
-#include <signal.h>
-#include <sysdep.h>
-#include <tls.h>
+#include_next <kernel-features.h>
 
-
-#define ARCH_FORK()							\
-  INLINE_SYSCALL (clone, 5,						\
-		  CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD,	\
-		  NULL, NULL, NULL, &THREAD_SELF->tid)
+#undef __ASSUME_CLONE_DEFAULT
+#define __ASSUME_CLONE_BACKWARDS 1
diff --git a/sysdeps/unix/sysv/linux/s390/arch-fork.h b/sysdeps/unix/sysv/linux/s390/arch-fork.h
deleted file mode 100644
index 152b465e8b..0000000000
--- a/sysdeps/unix/sysv/linux/s390/arch-fork.h
+++ /dev/null
@@ -1,29 +0,0 @@
-/* ARCH_FORK definition for Linux fork implementation. S390 version.
-   Copyright (C) 2003-2018 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
-
-   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 <sched.h>
-#include <signal.h>
-#include <sysdep.h>
-#include <tls.h>
-
-
-#define ARCH_FORK() \
-  INLINE_SYSCALL (clone, 5,						      \
-		  0, CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD,     \
-		  NULL, &THREAD_SELF->tid, NULL)
diff --git a/sysdeps/unix/sysv/linux/s390/kernel-features.h b/sysdeps/unix/sysv/linux/s390/kernel-features.h
index 3caca981f1..f718264926 100644
--- a/sysdeps/unix/sysv/linux/s390/kernel-features.h
+++ b/sysdeps/unix/sysv/linux/s390/kernel-features.h
@@ -50,3 +50,6 @@
 
 /* s390 only supports ipc syscall.  */
 #undef __ASSUME_DIRECT_SYSVIPC_SYSCALLS
+
+#undef __ASSUME_CLONE_DEFAULT
+#define __ASSUME_CLONE_BACKWARDS2
diff --git a/sysdeps/unix/sysv/linux/sh/arch-fork.h b/sysdeps/unix/sysv/linux/sh/arch-fork.h
deleted file mode 100644
index a29f61c8bb..0000000000
--- a/sysdeps/unix/sysv/linux/sh/arch-fork.h
+++ /dev/null
@@ -1,28 +0,0 @@
-/* ARCH_FORK definition for Linux fork implementation.  SH version.
-   Copyright (C) 2003-2018 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 <sched.h>
-#include <signal.h>
-#include <sysdep.h>
-#include <tls.h>
-
-/* TLS pointer argument is passed as the 5-th argument.  */
-#define ARCH_FORK() \
-  INLINE_SYSCALL (clone, 5,						      \
-		  CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD, 0,     \
-		  NULL, &THREAD_SELF->tid, NULL)
diff --git a/sysdeps/unix/sysv/linux/sparc/arch-fork.h b/sysdeps/unix/sysv/linux/sparc/arch-fork.h
deleted file mode 100644
index 03ccc9aeef..0000000000
--- a/sysdeps/unix/sysv/linux/sparc/arch-fork.h
+++ /dev/null
@@ -1,27 +0,0 @@
-/* ARCH_FORK definition for Linux fork implementation.  SPARC version.
-   Copyright (C) 2003-2018 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Contributed by Jakub Jelinek <jakub@redhat.com>, 2003.
-
-   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 <sched.h>
-#include <signal.h>
-#include <sysdep.h>
-#include <tls.h>
-
-#define ARCH_FORK() \
-  INLINE_CLONE_SYSCALL (CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD, \
-			0, NULL, NULL, &THREAD_SELF->tid)
diff --git a/sysdeps/unix/sysv/linux/tile/arch-fork.h b/sysdeps/unix/sysv/linux/tile/arch-fork.h
deleted file mode 100644
index d0526d880d..0000000000
--- a/sysdeps/unix/sysv/linux/tile/arch-fork.h
+++ /dev/null
@@ -1,29 +0,0 @@
-/* ARCH_FORK definition for Linux fork implementation.  Tile* version.
-   Copyright (C) 2011-2018 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011.
-   Based on work contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
-
-   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 <sched.h>
-#include <signal.h>
-#include <sysdep.h>
-#include <tls.h>
-
-#define ARCH_FORK() \
-  INLINE_SYSCALL (clone, 4,						      \
-		  CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD,        \
-		  0, NULL, &THREAD_SELF->tid)
diff --git a/sysdeps/unix/sysv/linux/x86_64/arch-fork.h b/sysdeps/unix/sysv/linux/x86_64/arch-fork.h
deleted file mode 100644
index 4471970f10..0000000000
--- a/sysdeps/unix/sysv/linux/x86_64/arch-fork.h
+++ /dev/null
@@ -1,27 +0,0 @@
-/* Internal definitions for thread-friendly fork implementation.  Linux/x86_64.
-   Copyright (C) 2003-2018 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
-
-   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 <sched.h>
-#include <sysdep.h>
-#include <tls.h>
-
-#define ARCH_FORK() \
-  INLINE_SYSCALL (clone, 4,                                                   \
-                  CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD, 0,     \
-                  NULL, &THREAD_SELF->tid)