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.

1 files changed, 34 insertions, 9 deletions

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  */