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, 35 insertions, 0 deletions

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