arm: Add the clone3 wrapper

It follows the internal signature:

  extern int clone3 (struct clone_args *__cl_args, size_t __size,
		    int (*__func) (void *__arg), void *__arg);

Checked on arm-linux-gnueabihf.

sysdeps/unix/sysv/linux/arm/clone3.S

@@ -0,0 +1,80 @@
+/* The clone3 syscall wrapper.  Linux/arm 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+#define _ERRNO_H	1
+#include <bits/errno.h>
+
+/* The userland implementation is:
+   int clone3 (struct clone_args *cl_args, size_t size,
+               int (*func)(void *arg), void *arg);
+
+   the kernel entry is:
+   int clone3 (struct clone_args *cl_args, size_t size);
+
+   The parameters are passed in registers from userland:
+   r0: cl_args
+   r1: size
+   r2: func
+   r3: arg  */
+
+        .text
+ENTRY(__clone3)
+	/* Sanity check args.  */
+	cmp	r0, #0
+	ite	ne
+	cmpne	r1, #0
+	moveq	r0, #-EINVAL
+	beq	PLTJMP(syscall_error)
+
+	/* Do the syscall, the kernel expects:
+	   r7: system call number:
+	   r0: cl_args
+	   r1: size  */
+	push    { r7 }
+	cfi_adjust_cfa_offset (4)
+	cfi_rel_offset (r7, 0)
+	ldr     r7, =SYS_ify(clone3)
+	swi	0x0
+	cfi_endproc
+
+	cmp	r0, #0
+	beq	1f
+	pop     {r7}
+	blt	PLTJMP(C_SYMBOL_NAME(__syscall_error))
+	RETINSTR(, lr)
+
+	cfi_startproc
+PSEUDO_END (__clone3)
+
+1:
+	.fnstart
+	.cantunwind
+	mov	r0, r3
+	mov	ip, r2
+	BLX (ip)
+
+	/* And we are done, passing the return value through r0.  */
+	ldr	r7, =SYS_ify(exit)
+	swi	0x0
+
+	.fnend
+
+libc_hidden_def (__clone3)
+weak_alias (__clone3, clone3)

sysdeps/unix/sysv/linux/arm/sysdep.h

@@ -362,6 +362,7 @@ __local_syscall_error:						\
 #define HAVE_CLOCK_GETTIME_VSYSCALL	"__vdso_clock_gettime"
 #define HAVE_CLOCK_GETTIME64_VSYSCALL	"__vdso_clock_gettime64"
 #define HAVE_GETTIMEOFDAY_VSYSCALL	"__vdso_gettimeofday"
+#define HAVE_CLONE3_WRAPPER		1
 
 #define LOAD_ARGS_0()
 #define ASM_ARGS_0