glibc/sysdeps/unix/sysv/linux/s390/s390-64/clone.S

/* Wrapper around clone system call.  64 bit S/390 version.
   Copyright (C) 2001-2023 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/>.  */

/* clone is even more special than fork as it mucks with stacks
   and invokes a function in the right context after its all over.  */

#include <sysdep.h>
#include <tls.h>
#define _ERRNO_H	1
#include <bits/errno.h>

/* int __clone(int (*fn)(void *arg), void *child_stack, int flags, void *arg,
               pid_t *parent_tid, void *tls, pid_t *child_tid);  */
/* sys_clone  (void *child_stack, unsigned long flags,
               pid_t *parent_tid, pid_t *child_tid, void *tls);  */

	.text
ENTRY(__clone)
	stmg	%r6,%r7,48(%r15)	/* Save registers.  */
	cfi_offset (%r7,-104)
	cfi_offset (%r6,-112)
	ltgr    %r7,%r2			/* check fn and move to %r7 */
	jz      error			/* no NULL function pointers */
	lghi	%r0,-16			/* Align the child_stack to a ...  */
	ngr	%r3,%r0			/* double word boundary and ...  */
	jz	error			/* avoid NULL stack pointers.  */
	lgr	%r0,%r5			/* move *arg out of the way */
	lgr	%r2,%r3			/* move child_stack to %r2  */
	lgr	%r3,%r4			/* move flags to %r3 */
	lgr	%r4,%r6			/* move parent_tid to %r4 */
	lg	%r5,168(%r15)		/* load child_tid from stack */
	lg	%r6,160(%r15)		/* load tls from stack */
	lghi	%r1,SYS_ify (clone)
	svc	0
	ltgr	%r2,%r2			/* check return code */
	jz	thread_start
	lmg	%r6,%r7,48(%r15)	/* Restore registers.  */
	jgm	SYSCALL_ERROR_LABEL
	br	%r14
error:
	lghi	%r2,-EINVAL
	jg	SYSCALL_ERROR_LABEL
PSEUDO_END (__clone)

thread_start:
	cfi_startproc
	/* Mark r14 as undefined in order to stop unwinding here!  */
	cfi_undefined (r14)
	/* fn is in gpr 7, arg in gpr 0 */
	lgr	%r2,%r0		/* set first parameter to void *arg */
	aghi	%r15,-160	/* make room on the stack for the save area */
	xc	0(8,%r15),0(%r15)
	basr	%r14,%r7	/* jump to fn */
	DO_CALL	(exit, 1)
	cfi_endproc

libc_hidden_def (__clone)
weak_alias (__clone, clone)