[PATCH v2 5/9] s390x: Add the clone3 wrapper

[Adhemerval Zanella]

It follows the internal signature:

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

And x86_64 semantics to return EINVAL if either cl_args or func
is NULL.  The stack is 16-byte aligned prior executing func.

Checked on s390x-linux-gnu.
---
 sysdeps/unix/sysv/linux/s390/s390-64/clone3.S | 84 +++++++++++++++++++
 sysdeps/unix/sysv/linux/s390/sysdep.h         |  1 +
 2 files changed, 85 insertions(+)
 create mode 100644 sysdeps/unix/sysv/linux/s390/s390-64/clone3.S

diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/clone3.S b/sysdeps/unix/sysv/linux/s390/s390-64/clone3.S
new file mode 100644
index 0000000000..d338acfc9c
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/clone3.S
@@ -0,0 +1,84 @@
+/* The clone3 syscall wrapper.  Linux/s390x version.
+   Copyright (C) 2022 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:
+   r2: cl_args
+   r3: size
+   r4: func
+   r5: arg  */
+
+        .text
+ENTRY(__clone3)
+	stg	%r6, 48(%r15)
+
+	/* Sanity check args.  */
+	ltgr	%r2, %r2
+	je	error
+	ltgr	%r6, %r4
+	je	error
+
+	/* Do the system call, the kernel expects:
+	   r1: system call number
+	   r2: cl_args
+	   r3: size  */
+	lghi	%r1, SYS_ify(clone3)
+	svc	0
+	ltgr	%r2,%r2			/* check return code */
+	jz	thread_start
+	lg	%r6, 48(%r15)
+	jgm	SYSCALL_ERROR_LABEL
+	br	%r14
+error:
+	lghi	%r2,-EINVAL
+	jg	SYSCALL_ERROR_LABEL
+PSEUDO_END (__clone3)
+
+	.align 4
+	.type thread_start, %function
+thread_start:
+	cfi_startproc
+	/* Mark r14 as undefined in order to stop unwinding here.  */
+	cfi_undefined (r14)
+
+	/* Align stack.  */
+	nill    %r15, 0xfff0
+
+	/* func is in gpr 6, arg in gpr 5.  */
+	lgr	%r2, %r5
+	aghi	%r15, -160
+	xc	0(8,%r15),0(%r15)
+	basr	%r14, %r6
+
+	DO_CALL (exit, 1)
+	cfi_endproc
+	.size thread_start, .-thread_start
+
+libc_hidden_def (__clone3)
+weak_alias (__clone3, clone3)
diff --git a/sysdeps/unix/sysv/linux/s390/sysdep.h b/sysdeps/unix/sysv/linux/s390/sysdep.h
index 930d7efe03..366c797ef1 100644
--- a/sysdeps/unix/sysv/linux/s390/sysdep.h
+++ b/sysdeps/unix/sysv/linux/s390/sysdep.h
@@ -72,6 +72,7 @@
 #ifdef __s390x__
 #define HAVE_CLOCK_GETRES64_VSYSCALL	"__kernel_clock_getres"
 #define HAVE_CLOCK_GETTIME64_VSYSCALL	"__kernel_clock_gettime"
+#define HAVE_CLONE3_WRAPPER		1
 #else
 #define HAVE_CLOCK_GETRES_VSYSCALL	"__kernel_clock_getres"
 #define HAVE_CLOCK_GETTIME_VSYSCALL	"__kernel_clock_gettime"
-- 
2.34.1