Re: [PATCH 1/2] ARC: Add the clone3 wrapper

[Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>]

On 02/03/23 13:10, Pavel Kozlov via Libc-alpha wrote:
> From: Pavel Kozlov <pavel.kozlov@synopsys.com>
> 
> Use the clone3 wrapper on ARC. It doesn't care about stack alignment.
> All callers should provide an aligned stack.
> It follows the internal signature:
> 
> extern int clone3 (struct clone_args *__cl_args, size_t __size,
>  int (*__func) (void *__arg), void *__arg);

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
> Checked on arc-linux-gnu. Previously observed tst-misaling-clone-internal
> test fail was because I used outdated master branch.
> Full testsuite runs without regressions.
> But I also see fail of the new tst-spawn7, as already repoted at [1].
> 
> [1]
> https://sourceware.org/pipermail/libc-alpha/2023-February/145937.html
> 
>  sysdeps/unix/sysv/linux/arc/clone3.S | 90 ++++++++++++++++++++++++++++
>  sysdeps/unix/sysv/linux/arc/sysdep.h |  2 +
>  2 files changed, 92 insertions(+)
>  create mode 100644 sysdeps/unix/sysv/linux/arc/clone3.S
> 
> diff --git a/sysdeps/unix/sysv/linux/arc/clone3.S b/sysdeps/unix/sysv/linux/arc/clone3.S
> new file mode 100644
> index 000000000000..87a8272a3977
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/arc/clone3.S
> @@ -0,0 +1,90 @@
> +/* The clone3 syscall wrapper.  Linux/arc 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  */
> +
> +ENTRY(__clone3)
> +
> +	/* Save args for the child.  */
> +	mov	r10, r0		/* cl_args  */
> +	mov	r11, r2		/* func	 */
> +	mov	r12, r3		/* args  */
> +
> +	/* Sanity check args.  */
> +	breq	r10, 0, L (__sys_err)	/* No NULL cl_args pointer.  */
> +	breq	r11, 0, L (__sys_err)	/* No NULL function pointer.  */
> +
> +	/* Do the system call, the kernel expects:
> +	   r8: system call number
> +	   r0: cl_args
> +	   r1: size  */
> +	mov	r0, r10
> +	mov	r8, __NR_clone3
> +	ARC_TRAP_INSN
> +
> +	cmp	r0, 0
> +	beq	thread_start_clone3	/* Child returns.  */
> +	blt	L (__sys_err2)
> +	j	[blink]			/* Parent returns.  */
> +
> +L (__sys_err):
> +	mov	r0, -EINVAL
> +L (__sys_err2):
> +	b	__syscall_error
> +PSEUDO_END (__clone3)
> +
> +
> +	.align 4
> +	.type thread_start_clone3, %function
> +thread_start_clone3:
> +	cfi_startproc
> +	/* Terminate call stack by noting ra is undefined.  */
> +	cfi_undefined (blink)
> +
> +	/* Child jumps off to @fn with @arg as argument.  */
> +	jl.d	[r11]
> +	mov	r0, r12
> +
> +	/* exit() with result from @fn (already in r0).  */
> +	mov	r8, __NR_exit
> +	ARC_TRAP_INSN
> +
> +	/* In case it ever came back.  */
> +	flag	1
> +
> +	cfi_endproc
> +	.size thread_start_clone3, .-thread_start_clone3
> +
> +libc_hidden_def (__clone3)
> +weak_alias (__clone3, clone3)
> diff --git a/sysdeps/unix/sysv/linux/arc/sysdep.h b/sysdeps/unix/sysv/linux/arc/sysdep.h
> index dd6fe73445f9..88dc1dff017f 100644
> --- a/sysdeps/unix/sysv/linux/arc/sysdep.h
> +++ b/sysdeps/unix/sysv/linux/arc/sysdep.h
> @@ -141,6 +141,8 @@ hidden_proto (__syscall_error)
>  
>  # define ARC_TRAP_INSN	"trap_s 0	\n\t"
>  
> +# define HAVE_CLONE3_WRAPPER	1
> +
>  # undef INTERNAL_SYSCALL_NCS
>  # define INTERNAL_SYSCALL_NCS(number, nr_args, args...)	\
>    ({								\