Re: [PATCH v2 1/4] s390x: Add the clone3 wrapper

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

On 13/07/23 06:30, Stefan Liebler wrote:
> Hi Adhemerval,
> 
> I had a further look into the implementation. And we can get rid of
> save/restore of r6 to stack at all. Despite of r2 (return-value), the
> syscall does not clobber the registers. Thus we can just keep func in r4
> and arg in r5 and use both directly in thread_start.
> 
> Furthermore I've added a clone3.S in s390-32 directory and define
> HAVE_CLONE3_WRAPPER to 1 for s390x(64bit)/s390(31bit).
> The testsuite runs fine for both modes.
> 
> Both changes are within the patch-file attached (I'm not quite sure if
> my mail-client corrupts an inlined patch).
> 
> Bye,
> Stefan

LGTM, thanks for check the s390 version.  I will install the patch.

> 
> On 12.07.23 20:08, Adhemerval Zanella Netto wrote:
>>
>>
>> On 12/07/23 11:51, Stefan Liebler via Libc-alpha wrote:
>>> Hi Adhemerval,
>>>
>>> I have applied your patches and tested it on s390x. I've ensured that
>>> the wrapper is now used for pthread_create/posix_spawn and the testsuite
>>> runs fine. Nevertheless I have some minor comments: see below.
>>>
>>> And one more question:
>>> Is there a reason, why the wrapper is only added to s390x (64bit), but
>>> not for s390 (31bit)? Should there be an #undef __ASSUME_CLONE3?
>>> According to the kernel commit it is also available for compat-mode:
>>> "s390: wire up clone3 system call"
>>> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=5518aed82d2abd97f8d3ec91d8ba455d939e8cd1
>>
>> Mainly because I could not test it properly: there is no easy access to
>> s390x machine (such as on gcc build farm), there is no qemu-user support
>> for 31-bit, and I saw strange results running s390 binaries on a s390x
>> qemu vm.
>>
>>>
>>> On 10.07.23 20:40, Adhemerval Zanella via Libc-alpha wrote:
>>>> It follows the internal signature:
>>>>
>>>>   extern int clone3 (struct clone_args *__cl_args, size_t __size,
>>>>  int (*__func) (void *__arg), void *__arg);
>>>>
>>>> Checked on s390x-linux-gnu.
>>>> ---
>>>>  sysdeps/unix/sysv/linux/s390/s390-64/clone3.S | 81 +++++++++++++++++++
>>>>  sysdeps/unix/sysv/linux/s390/sysdep.h         |  1 +
>>>>  2 files changed, 82 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..417fdcb785
>>>> --- /dev/null
>>>> +++ b/sysdeps/unix/sysv/linux/s390/s390-64/clone3.S
>>>> @@ -0,0 +1,81 @@
>>>> +/* The clone3 syscall wrapper.  Linux/s390x 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:
>>>> +   r2: cl_args
>>>> +   r3: size
>>>> +   r4: func
>>>> +   r5: arg  */
>>>> +
>>>> +        .text
>>>> +ENTRY(__clone3)
>>>> +	stg	%r6, 48(%r15)
>>> Add cfi_offset (%r6,-112)
>>>
>>>
>>>> +
>>>> +	/* 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
>>> The ENTRY-macro from sysdep.h is using an alignment of 16 bytes. Can you
>>> please also use it here?
>>>
>>>> +	.type thread_start, %function
>>>> +thread_start:
>>>> +	cfi_startproc
>>>> +	/* Mark r14 as undefined in order to stop unwinding here.  */
>>>> +	cfi_undefined (r14)
>>>> +
>>>> +	/* 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
>>> If you want, you can use ASM_SIZE_DIRECTIVE (thread_start) from sysdep.h
>>> here, which is also used in END-macros.
>>>> +
>>>> +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 3bde8ba19c..b099fea9c6 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"
>>
>> Updated patch below.
>>
>> From 74f79943014c4df13f2ce6d6ccd60b8b271319b3 Mon Sep 17 00:00:00 2001
>> From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
>> Date: Tue, 27 Sep 2022 17:00:27 -0300
>> Subject: [PATCH 1/9] s390x: 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 s390x-linux-gnu.
>> ---
>>  sysdeps/unix/sysv/linux/s390/s390-64/clone3.S | 82 +++++++++++++++++++
>>  sysdeps/unix/sysv/linux/s390/sysdep.h         |  1 +
>>  2 files changed, 83 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..22e07fa450
>> --- /dev/null
>> +++ b/sysdeps/unix/sysv/linux/s390/s390-64/clone3.S
>> @@ -0,0 +1,82 @@
>> +/* The clone3 syscall wrapper.  Linux/s390x 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:
>> +   r2: cl_args
>> +   r3: size
>> +   r4: func
>> +   r5: arg  */
>> +
>> +        .text
>> +ENTRY(__clone3)
>> +	stg	%r6, 48(%r15)
>> +	cfi_offset (%r6, -112)
>> +
>> +	/* 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 16
>> +	.type thread_start, %function
>> +thread_start:
>> +	cfi_startproc
>> +	/* Mark r14 as undefined in order to stop unwinding here.  */
>> +	cfi_undefined (r14)
>> +
>> +	/* 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
>> +	ASM_SIZE_DIRECTIVE (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 3bde8ba19c..b099fea9c6 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"