linux-kernel - Re: [PATCH RESEND^2] nios2: support clone3() syscall

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Date:   Sun, 6 Aug 2023 12:52:35 -0500
From:   Dinh Nguyen <dinguyen@...nel.org>
To:     Randy Dunlap <rdunlap@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Christian Brauner <brauner@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Christian Brauner <christian@...uner.io>
Subject: Re: [PATCH RESEND^2] nios2: support clone3() syscall



On 8/2/23 10:43, Randy Dunlap wrote:
> 
> 
> On 8/2/23 01:16, Arnd Bergmann wrote:
>> On Wed, Aug 2, 2023, at 09:40, Christian Brauner wrote:
>>> On Tue, Aug 01, 2023 at 10:19:24PM -0700, Randy Dunlap wrote:
>>>> Add support for the clone3() syscall to prevent a warning from
>>>> checksyscalls.sh:
>>>>
>>>> <stdin>:1517:2: warning: #warning syscall clone3 not implemented [-Wcpp]
>>>>
>>>> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
>>>> Cc: Dinh Nguyen <dinguyen@...nel.org>
>>>> Cc: Christian Brauner <christian@...uner.io>
>>>> ---
>>>> Is there some reason that NIOS2 should not (does not) support clone3()?
>>>
>>> Cc Arnd, in case he knows.
>>
>> As far as I remember, you left a few architectures without clone3
>> during the introduction when there was neither an obvious way to
>> handle the syscall entry nor a maintainer to have a look.
>>
>> Right now, it seems to be missing on alpha, hexagon, ia64,
>> microblaze, nios2, sh and sparc.
>>
>> There are a few architectures that implement a custom entry
>> point for both clone and clone3. The other architectures that
>> provide the generic sys_clone3 also use the generic sys_clone.
>> These are the wrappers I see:
>>
>> # ARC
>> ENTRY(sys_clone3_wrapper)
>>          SAVE_CALLEE_SAVED_USER
>>          bl  @sys_clone3
>>          DISCARD_CALLEE_SAVED_USER
>>
>>          GET_CURR_THR_INFO_FLAGS   r10
>>          and.f 0, r10, _TIF_SYSCALL_WORK
>>          bnz   tracesys_exit
>>
>>          b .Lret_from_system_call
>> END(sys_clone3_wrapper)
>>
>> # m68k
>> ENTRY(__sys_clone3)
>>          SAVE_SWITCH_STACK
>>          pea     %sp@(SWITCH_STACK_SIZE)
>>          jbsr    m68k_clone3
>>          lea     %sp@(28),%sp
>>          rts
>>
>>
>> # mips
>> save_static_function(sys_clone3);
>>
>> # openrisc
>> ENTRY(__sys_clone3)
>>          l.movhi r29,hi(sys_clone3)
>>          l.j     _fork_save_extra_regs_and_call
>>           l.ori  r29,r29,lo(sys_clone3)
>>
>> # parisc
>>          .macro  fork_like name
>> ENTRY_CFI(sys_\name\()_wrapper)
>>          mfctl   %cr30,%r1
>>          ldo     TASK_REGS(%r1),%r1
>>          reg_save %r1
>>          mfctl   %cr27, %r28
>>          ldil    L%sys_\name, %r31
>>          be      R%sys_\name(%sr4,%r31)
>>          STREG   %r28, PT_CR27(%r1)
>> ENDPROC_CFI(sys_\name\()_wrapper)
>>          .endm
>> fork_like clone
>> fork_like clone3
>>
>> Nios3 in turn has a wrapper for sys_clone:
>> ENTRY(sys_clone)
>>          SAVE_SWITCH_STACK
>>          subi    sp, sp, 4 /* make space for tls pointer */
>>          stw     r8, 0(sp) /* pass tls pointer (r8) via stack (5th argument) */
>>          call    nios2_clone
>>          addi    sp, sp, 4
>>          RESTORE_SWITCH_STACK
>>          ret
>>
>> so my guess would be that it needs the same thing
>> for clone3 as well. Same thing on alpha, ia64 and
>> sparc. On the other hand hexagon, microblaze and sh
>> use the generic sys_clone() and can probably just
>> enable sys_clone3() without extra work unless it's
>> already broken.
> 
> OK, thanks for the help.
> 

Applied!

Thank you,
Dinh