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

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Date:   Wed, 2 Aug 2023 08:43:23 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Arnd Bergmann <arnd@...db.de>,
        Christian Brauner <brauner@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Dinh Nguyen <dinguyen@...nel.org>,
        Christian Brauner <christian@...uner.io>
Subject: Re: [PATCH RESEND^2] nios2: support clone3() syscall



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.

-- 
~Randy