From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH 2/2] arch: Reserve map_shadow_stack() syscall number for
 all architectures
Date: Thu, 14 Sep 2023 22:26:47 +1000
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To: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>, "Mehta, Sohil" <sohil.mehta@intel.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>, "linux-api@vger.kernel.org" <linux-api@vger.kernel.org>
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"Edgecombe, Rick P" <rick.p.edgecombe@intel.com> writes:
> On Mon, 2023-09-11 at 18:02 +0000, Sohil Mehta wrote:
>> diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl
>> b/arch/powerpc/kernel/syscalls/syscall.tbl
>> index 20e50586e8a2..2767b8a42636 100644
>> --- a/arch/powerpc/kernel/syscalls/syscall.tbl
>> +++ b/arch/powerpc/kernel/syscalls/syscall.tbl
>> @@ -539,3 +539,4 @@
>> =C2=A0450=C2=A0=C2=A0=C2=A0=C2=A0nospu=C2=A0=C2=A0=C2=A0set_mempolicy_ho=
me_node=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0sys_set_mempol=
icy_hom
>> e_node
>> =C2=A0451=C2=A0=C2=A0=C2=A0=C2=A0common=C2=A0=C2=A0cachestat=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0sys_cachestat
>> =C2=A0452=C2=A0=C2=A0=C2=A0=C2=A0common=C2=A0=C2=A0fchmodat2=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0sys_fchmodat2
>> +453=C2=A0=C2=A0=C2=A0=C2=A0common=C2=A0=C2=A0map_shadow_stack=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0sys_map_shadow_stack
>
> I noticed in powerpc, the not implemented syscalls are manually mapped
> to sys_ni_syscall. It also has some special extra sys_ni_syscall()
> implementation bits to handle both ARCH_HAS_SYSCALL_WRAPPER and
> !ARCH_HAS_SYSCALL_WRAPPER. So wondering if it might need special
> treatment. Did you see those parts?

I don't think it needs any special treatment. It's processed by the same
script as other arches (scripts/syscalltbl.sh). So if there's no compat
or native entry it will default to sys_ni_syscall.

I think it's just habit/historical that we always spell out sys_ni_syscall.

cheers