linux-kernel - Re: [PATCH v2] signal: add procfd

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Date:   Fri, 30 Nov 2018 08:16:52 +1300
From:   Christian Brauner <christian@...uner.io>
To:     Andy Lutomirski <luto@...capital.net>,
        Florian Weimer <fweimer@...hat.com>
CC:     ebiederm@...ssion.com, linux-kernel@...r.kernel.org,
        serge@...lyn.com, jannh@...gle.com, luto@...nel.org,
        akpm@...ux-foundation.org, oleg@...hat.com, cyphar@...har.com,
        viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
        linux-api@...r.kernel.org, dancol@...gle.com, timmurray@...gle.com,
        linux-man@...r.kernel.org, Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v2] signal: add procfd_signal() syscall

On November 30, 2018 5:54:18 AM GMT+13:00, Andy Lutomirski <luto@...capital.net> wrote:
>
>
>> On Nov 29, 2018, at 4:28 AM, Florian Weimer <fweimer@...hat.com>
>wrote:
>> 
>> Disclaimer: I'm looking at this patch because Christian requested it.
>> I'm not a kernel developer.
>> 
>> * Christian Brauner:
>> 
>>> diff --git a/arch/x86/entry/syscalls/syscall_32.tbl
>b/arch/x86/entry/syscalls/syscall_32.tbl
>>> index 3cf7b533b3d1..3f27ffd8ae87 100644
>>> --- a/arch/x86/entry/syscalls/syscall_32.tbl
>>> +++ b/arch/x86/entry/syscalls/syscall_32.tbl
>>> @@ -398,3 +398,4 @@
>>> 384    i386    arch_prctl        sys_arch_prctl           
>__ia32_compat_sys_arch_prctl
>>> 385    i386    io_pgetevents        sys_io_pgetevents       
>__ia32_compat_sys_io_pgetevents
>>> 386    i386    rseq            sys_rseq            __ia32_sys_rseq
>>> +387    i386    procfd_signal        sys_procfd_signal       
>__ia32_compat_sys_procfd_signal
>>> diff --git a/arch/x86/entry/syscalls/syscall_64.tbl
>b/arch/x86/entry/syscalls/syscall_64.tbl
>>> index f0b1709a5ffb..8a30cde82450 100644
>>> --- a/arch/x86/entry/syscalls/syscall_64.tbl
>>> +++ b/arch/x86/entry/syscalls/syscall_64.tbl
>>> @@ -343,6 +343,7 @@
>>> 332    common    statx            __x64_sys_statx
>>> 333    common    io_pgetevents        __x64_sys_io_pgetevents
>>> 334    common    rseq            __x64_sys_rseq
>>> +335    64    procfd_signal        __x64_sys_procfd_signal
>>> 
>>> #
>>> # x32-specific system call numbers start at 512 to avoid cache
>impact
>>> @@ -386,3 +387,4 @@
>>> 545    x32    execveat        __x32_compat_sys_execveat/ptregs
>>> 546    x32    preadv2            __x32_compat_sys_preadv64v2
>>> 547    x32    pwritev2        __x32_compat_sys_pwritev64v2
>>> +548    x32    procfd_signal        __x32_compat_sys_procfd_signal
>> 
>> Is there a reason why these numbers have to be different?
>> 
>> (See the recent discussion with Andy Lutomirski.)
>
>Hah, I missed this part of the patch.  Let’s not add new x32 syscall
>numbers.
>
>Also, can we perhaps rework this a bit to get rid of the compat entry
>point?  The easier way would be to check in_compat_syscall(). The nicer
>way IMO would be to use the 64-bit structure for 32-bit as well.

Do you have a syscall which set precedence/did this before I could look at?
Just if you happen to remember one.
Fwiw, I followed the other signal syscalls.
They all introduce compat syscalls.