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

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Date:   Thu, 29 Nov 2018 08:54:18 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Florian Weimer <fweimer@...hat.com>
Cc:     Christian Brauner <christian@...uner.io>, 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 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.