linux-kernel - Re: [PATCH 2/2] arch: add pidfd and io

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Date:   Thu, 04 Apr 2019 17:08:59 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Jens Axboe <axboe@...nel.dk>, Will Deacon <will.deacon@....com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Michal Simek <monstr@...str.eu>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        "James E . J . Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Rich Felker <dalias@...c.org>,
        "David S . Miller" <davem@...emloft.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        Firoz Khan <firoz.khan@...aro.org>,
        linux-alpha@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org
Subject: Re: [PATCH 2/2] arch: add pidfd and io_uring syscalls everywhere

Jens Axboe <axboe@...nel.dk> writes:
> On 4/3/19 5:11 AM, Will Deacon wrote:
>> On Wed, Apr 03, 2019 at 01:47:50PM +1100, Michael Ellerman wrote:
>>> Arnd Bergmann <arnd@...db.de> writes:
>>>> diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
>>>> index b18abb0c3dae..00f5a63c8d9a 100644
>>>> --- a/arch/powerpc/kernel/syscalls/syscall.tbl
>>>> +++ b/arch/powerpc/kernel/syscalls/syscall.tbl
>>>> @@ -505,3 +505,7 @@
>>>>  421	32	rt_sigtimedwait_time64		sys_rt_sigtimedwait		compat_sys_rt_sigtimedwait_time64
>>>>  422	32	futex_time64			sys_futex			sys_futex
>>>>  423	32	sched_rr_get_interval_time64	sys_sched_rr_get_interval	sys_sched_rr_get_interval
>>>> +424	common	pidfd_send_signal		sys_pidfd_send_signal
>>>> +425	common	io_uring_setup			sys_io_uring_setup
>>>> +426	common	io_uring_enter			sys_io_uring_enter
>>>> +427	common	io_uring_register		sys_io_uring_register
>>>
>>> Acked-by: Michael Ellerman <mpe@...erman.id.au> (powerpc)
>>>
>>> Lightly tested.
>>>
>>> The pidfd_test selftest passes.
>> 
>> That reports pass for me too, although it fails to unshare the pid ns, which I
>> assume is benign.

If you run it as root it should work?

>>> Ran the io_uring example from fio, which prints lots of:
>> 
>> How did you invoke that? I had a play with the tests in:
>
> It's t/io_uring from the fio repo:
>
> git://git.kernel.dk/fio
>
> and you just run it ala:
>
> # make t/io_uring
> # t/io_uring /dev/some_device

Yeah that's all I did.

>> will@...oplooker:~/liburing/test$ ./io_uring_register 
>> RELIMIT_MEMLOCK: 67108864 (67108864)
>> [   35.477875] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000070
>> [   35.478969] Mem abort info:
>> [   35.479296]   ESR = 0x96000004
>> [   35.479785]   Exception class = DABT (current EL), IL = 32 bits
>> [   35.480528]   SET = 0, FnV = 0
>> [   35.480980]   EA = 0, S1PTW = 0
>> [   35.481345] Data abort info:
>> [   35.481680]   ISV = 0, ISS = 0x00000004
>> [   35.482267]   CM = 0, WnR = 0
>> [   35.482618] user pgtable: 4k pages, 48-bit VAs, pgdp = (____ptrval____)
>> [   35.483486] [0000000000000070] pgd=0000000000000000
>> [   35.484041] Internal error: Oops: 96000004 [#1] PREEMPT SMP
>> [   35.484788] Modules linked in:
>> [   35.485311] CPU: 113 PID: 3973 Comm: io_uring_regist Not tainted 5.1.0-rc3-00012-g40b114779944 #1
>> [   35.486712] Hardware name: linux,dummy-virt (DT)
>> [   35.487450] pstate: 20400005 (nzCv daif +PAN -UAO)
>> [   35.488228] pc : link_pwq+0x10/0x60
>> [   35.488794] lr : apply_wqattrs_commit+0xe0/0x118
>> [   35.489550] sp : ffff000017e2bbc0
>
> Huh, this looks odd, it's crashing inside the wq setup.

Looks like you found a bug :)

cheers