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Date:   Wed, 3 Apr 2019 12:11:34 +0100
From:   Will Deacon <will.deacon@arm.com>
To:     Michael Ellerman <mpe@ellerman.id.au>, axboe@kernel.dk
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Richard Henderson <rth@twiddle.net>,
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        Tony Luck <tony.luck@intel.com>,
        Fenghua Yu <fenghua.yu@intel.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
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        Ralf Baechle <ralf@linux-mips.org>,
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Subject: Re: [PATCH 2/2] arch: add pidfd and io_uring syscalls everywhere
Message-ID: <20190403111134.GA7159@fuggles.cambridge.arm.com>
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 <87tvff24a1.fsf@concordia.ellerman.id.au>
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Hi Michael,

On Wed, Apr 03, 2019 at 01:47:50PM +1100, Michael Ellerman wrote:
> Arnd Bergmann <arnd@arndb.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@ellerman.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.

> Ran the io_uring example from fio, which prints lots of:

How did you invoke that? I had a play with the tests in:

  git://git.kernel.dk/liburing

but I quickly ran into the kernel oops below.

Will

--->8

will@autoplooker:~/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
[   35.490088] x29: ffff000017e2bbc0 x28: ffff8004b9118000 
[   35.490939] x27: 0000000000000000 x26: ffff8004c21c4200 
[   35.491786] x25: 0000000000000004 x24: ffff00001123e1b0 
[   35.492640] x23: ffff8004c5390000 x22: ffff8004bb440500 
[   35.493502] x21: ffff8004bb440500 x20: 0000000000000070 
[   35.494355] x19: 0000000000000022 x18: 0000000000000000 
[   35.495202] x17: 0000000000000000 x16: 0000000000000000 
[   35.496054] x15: 0000000000000000 x14: ffff7e0012e8a240 
[   35.496910] x13: 00004a73a5e663e2 x12: 0000000000000000 
[   35.497764] x11: 0000000000000001 x10: 0000000000000070 
[   35.498611] x9 : ffff8004cb49d610 x8 : 00000000ffffffff 
[   35.499462] x7 : ffff8004c4ff9c70 x6 : ffff8004cb49ccb0 
[   35.500308] x5 : ffff8004c66cc4c0 x4 : 0000000000000001 
[   35.501173] x3 : 0000000000000000 x2 : 0000000000000040 
[   35.502019] x1 : 0000000000000004 x0 : 0000000000000000 
[   35.502872] Process io_uring_regist (pid: 3973, stack limit = 0x(____ptrval____))
[   35.504052] Call trace:
[   35.504463]  link_pwq+0x10/0x60
[   35.504987]  apply_wqattrs_commit+0xe0/0x118
[   35.505681]  apply_workqueue_attrs_locked+0x3c/0x80
[   35.506460]  apply_workqueue_attrs+0x3c/0x60
[   35.507152]  alloc_workqueue+0x264/0x430
[   35.507786]  io_uring_setup+0x478/0x6a8
[   35.508414]  __arm64_sys_io_uring_setup+0x18/0x20
[   35.509183]  el0_svc_common+0x80/0xf0
[   35.509786]  el0_svc_handler+0x2c/0x80
[   35.510393]  el0_svc+0x8/0xc
[   35.510873] Code: a9bd7bfd 910003fd a90153f3 9101c014 (f9403802) 
[   35.511843] ---[ end trace 0a53e45ee26def4c ]---
Segmentation fault