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Date:   Mon, 9 Apr 2018 18:57:51 +0900
From:   Jean-Baptiste Theou <jb@essential.com>
To:     Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc:     Greg KH <gregkh@linuxfoundation.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Will Deacon <will.deacon@arm.com>,
        Dan Rue <dan.rue@linaro.org>,
        Mark Brown <mark.brown@linaro.org>,
        Marc Zyngier <marc.zyngier@arm.com>,
        Greg Hackmann <ghackmann@google.com>
Subject: Re: Linux 4.9.93
Message-ID: <20180409185751.247a0ac7@jbtheou>
In-Reply-To: <CAKv+Gu9Ny=EatuqrVOEFbOt+h0rH5uqxxDyHFT-PLH72ZzvZiw@mail.gmail.com>
References: <20180409180534.1768583293d0abe207168c5a@essential.com>
        <20180409093028.GA3398@kroah.com>
        <CAKv+Gu9Ny=EatuqrVOEFbOt+h0rH5uqxxDyHFT-PLH72ZzvZiw@mail.gmail.com>
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On Mon, 9 Apr 2018 11:49:37 +0200
Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:

> On 9 April 2018 at 11:30, Greg KH <gregkh@linuxfoundation.org> wrote:
> > On Mon, Apr 09, 2018 at 06:05:34PM +0900, Jean-Baptiste Theou wrote: =20
> >> Hi,
> >>
> >> After this patchset, a kernel built with CFI fails. Disabling
> >> UNMAP_KERNEL_AT_EL0 fix the issue obviously. =20
>=20
> How does one 'build a kernel with CFI' for arm64?

=46rom Google work on Android-4.9

https://android.googlesource.com/kernel/common/+/00a195e7c0752ff5d65c9caadf=
bcc226270ca232

I am not sure what is the plan on their side to upstream (Greg?), but defin=
itely
useful to isolate actual issues.

>=20
> >
> > Is this a "clean" 4.9.93 tree or a "4.9.93 merged into
> > android-common-4.9?

It's a "clean 4.9.93" + whatever is needed for Clang/CFI support

My take is that CFI doesn't like=20

 * void __kpti_install_ng_mappings(int cpu, int num_cpus, phys_addr_t swapp=
er)

and=20

remap_fn =3D (void *)__pa_symbol(idmap_kpti_install_ng_mappings);

Maybe just flag this function to not use CFI? I remember that Sami Tolvanen=
 did
similar changes.

I know it's a bit out of context since CFI support for ARM64 is not upstrea=
m yet,
but unfortunate that an stable patchset trigger such failures.

Thanks a lot

Best regards

> > =20
> >> Wondering if there is one of the test suite used on the review patchse=
t that covers the CFI usecase.
> >>
> >> Best regards,
> >>
> >> [    0.249191] CPU features: detected feature: GIC system register CPU=
 interface
> >> [    0.256391] CPU features: detected feature: Privileged Access Never
> >> [    0.262719] CPU features: detected feature: User Access Override
> >> [    0.268791] CPU features: detected feature: 32-bit EL0 Support
> >> [    0.274683] CPU features: detected feature: Kernel page table isola=
tion (KPTI)
> >> [    0.282166] CFI failure:
> >> [    0.282169] CFI failure:
> >> [    0.282172] CFI failure:
> >> [    0.282173] CFI failure:
> >> [    0.282175] CFI failure:
> >> [    0.282176] CFI failure:
> >> [    0.282177] CFI failure:
> >> [    0.282178] CFI failure:
> >> [    0.282188] ------------[ cut here ]------------
> >> [    0.282189] ------------[ cut here ]------------
> >> [    0.282190] ------------[ cut here ]------------
> >> [    0.282191] ------------[ cut here ]------------
> >> [    0.282193] ------------[ cut here ]------------
> >> [    0.282196] kernel BUG at kernel/cfi.c:32!
> >> [    0.282198] ------------[ cut here ]------------
> >> [    0.282201] kernel BUG at kernel/cfi.c:32!
> >> [    0.282202] ------------[ cut here ]------------
> >> [    0.282204] kernel BUG at kernel/cfi.c:32!
> >> [    0.282207] kernel BUG at kernel/cfi.c:32!
> >> [    0.282209] kernel BUG at kernel/cfi.c:32!
> >> [    0.282211] kernel BUG at kernel/cfi.c:32!
> >> [    0.282214] kernel BUG at kernel/cfi.c:32!
> >> [    0.282215] ------------[ cut here ]------------
> >> [    0.282216] kernel BUG at kernel/cfi.c:32!
> >> [    0.282218] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
> >> [    0.282224] Modules linked in:
> >> [    0.282230] CPU: 2 PID: 25 Comm: migration/2 Not tainted 4.9.93-per=
f+ #39
> >> [    0.282232] Hardware name: <REMOVED>
> >> [    0.282235] task: fffffffbb3b36580 task.stack: fffffffbb30cc000
> >> [    0.282250] PC is at __cfi_check_fail+0x14/0x1c
> >> [    0.282253] LR is at __cfi_check_fail+0x14/0x1c
> >> [    0.282255] pc : [<ffffff93b3f03d90>] lr : [<ffffff93b3f03d90>] pst=
ate: 60c00085
> >> [    0.282256] sp : fffffffbb30cfc30
> >> [    0.282259] x29: fffffffbb30cfc30 x28: ffffff93b6415000
> >> [    0.282261] x27: 00000013b65c1000 x26: ffffff93b5ce6000
> >> [    0.282264] x25: ffffff93b5ce6000 x24: ffffff93b6419000
> >> [    0.282266] x23: ffffff93b65c1000 x22: ffffff93b65c4000
> >> [    0.282268] x21: 9d12f8172cb2f296 x20: 000000008180e3e0
> >> [    0.282271] x19: 0000000000000000 x18: 000000000000002c
> >> [    0.282274] x17: 00000000000fd054 x16: 0000000000000000
> >> [    0.282276] x15: ffffff93b65ec000 x14: 000000000000000c
> >> [    0.282279] x13: 0000000000000004 x12: 0000000000000000
> >> [    0.282281] x11: 0000000000000000 x10: 0000000001440144
> >> [    0.282283] x9 : 260822e8751d5000 x8 : 260822e8751d5000
> >> [    0.282286] x7 : 0000000000000000 x6 : fffffffbbac75b60
> >> [    0.282288] x5 : 0000000000000000 x4 : 0000000000000000
> >> [    0.282290] x3 : 000000003a657275 x2 : 0000000000000000
> >> [    0.282292] x1 : 0000000000000000 x0 : 000000000000000c
> >> [    0.282294]
> >> [    0.282294] PC: 0xffffff93b3f03d50:
> >> [    0.282308] 3d50  b9001ac8 f94002c8 370ffec8 17ffffbe d4210000 1400=
0000 aa1603e0 f90007e8
> >> [    0.282315] 3d70  94536017 f94007e8 17ffffe2 a9bf7bfd 910003fd d000=
d100 913ee400 94533cc7
> >> [    0.282322] 3d90  d4210000 14000000 b0013788 2a1f03e0 f901c51f d65f=
03c0 f940406b 2a0203e8
> >> [    0.282329] 3db0  2a0103e9 aa0003ea b400008b f9000145 f94000cb b400=
01ab a9bf7bfd 910003fd
> >> [    0.282330]
> >> [    0.282330] LR: 0xffffff93b3f03d50:
> >> [    0.282336] 3d50  b9001ac8 f94002c8 370ffec8 17ffffbe d4210000 1400=
0000 aa1603e0 f90007e8
> >> [    0.282343] 3d70  94536017 f94007e8 17ffffe2 a9bf7bfd 910003fd d000=
d100 913ee400 94533cc7
> >> [    0.282350] 3d90  d4210000 14000000 b0013788 2a1f03e0 f901c51f d65f=
03c0 f940406b 2a0203e8
> >> [    0.282357] 3db0  2a0103e9 aa0003ea b400008b f9000145 f94000cb b400=
01ab a9bf7bfd 910003fd
> >> [    0.282358]
> >> [    0.282358] SP: 0xfffffffbb30cfbf0:
> >> [    0.282365] fbf0  b3f03d90 ffffff93 b30cfc30 fffffffb b3f03d90 ffff=
ff93 60c00085 00000000
> >> [    0.282372] fc10  b6415000 ffffff93 b642fa00 ffffff93 ffffffff ffff=
ffff b3f03d90 ffffff93
> >> [    0.282378] fc30  b30cfc70 fffffffb b3d458c0 ffffff93 00000080 0000=
0000 00000001 00000000
> >> [    0.282385] fc50  b65c4000 ffffff93 b64420f0 ffffff93 8180e3e0 0000=
0000 00000002 00000000
> >> [    0.282387] Process migration/2 (pid: 25, stack limit =3D 0xfffffff=
bb30cc000)
> >> [    0.282389] Call trace:
> >> [    0.282391] Exception stack(0xfffffffbb30cfb00 to 0xfffffffbb30cfc3=
0)
> >> [    0.282395] fb00: 000000000000000c 0000000000000000 000000000000000=
0 000000003a657275
> >> [    0.282397] fb20: 0000000000000000 0000000000000000 fffffffbbac75b6=
0 0000000000000000
> >> [    0.282400] fb40: 260822e8751d5000 260822e8751d5000 000000000144014=
4 0000000000000000
> >> [    0.282403] fb60: 0000000000000000 0000000000000004 000000000000000=
c ffffff93b65ec000
> >> [    0.282405] fb80: 0000000000000000 00000000000fd054 000000000000002=
c 0000000000000000
> >> [    0.282408] fba0: 000000008180e3e0 9d12f8172cb2f296 ffffff93b65c400=
0 ffffff93b65c1000
> >> [    0.282411] fbc0: ffffff93b6419000 ffffff93b5ce6000 ffffff93b5ce600=
0 00000013b65c1000
> >> [    0.282413] fbe0: ffffff93b6415000 fffffffbb30cfc30 ffffff93b3f03d9=
0 fffffffbb30cfc30
> >> [    0.282416] fc00: ffffff93b3f03d90 0000000060c00085 ffffff93b641500=
0 ffffff93b642fa00
> >> [    0.282418] fc20: ffffffffffffffff ffffff93b3f03d90
> >> [    0.282421] [<ffffff93b3f03d90>] __cfi_check_fail+0x14/0x1c
> >> [    0.282430] [<ffffff93b3d458c0>] name_to_dev_t+0x0/0x47c
> >> [    0.282436] [<ffffff93b3d51b80>] kpti_install_ng_mappings+0x178/0x2=
e0
> >> [    0.282443] [<ffffff93b3eae950>] multi_cpu_stop+0x114/0x170
> >> [    0.282445] [<ffffff93b3eaf08c>] cpu_stopper_thread+0x128/0x2e8
> >> [    0.282452] [<ffffff93b3db5504>] smpboot_thread_fn+0x230/0x558
> >> [    0.282455] [<ffffff93b3dae848>] kthread+0x21c/0x238
> >> [    0.282459] [<ffffff93b3c838f0>] ret_from_fork+0x10/0x20
> >> [    0.282464] Code: 910003fd d000d100 913ee400 94533cc7 (d4210000) =20
> >
> > Oh fun :(
> >
> > Dragging in a bunch more people to the cc: and to: lines to have them
> > look at this...
> >
> > thanks,
> >
> > greg k-h =20