From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tyler Hicks To: op-tee@lists.trustedfirmware.org Subject: Re: [PATCH] optee: Disable shm cache when booting the crash kernel Date: Fri, 07 May 2021 08:17:22 -0500 Message-ID: <20210507131722.GI4967@sequoia> In-Reply-To: < > MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="===============9027060188160228172==" List-Id: --===============9027060188160228172== Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On 2021-05-07 11:23:17, Jens Wiklander wrote: > On Fri, May 7, 2021 at 9:00 AM Allen Pais wro= te: > > > > > > > > > On 07-May-2021, at 9:28 AM, Tyler Hicks = wrote: > > > > > > The .shutdown hook is not called after a kernel crash when a kdump > > > kernel is pre-loaded. A kexec into the kdump kernel takes place as > > > quickly as possible without allowing drivers to clean up. > > > > > > That means that the OP-TEE shared memory cache, which was initialized by > > > the kernel that crashed, is still in place when the kdump kernel is > > > booted. As the kdump kernel is shutdown, the .shutdown hook is called, > > > which calls optee_disable_shm_cache(), and OP-TEE's > > > OPTEE_SMC_DISABLE_SHM_CACHE API returns virtual addresses that are not > > > mapped for the kdump kernel since the cache was set up by the previous > > > kernel. Trying to dereference the tee_shm pointer or otherwise translate > > > the address results in a fault that cannot be handled: > > > > > > Unable to handle kernel paging request at virtual address ffff4317b9c09= 744 > > > Mem abort info: > > > ESR =3D 0x96000004 > > > EC =3D 0x25: DABT (current EL), IL =3D 32 bits > > > SET =3D 0, FnV =3D 0 > > > EA =3D 0, S1PTW =3D 0 > > > Data abort info: > > > ISV =3D 0, ISS =3D 0x00000004 > > > CM =3D 0, WnR =3D 0 > > > swapper pgtable: 4k pages, 48-bit VAs, pgdp=3D0000000970b1e000 > > > [ffff4317b9c09744] pgd=3D0000000000000000, p4d=3D0000000000000000 > > > Internal error: Oops: 96000004 [#1] SMP > > > Modules linked in: bnxt_en pcie_iproc_platform pcie_iproc diagbe(O) > > > CPU: 4 PID: 1 Comm: systemd-shutdow Tainted: G O 5.10.19= .8 #1 > > > Hardware name: Redacted (DT) > > > pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=3D--) > > > pc : tee_shm_free (/usr/src/kernel/drivers/tee/tee_shm.c:363) > > > lr : optee_disable_shm_cache (/usr/src/kernel/drivers/tee/optee/call.c:= 441) > > > sp : ffff80001005bb70 > > > x29: ffff80001005bb70 x28: ffff608e74648e00 > > > x27: ffff80001005bb98 x26: dead000000000100 > > > x25: ffff80001005bbb8 x24: aaaaaaaaaaaaaaaa > > > x23: ffff608e74cf8818 x22: ffff608e738be600 > > > x21: ffff80001005bbc8 x20: ffff608e738be638 > > > x19: ffff4317b9c09700 x18: ffffffffffffffff > > > x17: 0000000000000041 x16: ffffba61b5171764 > > > x15: 0000000000000004 x14: 0000000000000fff > > > x13: ffffba61b5c9dfc8 x12: 0000000000000003 > > > x11: 0000000000000000 x10: 0000000000000000 > > > x9 : ffffba61b5413824 x8 : 00000000ffff4317 > > > x7 : 0000000000000000 x6 : 0000000000000000 > > > x5 : 0000000000000000 x4 : 0000000000000000 > > > x3 : 0000000000000000 x2 : ffff4317b9c09700 > > > x1 : 00000000ffff4317 x0 : ffff4317b9c09700 > > > Call trace: > > > tee_shm_free (/usr/src/kernel/drivers/tee/tee_shm.c:363) > > > optee_disable_shm_cache (/usr/src/kernel/drivers/tee/optee/call.c:441) > > > optee_shutdown (/usr/src/kernel/drivers/tee/optee/core.c:636) > > > platform_drv_shutdown (/usr/src/kernel/drivers/base/platform.c:800) > > > device_shutdown (/usr/src/kernel/include/linux/device.h:758 /usr/src/ke= rnel/drivers/base/core.c:4078) > > > kernel_restart (/usr/src/kernel/kernel/reboot.c:221 /usr/src/kernel/ker= nel/reboot.c:248) > > > __arm64_sys_reboot (/usr/src/kernel/kernel/reboot.c:349 /usr/src/kernel= /kernel/reboot.c:312 /usr/src/kernel/kernel/reboot.c:312) > > > do_el0_svc (/usr/src/kernel/arch/arm64/kernel/syscall.c:56 /usr/src/ker= nel/arch/arm64/kernel/syscall.c:158 /usr/src/kernel/arch/arm64/kernel/syscall= .c:197) > > > el0_svc (/usr/src/kernel/arch/arm64/kernel/entry-common.c:368) > > > el0_sync_handler (/usr/src/kernel/arch/arm64/kernel/entry-common.c:428) > > > el0_sync (/usr/src/kernel/arch/arm64/kernel/entry.S:671) > > > Code: aa0003f3 b5000060 12800003 14000002 (b9404663) > > > > > > When booting the kdump kernel, drain the shared memory cache while being > > > careful to not translate the addresses returned from > > > OPTEE_SMC_DISABLE_SHM_CACHE. Once the invalid cache objects are drained > > > and the cache is disabled, proceed with re-enabling the cache so that we > > > aren't dealing with invalid addresses while shutting down the kdump > > > kernel. > > > > > > Signed-off-by: Tyler Hicks > > > --- > > > > > > This patch fixes a crash introduced by "optee: fix tee out of memory > > > failure seen during kexec reboot"[1]. However, I don't think that the > > > original two patch series[2] plus this patch is the full solution to > > > properly handling OP-TEE shared memory across kexec. > > > > > > While testing this fix, I did about 10 kexec reboots and then triggered > > > a kernel crash by writing 'c' to /proc/sysrq-trigger. The kdump kernel > > > became unresponsive during boot while steadily streaming the following > > > errors to the serial console: > > > > > > arm-smmu 64000000.mmu: Blocked unknown Stream ID 0x2000; boot with "arm= -smmu.disable_bypass=3D0" to allow, but this may have security implications > > > arm-smmu 64000000.mmu: GFSR 0x00000002, GFSYNR0 0x00000002, GFSYNR1= 0x00002000, GFSYNR2 0x00000000 > > > > > > I suspect that this is related to the problems of OP-TEE shared memory > > > handling across kexec. My current hunch is that while we've disabled the > > > shared memory cache with this patch, we haven't unregistered all of the > > > addresses that the previous kernel (which crashed) had registered with > > > OP-TEE and that perhaps OP-TEE OS is still trying to make use those > > > addresses? @Jens did you have any thoughts on what could be happening here with the arm-smmu errors? Do I need to try to unregister the cached shared memory addresses when booting the kdump kernel, rather than just disabling the caches? Tyler > > > > > > I'm still pretty early in investigating that assumption and > > > I'm learning about OP-TEE as I go but I wanted to get this initial > > > fix-of-the-fix out so that it was clear that the v2 of the series[2] is > > > not complete. > > > > > > [1] https://lore.kernel.org/lkml/20210225090610.242623-2-allen.lkml(a)g= mail.com/ > > > [2] https://lore.kernel.org/lkml/20210225090610.242623-1-allen.lkml(a)g= mail.com/#t > > > > > > drivers/tee/optee/call.c | 11 ++++++++++- > > > drivers/tee/optee/core.c | 13 +++++++++++-- > > > drivers/tee/optee/optee_private.h | 2 +- > > > 3 files changed, 22 insertions(+), 4 deletions(-) > > > > > > diff --git a/drivers/tee/optee/call.c b/drivers/tee/optee/call.c > > > index 6132cc8d014c..799e84bec63d 100644 > > > --- a/drivers/tee/optee/call.c > > > +++ b/drivers/tee/optee/call.c > > > @@ -417,8 +417,10 @@ void optee_enable_shm_cache(struct optee *optee) > > > * optee_disable_shm_cache() - Disables caching of some shared memory a= llocation > > > * in OP-TEE > > > * @optee: main service struct > > > + * @is_mapped: true if the cached shared memory addresses were m= apped by this > > > + * kernel, are safe to dereference, and should be freed > > > */ > > > -void optee_disable_shm_cache(struct optee *optee) > > > +void optee_disable_shm_cache(struct optee *optee, bool is_mapped) > > > { > > > struct optee_call_waiter w; > > > > > > @@ -437,6 +439,13 @@ void optee_disable_shm_cache(struct optee *optee) > > > if (res.result.status =3D=3D OPTEE_SMC_RETURN_OK) { > > > struct tee_shm *shm; > > > > > > > Thanks Tyler. > > From what I understand from my email exchange with Jens, I don=E2=80=99t > > Think we want to touch optee_disable_shm_cache(), I could be wrong too, > > @Jens, comments? >=20 > Changing optee_disable_shm_cache() is fine. Bear in mind that there > are other times where we can't recover from a kernel crash. For > instance if a thread is executing in OP-TEE in secure world. >=20 > Cheers, > Jens >=20 --===============9027060188160228172==--