Re: [PATCH v6] tee: optee: Add SMC for loading OP-TEE image

From: Sumit Garg
Date: Wed Mar 15 2023 - 09:56:25 EST

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In reply to: Jeffrey Kardatzke: "Re: [PATCH v6] tee: optee: Add SMC for loading OP-TEE image"
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On Wed, 15 Mar 2023 at 02:26, Jeffrey Kardatzke <jkardatzke@xxxxxxxxxxxx> wrote:
>
> On Tue, Mar 14, 2023 at 5:41 AM Sumit Garg <sumit.garg@xxxxxxxxxx> wrote:
> >
> > On Mon, 13 Mar 2023 at 22:47, Jeffrey Kardatzke <jkardatzke@xxxxxxxxxxxx> wrote:
> > >
> > > On Mon, Mar 13, 2023 at 1:03 AM Sumit Garg <sumit.garg@xxxxxxxxxx> wrote:
> > > >
> > > > On Fri, 10 Mar 2023 at 01:13, Jeffrey Kardatzke <jkardatzke@xxxxxxxxxxxx> wrote:
> > > > >
> > > > > Adds an SMC call that will pass an OP-TEE binary image to EL3 and
> > > > > instruct it to load it as the BL32 payload. This works in conjunction
> > > > > with a feature added to Trusted Firmware for ARMv8 and above
> > > > > architectures that supports this.
> > > > >
> > > > > The main purpose of this change is to facilitate updating the OP-TEE
> > > > > component on devices via a rootfs change rather than having to do a
> > > > > firmware update. Further details are linked to in the Kconfig file.
> > > > >
> > > > > Signed-off-by: Jeffrey Kardatzke <jkardatzke@xxxxxxxxxxxx>
> > > > > Signed-off-by: Jeffrey Kardatzke <jkardatzke@xxxxxxxxxx>
> > > > > ---
> > > > >
> > > > > Changes in v6:
> > > > > - Expanded Kconfig documentation
> > > > >
> > > > > Changes in v5:
> > > > > - Renamed config option
> > > > > - Added runtime warning when config is used
> > > > >
> > > > > Changes in v4:
> > > > > - Update commit message
> > > > > - Added more documentation
> > > > > - Renamed config option, added ARM64 dependency
> > > > >
> > > > > Changes in v3:
> > > > > - Removed state tracking for driver reload
> > > > > - Check UID of service to verify it needs image load
> > > > >
> > > > > Changes in v2:
> > > > > - Fixed compile issue when feature is disabled
> > > > > - Addressed minor comments
> > > > > - Added state tracking for driver reload
> > > > >
> > > > > drivers/tee/optee/Kconfig | 29 +++++++++++
> > > > > drivers/tee/optee/optee_msg.h | 12 +++++
> > > > > drivers/tee/optee/optee_smc.h | 24 +++++++++
> > > > > drivers/tee/optee/smc_abi.c | 97 +++++++++++++++++++++++++++++++++++
> > > > > 4 files changed, 162 insertions(+)
> > > > >
> > > > > diff --git a/drivers/tee/optee/Kconfig b/drivers/tee/optee/Kconfig
> > > > > index f121c224e682..8d4836c58486 100644
> > > > > --- a/drivers/tee/optee/Kconfig
> > > > > +++ b/drivers/tee/optee/Kconfig
> > > > > @@ -7,3 +7,32 @@ config OPTEE
> > > > > help
> > > > > This implements the OP-TEE Trusted Execution Environment (TEE)
> > > > > driver.
> > > > > +
> > > > > +config OPTEE_INSECURE_LOAD_IMAGE
> > > > > + bool "Load OP-TEE image as firmware"
> > > > > + default n
> > > > > + depends on OPTEE && ARM64
> > > > > + help
> > > > > + This loads the BL32 image for OP-TEE as firmware when the driver is
> > > > > + probed. This returns -EPROBE_DEFER until the firmware is loadable from
> > > > > + the filesystem which is determined by checking the system_state until
> > > > > + it is in SYSTEM_RUNNING. This also requires enabling the corresponding
> > > > > + option in Trusted Firmware for Arm. The documentation there explains
> > > > > + the security threat associated with enabling this as well as
> > > > > + mitigations at the firmware and platform level.
> > > > > + https://trustedfirmware-a.readthedocs.io/en/latest/threat_model/threat_model.html
> > > > > +
> > > > > + When utilizing this option, the following mitigations should be
> > > > > + implemented to prevent attacks at the kernel level.
> > > > > + 1. There must be boot chain security that verifies the kernel and
> > > > > + rootfs, otherwise an attacker can modify the loaded OP-TEE binary.
> > > > > + 2. It is recommended to build it as an included driver rather than
> > > > > + a module to prevent exploits that may cause the module to not be
> > > > > + loaded.
> > > > > + 3. If there are alternate methods of booting the device, such as a
> > > > > + recovery mode, it should be ensured that the same mitigations are
> > > > > + applied in that mode.
> > > > > + 4. The OP-TEE driver must be loaded before any potential attack
> > > > > + vectors are opened up. This should include mounting of any
> > > > > + modifiable filesystems, opening of network ports or communicating
> > > > > + with external devices (such a USB).
> > > >
> > > > This detailed threat model documentation belongs here [1] and it
> > > > should rather be in following format for every bullet point:
> > > >
> > > > Attack vector: <>
> > > > Mitigation: <>
> > > >
> > > > [1] https://docs.kernel.org/staging/tee.html?highlight=tee#op-tee-driver
> > > >
> > >
> > > Done in v7 patch set.
> > >
> > > > > diff --git a/drivers/tee/optee/optee_msg.h b/drivers/tee/optee/optee_msg.h
> > > > > index 70e9cc2ee96b..e8840a82b983 100644
> > > > > --- a/drivers/tee/optee/optee_msg.h
> > > > > +++ b/drivers/tee/optee/optee_msg.h
> > > > > @@ -241,11 +241,23 @@ struct optee_msg_arg {
> > > > > * 384fb3e0-e7f8-11e3-af63-0002a5d5c51b.
> > > > > * Represented in 4 32-bit words in OPTEE_MSG_UID_0, OPTEE_MSG_UID_1,
> > > > > * OPTEE_MSG_UID_2, OPTEE_MSG_UID_3.
> > > > > + *
> > > > > + * In the case where the OP-TEE image is loaded by the kernel, this will
> > > > > + * initially return an alternate UID to reflect that we are communicating with
> > > > > + * the TF-A image loading service at that time instead of OP-TEE. That UID is:
> > > > > + * a3fbeab1-1246-315d-c7c4-06b9c03cbea4.
> > > > > + * Represented in 4 32-bit words in OPTEE_MSG_IMAGE_LOAD_UID_0,
> > > > > + * OPTEE_MSG_IMAGE_LOAD_UID_1, OPTEE_MSG_IMAGE_LOAD_UID_2,
> > > > > + * OPTEE_MSG_IMAGE_LOAD_UID_3.
> > > > > */
> > > > > #define OPTEE_MSG_UID_0 0x384fb3e0
> > > > > #define OPTEE_MSG_UID_1 0xe7f811e3
> > > > > #define OPTEE_MSG_UID_2 0xaf630002
> > > > > #define OPTEE_MSG_UID_3 0xa5d5c51b
> > > > > +#define OPTEE_MSG_IMAGE_LOAD_UID_0 0xa3fbeab1
> > > > > +#define OPTEE_MSG_IMAGE_LOAD_UID_1 0x1246315d
> > > > > +#define OPTEE_MSG_IMAGE_LOAD_UID_2 0xc7c406b9
> > > > > +#define OPTEE_MSG_IMAGE_LOAD_UID_3 0xc03cbea4
> > > > > #define OPTEE_MSG_FUNCID_CALLS_UID 0xFF01
> > > > >
> > > > > /*
> > > > > diff --git a/drivers/tee/optee/optee_smc.h b/drivers/tee/optee/optee_smc.h
> > > > > index 73b5e7760d10..7d9fa426505b 100644
> > > > > --- a/drivers/tee/optee/optee_smc.h
> > > > > +++ b/drivers/tee/optee/optee_smc.h
> > > > > @@ -104,6 +104,30 @@ struct optee_smc_call_get_os_revision_result {
> > > > > unsigned long reserved1;
> > > > > };
> > > > >
> > > > > +/*
> > > > > + * Load Trusted OS from optee/tee.bin in the Linux firmware.
> > > > > + *
> > > > > + * WARNING: Use this cautiously as it could lead to insecure loading of the
> > > > > + * Trusted OS.
> > > > > + * This SMC instructs EL3 to load a binary and execute it as the Trusted OS.
> > > > > + *
> > > > > + * Call register usage:
> > > > > + * a0 SMC Function ID, OPTEE_SMC_CALL_LOAD_IMAGE
> > > > > + * a1 Upper 32bit of a 64bit size for the payload
> > > > > + * a2 Lower 32bit of a 64bit size for the payload
> > > > > + * a3 Upper 32bit of the physical address for the payload
> > > > > + * a4 Lower 32bit of the physical address for the payload
> > > > > + *
> > > > > + * The payload is in the OP-TEE image format.
> > > > > + *
> > > > > + * Returns result in a0, 0 on success and an error code otherwise.
> > > > > + */
> > > > > +#define OPTEE_SMC_FUNCID_LOAD_IMAGE 2
> > > > > +#define OPTEE_SMC_CALL_LOAD_IMAGE \
> > > > > + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32, \
> > > > > + ARM_SMCCC_OWNER_TRUSTED_OS_END, \
> > > > > + OPTEE_SMC_FUNCID_LOAD_IMAGE)
> > > > > +
> > > > > /*
> > > > > * Call with struct optee_msg_arg as argument
> > > > > *
> > > > > diff --git a/drivers/tee/optee/smc_abi.c b/drivers/tee/optee/smc_abi.c
> > > > > index a1c1fa1a9c28..00b6b69b6f79 100644
> > > > > --- a/drivers/tee/optee/smc_abi.c
> > > > > +++ b/drivers/tee/optee/smc_abi.c
> > > > > @@ -8,9 +8,11 @@
> > > > >
> > > > > #include <linux/arm-smccc.h>
> > > > > #include <linux/errno.h>
> > > > > +#include <linux/firmware.h>
> > > > > #include <linux/interrupt.h>
> > > > > #include <linux/io.h>
> > > > > #include <linux/irqdomain.h>
> > > > > +#include <linux/kernel.h>
> > > > > #include <linux/mm.h>
> > > > > #include <linux/module.h>
> > > > > #include <linux/of.h>
> > > > > @@ -1149,6 +1151,22 @@ static bool optee_msg_api_uid_is_optee_api(optee_invoke_fn *invoke_fn)
> > > > > return false;
> > > > > }
> > > > >
> > > > > +#ifdef CONFIG_OPTEE_INSECURE_LOAD_IMAGE
> > > > > +static bool optee_msg_api_uid_is_optee_image_load(optee_invoke_fn *invoke_fn)
> > > > > +{
> > > > > + struct arm_smccc_res res;
> > > > > +
> > > > > + invoke_fn(OPTEE_SMC_CALLS_UID, 0, 0, 0, 0, 0, 0, 0, &res);
> > > > > +
> > > > > + if (res.a0 == OPTEE_MSG_IMAGE_LOAD_UID_0 &&
> > > > > + res.a1 == OPTEE_MSG_IMAGE_LOAD_UID_1 &&
> > > > > + res.a2 == OPTEE_MSG_IMAGE_LOAD_UID_2 &&
> > > > > + res.a3 == OPTEE_MSG_IMAGE_LOAD_UID_3)
> > > > > + return true;
> > > > > + return false;
> > > > > +}
> > > > > +#endif
> > > > > +
> > > > > static void optee_msg_get_os_revision(optee_invoke_fn *invoke_fn)
> > > > > {
> > > > > union {
> > > > > @@ -1354,6 +1372,81 @@ static void optee_shutdown(struct platform_device *pdev)
> > > > > optee_disable_shm_cache(optee);
> > > > > }
> > > > >
> > > > > +#ifdef CONFIG_OPTEE_INSECURE_LOAD_IMAGE
> > > > > +
> > > > > +#define OPTEE_FW_IMAGE "optee/tee.bin"
> > > > > +
> > > > > +static int optee_load_fw(struct platform_device *pdev,
> > > > > + optee_invoke_fn *invoke_fn)
> > > > > +{
> > > > > + const struct firmware *fw = NULL;
> > > > > + struct arm_smccc_res res;
> > > > > + phys_addr_t data_pa;
> > > > > + u8 *data_buf = NULL;
> > > > > + u64 data_size;
> > > > > + u32 data_pa_high, data_pa_low;
> > > > > + u32 data_size_high, data_size_low;
> > > > > + int rc;
> > > > > +
> > > > > + if (!optee_msg_api_uid_is_optee_image_load(invoke_fn))
> > > > > + return 0;
> > > > > +
> > > > > + rc = request_firmware(&fw, OPTEE_FW_IMAGE, &pdev->dev);
> > > > > + if (rc) {
> > > > > + /*
> > > > > + * The firmware in the rootfs will not be accessible until we
> > > > > + * are in the SYSTEM_RUNNING state, so return EPROBE_DEFER until
> > > > > + * that point.
> > > > > + */
> > > > > + if (system_state < SYSTEM_RUNNING)
> > > > > + return -EPROBE_DEFER;
> > > > > + goto fw_err;
> > > > > + }
> > > > > +
> > > > > + data_size = fw->size;
> > > > > + /*
> > > > > + * This uses the GFP_DMA flag to ensure we are allocated memory in the
> > > > > + * 32-bit space since TF-A cannot map memory beyond the 32-bit boundary.
> > > > > + */
> > > > > + data_buf = kmalloc(fw->size, GFP_KERNEL | GFP_DMA);
> > > > > + if (!data_buf) {
> > > > > + rc = -ENOMEM;
> > > > > + goto fw_err;
> > > > > + }
> > > > > + memcpy(data_buf, fw->data, fw->size);
> > > > > + data_pa = virt_to_phys(data_buf);
> > > > > + reg_pair_from_64(&data_pa_high, &data_pa_low, data_pa);
> > > > > + reg_pair_from_64(&data_size_high, &data_size_low, data_size);
> > > > > + goto fw_load;
> > > > > +
> > > > > +fw_err:
> > > > > + pr_warn("image loading failed\n");
> > > > > + data_pa_high = data_pa_low = data_size_high = data_size_low = 0;
> > > > > +
> > > > > +fw_load:
> > > > > + /*
> > > > > + * Always invoke the SMC, even if loading the image fails, to indicate
> > > > > + * to EL3 that we have passed the point where it should allow invoking
> > > > > + * this SMC.
> > > > > + */
> > > > > + pr_warn("OP-TEE image loaded from kernel, this can be insecure");
> > > > > + invoke_fn(OPTEE_SMC_CALL_LOAD_IMAGE, data_size_high, data_size_low,
> > > > > + data_pa_high, data_pa_low, 0, 0, 0, &res);
> > > >
> > > > Apart from the security considerations discussed, I see an issue with
> > > > the implementation here. Here you only initialize OP-TEE on *CPUX*
> > > > that is performing OP-TEE probe. IIRC, it is required for that CPUX to
> > > > be primary CPU0. How do we ensure that here?
> > >
> > > I'm not aware of any restrictions that require OP-TEE to be loaded on
> > > CPU0, do you have a point to something that indicates such a
> > > requirement? (it's always worked fine for me no matter what core it
> > > inits on)
> >
> > You can grep in OP-TEE OS code base for keywords like "primary" and
> > "secondary". This will give you an idea how initialization differs
> > among primary and secondary CPUs.
> Yes, I can see there are different things for "primary" vs.
> "secondary", but what I'm not seeing is anything that indicates that
> "primary" must be core 0 and not just the first CPU that boots into
> OP-TEE. Can you point me to anything that establishes that
> requirement?

On most platforms *cold boot* primary CPU is CPU0 and it's an implicit
assumption during boot it will do all the heavy lifting including
handling interrupts. However, at runtime you can always re-route
interrupts or threads and there won't be any difference among CPUs.

>
> >I would be interested to see the
> > OP-TEE init log (LOG_LEVEL = 4) when the primary CPU is *not* CPU0.
> > You can try to force that environment using taskset [1] while
> > installing the OP-TEE module as an out-of-tree build.
>
> OK, here's the log from booting up with that. I changed the log line
> for "Primary CPU initializing" to include the core #.
>
> D/TC:6 plat_get_aslr_seed:111 Warning: no ASLR seed
> D/TC:6 add_phys_mem:635 ROUNDDOWN(0x0C000000 + 0x400000,
> CORE_MMU_PGDIR_SIZE) type IO_SEC 0x0c400000 size 0x00200000
> D/TC:6 add_phys_mem:635 ROUNDDOWN(0x0C000000 + 0x0,
> CORE_MMU_PGDIR_SIZE) type IO_SEC 0x0c000000 size 0x00200000
> D/TC:6 add_phys_mem:635 ROUNDDOWN(0x11001100, CORE_MMU_PGDIR_SIZE)
> type IO_NSEC 0x11000000 size 0x00200000
> D/TC:6 add_phys_mem:635 TEE_SHMEM_START type NSEC_SHM 0x43c00000
> size 0x00200000
> D/TC:6 add_phys_mem:635 TA_RAM_START type TA_RAM 0x43400000 size 0x00800000
> D/TC:6 add_phys_mem:635 VCORE_UNPG_RW_PA type TEE_RAM_RW 0x4325c000
> size 0x001a4000
> D/TC:6 add_phys_mem:635 VCORE_UNPG_RX_PA type TEE_RAM_RX 0x43200000
> size 0x0005c000
> D/TC:6 add_va_space:675 type RES_VASPACE size 0x00a00000
> D/TC:6 add_va_space:675 type SHM_VASPACE size 0x02000000
> D/TC:6 dump_mmap_table:800 type TEE_RAM_RX va
> 0x43200000..0x4325bfff pa 0x43200000..0x4325bfff size 0x0005c000
> (smallpg)
> D/TC:6 dump_mmap_table:800 type TEE_RAM_RW va
> 0x4325c000..0x433fffff pa 0x4325c000..0x433fffff size 0x001a4000
> (smallpg)
> D/TC:6 dump_mmap_table:800 type SHM_VASPACE va
> 0x43400000..0x453fffff pa 0x00000000..0x01ffffff size 0x02000000
> (pgdir)
> D/TC:6 dump_mmap_table:800 type RES_VASPACE va
> 0x45400000..0x45dfffff pa 0x00000000..0x009fffff size 0x00a00000
> (pgdir)
> D/TC:6 dump_mmap_table:800 type IO_SEC va
> 0x45e00000..0x45ffffff pa 0x0c000000..0x0c1fffff size 0x00200000
> (pgdir)
> D/TC:6 dump_mmap_table:800 type IO_SEC va
> 0x46000000..0x461fffff pa 0x0c400000..0x0c5fffff size 0x00200000
> (pgdir)
> D/TC:6 dump_mmap_table:800 type IO_NSEC va
> 0x46200000..0x463fffff pa 0x11000000..0x111fffff size 0x00200000
> (pgdir)
> D/TC:6 dump_mmap_table:800 type TA_RAM va
> 0x46400000..0x46bfffff pa 0x43400000..0x43bfffff size 0x00800000
> (pgdir)
> D/TC:6 dump_mmap_table:800 type NSEC_SHM va
> 0x46c00000..0x46dfffff pa 0x43c00000..0x43dfffff size 0x00200000
> (pgdir)
> D/TC:6 core_mmu_xlat_table_alloc:526 xlat tables used 1 / 5
> D/TC:6 core_mmu_xlat_table_alloc:526 xlat tables used 2 / 5
> I/TC:
> D/TC:6 0 select_vector_wa_spectre_bhb:650 Spectre-BHB CVE-2022-23960
> workaround enabled with "K" = 32
> I/TC: OP-TEE version: Unknown_3.18 (gcc version 11.2.0 (coreboot
> toolchain v_)) #1 Tue Mar 14 18:08:58 UTC 2023 aarch64
> I/TC: WARNING: This OP-TEE configuration might be insecure!
> I/TC: WARNING: Please check
> https://optee.readthedocs.io/en/latest/architecture/porting_guidelines.html
> I/TC: Primary CPU 6 initializing
> D/TC:6 0 boot_init_primary_late:1314 Executing at offset 0 with
> virtual load address 0x43200000
> D/TC:6 0 call_preinitcalls:21 level 2 mobj_mapped_shm_init()
> D/TC:6 0 mobj_mapped_shm_init:463 Shared memory address range:
> 43400000, 45400000
> D/TC:6 0 call_initcalls:40 level 1 register_time_source()
> D/TC:6 0 call_initcalls:40 level 1 teecore_init_pub_ram()
> D/TC:6 0 call_initcalls:40 level 3 check_ta_store()
> D/TC:6 0 check_ta_store:408 TA store: "Secure Storage TA"
> D/TC:6 0 check_ta_store:408 TA store: "REE"
> D/TC:6 0 call_initcalls:40 level 3 verify_pseudo_tas_conformance()
> D/TC:6 0 call_initcalls:40 level 3 tee_cryp_init()
> D/TC:6 0 call_initcalls:40 level 4 tee_fs_init_key_manager()
> D/TC:6 0 call_initcalls:40 level 6 mobj_init()
> D/TC:6 0 call_initcalls:40 level 6 default_mobj_init()
> I/TC: Primary CPU switching to normal world boot
> D/TC:6 tee_entry_exchange_capabilities:100 Asynchronous
> notifications are disabled
> D/TC:6 tee_entry_exchange_capabilities:109 Dynamic shared memory is enabled
> D/TC:6 0 core_mmu_xlat_table_alloc:526 xlat tables used 3 / 5
> D/TC:? 0 tee_ta_init_pseudo_ta_session:296 Lookup pseudo TA
> 7011a688-ddde-4053-a5a9-7b3c4ddf13b8
> D/TC:? 0 tee_ta_init_pseudo_ta_session:309 Open device.pta
> D/TC:? 0 tee_ta_init_pseudo_ta_session:326 device.pta :
> 7011a688-ddde-4053-a5a9-7b3c4ddf13b8
> F/TC:? 0 plat_prng_add_jitter_entropy:72 0xAC2D
> D/TC:? 0 tee_ta_close_session:511 csess 0x43289a10 id 1
> D/TC:? 0 tee_ta_close_session:530 Destroy session
> I/TC: Secondary CPU 4 initializing
> D/TC:4 select_vector_wa_spectre_bhb:650 Spectre-BHB CVE-2022-23960
> workaround enabled with "K" = 32
> I/TC: Secondary CPU 4 switching to normal world boot
> D/TC:? 0 tee_ta_init_pseudo_ta_session:296 Lookup pseudo TA
> a92d116c-ce27-4917-b30c-4a416e2d9351
> D/TC:? 0 ldelf_load_ldelf:96 ldelf load address 0x80006000
> D/LD: ldelf:134 Loading TS a92d116c-ce27-4917-b30c-4a416e2d9351
> F/TC:? 0 trace_syscall:151 syscall #3 (syscall_get_property)
> F/TC:? 0 trace_syscall:151 syscall #5 (syscall_open_ta_session)
> D/TC:? 0 ldelf_syscall_open_bin:142 Lookup user TA ELF
> a92d116c-ce27-4917-b30c-4a416e2d9351 (Secure Storage TA)
> D/TC:? 1 tee_ta_init_session_with_context:606 Re-open TA
> 7011a688-ddde-4053-a5a9-7b3c4ddf13b8
> F/TC:? 1 plat_prng_add_jitter_entropy:72 0xFC
> D/TC:? 1 tee_ta_close_session:511 csess 0x43288b40 id 2
> D/TC:? 1 tee_ta_close_session:530 Destroy session
> F/TC:? 0 plat_prng_add_jitter_entropy:72 0x16
> F/TC:? 0 plat_prng_add_jitter_entropy:72 0x36
> F/TC:? 0 plat_prng_add_jitter_entropy:72 0x23
> D/TC:? 0 ldelf_syscall_open_bin:146 res=0xffff0008
> D/TC:? 0 ldelf_syscall_open_bin:142 Lookup user TA ELF
> a92d116c-ce27-4917-b30c-4a416e2d9351 (REE)
> I/TC: Secondary CPU 1 initializing
> I/TC: Secondary CPU 1 switching to normal world boot
> I/TC: Secondary CPU 5 initializing
> D/TC:5 select_vector_wa_spectre_bhb:650 Spectre-BHB CVE-2022-23960
> workaround enabled with "K" = 32
> I/TC: Secondary CPU 5 switching to normal world boot
> I/TC: Secondary CPU 2 initializing
> I/TC: Secondary CPU 2 switching to normal world boot
> I/TC: Secondary CPU 0 initializing
> I/TC: Secondary CPU 0 switching to normal world boot
> D/TC:? 0 ldelf_syscall_open_bin:146 res=0
> F/TC:? 0 trace_syscall:151 syscall #7 (syscall_invoke_ta_command)
> F/TC:? 0 trace_syscall:151 syscall #11 (syscall_mask_cancellation)
> F/TC:? 0 trace_syscall:151 syscall #7 (syscall_invoke_ta_command)
> F/TC:? 0 trace_syscall:151 syscall #3 (syscall_get_property)
> F/TC:? 0 trace_syscall:151 syscall #8 (syscall_check_access_rights)
> F/TC:? 0 trace_syscall:151 syscall #8 (syscall_check_access_rights)
> F/TC:? 0 plat_prng_add_jitter_entropy:72 0x9B
> I/TC: Secondary CPU 7 initializing
> D/TC:7 select_vector_wa_spectre_bhb:650 Spectre-BHB CVE-2022-23960
> workaround enabled with "K" = 32
> I/TC: Secondary CPU 7 switching to normal world boot
> F/TC:? 0 plat_prng_add_jitter_entropy:72 0x31
> F/TC:? 0 plat_prng_add_jitter_entropy:72 0xB6
> I/TC: Secondary CPU 3 initializing
> I/TC: Secondary CPU 3 switching to normal world boot
> F/TC:? 0 plat_prng_add_jitter_entropy:72 0x23
> F/TC:? 0 trace_syscall:151 syscall #6 (syscall_close_ta_session)
> F/TC:? 0 trace_syscall:151 syscall #3 (syscall_get_property)
> D/LD: ldelf:168 ELF (a92d116c-ce27-4917-b30c-4a416e2d9351) at 0x80049000
> F/TC:? 0 trace_syscall:151 syscall #8 (syscall_check_access_rights)
> F/TC:? 0 trace_syscall:151 syscall #8 (syscall_check_access_rights)
> F/TC:? 0 trace_syscall:151 syscall #4 (syscall_get_property_name_to_index)
> F/TC:? 0 plat_prng_add_jitter_entropy:72 0x38
>

Thanks for this log, I can see how it works.

> >
> > The one thing that essentially pops out to me is that, with the
> > default SPI interrupt routing model (routed to CPU0), OP-TEE won't be
> > able to handle the secure interrupts until it has been initialized on
> > CPU0.
> >
> OK, so the actual concern is that we should initialize on all online
> CPUs at startup or we may miss S-EL1 interrupts, correct?
>

Yeah, having all the CPUs initialized at once would solve the interrupts issue.

> > [1] https://man7.org/linux/man-pages/man1/taskset.1.html
> >
> > > >
> > > > Also, I observe from the TF-A patch that you are doing lazy OP-TEE
> > > > initialization for other secondary CPUs. IOW, if there is an OP-TEE
> > > > SMC call invoked for a particular CPU then only you invoke
> > > > opteed_cpu_on_finish_handler(0) once. This can be a bit unsafe as
> > > > OP-TEE hasn't setup its context for those CPU which may involve some
> > > > CPU specific security bits too such as:
> > > > - GIC CPU interface initialization, secure vs non-secure interrupts.
> > > > - Any platform and CPU specific TrustZone configuration.
> > >
> > > When opteed_cpu_on_finish_handler(0) is invoked...that invokes
> > > opteed_init_optee_ep_state(...) which then sets up the CPU context for
> > > that CPU. It then invokes opteed_synchronous_sp_entry for the
> > > cpu_on_entry handler which should then do any other type of platform
> > > specific initialization in the OP-TEE code itself. What setup in
> > > OP-TEE are you referring to that isn't going to be invoked when doing
> > > it the lazy way?
> >
> > No, I am not worried about any missing setup but rather deferred
> > OP-TEE initialization for secondary CPUs after you open up the Linux
> > attack surface.
>
> What is the concern about initializing on secondary CPUs after the
> attack surface is opened up?

I have already mentions some concerns as follows:

- GIC CPU interface initialization, secure vs non-secure interrupts.
- Any platform and CPU specific TrustZone configuration.

Basically we should have OP-TEE context initialized for every online
core in a safe context to close down any possibilities for a
particular CPU go rogue wrt OP-TEE.

>
> >
> > >
> > > >
> > > > I would have rather expected you to utilize cpuhp_setup_state() and
> > > > friends to initialize OP-TEE for secondary CPUs during boot instead
> > > > which is safe as per your platform threat model.
> > > >
> > > That could be another way to do it (I'm not familiar with that kernel
> > > code currently)..
> >
> > AFAIK, there are many Linux kernel experts within Google who can guide
> > you through.
> >
> I was simply stating that I wasn't familiar with that API...I have no
> problems reading the API and understanding it myself. :)
>

That's good to hear.

> > > but I'd rather stick with what I have unless there is
> > > something technically wrong with it since it's already been approved
> > > in TF-A.
> >
> > We can very well amend the TF-A implementation with a followup patch.
> > Given above comments, the approach to initialize OP-TEE on all CPUs at
> > once during boot should be the correct approach.
> OK, so I've done this now in the v9 patchset. After it loads the
> OP-TEE image, then it invokes cpuhp_setup_state(), which receives a
> callback on each active core, which then simply gets the UID for
> OP-TEE, and that invocation will then cause TF-A to init the context
> for each core. Then it deregisters with cpuhp since that work is done.
> This will then ensure that all cores that have come online will have
> their CPU context initialized for OP-TEE. And any cores that may not
> be online at this time will get initialized when they come back
> online. This *should* address the concerns you have outlined above.

Yeah it does address my concerns. I will review it.

-Sumit

> >
> > -Sumit
> >
> > >
> > > > -Sumit
> > > >
> > > > > + if (!rc)
> > > > > + rc = res.a0;
> > > > > + if (fw)
> > > > > + release_firmware(fw);
> > > > > + kfree(data_buf);
> > > > > +
> > > > > + return rc;
> > > > > +}
> > > > > +#else
> > > > > +static inline int optee_load_fw(struct platform_device *__unused1,
> > > > > + optee_invoke_fn *__unused2) {
> > > > > + return 0;
> > > > > +}
> > > > > +#endif
> > > > > +
> > > > > static int optee_probe(struct platform_device *pdev)
> > > > > {
> > > > > optee_invoke_fn *invoke_fn;
> > > > > @@ -1372,6 +1465,10 @@ static int optee_probe(struct platform_device *pdev)
> > > > > if (IS_ERR(invoke_fn))
> > > > > return PTR_ERR(invoke_fn);
> > > > >
> > > > > + rc = optee_load_fw(pdev, invoke_fn);
> > > > > + if (rc)
> > > > > + return rc;
> > > > > +
> > > > > if (!optee_msg_api_uid_is_optee_api(invoke_fn)) {
> > > > > pr_warn("api uid mismatch\n");
> > > > > return -EINVAL;
> > > > > --
> > > > > 2.40.0.rc1.284.g88254d51c5-goog
> > > > >

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