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Date: Thu, 23 Feb 2023 10:28:29 +0100
From: Jens Wiklander <jens.wiklander@...aro.org>
To: Jeffrey Kardatzke <jkardatzke@...omium.org>
Cc: op-tee@...ts.trustedfirmware.org,
Jeffrey Kardatzke <jkardatzke@...gle.com>,
Sumit Garg <sumit.garg@...aro.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tee: optee: Add SMC for loading OP-TEE image
Hi,
On Wed, Feb 22, 2023 at 6:24 PM Jeffrey Kardatzke
<jkardatzke@...omium.org> 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 ARM that supports this.
>
> Signed-off-by: Jeffrey Kardatzke <jkardatzke@...omium.org>
> Signed-off-by: Jeffrey Kardatzke <jkardatzke@...gle.com>
> ---
>
> drivers/tee/optee/Kconfig | 10 +++++
> drivers/tee/optee/optee_msg.h | 14 +++++++
> drivers/tee/optee/optee_smc.h | 22 ++++++++++
> drivers/tee/optee/smc_abi.c | 77 +++++++++++++++++++++++++++++++++++
> 4 files changed, 123 insertions(+)
>
> diff --git a/drivers/tee/optee/Kconfig b/drivers/tee/optee/Kconfig
> index f121c224e682..5ffbeb3eaac0 100644
> --- a/drivers/tee/optee/Kconfig
> +++ b/drivers/tee/optee/Kconfig
> @@ -7,3 +7,13 @@ config OPTEE
> help
> This implements the OP-TEE Trusted Execution Environment (TEE)
> driver.
> +
> +config OPTEE_LOAD_IMAGE
> + bool "Load Op-Tee image as firmware"
OP-TEE
> + default n
> + depends on OPTEE
> + 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.
> diff --git a/drivers/tee/optee/optee_msg.h b/drivers/tee/optee/optee_msg.h
> index 70e9cc2ee96b..84c1b15032a9 100644
> --- a/drivers/tee/optee/optee_msg.h
> +++ b/drivers/tee/optee/optee_msg.h
> @@ -284,6 +284,20 @@ struct optee_msg_arg {
> */
> #define OPTEE_MSG_FUNCID_GET_OS_REVISION 0x0001
>
> +/*
> + * 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 excute it as the Trusted OS.
> + * The first two params are the high and low 32 bits of the size of the payload
> + * and the third and fourth params are the high and low 32 bits of the physical
> + * address of the payload. The payload is in the OP-TEE image format.
> + *
> + * Returns 0 on success and an error code otherwise.
> + */
> +#define OPTEE_MSG_FUNCID_LOAD_IMAGE 0x0002
There's no need to add anything to this file, you can define
OPTEE_SMC_FUNCID_LOAD_IMAGE to 2 directly in optee_smc.h below.
> +
> /*
> * Do a secure call with struct optee_msg_arg as argument
> * The OPTEE_MSG_CMD_* below defines what goes in struct optee_msg_arg::cmd
> diff --git a/drivers/tee/optee/optee_smc.h b/drivers/tee/optee/optee_smc.h
> index 73b5e7760d10..908b1005e9db 100644
> --- a/drivers/tee/optee/optee_smc.h
> +++ b/drivers/tee/optee/optee_smc.h
> @@ -104,6 +104,28 @@ 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 excute it as the Trusted OS.
execute
> + *
> + * 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 OPTEE_MSG_FUNCID_LOAD_IMAGE
> +#define OPTEE_SMC_CALL_LOAD_IMAGE \
> + OPTEE_SMC_FAST_CALL_VAL(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..c1abbee86b39 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>
> @@ -1354,6 +1356,77 @@ static void optee_shutdown(struct platform_device *pdev)
> optee_disable_shm_cache(optee);
> }
>
> +#ifdef CONFIG_OPTEE_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;
> +
> + 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.
> + */
> + invoke_fn(OPTEE_SMC_CALL_LOAD_IMAGE, data_size_high, data_size_low,
> + data_pa_high, data_pa_low, 0, 0, 0, &res);
Prior to this, you've done nothing to check that the firmware might do
what you're expecting. optee_msg_api_uid_is_optee_api() does this
under normal circumstances as that SMC function is defined in the SMC
Calling Convention. I'm not sure what is the best approach here
though.
> + 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 *__unused,
> + optee_invoke_fn *__unused) {
> + return 0;
> +}
> +#endif
> +
> static int optee_probe(struct platform_device *pdev)
> {
> optee_invoke_fn *invoke_fn;
> @@ -1372,6 +1445,10 @@ 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;
What if OP-TEE already was loaded?
This also causes trouble if unloading and loading the driver again.
I think we need a way of telling if OP-TEE must be loaded first or not.
Thanks,
Jens
> +
> if (!optee_msg_api_uid_is_optee_api(invoke_fn)) {
> pr_warn("api uid mismatch\n");
> return -EINVAL;
> --
> 2.39.2.637.g21b0678d19-goog
>
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