Re: [PATCH v2 4/4] remoteproc: stm32: Add support of an OP-TEE TA to load the firmware

[Mathieu Poirier]

On Thu, Jan 18, 2024 at 11:04:33AM +0100, Arnaud Pouliquen wrote:
> The new TEE remoteproc device is used to manage remote firmware in a
> secure, trusted context. The 'st,stm32mp1-m4-tee' compatibility is
> introduced to delegate the loading of the firmware to the trusted
> execution context. In such cases, the firmware should be signed and
> adhere to the image format defined by the TEE.
> 
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxxxxxxx>
> ---
> V1 to V2 update:
> - remove the select "TEE_REMOTEPROC" in STM32_RPROC config as detected by
>   the kernel test robot:
>      WARNING: unmet direct dependencies detected for TEE_REMOTEPROC
>      Depends on [n]: REMOTEPROC [=y] && OPTEE [=n]
>      Selected by [y]:
>      - STM32_RPROC [=y] && (ARCH_STM32 || COMPILE_TEST [=y]) && REMOTEPROC [=y]
> - Fix initialized trproc variable in  stm32_rproc_probe
> ---
>  drivers/remoteproc/stm32_rproc.c | 149 +++++++++++++++++++++++++++++--
>  1 file changed, 144 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/remoteproc/stm32_rproc.c b/drivers/remoteproc/stm32_rproc.c
> index fcc0001e2657..cf6a21bac945 100644
> --- a/drivers/remoteproc/stm32_rproc.c
> +++ b/drivers/remoteproc/stm32_rproc.c
> @@ -20,6 +20,7 @@
>  #include <linux/remoteproc.h>
>  #include <linux/reset.h>
>  #include <linux/slab.h>
> +#include <linux/tee_remoteproc.h>
>  #include <linux/workqueue.h>
>  
>  #include "remoteproc_internal.h"
> @@ -49,6 +50,9 @@
>  #define M4_STATE_STANDBY	4
>  #define M4_STATE_CRASH		5
>  
> +/* Remote processor unique identifier aligned with the Trusted Execution Environment definitions */
> +#define STM32_MP1_M4_PROC_ID    0
> +
>  struct stm32_syscon {
>  	struct regmap *map;
>  	u32 reg;
> @@ -90,6 +94,8 @@ struct stm32_rproc {
>  	struct stm32_mbox mb[MBOX_NB_MBX];
>  	struct workqueue_struct *workqueue;
>  	bool hold_boot_smc;
> +	bool fw_loaded;
> +	struct tee_rproc *trproc;
>  	void __iomem *rsc_va;
>  };
>  
> @@ -257,6 +263,91 @@ static int stm32_rproc_release(struct rproc *rproc)
>  	return err;
>  }
>  
> +static int stm32_rproc_tee_elf_sanity_check(struct rproc *rproc,
> +					    const struct firmware *fw)
> +{
> +	struct stm32_rproc *ddata = rproc->priv;
> +	unsigned int ret = 0;
> +
> +	if (rproc->state == RPROC_DETACHED)
> +		return 0;
> +
> +	ret = tee_rproc_load_fw(ddata->trproc, fw);
> +	if (!ret)
> +		ddata->fw_loaded = true;
> +
> +	return ret;
> +}
> +
> +static int stm32_rproc_tee_elf_load(struct rproc *rproc,
> +				    const struct firmware *fw)
> +{
> +	struct stm32_rproc *ddata = rproc->priv;
> +	unsigned int ret;
> +
> +	/*
> +	 * This function can be called by remote proc for recovery
> +	 * without the sanity check. In this case we need to load the firmware
> +	 * else nothing done here as the firmware has been preloaded for the
> +	 * sanity check to be able to parse it for the resource table.
> +	 */

This comment is very confusing - please consider refactoring.  

> +	if (ddata->fw_loaded)
> +		return 0;
> +

I'm not sure about keeping a flag to indicate the status of the loaded firmware.
It is not done for the non-secure method, I don't see why it would be needed for
the secure one.

> +	ret = tee_rproc_load_fw(ddata->trproc, fw);
> +	if (ret)
> +		return ret;
> +	ddata->fw_loaded = true;
> +
> +	/* Update the resource table parameters. */
> +	if (rproc_tee_get_rsc_table(ddata->trproc)) {
> +		/* No resource table: reset the related fields. */
> +		rproc->cached_table = NULL;
> +		rproc->table_ptr = NULL;
> +		rproc->table_sz = 0;
> +	}
> +
> +	return 0;
> +}
> +
> +static struct resource_table *
> +stm32_rproc_tee_elf_find_loaded_rsc_table(struct rproc *rproc,
> +					  const struct firmware *fw)
> +{
> +	struct stm32_rproc *ddata = rproc->priv;
> +
> +	return tee_rproc_get_loaded_rsc_table(ddata->trproc);
> +}
> +
> +static int stm32_rproc_tee_start(struct rproc *rproc)
> +{
> +	struct stm32_rproc *ddata = rproc->priv;
> +
> +	return tee_rproc_start(ddata->trproc);
> +}
> +
> +static int stm32_rproc_tee_attach(struct rproc *rproc)
> +{
> +	/* Nothing to do, remote proc already started by the secured context. */
> +	return 0;
> +}
> +
> +static int stm32_rproc_tee_stop(struct rproc *rproc)
> +{
> +	struct stm32_rproc *ddata = rproc->priv;
> +	int err;
> +
> +	stm32_rproc_request_shutdown(rproc);
> +
> +	err = tee_rproc_stop(ddata->trproc);
> +	if (err)
> +		return err;
> +
> +	ddata->fw_loaded = false;
> +
> +	return stm32_rproc_release(rproc);
> +}
> +
>  static int stm32_rproc_prepare(struct rproc *rproc)
>  {
>  	struct device *dev = rproc->dev.parent;
> @@ -319,7 +410,14 @@ static int stm32_rproc_prepare(struct rproc *rproc)
>  
>  static int stm32_rproc_parse_fw(struct rproc *rproc, const struct firmware *fw)
>  {
> -	if (rproc_elf_load_rsc_table(rproc, fw))
> +	struct stm32_rproc *ddata = rproc->priv;
> +	int ret;
> +
> +	if (ddata->trproc)
> +		ret = rproc_tee_get_rsc_table(ddata->trproc);
> +	else
> +		ret = rproc_elf_load_rsc_table(rproc, fw);
> +	if (ret)
>  		dev_warn(&rproc->dev, "no resource table found for this firmware\n");
>  
>  	return 0;
> @@ -693,8 +791,22 @@ static const struct rproc_ops st_rproc_ops = {
>  	.get_boot_addr	= rproc_elf_get_boot_addr,
>  };
>  
> +static const struct rproc_ops st_rproc_tee_ops = {
> +	.prepare	= stm32_rproc_prepare,
> +	.start		= stm32_rproc_tee_start,
> +	.stop		= stm32_rproc_tee_stop,
> +	.attach		= stm32_rproc_tee_attach,
> +	.kick		= stm32_rproc_kick,
> +	.parse_fw	= stm32_rproc_parse_fw,
> +	.find_loaded_rsc_table = stm32_rproc_tee_elf_find_loaded_rsc_table,
> +	.get_loaded_rsc_table = stm32_rproc_get_loaded_rsc_table,
> +	.sanity_check	= stm32_rproc_tee_elf_sanity_check,
> +	.load		= stm32_rproc_tee_elf_load,
> +};
> +
>  static const struct of_device_id stm32_rproc_match[] = {
> -	{ .compatible = "st,stm32mp1-m4" },
> +	{.compatible = "st,stm32mp1-m4",},
> +	{.compatible = "st,stm32mp1-m4-tee",},
>  	{},
>  };
>  MODULE_DEVICE_TABLE(of, stm32_rproc_match);
> @@ -853,6 +965,7 @@ static int stm32_rproc_probe(struct platform_device *pdev)
>  	struct device *dev = &pdev->dev;
>  	struct stm32_rproc *ddata;
>  	struct device_node *np = dev->of_node;
> +	struct tee_rproc *trproc = NULL;
>  	struct rproc *rproc;
>  	unsigned int state;
>  	int ret;
> @@ -861,11 +974,31 @@ static int stm32_rproc_probe(struct platform_device *pdev)
>  	if (ret)
>  		return ret;
>  
> -	rproc = rproc_alloc(dev, np->name, &st_rproc_ops, NULL, sizeof(*ddata));
> -	if (!rproc)
> -		return -ENOMEM;
> +	if (of_device_is_compatible(np, "st,stm32mp1-m4-tee")) {
> +		trproc = tee_rproc_register(dev, STM32_MP1_M4_PROC_ID);
> +		if (IS_ERR(trproc)) {
> +			dev_err_probe(dev, PTR_ERR(trproc),
> +				      "signed firmware not supported by TEE\n");
> +			return PTR_ERR(trproc);
> +		}
> +		/*
> +		 * Delegate the firmware management to the secure context.
> +		 * The firmware loaded has to be signed.
> +		 */
> +		dev_info(dev, "Support of signed firmware only\n");

Not sure what this adds.  Please remove.

> +	}
> +	rproc = rproc_alloc(dev, np->name,
> +			    trproc ? &st_rproc_tee_ops : &st_rproc_ops,
> +			    NULL, sizeof(*ddata));
> +	if (!rproc) {
> +		ret = -ENOMEM;
> +		goto free_tee;
> +	}
>  
>  	ddata = rproc->priv;
> +	ddata->trproc = trproc;
> +	if (trproc)
> +		trproc->rproc = rproc;
>  
>  	rproc_coredump_set_elf_info(rproc, ELFCLASS32, EM_NONE);
>  
> @@ -916,6 +1049,10 @@ static int stm32_rproc_probe(struct platform_device *pdev)
>  		device_init_wakeup(dev, false);
>  	}
>  	rproc_free(rproc);
> +free_tee:
> +	if (trproc)
> +		tee_rproc_unregister(trproc);
> +
>  	return ret;
>  }
>  
> @@ -937,6 +1074,8 @@ static void stm32_rproc_remove(struct platform_device *pdev)
>  		device_init_wakeup(dev, false);
>  	}
>  	rproc_free(rproc);
> +	if (ddata->trproc)
> +		tee_rproc_unregister(ddata->trproc);
>  }
>  
>  static int stm32_rproc_suspend(struct device *dev)
> -- 
> 2.25.1
>