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

From: Arnaud POULIQUEN
Date: Thu Feb 01 2024 - 13:59:39 EST

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In reply to: Mathieu Poirier: "Re: [PATCH v2 4/4] remoteproc: stm32: Add support of an OP-TEE TA to load the firmware"
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On 2/1/24 17:02, Mathieu Poirier wrote:
> On Thu, Feb 01, 2024 at 04:06:37PM +0100, Arnaud POULIQUEN wrote:
>> hello Mathieu,
>>
>> On 1/31/24 19:52, Mathieu Poirier wrote:
>>> On Tue, Jan 30, 2024 at 10:13:48AM +0100, Arnaud POULIQUEN wrote:
>>>>
>>>>
>>>> On 1/26/24 18:11, Mathieu Poirier wrote:
>>>>> 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.
>>>>>
>>>>
>>>> The difference is on the sanity check.
>>>> - in rproc_elf_sanity_check we parse the elf file to verify that it is
>>>> valid.
>>>> - in stm32_rproc_tee_elf_sanity_check we have to do the same, that means to
>>>> authenticate it. the authentication is done during the load.
>>>>
>>>> So this flag is used to avoid to reload it twice time.
>>>> refactoring the comment should help to understand this flag
>>>>
>>>>
>>>> An alternative would be to bypass the sanity check. But this lead to same
>>>> limitation.
>>>> Before loading the firmware in remoteproc_core, we call rproc_parse_fw() that is
>>>> used to get the resource table address. To get it from tee we need to
>>>> authenticate the firmware so load it...
>>>>
>>>
>>> I spent a long time thinking about this patchset. Looking at the code as it
>>> is now, request_firmware() in rproc_boot() is called even when the TEE is
>>> responsible for loading the firmware. There should be some conditional code
>>> that calls either request_firmware() or tee_rproc_load_fw(). The latter should
>>> also be renamed to tee_rproc_request_firmware() to avoid confusion.
>>
>>
>> The request_firmware() call is needed in both cases to get the image from the
>> filesystem. The tee_rproc_load_fw() gets, as input, the struct firmware provided
>> by request_firmware().
>
> The cover letter clearly state the secure side is responsible for loading the
> firmware image but here you're telling me it has to be loaded twice. This is
> very confusing.

Concerning the call of request_firmware()

By "both cases" I would say that the call of request_firmware() is needed in
both modes:
- the ELF firmware is parsed and loaded by linux (legacy)
- the binary firmware is parsed and loaded by OP-TEE.

The Op-TEE is not able to get the firmware image from the file system.

Concerning the call of tee_rproc_load_fw twice time

There are 2 use cases:

- First boot of the remote processor:

1) The Linux rproc gets the binary firmware image from the file system by
calling request_firmware(). A copy is stored in memory.
2) the linux performs a sanity check on the firmware calling
rproc_fw_sanity_check()
=> from OP-TEE point of view this means to autenticate the firmware
=> let consider in this exemple that we bypass this step
(ops->sanity_check = NULL)

3) the linux rproc call rproc_parse_fw() to get the resource table
=> From OP-TEE point of view the resource table is available only when
the firmware is loaded
=> We need to call tee_rproc_load_fw() to be able then to get the
address of the resource table.
4) The Linux rproc calls rproc_handle_resources() to parse the resource table.
5) The linux rproc calls rproc_start()
- load the firrmware calling rproc_load_segments()
=> we don't want to call tee_rproc_load_fw() it a second time
- start the firmware calling ops->start()

- Reboot on crash recovery using rproc_boot_recovery()

1) The Linux rproc gets the binary firmware image from the file system by
calling request_firmware(). A copy is stored in memory.
5) The linux rproc calls rproc_start()
- load the firrmware calling rproc_load_segments()
=> we have to call tee_rproc_load_fw() to reload the firmware
- start the firmware calling ops->start()

In first use case we have to load the firmware on rproc_parse_fw(), in second
usecase on rproc_load_segments().

This is the point I have tried to solve with the ddata->fw_loaded variable.

>
> I'm also confused as to why stm32_rproc_tee_elf_sanity_check() is calling
> tee_rproc_load_fw(). There should be one call to load the firmware and another
> to perform a sanity check on it. If the sanity check is done at load time by
> the secure world then ops::sanity_check() is NULL.

Sure, make sense to remove the sanity_check ops

Thanks,
Arnaud

>
> Most of what this patchset does makes sense, but some of it needs to be moved
> around.
>
> Thanks,
> Mathieu
>
>>
>> If we want to integrate in remoteproc_core the solution could probably have to
>> create the equivalent of the rproc_fw_boot() to load the firmware with an
>> external method. Here is an example based on a new rproc_ops ( not tested)
>>
>> + static int rproc_fw_ext_boot(struct rproc *rproc, const struct firmware *fw)
>> + {
>> + struct device *dev = &rproc->dev;
>> + const char *name = rproc->firmware;
>> + int ret;
>> +
>> +
>> + dev_info(dev, "Booting fw image %s, size %zd\n", name, fw->size);
>> +
>> + /* ops to load and start the remoteprocessor */
>> + ret = rproc->ops->boot(rproc, fw);
>> + if (ret)
>> + return ret;
>> +
>> + /*
>> + * if enabling an IOMMU isn't relevant for this rproc, this is
>> + * just a nop
>> + */
>> + ret = rproc_enable_iommu(rproc);
>> + if (ret) {
>> + dev_err(dev, "can't enable iommu: %d\n", ret);
>> + return ret;
>> + }
>> +
>> + /* Prepare rproc for firmware loading if needed */
>> + ret = rproc_prepare_device(rproc);
>> + if (ret) {
>> + dev_err(dev, "can't prepare rproc %s: %d\n", rproc->name, ret);
>> + goto disable_iommu;
>> + }
>> +
>> + ret = rproc_set_rsc_table(rproc);
>> + if (ret) {
>> + dev_err(dev, "can't load resource table: %d\n", ret);
>> + goto unprepare_device;
>> + }
>> +
>> +
>> + /* reset max_notifyid */
>> + rproc->max_notifyid = -1;
>> +
>> + /* reset handled vdev */
>> + rproc->nb_vdev = 0;
>> +
>> + /* handle fw resources which are required to boot rproc */
>> + ret = rproc_handle_resources(rproc, rproc_loading_handlers);
>> + if (ret) {
>> + dev_err(dev, "Failed to process resources: %d\n", ret);
>> + goto clean_up_resources;
>> + }
>> +
>> + /* Allocate carveout resources associated to rproc */
>> + ret = rproc_alloc_registered_carveouts(rproc);
>> + if (ret) {
>> + dev_err(dev, "Failed to allocate associated carveouts: %d\n",
>> + ret);
>> + goto clean_up_resources;
>> + }
>> +
>> + return 0;
>> +
>> + clean_up_resources:
>> + rproc_resource_cleanup(rproc);
>> + unprepare_rproc:
>> + /* release HW resources if needed */
>> + rproc_unprepare_device(rproc);
>> + disable_iommu:
>> + rproc_disable_iommu(rproc);
>> + return ret;
>> + }
>>
>>
>> int rproc_boot(struct rproc *rproc)
>> {
>> [...]
>>
>> - ret = rproc_fw_boot(rproc, firmware_p);
>> + if(rproc->ops->boot)
>> + ret = rproc_fw_ext_boot(rproc, firmware_p);
>> + else
>> + ret = rproc_fw_boot(rproc, firmware_p);
>>
>> Another advantage of this solution is that it opens the framework to other
>> formats. For instance it could be a way to support dtb format requested in [RFC]
>> Passing device-tree to remoteproc [1].
>>
>> [1]
>> https://lore.kernel.org/linux-remoteproc/f67cd822-4e29-71f2-7c42-e11dbaa6cd8c@xxxxxxxxxxxxx/T/#t
>>
>> Thanks,
>> Arnaud
>>
>>
>>
>>>
>>> I touched on that before but please rename rproc_tee_get_rsc_table() to
>>> rproc_tee_elf_load_rsc_table(). I also suggest to introduce a new function,
>>> rproc_tee_get_loaded_rsc_table() that would be called from
>>> rproc_tee_elf_load_rsc_table(). That way we don't need trproc->rsc_va.
>>>
>>> I also think tee_rproc should be renamed to "rproc_tee_interface" and folded
>>> under struct rproc.
>>>
>>> With the above most of the problems with the current implementation should
>>> naturally go away.
>>>
>>> Thanks,
>>> Mathieu
>>>
>>>>
>>>>>> + 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.
>>>>
>>>> This is used to inform the user that only a signed firmware can be loaded, not
>>>> an ELF file.
>>>> I have a patch in my pipe to provide the supported format in the debugfs. In a
>>>> first step, I can suppress this message and we can revisit the issue when I push
>>>> the debugfs proposal.
>>>>
>>>> Thanks,
>>>> Arnaud
>>>>
>>>>>
>>>>>> + }
>>>>>> + 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
>>>>>>

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