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

From: Mathieu Poirier
Date: Fri Feb 02 2024 - 14:54:04 EST

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In reply to: Arnaud POULIQUEN: "Re: [PATCH v2 4/4] remoteproc: stm32: Add support of an OP-TEE TA to load the firmware"
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On Thu, Feb 01, 2024 at 07:33:35PM +0100, Arnaud POULIQUEN wrote:
>
>
> 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.

Right. And I think tee_rproc_load_fw() should be called right after
request_firmware() if rproc::tee_rproc_interface is valid. At that point the TEE
app may or may not do the firmware authentication, that is application specific.

> 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)

Ok

>
> 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

Right, and it should have been loaded already. If it is not then the TEE should
return an error.

> => We need to call tee_rproc_load_fw() to be able then to get the
> address of the resource table.

See my comment above - at this point the TEE should already have the firmware.
As such the only thing left is to get the address of the resource table, which
you already do in rproc_tee_get_rsc_table(). The upper part of that function
should be spun off in a new static function to deal with the TEE API, something
like _rproc_tee_get_rsc_table(). The new function should also be called in
tee_rproc_get_loaded_rsc_table() rather than keeping a cache value in
trproc->rsc_va.

> 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

And that is fine if the TEE app has already placed the program segments in
memory.

> - 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

Loading the firmware in the TEE should be done right after request_firmware()
has been called, the same way it is done in the boot path. If there isn't a
need to reload the TEE firmware than the TEE application should ignore the
request.

> - 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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