On 2/22/24 10:55, Naman Jain wrote: > On 2/22/2024 2:17 PM, Arnaud POULIQUEN wrote: >> Hello Naman, >> >> On 2/22/24 06:43, Naman Jain wrote: >>> On 2/14/2024 10:51 PM, Arnaud Pouliquen wrote: >>>> Updates from the previous version [1]: >>>> >>>> This version proposes another approach based on an alternate load and boot >>>> of the coprocessor. Therefore, the constraint introduced by tee_remoteproc >>>> is that the firmware has to be authenticated and loaded before the resource >>>> table can be obtained. >>>> >>>> The existing boot sequence is: > >>>> 1) Get the resource table and store it in a cache, >>>> calling rproc->ops->parse_fw(). >>>> 2) Parse the resource table and handle resources, >>>> calling rproc_handle_resources. >>>> 3) Load the firmware, calling rproc->ops->load(). >>>> 4) Start the firmware, calling rproc->ops->start(). >>>> => Steps 1 and 2 are executed in rproc_fw_boot(), while steps 3 and 4 are >>>> executed in rproc_start(). >>>> => the use of rproc->ops->load() ops is mandatory >>>> >>>> The boot sequence needed for TEE boot is: >>>> >>>> 1) Load the firmware. >>>> 2) Get the loaded resource, no cache. >>>> 3) Parse the resource table and handle resources. >>>> 4) Start the firmware. >>> >>> Hi, >>> What problem are we really addressing here by reordering load, parse of >>> FW resources? >> >> The feature introduced in TEE is the signature of the firmware images. That >> means that before getting the resource table, we need to first authenticate the >> firmware images. >> Authenticating a firmware image means that we have to copy the firmware into >> protected memory that cannot be corrupted by the non-secure and then verify the >> signature. >> The strategy implemented in OP-TEE is to load the firmware into destination >> memory and then authenticate it. >> This strategy avoids having a temporary copy of the whole images in a secure >> memory. >> This strategy imposes loading the firmware images before retrieving the resource >> table. >> >>> Basically, what are the limitations of the current design you are referring to? >>> I understood that TEE is designed that way. >> >> The limitation of the current design is that we obtain the resource table before >> loading the firmware. Following the current design would impose constraints in >> TEE that are not straightforward. Step 1 (getting the resource table and storing >> it in a cache) would require having a copy of the resource table in TEE after >> authenticating the images. However, authenticating the firmware, as explained >> before, depends on the strategy implemented. In TEE implementation, we load the >> firmware to authenticate it in the destination memory. >> >> Regards, >> Arnaud > > > Hello Arnaud, > I think now I got your point. In TEE, you don't want to do anything(read > resource table) with FW images, until its loaded and authenticated. > Since current design was not allowing you to do it, you had to reorganize the > code so that this can be achieved. > > Generally speaking, in current design, if authentication fails for some > reason later, one can handle it, but it depends on the implementation of > parse_fw op if the damage is already done. > > Please correct me if this is wrong assumption. That's correct. Regards, Arnaud > Patch looks good to me. > > Regards, > Naman Jain
