Hi Mimi, > On Tue, 2026-04-21 at 13:50 +0100, Yeoreum Yun wrote: > > Hi Mimi, > > > > > On Fri, 2026-04-17 at 18:57 +0100, Yeoreum Yun wrote: > > > > To generate the boot_aggregate log in the IMA subsystem with TPM PCR > > > > values, > > > > the TPM driver must be built as built-in and > > > > must be probed before the IMA subsystem is initialized. > > > > > > > > However, when the TPM device operates over the FF-A protocol using > > > > the CRB interface, probing fails and returns -EPROBE_DEFER if > > > > the tpm_crb_ffa device — an FF-A device that provides the communication > > > > interface to the tpm_crb driver — has not yet been probed. > > > > > > > > To ensure the TPM device operating over the FF-A protocol with > > > > the CRB interface is probed before IMA initialization, > > > > the following conditions must be met: > > > > > > > > 1. The corresponding ffa_device must be registered, > > > > which is done via ffa_init(). > > > > > > > > 2. The tpm_crb_driver must successfully probe this device via > > > > tpm_crb_ffa_init(). > > > > > > > > 3. The tpm_crb driver using CRB over FF-A can then > > > > be probed successfully. (See crb_acpi_add() and > > > > tpm_crb_ffa_init() for reference.) > > > > > > > > Unfortunately, ffa_init(), tpm_crb_ffa_init(), and > > > > crb_acpi_driver_init() are > > > > all registered with device_initcall, which means crb_acpi_driver_init() > > > > may > > > > be invoked before ffa_init() and tpm_crb_ffa_init() are completed. > > > > > > > > When this occurs, probing the TPM device is deferred. > > > > However, the deferred probe can happen after the IMA subsystem > > > > has already been initialized, since IMA initialization is performed > > > > during late_initcall, and deferred_probe_initcall() is performed > > > > at the same level. > > > > > > > > To resolve this, move ima_init() into late_inicall_sync level > > > > so that let IMA not miss TPM PCR value when generating boot_aggregate > > > > log though TPM device presents in the system. > > > > > > > > Signed-off-by: Yeoreum Yun <[email protected]> > > > > > > IMA should be initialized as early as possible. I'm really hesitant to > > > defer > > > ima_init() to late_initcall_sync() for systems that the TPM is currently > > > initialized in time. For these systems, continue initializing IMA at > > > late_initcall(). As a compromise for those systems that the TPM isn't > > > properly > > > initialized in time, define and instantiate the late_initcall_sync(). > > > > > > ima_init() would need to differentiate between the late_initcall and > > > late_initcall_sync. On late_initcall(), instead of saying "No TPM chip > > > found, > > > activating TPM-bypass!", it should say "No TPM chip found, deferring to > > > late_initcall_sync" or something similar. > > > > But can we really move those initialisations to be called again? > > > > I am referring to functions such as ima_init_crypto(), > > ima_add_boot_aggregate(), and ima_measure_critical_data() in ima_init()— > > first without TPM, and then a second time once TPM becomes available. > > I don’t think that approach would work. > > > > In other words, unless tpm_default_chip() can differentiate between a TPM > > device that is deferred and one that does not exist, we cannot distinguish > > between the “defer” case and “-EEXIST”. > > > > It might be possible if the TPM core tracked the state when a driver returns > > -EPROBE_DEFER, but I am not sure that is the right approach. > > For deferred probe cases, the “device initialised in time” check should > > likely be done at late_initcall_sync, rather than late_initcall. > > > > This implies that any such check performed before late_initcall_sync > > does not reflect a valid state, as it cannot distinguish between “not > > present” and “deferred”. > > > > Therefore, I think the TPM check in IMA should be performed at > > late_initcall_sync. > > > > > > Am I missing something? > > In ima_init() you short circuit out, when called by late_initcall(), if the > TPM > hasn't been initialized. So the rest of the ima_init() isn't called. Roughly > something like this (needs some cleanup): > > int __init ima_init(void) > { > static int first = 1; > int rc; > > if (ima_tpm_chip) > return 0; > > ima_tpm_chip = tpm_default_chip(); > if (!ima_tpm_chip && first) { > pr_info("No TPM chip found, deferring te > late_initcall_sync()\n"); > first = 0; > return 0; > }
I see. then I'll respin in v2. Thanks! -- Sincerely, Yeoreum Yun
