Re: [tpmdd-devel] [PATCH v2 2/3] efi: call get_event_log before ExitBootServices

[Javier Martinez Canillas]

On 09/18/2017 02:11 PM, Thiebaud Weksteen wrote:
> On Thu, Sep 14, 2017 at 12:24 PM, Javier Martinez Canillas
>  wrote:
>> On 09/11/2017 12:00 PM, Thiebaud Weksteen via tpmdd-devel wrote:

[snip]

>>> +
>>> + if (status != EFI_SUCCESS) {
>>> + efi_printk(sys_table_arg,
>>> +"Unable to allocate memory for event log\n");
>>> + return;
>>> + }
>>
>> If this fails or any previous error that will prevent the event log table + 
>> logs
>> to be allocated, shouldn't tpm_read_log_efi() be notified somehow? Since 
>> AFAICT
>> it will still try to access them even if the EFI allocate_pool did not 
>> succeed.
>>
> 
> The implicit part that covers this case is in
> drivers/firmware/efi/efi.c. The match_config_table function will go
> through all the installed configuration tables and only fill up the
> associated member of the efi structure if it exists. In this case,
> .tpm_log will remains at EFI_INVALID_TABLE_ADDR unless
> efi_call_early(install_configuration_table, ...) is called. So no
> further processing is to be expected should the allocation failed.
>

I see, missed that. Thanks a lot for the explanation.

>>> + */
>>> +int __init efi_tpm_eventlog_init(void)
>>> +{
>>> + struct linux_efi_tpm_eventlog *tbl;
>>> + unsigned int tbl_size;
>>> +
>>
>> The functions efi_retrieve_tpm2_eventlog_1_2() and tpm_read_log_efi() are 
>> using
>> log_tbl as variable name, so I would use it here too for consistency.
>>
> 
> Done.
> 
>>> + if (efi.tpm_log == EFI_INVALID_TABLE_ADDR)
>>> + return 0;
>>> +
>>> + tbl = early_memremap(efi.tpm_log, sizeof(*tbl));
>>> + if (!tbl) {
>>> + pr_err("Failed to map TPM Event Log table @ 0x%lx\n",
>>> + efi.tpm_log);
>>> + return -ENOMEM;
>>> + }
>>> +
>>
>> Same question than before, if this fails then the table + logs memory won't 
>> be
>> reserved but tpm_read_log_efi() will still try to access it. I'm not sure 
>> what
>> is the correct way to notify though, maybe setting efi.tpm_log to 0 and then 
>> in
>> tpm_read_log_efi() check efi.tpm_log for 0 or EFI_INVALID_TABLE_ADDR instead?
>>
> 
> That's right. To keep it simple, it might be easier to just set
> tpm_log to EFI_INVALID_TABLE_ADDR if that happens. Added in the next
> version of the patch set.
>

Right. I wasn't sure if you wanted to distinguish between the two cases, but 
that
is simpler indeed.

Best regards,
-- 
Javier Martinez Canillas
Software Engineer - Desktop Hardware Enablement
Red Hat
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Re: [tpmdd-devel] [PATCH v2 2/3] efi: call get_event_log before ExitBootServices

[Thiebaud Weksteen]

On Thu, Sep 14, 2017 at 12:24 PM, Javier Martinez Canillas
 wrote:
> On 09/11/2017 12:00 PM, Thiebaud Weksteen via tpmdd-devel wrote:
>> With TPM 2.0 specification, the event logs may only be accessible by
>> calling an EFI Boot Service. Modify the EFI stub to copy the log area to
>> a new Linux-specific EFI configuration table so it remains accessible
>> once booted.
>>
>> When calling this service, it is possible to specify the expected format
>> of the logs: TPM 1.2 (SHA1) or TPM 2.0 ("Crypto Agile"). For now, only the
>> first format is retrieved.
>>
>> Signed-off-by: Thiebaud Weksteen 
>> ---
>
> [snip]
>
>> +void efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t *sys_table_arg)
>> +{
>
> [snip]
>
>> +
>> + /* Allocate space for the logs and copy them. */
>> + status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
>> + sizeof(*log_tbl) + log_size,
>> + (void **) _tbl);
>> +
>> + if (status != EFI_SUCCESS) {
>> + efi_printk(sys_table_arg,
>> +"Unable to allocate memory for event log\n");
>> + return;
>> + }
>
> If this fails or any previous error that will prevent the event log table + 
> logs
> to be allocated, shouldn't tpm_read_log_efi() be notified somehow? Since 
> AFAICT
> it will still try to access them even if the EFI allocate_pool did not 
> succeed.
>

The implicit part that covers this case is in
drivers/firmware/efi/efi.c. The match_config_table function will go
through all the installed configuration tables and only fill up the
associated member of the efi structure if it exists. In this case,
.tpm_log will remains at EFI_INVALID_TABLE_ADDR unless
efi_call_early(install_configuration_table, ...) is called. So no
further processing is to be expected should the allocation failed.

>> + */
>> +int __init efi_tpm_eventlog_init(void)
>> +{
>> + struct linux_efi_tpm_eventlog *tbl;
>> + unsigned int tbl_size;
>> +
>
> The functions efi_retrieve_tpm2_eventlog_1_2() and tpm_read_log_efi() are 
> using
> log_tbl as variable name, so I would use it here too for consistency.
>

Done.

>> + if (efi.tpm_log == EFI_INVALID_TABLE_ADDR)
>> + return 0;
>> +
>> + tbl = early_memremap(efi.tpm_log, sizeof(*tbl));
>> + if (!tbl) {
>> + pr_err("Failed to map TPM Event Log table @ 0x%lx\n",
>> + efi.tpm_log);
>> + return -ENOMEM;
>> + }
>> +
>
> Same question than before, if this fails then the table + logs memory won't be
> reserved but tpm_read_log_efi() will still try to access it. I'm not sure what
> is the correct way to notify though, maybe setting efi.tpm_log to 0 and then 
> in
> tpm_read_log_efi() check efi.tpm_log for 0 or EFI_INVALID_TABLE_ADDR instead?
>

That's right. To keep it simple, it might be easier to just set
tpm_log to EFI_INVALID_TABLE_ADDR if that happens. Added in the next
version of the patch set.

>> + tbl_size = sizeof(*tbl) + tbl->size;
>> + memblock_reserve(efi.tpm_log, tbl_size);
>> + early_memunmap(tbl, sizeof(*tbl));
>> + return 0;
>
> Best regards,
> --
> Javier Martinez Canillas
> Software Engineer - Desktop Hardware Enablement
> Red Hat
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Re: [tpmdd-devel] [PATCH v2 2/3] efi: call get_event_log before ExitBootServices

[Javier Martinez Canillas]

On 09/11/2017 12:00 PM, Thiebaud Weksteen via tpmdd-devel wrote:
> With TPM 2.0 specification, the event logs may only be accessible by
> calling an EFI Boot Service. Modify the EFI stub to copy the log area to
> a new Linux-specific EFI configuration table so it remains accessible
> once booted.
> 
> When calling this service, it is possible to specify the expected format
> of the logs: TPM 1.2 (SHA1) or TPM 2.0 ("Crypto Agile"). For now, only the
> first format is retrieved.
> 
> Signed-off-by: Thiebaud Weksteen 
> ---

[snip]

> +void efi_retrieve_tpm2_eventlog_1_2(efi_system_table_t *sys_table_arg)
> +{

[snip]

> +
> + /* Allocate space for the logs and copy them. */
> + status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
> + sizeof(*log_tbl) + log_size,
> + (void **) _tbl);
> +
> + if (status != EFI_SUCCESS) {
> + efi_printk(sys_table_arg,
> +"Unable to allocate memory for event log\n");
> + return;
> + }

If this fails or any previous error that will prevent the event log table + logs
to be allocated, shouldn't tpm_read_log_efi() be notified somehow? Since AFAICT
it will still try to access them even if the EFI allocate_pool did not succeed.

> + */
> +int __init efi_tpm_eventlog_init(void)
> +{
> + struct linux_efi_tpm_eventlog *tbl;
> + unsigned int tbl_size;
> +

The functions efi_retrieve_tpm2_eventlog_1_2() and tpm_read_log_efi() are using
log_tbl as variable name, so I would use it here too for consistency.

> + if (efi.tpm_log == EFI_INVALID_TABLE_ADDR)
> + return 0;
> +
> + tbl = early_memremap(efi.tpm_log, sizeof(*tbl));
> + if (!tbl) {
> + pr_err("Failed to map TPM Event Log table @ 0x%lx\n",
> + efi.tpm_log);
> + return -ENOMEM;
> + }
> +

Same question than before, if this fails then the table + logs memory won't be
reserved but tpm_read_log_efi() will still try to access it. I'm not sure what
is the correct way to notify though, maybe setting efi.tpm_log to 0 and then in
tpm_read_log_efi() check efi.tpm_log for 0 or EFI_INVALID_TABLE_ADDR instead?

> + tbl_size = sizeof(*tbl) + tbl->size;
> + memblock_reserve(efi.tpm_log, tbl_size);
> + early_memunmap(tbl, sizeof(*tbl));
> + return 0;

Best regards,
-- 
Javier Martinez Canillas
Software Engineer - Desktop Hardware Enablement
Red Hat
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