[PATCH] efi_loader: fix FinalEvent table initial position

[Heinrich Schuchardt]

On 11/17/21 00:24, Ilias Apalodimas wrote:
> When initializing the final event table in create_final_event() we are
> setting the initial buffer position to sizeof(*final_event).  Although
> we clear the buffer correctly and won't cause any problems,  we should
> start logging events starting from zero.
> While at it add a cast when defining the final_event.
>
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> ---
>   lib/efi_loader/efi_tcg2.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
> index 189e4a5ba59c..634556342a7c 100644
> --- a/lib/efi_loader/efi_tcg2.c
> +++ b/lib/efi_loader/efi_tcg2.c
> @@ -1257,10 +1257,11 @@ static efi_status_t create_final_event(void)
>   		goto out;
>
>   	memset(event_log.final_buffer, 0xff, TPM2_EVENT_LOG_SIZE);
> -	final_event = event_log.final_buffer;
> +	final_event =
> +		(struct efi_tcg2_final_events_table *)event_log.final_buffer;

final_buffer is defined as void *. So this cast is superfluous and
should be avoided. Cf.
https://www.kernel.org/doc/html/latest/process/coding-style.html#allocating-memory

There is a further unneeded conversion of the same type in the file.

Why didn't you define component final_buffer as struct
efi_tcg2_final_events_table * and just added a void ** conversion to the
efi_allocate_pool() call?

This would allow to eliminate the variable final_event here and in
tcg2_agile_log_append().

Best regards

Heinrich

>   	final_event->number_of_events = 0;
>   	final_event->version = EFI_TCG2_FINAL_EVENTS_TABLE_VERSION;
> -	event_log.final_pos = sizeof(*final_event);
> +	event_log.final_pos = 0;
>   	ret = efi_install_configuration_table(&efi_guid_final_events,
>   					      final_event);
>   	if (ret != EFI_SUCCESS) {
>