Re: [SeaBIOS] [PATCH v9 2/6] Implementation of the TCG BIOS extensions

[Kevin O'Connor]

On Fri, Mar 20, 2015 at 02:00:37PM -0400, Stefan Berger wrote:
> From: Stefan Berger
>
> This patch implements the main part of the TCG BIOS extensions. It provides
> the following functionality:
> initialization of the TCPA ACPI table used for logging of measurements
> initialization of the TPM by sending a sequence of commands to it
> proper setup of the TPM before the BIOS hands over control to the bootloader
> support for S3 resume; BIOS sends TPM_Startup(ST_STATE) to TPM
> enable configuration of SeaBIOS to be built with TCGBIOS extensions
> All TCG BIOS extensions are activated with CONFIG_TCGBIOS.

[...]
> --- a/src/Kconfig
> +++ b/src/Kconfig
> @@ -421,6 +421,13 @@ menu "BIOS interfaces"
>              modified by programs.  However, some old DOS high memory
>              managers may require the UMB region to be read-only.
> config TCGBIOS
>    select S3_RESUME
>    bool "TPM support and TCG BIOS extensions"
>    default y
>    help
>        Provide TPM support along with TCG BIOS extensions

I don't think TCGBIOS should select S3_RESUME.  If resume processing
is an absolute requirement then I think it should use "depends on".

[...]
> --- a/src/boot.c
> +++ b/src/boot.c
> @@ -19,6 +19,7 @@
>  #include "std/disk.h" // struct mbr_s
>  #include "string.h" // memset
>  #include "util.h" // irqtimer_calc
> +#include "tcgbios.h" // tpm_*
>
> /****************************************************************
> @@ -475,6 +476,7 @@ interactive_bootmenu(void)
>  printf("Select boot device:\n\n");
>  wait_threads();
> tpm_leave_bios();

Is this call really supposed to be in the boot menu?  The call wont
get invoked if the boot menu isn't selected.
> --- a/src/post.c
> +++ b/src/post.c
> @@ -28,6 +28,7 @@
>  #include "output.h" // dprintf
>  #include "string.h" // memset
>  #include "util.h" // kbd_init
> +#include "tcgbios.h" // tpm_*
>
> /****************************************************************
> @@ -220,6 +221,10 @@ maininit(void)
>      if (threads_during_optionroms())
>          device_hardware_setup();
> // Initialize tpm (after acpi tables were written)
> tpm_acpi_init();
> tpm_startup();

I think this should be just one call - such as "tpm_setup()", which in
turn calls tpm_xyz().

Also, functions with "_init" and "_setup" suffixes have specific
meaning in the bootstrap ordering sequence.  So tpm shouldn't export
functions with these suffixes unless they are invoked during the given
sequence.

[...]
> +u32
> +tpm_startup(void)
> +{
> u32 rc;
> u32 returnCode;
> if (!CONFIG_TCGBIOS)
>    return 0;
> if (!has_working_tpm())
>    return TCG_GENERAL_ERROR;
> dprintf(DEBUG_tcg, "TCGBIOS: Starting with TPM_Startup(ST_CLEAR)\n");
> rc = build_and_send_cmd(TPM_ORD_Startup,
>                        Startup_ST_CLEAR, sizeof(Startup_ST_CLEAR),
>                        NULL, 10, &returnCode, TPM_DURATION_TYPE_SHORT);
> dprintf(DEBUG_tcg, "Return code from TPM_Startup = 0x%08x\n",
>        returnCode);
>
> +#if CONFIG_COREBOOT
> /* with other firmware on the system the TPM may already have been
> * initialized
> */
> if (returnCode == TPM_INVALID_POSTINIT)
>    returnCode = 0;
>
> +#endif

That '#if' should be turned into an 'if (...)'.

[...]
> +u32
> +tpm_s3_resume(void)
> +{
> u32 rc;
> u32 returnCode;
> if (!CONFIG_TCGBIOS)
>    return 0;
> if (!has_working_tpm())
>    return TCG_GENERAL_ERROR;
> timer_setup();

Why is the timer reinitialized here?  There may be implications in
touching that hardware during an S3 resume.
> dprintf(DEBUG_tcg, "TCGBIOS: Resuming with TPM_Startup(ST_STATE)\n");
> rc = build_and_send_cmd(TPM_ORD_Startup,
>                        Startup_ST_STATE, sizeof(Startup_ST_STATE),
>                        NULL, 10, &returnCode, TPM_DURATION_TYPE_SHORT);
> dprintf(DEBUG_tcg, "TCGBIOS: ReturnCode from TPM_Startup = 0x%08x\n",
>        returnCode);
> if (rc || returnCode)
>    goto err_exit;
> return 0;
>
> +err_exit:
> dprintf(DEBUG_tcg, "TCGBIOS: TPM malfunctioning (line %d).\n", __LINE__);
> tpm_state.tpm_working = 0;
> if (rc)
>    return rc;
> return TCG_TCG_COMMAND_ERROR;
>
> +}
> diff --git a/src/tcgbios.h b/src/tcgbios.h
> new file mode 100644
> index 0000000..7be89f8
> --- /dev/null
> +++ b/src/tcgbios.h
> @@ -0,0 +1,388 @@
> +#ifndef TCGBIOS_H
> +#define TCGBIOS_H
>
> +#include "types.h"
> +#include "bregs.h" /* struct bregs */

Why is "bregs.h" needed in the header - can it be included in the
individual C files that need it?

As before, the above look minor to me and I think they could be
addressed after merging.  Based on your previous mail, I'm focusing
review comments on patches 1 and 2 right now.

-Kevin