Re: [PATCH v5 1/2] acpi: Extend TPM2 ACPI table with missing log fields

On Thu, Jun 25, 2020 at 05:52:56AM +0300, Jarkko Sakkinen wrote:

On Thu, Jun 25, 2020 at 05:34:38AM +0300, Jarkko Sakkinen wrote:

quoted

On Wed, Jun 24, 2020 at 08:38:25PM -0400, Stefan Berger wrote:

quoted

On 6/24/20 8:00 PM, Jarkko Sakkinen wrote:

quoted

On Tue, Jun 23, 2020 at 08:06:35AM -0400, Stefan Berger wrote:

quoted

From: Stefan Berger <stefanb@linux.ibm.com>

Recent extensions of the TPM2 ACPI table added 3 more fields
including 12 bytes of start method specific parameters and Log Area
Minimum Length (u32) and Log Area Start Address (u64). So, we extend
the existing structure with these fields to allow non-UEFI systems
to access the TPM2's log.

The specification that has the new fields is the following:
   TCG ACPI Specification
   Family "1.2" and "2.0"
   Version 1.2, Revision 8

Adapt all existing table size calculations to use
offsetof(struct acpi_table_tpm2, start_method_specific)
[where start_method_specific is a newly added field]
rather than sizeof(struct acpi_table_tpm2) so that the addition
of the new fields does not affect current systems that may not
have them.

I found at least one regression from this patch. Please remove my
reviewed-by comment form the next version.

Should have:

   Link: https://trustedcomputinggroup.org/wp-content/uploads/TCG_ACPIGeneralSpecification_v1.20_r8.pdf

Please, add this.

quoted

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Cc: linux-acpi@vger.kernel.org
Acked-by: Rafael J. Wysocki <redacted>
Reviewed-by: Jarkko Sakkinen <redacted>
---
  drivers/char/tpm/tpm_crb.c | 13 ++++++++++---
  drivers/char/tpm/tpm_tis.c |  4 +++-
  include/acpi/actbl3.h      |  5 +++--
  3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
index a9dcf31eadd2..0565aa5482f9 100644
--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c

@@ -669,7 +669,9 @@ static int crb_acpi_add(struct acpi_device *device)
  	status = acpi_get_table(ACPI_SIG_TPM2, 1,
  				(struct acpi_table_header **) &buf);
-	if (ACPI_FAILURE(status) || buf->header.length < sizeof(*buf)) {
+	if (ACPI_FAILURE(status) || buf->header.length <
+			offsetof(struct acpi_table_tpm2,
+				 start_method_specific)) {
  		dev_err(dev, FW_BUG "failed to get TPM2 ACPI table\n");
  		return -EINVAL;
  	}

@@ -684,14 +686,19 @@ static int crb_acpi_add(struct acpi_device *device)
  		return -ENOMEM;
  	if (sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC) {
-		if (buf->header.length < (sizeof(*buf) + sizeof(*crb_smc))) {
+		if (buf->header.length <
+			(offsetof(struct acpi_table_tpm2,
+				  start_method_specific) +

Should be

   offsetof(struct acpti_table_tpm2, log_area_minimum_length)

The old code had sizeof(*buf) with buf being 'struct acpi_table_tpm2' and
that was equivalent to offsetof(struct acpi_table_tpm2,
start_method_specific) since 'start_method_specific' is the first new field
that we are adding right here. Also see 3rd paragraph in the patch
description. The replacement rule described there should apply to all
sizeof() calculations on 'struct acpi_table_tpm2.'

Aren't you ignoring sizeof(*crb_smc) then?

Duh, it's there I see. Sorry, my mistake.

Please put the new fields in a separate struct:

struct acpi_tpm2_phy {
	u8  start_method_specific[12];
	u32 log_area_minimum_length;
	u64 log_area_start_address;
};

This way we don't have to obfuscate all the calculations and zero out
the need for 1/2 in this patch set.

Also remark that, if you continue the current patch, that would need
tested-by from ARM whereas a new struct does not because the ARM code
is intact.

/Jarkko