From patchwork Fri Mar 22 12:35:36 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jarkko Sakkinen X-Patchwork-Id: 13600036 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 590322F844; Fri, 22 Mar 2024 12:35:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711110950; cv=none; b=GBP633D0mUZBXJU15Rmcqqhx/W2pjsmbXvAv0HZGaztR27kFnDhBXzmDfrIuCNFIuhWoSk/5ZT+Cq5wiroukp3q6gmcAf7gX3xWXHWPeb5tiVpd+gid3H8FAAc7RyjSFkFNwdDXQeDcll6lkW9kILu2xjkaSbLihLVSFoN1tDUo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711110950; c=relaxed/simple; bh=DIU/riHW7d/Q828EtRoJMXqE8kp8ZnSjYwedK5XPRbA=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=W7C3pUp6GAb9CYmMtAcJX3YTiXoXZGay86lpN+DotnckeUPvFCOobBi56peNtzZK6xovrxfd8sK07z+M5KyI8cGQAsXSr6RF4gCm7DJ/pVAd9tncs98ynRovyFLyM6hx368SXdS7trCr1RZ4oN5BJ/ltgZjGmngm0evi5df0cCE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=u/P+vTaH; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="u/P+vTaH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5AF17C433F1; Fri, 22 Mar 2024 12:35:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711110949; bh=DIU/riHW7d/Q828EtRoJMXqE8kp8ZnSjYwedK5XPRbA=; h=From:To:Cc:Subject:Date:From; b=u/P+vTaHBL1Qwg9rMUybG08tJuaCL6vcumDRR7PHiRZWZa0Ku+VsguA6Jz/oYwY/Y qNNIoY2JogVZ1Ih34hgni6rT+X0sJF9I3IoX44804pCZ7LbSe3umt2A5+eqqmmLAiM AUmjdLAmJGbLoBKHalDymv2gFjrcc/2aEUdPpgJpY2wEqv2Rq7FOxNtzSv0t8bS7cC AncIoFdtkl1HZmLT46qeG+GrUD80IwC58ceIku1ALmyCFxfPw6P6JRGyzbAMvlCjWC 97XsAbbG1AQeTTAN6L4XZNUyXSmtZnEbDSZ33HwDvGBjmNtvCJ428TANpIUMF1rXwd Z9ItmEWNNiCQQ== From: Jarkko Sakkinen To: linux-integrity@vger.kernel.org Cc: Jarkko Sakkinen , Jonathan Corbet , "Daniel P . Smith" , Lino Sanfilippo , Jason Gunthorpe , Peter Huewe , James Bottomley , Alexander Steffen , keyrings@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Randy Dunlap , Richard Cochran , netdev@vger.kernel.org (open list:PTP HARDWARE CLOCK SUPPORT:Keyword:(?:\b|_)ptp(?:\b|_)) Subject: [PATCH v4] Documentation: tpm_tis Date: Fri, 22 Mar 2024 14:35:36 +0200 Message-ID: <20240322123542.24158-1-jarkko@kernel.org> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Based recent discussions on LKML, provide preliminary bits of tpm_tis_core dependent drivers. Includes only bare essentials but can be extended later on case by case. This way some people may even want to read it later on. Cc: Jonathan Corbet CC: Daniel P. Smith Cc: Lino Sanfilippo Cc: Jason Gunthorpe Cc: Peter Huewe Cc: James Bottomley Cc: Alexander Steffen Cc: keyrings@vger.kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: linux-integrity@vger.kernel.org Cc: Randy Dunlap Signed-off-by: Jarkko Sakkinen --- v4: - Extended the text to address some of Stefan's concerns with v2. - Had to unfortunately remove Randy's reviewed-by because of this, given the amount of text added. v3: - Fixed incorrect buffer size: https://lore.kernel.org/linux-integrity/d957dbd3-4975-48d7-abc5-1a01c0959ea3@linux.ibm.com/ v2: - Fixed errors reported by Randy: https://lore.kernel.org/all/aed28265-d677-491a-a045-24b351854b24@infradead.org/ - Improved the text a bit to have a better presentation. --- Documentation/security/tpm/index.rst | 1 + Documentation/security/tpm/tpm_tis.rst | 46 ++++++++++++++++++++++++++ 2 files changed, 47 insertions(+) create mode 100644 Documentation/security/tpm/tpm_tis.rst diff --git a/Documentation/security/tpm/index.rst b/Documentation/security/tpm/index.rst index fc40e9f23c85..f27a17f60a96 100644 --- a/Documentation/security/tpm/index.rst +++ b/Documentation/security/tpm/index.rst @@ -5,6 +5,7 @@ Trusted Platform Module documentation .. toctree:: tpm_event_log + tpm_tis tpm_vtpm_proxy xen-tpmfront tpm_ftpm_tee diff --git a/Documentation/security/tpm/tpm_tis.rst b/Documentation/security/tpm/tpm_tis.rst new file mode 100644 index 000000000000..b448ea3db71d --- /dev/null +++ b/Documentation/security/tpm/tpm_tis.rst @@ -0,0 +1,46 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========================= +TPM FIFO interface driver +========================= + +TCG PTP Specification defines two interface types: FIFO and CRB. The former is +based on sequenced read and write operations, and the latter is based on a +buffer containing the full command or response. + +FIFO (First-In-First-Out) interface is used by the tpm_tis_core dependent +drivers. Originally Linux had only a driver called tpm_tis, which covered +memory mapped (aka MMIO) interface but it was later on extended to cover other +physical interfaces supported by the TCG standard. + +For legacy compliance the original MMIO driver is called tpm_tis and the +framework for FIFO drivers is named as tpm_tis_core. The postfix "tis" in +tpm_tis comes from the TPM Interface Specification, which is the hardware +interface specification for TPM 1.x chips. + +Communication is based on a 20 KiB buffer shared by the TPM chip through a +hardware bus or memory map, depending on the physical wiring. The buffer is +further split into five equal-size 4 KiB buffers, which provide equivalent +sets of registers for communication between the CPU and TPM. These +communication endpoints are called localities in the TCG terminology. + +When the kernel wants to send commands to the TPM chip, it first reserves +locality 0 by setting the requestUse bit in the TPM_ACCESS register. The bit is +cleared by the chip when the access is granted. Once it completes its +communication, the kernel writes the TPM_ACCESS.activeLocality bit. This +informs the chip that the locality has been relinquished. + +Pending localities are served in order by the chip in descending order, one at +a time: + +- Locality 0 has the lowest priority. +- Locality 5 has the highest priority. + +Further information on the purpose and meaning of the localities can be found +in section 3.2 of the TCG PC Client Platform TPM Profile Specification. + +References +========== + +TCG PC Client Platform TPM Profile (PTP) Specification +https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/