linux-kernel - RE: ibmvtpm byteswapping inconsistency

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6DB0273BCA@AcuExch.aculab.com>
Date:   Mon, 30 Jan 2017 14:42:25 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Tyrel Datwyler' <tyreld@...ux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Michal Suchánek <msuchanek@...e.de>,
        Ashley Lai <ashleydlai@...il.com>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Peter Huewe <peterhuewe@....de>,
        Marcel Selhorst <tpmdd@...horst.net>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        "tpmdd-devel@...ts.sourceforge.net" 
        <tpmdd-devel@...ts.sourceforge.net>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: ibmvtpm byteswapping inconsistency

From: Tyrel Datwyler
> Sent: 27 January 2017 18:03
> On 01/26/2017 05:50 PM, Benjamin Herrenschmidt wrote:
> > On Thu, 2017-01-26 at 17:42 -0800, Tyrel Datwyler wrote:
> >> On 01/26/2017 12:22 PM, Michal Suchnek wrote:
> >>> Hello,
> >>>
> >>> building ibmvtpm I noticed gcc warning complaining that second word
> >>> of
> >>> struct ibmvtpm_crq in tpm_ibmvtpm_suspend is uninitialized.
> >>>
> >>> The structure is defined as
> >>>
> >>> struct ibmvtpm_crq {
> >>>         u8 valid;
> >>>         u8 msg;
> >>>         __be16 len;
> >>>         __be32 data;
> >>>         __be64 reserved;
> >>> } __attribute__((packed, aligned(8)));
> >>>
> >>> initialized as
> >>>
> >>>         struct ibmvtpm_crq crq;
> >>>         u64 *buf = (u64 *) &crq;
> >>> ...
> >>>         crq.valid = (u8)IBMVTPM_VALID_CMD;
> >>>         crq.msg = (u8)VTPM_PREPARE_TO_SUSPEND;
> >>>
> >>> and submitted with
> >>>
> >>>         rc = ibmvtpm_send_crq(ibmvtpm->vdev, cpu_to_be64(buf[0]),
> >>>                               cpu_to_be64(buf[1]));

Isn't the real fubar here the use of that memory layout structure at all?
It would probably all be better if the call looked like:
	rc = ibmvtpm_send_crq(ibmvtpm->vdev, MAKE_REQ(IBMVTPM_VALID_CMD,
		VTPM_PREPARE_TO_SUSPEND, xxx_len, xxx_data), 0);
and MAKE_REQ() did all the required endian independant shifts to generate
the correct 32bit value.

	David