linux-kernel - Re: ibmvtpm byteswapping inconsistency

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Date:   Thu, 02 Feb 2017 21:55:57 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Vicky <honclo@...ux.vnet.ibm.com>,
        Ashley Lai <ashleydlai@...il.com>
Cc:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        "Michal Such\?\?nek" <msuchanek@...e.de>,
        Nayna Jain <nayna@...ux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Peter Huewe <peterhuewe@....de>,
        Marcel Selhorst <tpmdd@...horst.net>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        tpmdd-devel@...ts.sourceforge.net, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: ibmvtpm byteswapping inconsistency

Vicky <honclo@...ux.vnet.ibm.com> writes:

>> On Jan 26, 2017, at 5:58 PM, Ashley Lai <ashleydlai@...il.com> wrote:
>> 
>> Adding Vicky from IBM.
>> 
>> 
>> On 01/26/2017 04:05 PM, Jason Gunthorpe wrote:
>>> On Thu, Jan 26, 2017 at 09:22:48PM +0100, Michal Such??nek wrote:
>>> 
>>>> This is repeated a few times in the driver so I added memset to quiet
>>>> gcc and make behavior deterministic in case the unused fields get some
>>>> meaning in the future.
>>> Yep, reserved certainly needs to be zeroed.. Can you send a patch?
>>> memset is overkill...
>>> 
>>>> However, in tpm_ibmvtpm_send the structure is initialized as
>>>> 
>>>> 	struct ibmvtpm_crq crq;
>>>>         __be64 *word = (__be64 *)&crq;
>>>> ...
>>>>         crq.valid = (u8)IBMVTPM_VALID_CMD;
>>>>         crq.msg = (u8)VTPM_TPM_COMMAND;
>>>>         crq.len = cpu_to_be16(count);
>>>>         crq.data = cpu_to_be32(ibmvtpm->rtce_dma_handle);
>>>> 
>>>> and submitted with
>>>> 
>>>> 	rc = ibmvtpm_send_crq(ibmvtpm->vdev, be64_to_cpu(word[0]),
>>>>                               be64_to_cpu(word[1]));
>>>> meaning it is swapped twice.
>>> No idea, Nayna may know.
>>> 
>>> My guess is that '__be64 *word' should be 'u64 *word'...
>>> 
>>> Jason
>> 
>
> I don’t think we want ‘word' to be changed back to be of type ‘u64’.   Please see commit 62dfd912ab3b5405b6fe72d0135c37e9648071f1

The type of word is basically irrelevant. Unless you're running sparse
and actually checking the errors, which it seems you're not doing:

  drivers/char/tpm/tpm_ibmvtpm.c:90:30: warning: cast removes address space of expression
  drivers/char/tpm/tpm_ibmvtpm.c:91:23: warning: incorrect type in argument 1 (different address spaces)
  drivers/char/tpm/tpm_ibmvtpm.c:91:23:    expected void *<noident>
  drivers/char/tpm/tpm_ibmvtpm.c:91:23:    got void [noderef] <asn:2>*rtce_buf
  drivers/char/tpm/tpm_ibmvtpm.c:136:17: warning: cast removes address space of expression
  drivers/char/tpm/tpm_ibmvtpm.c:188:46: warning: incorrect type in argument 2 (different base types)
  drivers/char/tpm/tpm_ibmvtpm.c:188:46:    expected unsigned long long [unsigned] [usertype] w1
  drivers/char/tpm/tpm_ibmvtpm.c:188:46:    got restricted __be64 [usertype] <noident>
  drivers/char/tpm/tpm_ibmvtpm.c:189:31: warning: incorrect type in argument 3 (different base types)
  drivers/char/tpm/tpm_ibmvtpm.c:189:31:    expected unsigned long long [unsigned] [usertype] w2
  drivers/char/tpm/tpm_ibmvtpm.c:189:31:    got restricted __be64 [usertype] <noident>
  drivers/char/tpm/tpm_ibmvtpm.c:215:46: warning: incorrect type in argument 2 (different base types)
  drivers/char/tpm/tpm_ibmvtpm.c:215:46:    expected unsigned long long [unsigned] [usertype] w1
  drivers/char/tpm/tpm_ibmvtpm.c:215:46:    got restricted __be64 [usertype] <noident>
  drivers/char/tpm/tpm_ibmvtpm.c:216:31: warning: incorrect type in argument 3 (different base types)
  drivers/char/tpm/tpm_ibmvtpm.c:216:31:    expected unsigned long long [unsigned] [usertype] w2
  drivers/char/tpm/tpm_ibmvtpm.c:216:31:    got restricted __be64 [usertype] <noident>
  drivers/char/tpm/tpm_ibmvtpm.c:294:30: warning: incorrect type in argument 1 (different address spaces)
  drivers/char/tpm/tpm_ibmvtpm.c:294:30:    expected void const *<noident>
  drivers/char/tpm/tpm_ibmvtpm.c:294:30:    got void [noderef] <asn:2>*rtce_buf
  drivers/char/tpm/tpm_ibmvtpm.c:342:46: warning: incorrect type in argument 2 (different base types)
  drivers/char/tpm/tpm_ibmvtpm.c:342:46:    expected unsigned long long [unsigned] [usertype] w1
  drivers/char/tpm/tpm_ibmvtpm.c:342:46:    got restricted __be64 [usertype] <noident>
  drivers/char/tpm/tpm_ibmvtpm.c:343:31: warning: incorrect type in argument 3 (different base types)
  drivers/char/tpm/tpm_ibmvtpm.c:343:31:    expected unsigned long long [unsigned] [usertype] w2
  drivers/char/tpm/tpm_ibmvtpm.c:343:31:    got restricted __be64 [usertype] <noident>
  drivers/char/tpm/tpm_ibmvtpm.c:494:43: warning: incorrect type in assignment (different address spaces)
  drivers/char/tpm/tpm_ibmvtpm.c:494:43:    expected void [noderef] <asn:2>*rtce_buf
  drivers/char/tpm/tpm_ibmvtpm.c:494:43:    got void *
  drivers/char/tpm/tpm_ibmvtpm.c:501:52: warning: incorrect type in argument 2 (different address spaces)
  drivers/char/tpm/tpm_ibmvtpm.c:501:52:    expected void *ptr
  drivers/char/tpm/tpm_ibmvtpm.c:501:52:    got void [noderef] <asn:2>*rtce_buf
  drivers/char/tpm/tpm_ibmvtpm.c:507:46: warning: incorrect type in argument 1 (different address spaces)
  drivers/char/tpm/tpm_ibmvtpm.c:507:46:    expected void const *<noident>
  drivers/char/tpm/tpm_ibmvtpm.c:507:46:    got void [noderef] <asn:2>*rtce_buf


What matters is how you actually do the byte swaps.

cheers