[v4,3/7] tpm: tpm_tis: rewrite "tpm_tis_req_canceled()"

Commit Message

Amir Mizinski March 31, 2020, 11:32 a.m. UTC

From: Amir Mizinski <[e-mail]>

Using this function while read/write data resulted in aborted operation.
After investigating according to TCG TPM Profile (PTP) Specifications,
i found cancel should happen only if TPM_STS.commandReady bit is lit and
couldn't find a case when the current condition is valid.
Also only cmdReady bit need to be compared instead of the full lower status
register byte.

Signed-off-by: Amir Mizinski <[e-mail]>
---
 drivers/char/tpm/tpm_tis_core.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

--
2.7.4



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Comments

Jarkko Sakkinen March 31, 2020, 12:13 p.m. UTC | #1

On Tue, Mar 31, 2020 at 02:32:03PM +0300, [e-mail] wrote:
> From: Amir Mizinski <[e-mail]>
> 
> Using this function while read/write data resulted in aborted operation.
> After investigating according to TCG TPM Profile (PTP) Specifications,
> i found cancel should happen only if TPM_STS.commandReady bit is lit and
> couldn't find a case when the current condition is valid.
> Also only cmdReady bit need to be compared instead of the full lower status
> register byte.
> 
> Signed-off-by: Amir Mizinski <[e-mail]>

We don't care about spec's. We care about hardware and not all hardware
follows specifications.

Please fix the exact thing you want to fix (and please provide a fixes
tag).

/Jarkko

Ken Goldman March 31, 2020, 1:52 p.m. UTC | #2

On 3/31/2020 8:13 AM, Jarkko Sakkinen wrote:
> On Tue, Mar 31, 2020 at 02:32:03PM +0300, [e-mail] wrote:
>> From: Amir Mizinski <[e-mail]>
>>
>> Using this function while read/write data resulted in aborted operation.
>> After investigating according to TCG TPM Profile (PTP) Specifications,
>> i found cancel should happen only if TPM_STS.commandReady bit is lit and
>> couldn't find a case when the current condition is valid.
>> Also only cmdReady bit need to be compared instead of the full lower status
>> register byte.
>>
>> Signed-off-by: Amir Mizinski <[e-mail]>
> 
> We don't care about spec's. We care about hardware and not all hardware
> follows specifications.
> 
> Please fix the exact thing you want to fix (and please provide a fixes
> tag).

I edit the TPM main spec, not the PTP.  As I discover TPMs that don't 
meet the spec, or where the spec has changed over time, I add 
informative comments to guide developers.

If you know of TPM hardware that does not meet the PTP specification, 
let me know the specifics.  I can bring it to the PTP work group and try 
to get comments added.

I do not need to know the TPM vendor.  That information would not go 
into the specification anyway.

Patch

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 6c4f232..18b9dc4 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -710,17 +710,7 @@  static int probe_itpm(struct tpm_chip *chip)

 static bool tpm_tis_req_canceled(struct tpm_chip *chip, u8 status)
 {
-       struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
-
-       switch (priv->manufacturer_id) {
-       case TPM_VID_WINBOND:
-               return ((status == TPM_STS_VALID) ||
-                       (status == (TPM_STS_VALID | TPM_STS_COMMAND_READY)));
-       case TPM_VID_STM:
-               return (status == (TPM_STS_VALID | TPM_STS_COMMAND_READY));
-       default:
-               return (status == TPM_STS_COMMAND_READY);
-       }
+       return ((status & TPM_STS_COMMAND_READY) == TPM_STS_COMMAND_READY);
 }

 static irqreturn_t tis_int_handler(int dummy, void *dev_id)