| Message ID | 20170704135648.7360-1-Alexander.Steffen@infineon.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Jul 04, 2017 at 03:56:46PM +0200, Alexander Steffen wrote: > According to the comments, adding/removing the chip from the list should be > the first/last action in (un)register. The comments are misleading.. > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c > index 67ec9d3..a353b7a 100644 > +++ b/drivers/char/tpm/tpm-chip.c > @@ -327,11 +327,6 @@ static int tpm_add_char_device(struct tpm_chip *chip) > } > } > > - /* Make the chip available. */ > - mutex_lock(&idr_lock); > - idr_replace(&dev_nums_idr, chip, chip->dev_num); > - mutex_unlock(&idr_lock); This is actually in the wrong place already, it needs to be done before cdev_device_add - this is because cdev_device_add generates the uevent to userspace which could trigger userspace to use the kernel device. So a patch to move it to the start of this function woud be good. The function would be better described as 'make visible' Maybe resend this patch with only that change.. > { > cdev_device_del(&chip->cdev, &chip->dev); > > - /* Make the chip unavailable. */ > - mutex_lock(&idr_lock); > - idr_replace(&dev_nums_idr, NULL, chip->dev_num); > - mutex_unlock(&idr_lock); > - The placement of this does not matter so much, but keeping it after the cdev_device_del is easier to understand as it matches the (corrected) setup order.. Jason ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c > > index 67ec9d3..a353b7a 100644 > > +++ b/drivers/char/tpm/tpm-chip.c > > @@ -327,11 +327,6 @@ static int tpm_add_char_device(struct tpm_chip > *chip) > > } > > } > > > > - /* Make the chip available. */ > > - mutex_lock(&idr_lock); > > - idr_replace(&dev_nums_idr, chip, chip->dev_num); > > - mutex_unlock(&idr_lock); > > This is actually in the wrong place already, it needs to be done before > cdev_device_add - this is because cdev_device_add generates the uevent to > userspace which could trigger userspace to use the kernel device. So a patch > to move it to the start of this function woud be good. The function would be > better described as 'make visible' I have looked again at the code and I am not sure this is an issue. The call to idr_replace is only necessary to enable in-kernel usage (i.e. RNG, IMA, ...) of the TPM, but it should not affect userspace in any way. So the location of the idr_replace call does not matter much, as long as the TPM is already initialized. In fact, the main purpose of this patch series (please see PATCH 3/3) is to export the device to userspace without calling idr_replace at all under some circumstances. Or is there something I missed? The only function that ever tries to access the value stored by idr_replace is tpm_chip_find_get. It is usually called with TPM_ANY_NUM, selecting any TPM that might be present. If no TPM is present (or if idr_replace has not been called) the caller needs to deal with the situation already. Alexander ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c index 67ec9d3..a353b7a 100644 --- a/drivers/char/tpm/tpm-chip.c +++ b/drivers/char/tpm/tpm-chip.c @@ -327,11 +327,6 @@ static int tpm_add_char_device(struct tpm_chip *chip) } } - /* Make the chip available. */ - mutex_lock(&idr_lock); - idr_replace(&dev_nums_idr, chip, chip->dev_num); - mutex_unlock(&idr_lock); - return rc; } @@ -339,11 +334,6 @@ static void tpm_del_char_device(struct tpm_chip *chip) { cdev_device_del(&chip->cdev, &chip->dev); - /* Make the chip unavailable. */ - mutex_lock(&idr_lock); - idr_replace(&dev_nums_idr, NULL, chip->dev_num); - mutex_unlock(&idr_lock); - /* Make the driver uncallable. */ down_write(&chip->ops_sem); if (chip->flags & TPM_CHIP_FLAG_TPM2) @@ -438,6 +428,11 @@ int tpm_chip_register(struct tpm_chip *chip) return rc; } + /* Make the chip available. */ + mutex_lock(&idr_lock); + idr_replace(&dev_nums_idr, chip, chip->dev_num); + mutex_unlock(&idr_lock); + return 0; } EXPORT_SYMBOL_GPL(tpm_chip_register); @@ -457,6 +452,11 @@ EXPORT_SYMBOL_GPL(tpm_chip_register); */ void tpm_chip_unregister(struct tpm_chip *chip) { + /* Make the chip unavailable. */ + mutex_lock(&idr_lock); + idr_replace(&dev_nums_idr, NULL, chip->dev_num); + mutex_unlock(&idr_lock); + tpm_del_legacy_sysfs(chip); tpm_bios_log_teardown(chip); if (chip->flags & TPM_CHIP_FLAG_TPM2)
According to the comments, adding/removing the chip from the list should be the first/last action in (un)register. But currently it is done in a subfunction in the middle of the process. Moving the code from the subfunctions to the appropriate places within (un)register ensures that the code matches the comments. Signed-off-by: Alexander Steffen <Alexander.Steffen@infineon.com> --- drivers/char/tpm/tpm-chip.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-)