Re: [PATCH v3] tpm_crb: request and relinquish locality 0

From: Jerry Snitselaar
Date: Fri Mar 17 2017 - 13:26:32 EST


Jarkko Sakkinen @ 2017-03-16 11:55 GMT:

> On Wed, Mar 15, 2017 at 08:27:54PM -0700, Jerry Snitselaar wrote:
>>
>> Jerry Snitselaar @ 2017-03-16 02:38 GMT:
>>
>> > Jarkko Sakkinen @ 2017-03-15 05:57 GMT:
>> >
>> >> From: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
>> >>
>> >> This commit adds support for requesting and relinquishing locality 0 in
>> >> tpm_crb for the course of command transmission.
>> >>
>> >> In order to achieve this, two new callbacks are added to struct
>> >> tpm_class_ops:
>> >>
>> >> - request_locality
>> >> - relinquish_locality
>> >>
>> >> These are called before sending and receiving data from the TPM. We
>> >> update also tpm_tis_core to use these callbacks. A small modification to
>> >> request_locality() is done so that it returns -EBUSY instead of locality
>> >> number when check_locality() fails in order to return something
>> >> meaningful to the user space.
>> >>
>> >> With CRB interface you first set either requestAccess or relinquish bit
>> >> from TPM_LOC_CTRL_x register and then wait for locAssigned and
>> >> tpmRegValidSts bits to be set in the TPM_LOC_STATE_x register.
>> >>
>> >> The reason why were are doing this is to make sure that the driver
>> >> will work properly with Intel TXT that uses locality 2. There's no
>> >> explicit guarantee that it would relinquish this locality. In more
>> >> general sense this commit enables tpm_crb to be a well behaving
>> >> citizen in a multi locality environment.
>> >>
>> >> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
>> >> ---
>> >> v2:
>> >> - TPM driver level calllbacks
>> >> v3:
>> >> - Call ops->relinquish_locality only if ops->request_locality has been
>> >> successful.
>> >> - Do not reserve locality in nested tpm_transmit calls.
>> >> - Check for tpmRegValidSts to make sure that the value in TPM_LOC_STATE_x is
>> >> stable.
>> >> drivers/char/tpm/tpm-interface.c | 10 ++++++++++
>> >> drivers/char/tpm/tpm.h | 3 ++-
>> >> drivers/char/tpm/tpm2-space.c | 15 +++++++++------
>> >> drivers/char/tpm/tpm_crb.c | 41 ++++++++++++++++++++++++++++++++++++++++
>> >> drivers/char/tpm/tpm_tis_core.c | 12 ++++--------
>> >> include/linux/tpm.h | 3 ++-
>> >> 6 files changed, 68 insertions(+), 16 deletions(-)
>> >>
>> >> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
>> >> index 95c6f98..4cd216f 100644
>> >> --- a/drivers/char/tpm/tpm-interface.c
>> >> +++ b/drivers/char/tpm/tpm-interface.c
>> >> @@ -384,6 +384,7 @@ ssize_t tpm_transmit(struct tpm_chip *chip, struct tpm_space *space,
>> >> ssize_t len = 0;
>> >> u32 count, ordinal;
>> >> unsigned long stop;
>> >> + bool no_locality = !(flags & TPM_TRANSMIT_HAS_LOCALITY);
>> >>
>> >> if (!tpm_validate_command(chip, buf, bufsiz))
>> >> return -EINVAL;
>> >> @@ -407,6 +408,12 @@ ssize_t tpm_transmit(struct tpm_chip *chip, struct tpm_space *space,
>> >> if (chip->dev.parent)
>> >> pm_runtime_get_sync(chip->dev.parent);
>> >>
>> >> + if (no_locality && chip->ops->request_locality) {
>> >> + rc = chip->ops->request_locality(chip, 0);
>> >> + if (rc)
>> >> + goto out_no_locality;
>> >> + }
>> >> +
>> >> rc = tpm2_prepare_space(chip, space, ordinal, buf);
>> >> if (rc)
>> >> goto out;
>> >> @@ -466,6 +473,9 @@ ssize_t tpm_transmit(struct tpm_chip *chip, struct tpm_space *space,
>> >> rc = tpm2_commit_space(chip, space, ordinal, buf, &len);
>> >>
>> >> out:
>> >> + if (no_locality && chip->ops->relinquish_locality)
>> >> + chip->ops->relinquish_locality(chip, 0, false);
>> >> +out_no_locality:
>> >> if (chip->dev.parent)
>> >> pm_runtime_put_sync(chip->dev.parent);
>> >>
>> >> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
>> >> index 5eacb3f..ba2c00d 100644
>> >> --- a/drivers/char/tpm/tpm.h
>> >> +++ b/drivers/char/tpm/tpm.h
>> >> @@ -521,7 +521,8 @@ extern const struct file_operations tpmrm_fops;
>> >> extern struct idr dev_nums_idr;
>> >>
>> >> enum tpm_transmit_flags {
>> >> - TPM_TRANSMIT_UNLOCKED = BIT(0),
>> >> + TPM_TRANSMIT_UNLOCKED = BIT(0),
>> >> + TPM_TRANSMIT_HAS_LOCALITY = BIT(1),
>> >> };
>> >>
>> >> ssize_t tpm_transmit(struct tpm_chip *chip, struct tpm_space *space,
>> >> diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
>> >> index d36d81e..43d05ab 100644
>> >> --- a/drivers/char/tpm/tpm2-space.c
>> >> +++ b/drivers/char/tpm/tpm2-space.c
>> >> @@ -19,6 +19,9 @@
>> >> #include <asm/unaligned.h>
>> >> #include "tpm.h"
>> >>
>> >> +#define TPM_TRANSMIT_NESTED \
>> >> + (TPM_TRANSMIT_UNLOCKED | TPM_TRANSMIT_HAS_LOCALITY)
>> >> +
>> >> enum tpm2_handle_types {
>> >> TPM2_HT_HMAC_SESSION = 0x02000000,
>> >> TPM2_HT_POLICY_SESSION = 0x03000000,
>> >> @@ -39,7 +42,7 @@ static void tpm2_flush_sessions(struct tpm_chip *chip, struct tpm_space *space)
>> >> for (i = 0; i < ARRAY_SIZE(space->session_tbl); i++) {
>> >> if (space->session_tbl[i])
>> >> tpm2_flush_context_cmd(chip, space->session_tbl[i],
>> >> - TPM_TRANSMIT_UNLOCKED);
>> >> + TPM_TRANSMIT_NESTED);
>> >> }
>> >> }
>> >>
>> >> @@ -84,7 +87,7 @@ static int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
>> >> tpm_buf_append(&tbuf, &buf[*offset], body_size);
>> >>
>> >> rc = tpm_transmit_cmd(chip, NULL, tbuf.data, PAGE_SIZE, 4,
>> >> - TPM_TRANSMIT_UNLOCKED, NULL);
>> >> + TPM_TRANSMIT_NESTED, NULL);
>> >> if (rc < 0) {
>> >> dev_warn(&chip->dev, "%s: failed with a system error %d\n",
>> >> __func__, rc);
>> >> @@ -132,7 +135,7 @@ static int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 *buf,
>> >> tpm_buf_append_u32(&tbuf, handle);
>> >>
>> >> rc = tpm_transmit_cmd(chip, NULL, tbuf.data, PAGE_SIZE, 0,
>> >> - TPM_TRANSMIT_UNLOCKED, NULL);
>> >> + TPM_TRANSMIT_NESTED, NULL);
>> >> if (rc < 0) {
>> >> dev_warn(&chip->dev, "%s: failed with a system error %d\n",
>> >> __func__, rc);
>> >> @@ -169,7 +172,7 @@ static void tpm2_flush_space(struct tpm_chip *chip)
>> >> for (i = 0; i < ARRAY_SIZE(space->context_tbl); i++)
>> >> if (space->context_tbl[i] && ~space->context_tbl[i])
>> >> tpm2_flush_context_cmd(chip, space->context_tbl[i],
>> >> - TPM_TRANSMIT_UNLOCKED);
>> >> + TPM_TRANSMIT_NESTED);
>> >>
>> >> tpm2_flush_sessions(chip, space);
>> >> }
>> >> @@ -376,7 +379,7 @@ static int tpm2_map_response_header(struct tpm_chip *chip, u32 cc, u8 *rsp,
>> >>
>> >> return 0;
>> >> out_no_slots:
>> >> - tpm2_flush_context_cmd(chip, phandle, TPM_TRANSMIT_UNLOCKED);
>> >> + tpm2_flush_context_cmd(chip, phandle, TPM_TRANSMIT_NESTED);
>> >> dev_warn(&chip->dev, "%s: out of slots for 0x%08X\n", __func__,
>> >> phandle);
>> >> return -ENOMEM;
>> >> @@ -468,7 +471,7 @@ static int tpm2_save_space(struct tpm_chip *chip)
>> >> return rc;
>> >>
>> >> tpm2_flush_context_cmd(chip, space->context_tbl[i],
>> >> - TPM_TRANSMIT_UNLOCKED);
>> >> + TPM_TRANSMIT_NESTED);
>> >> space->context_tbl[i] = ~0;
>> >> }
>> >>
>> >> diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
>> >> index 1dfc37e..eb2fcf1 100644
>> >> --- a/drivers/char/tpm/tpm_crb.c
>> >> +++ b/drivers/char/tpm/tpm_crb.c
>> >> @@ -34,6 +34,16 @@ enum crb_defaults {
>> >> CRB_ACPI_START_INDEX = 1,
>> >> };
>> >>
>> >> +enum crb_loc_ctrl {
>> >> + CRB_LOC_CTRL_REQUEST_ACCESS = BIT(0),
>> >> + CRB_LOC_CTRL_RELINQUISH = BIT(1),
>> >> +};
>> >> +
>> >> +enum crb_loc_state {
>> >> + CRB_LOC_STATE_LOC_ASSIGNED = BIT(1),
>> >> + CRB_LOC_STATE_TPM_REG_VALID_STS = BIT(7),
>> >> +};
>> >> +
>> >> enum crb_ctrl_req {
>> >> CRB_CTRL_REQ_CMD_READY = BIT(0),
>> >> CRB_CTRL_REQ_GO_IDLE = BIT(1),
>> >> @@ -172,6 +182,35 @@ static int __maybe_unused crb_cmd_ready(struct device *dev,
>> >> return 0;
>> >> }
>> >>
>> >> +static int crb_request_locality(struct tpm_chip *chip, int loc)
>> >> +{
>> >> + struct crb_priv *priv = dev_get_drvdata(&chip->dev);
>> >> + u32 value = CRB_LOC_STATE_LOC_ASSIGNED |
>> >> + CRB_LOC_STATE_TPM_REG_VALID_STS;
>> >> +
>> >> + if (!priv->regs_h)
>> >> + return 0;
>> >> +
>> >> + iowrite32(CRB_LOC_CTRL_REQUEST_ACCESS, &priv->regs_h->loc_ctrl);
>> >> + if (!crb_wait_for_reg_32(&priv->regs_h->loc_state, value, value,
>> >> + TPM2_TIMEOUT_C)) {
>> >> + dev_warn(&chip->dev, "TPM_LOC_STATE_x.requestAccess timed out\n");
>> >> + return -ETIME;
>> >> + }
>> >> +
>> >> + return 0;
>> >> +}
>> >> +
>> >> +static void crb_relinquish_locality(struct tpm_chip *chip, int loc, bool force)
>> >> +{
>> >> + struct crb_priv *priv = dev_get_drvdata(&chip->dev);
>> >> +
>> >> + if (!priv->regs_h)
>> >> + return;
>> >> +
>> >> + iowrite32(CRB_LOC_CTRL_RELINQUISH, &priv->regs_h->loc_ctrl);
>> >> +}
>> >> +
>> >> static u8 crb_status(struct tpm_chip *chip)
>> >> {
>> >> struct crb_priv *priv = dev_get_drvdata(&chip->dev);
>> >> @@ -278,6 +317,8 @@ static const struct tpm_class_ops tpm_crb = {
>> >> .send = crb_send,
>> >> .cancel = crb_cancel,
>> >> .req_canceled = crb_req_canceled,
>> >> + .request_locality = crb_request_locality,
>> >> + .relinquish_locality = crb_relinquish_locality,
>> >> .req_complete_mask = CRB_DRV_STS_COMPLETE,
>> >> .req_complete_val = CRB_DRV_STS_COMPLETE,
>> >> };
>> >> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
>> >> index fc0e9a2..c3cbe24 100644
>> >> --- a/drivers/char/tpm/tpm_tis_core.c
>> >> +++ b/drivers/char/tpm/tpm_tis_core.c
>> >> @@ -73,7 +73,7 @@ static int check_locality(struct tpm_chip *chip, int l)
>> >> return -1;
>> >> }
>> >>
>> >> -static void release_locality(struct tpm_chip *chip, int l, int force)
>> >> +static void release_locality(struct tpm_chip *chip, int l, bool force)
>> >> {
>> >> struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
>> >> int rc;
>> >> @@ -97,7 +97,7 @@ static int request_locality(struct tpm_chip *chip, int l)
>> >> long rc;
>> >>
>> >> if (check_locality(chip, l) >= 0)
>> >> - return l;
>> >> + return -EBUSY;
>> >>
>> >> rc = tpm_tis_write8(priv, TPM_ACCESS(l), TPM_ACCESS_REQUEST_USE);
>> >> if (rc < 0)
>> >> @@ -252,7 +252,6 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
>> >>
>> >> out:
>> >> tpm_tis_ready(chip);
>> >> - release_locality(chip, priv->locality, 0);
>> >> return size;
>> >> }
>> >>
>> >> @@ -268,9 +267,6 @@ static int tpm_tis_send_data(struct tpm_chip *chip, u8 *buf, size_t len)
>> >> size_t count = 0;
>> >> bool itpm = priv->flags & TPM_TIS_ITPM_WORKAROUND;
>> >>
>> >> - if (request_locality(chip, 0) < 0)
>> >> - return -EBUSY;
>> >> -
>> >> status = tpm_tis_status(chip);
>> >> if ((status & TPM_STS_COMMAND_READY) == 0) {
>> >> tpm_tis_ready(chip);
>> >> @@ -329,7 +325,6 @@ static int tpm_tis_send_data(struct tpm_chip *chip, u8 *buf, size_t len)
>> >>
>> >> out_err:
>> >> tpm_tis_ready(chip);
>> >> - release_locality(chip, priv->locality, 0);
>> >> return rc;
>> >> }
>> >>
>> >> @@ -390,7 +385,6 @@ static int tpm_tis_send_main(struct tpm_chip *chip, u8 *buf, size_t len)
>> >> return len;
>> >> out_err:
>> >> tpm_tis_ready(chip);
>> >> - release_locality(chip, priv->locality, 0);
>> >> return rc;
>> >> }
>> >>
>> >> @@ -681,6 +675,8 @@ static const struct tpm_class_ops tpm_tis = {
>> >> .send = tpm_tis_send,
>> >> .cancel = tpm_tis_ready,
>> >> .update_timeouts = tpm_tis_update_timeouts,
>> >> + .request_locality = request_locality,
>> >> + .relinquish_locality = release_locality,
>> >> .req_complete_mask = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
>> >> .req_complete_val = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
>> >> .req_canceled = tpm_tis_req_canceled,
>> >> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
>> >> index da158f0..65e05f9 100644
>> >> --- a/include/linux/tpm.h
>> >> +++ b/include/linux/tpm.h
>> >> @@ -48,7 +48,8 @@ struct tpm_class_ops {
>> >> u8 (*status) (struct tpm_chip *chip);
>> >> bool (*update_timeouts)(struct tpm_chip *chip,
>> >> unsigned long *timeout_cap);
>> >> -
>> >> + int (*request_locality)(struct tpm_chip *chip, int loc);
>> >> + void (*relinquish_locality)(struct tpm_chip *chip, int loc, bool force);
>> >> };
>> >>
>> >> #if defined(CONFIG_TCG_TPM) || defined(CONFIG_TCG_TPM_MODULE)
>> >
>> > This is broken for me on tpm_tis at the moment. release_locality only
>> > actually follows through with releasing if you've set force or there is
>> > a pending request for the TPM from another locality. So first time
>> > through it requests and gets the locality, does its work, goes
>> > to release it and doesn't because there is no pending request. Then
>> > next time through, request_locality calls check_locality and returns
>> > -EBUSY causing it to bail out of tpm_transmit.
>>
>> Actually I should amend that, I'd been debugging a bit. With the
>> patch itself, tpm_tis_core_init() calls tpm2_probe() which fails
>> because tpm_transmit_cmd -> tpm_transmit -> request_locality returns
>> -EBUSY. There is a request_locality() call right before the
>> tpm2_probe(). I'd dropped that as part of my debugging which allowed
>> it to get further along, but then run into the problem mentioned above.
>
> I see.
>
> The request_locality call in tpm_tis_core_init should works with this
> change because it does only whether the return value is zero so that
> can be safely ignored.
>

Yes, the request_locality call works there, I just wasn't sure it was
necessary since tpm2_probe will end up calling it (and returning
-EBUSY). I guess it would be needed prior to the probe_itpm call since
nothing in there calls request_locality now. It seems a bit odd
that probe_iptm calls release_locality twice though.

> The send data case totally breaks.
>
> Changing the return value to -EBUSY was a stupid mistake from my side.
>
> I'll try revise this a bit in a way that the API will allow positive
> value for stating that the given locality has been already taking.
>

Is there a big performance hit with requesting and releasing locality?
If instead it just released it when release_locality is called I think
the changes are pretty minor.

> Thank you for catching this up.
>
> [1] http://lxr.free-electrons.com/source/drivers/char/tpm/tpm_tis_core.c
>
> /Jarkko