tpm: use struct tpm_chip for tpm_chip_find_get()

Device number (the character device index) is not a stable identifier
for a TPM chip. That is the reason why every call site passes
TPM_ANY_NUM to tpm_chip_find_get().

This commit changes the API in a way that instead a struct tpm_chip
instance is given and NULL means the default chip. In addition, this
commit refines the documentation to be up to date with the
implementation.

Suggested-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com> (@chip_num -> @chip part)
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgg@ziepe.ca>
Tested-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>

4 files changed, 87 insertions, 76 deletions

diff --git a/drivers/char/hw_random/tpm-rng.c b/drivers/char/hw_random/tpm-rng.c
index d6d448266f07..c5e363825af0 100644
--- a/drivers/char/hw_random/tpm-rng.c
+++ b/drivers/char/hw_random/tpm-rng.c
@@ -25,7 +25,7 @@
 
 static int tpm_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
 {
-	return tpm_get_random(TPM_ANY_NUM, data, max);
+	return tpm_get_random(NULL, data, max);
 }
 
 static struct hwrng tpm_rng = {
diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index a114e8f7fb90..bab9c14e040c 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -81,21 +81,26 @@ void tpm_put_ops(struct tpm_chip *chip)
 EXPORT_SYMBOL_GPL(tpm_put_ops);
 
 /**
- * tpm_chip_find_get() - return tpm_chip for a given chip number
- * @chip_num: id to find
+ * tpm_chip_find_get() - find and reserve a TPM chip
+ * @chip:	a &struct tpm_chip instance, %NULL for the default chip
  *
- * The return'd chip has been tpm_try_get_ops'd and must be released via
- * tpm_put_ops
+ * Finds a TPM chip and reserves its class device and operations. The chip must
+ * be released with tpm_chip_put_ops() after use.
+ *
+ * Return:
+ * A reserved &struct tpm_chip instance.
+ * %NULL if a chip is not found.
+ * %NULL if the chip is not available.
  */
-struct tpm_chip *tpm_chip_find_get(int chip_num)
+struct tpm_chip *tpm_chip_find_get(struct tpm_chip *chip)
 {
-	struct tpm_chip *chip, *res = NULL;
+	struct tpm_chip *res = NULL;
+	int chip_num = 0;
 	int chip_prev;
 
 	mutex_lock(&idr_lock);
 
-	if (chip_num == TPM_ANY_NUM) {
-		chip_num = 0;
+	if (!chip) {
 		do {
 			chip_prev = chip_num;
 			chip = idr_get_next(&dev_nums_idr, &chip_num);
@@ -105,8 +110,7 @@ struct tpm_chip *tpm_chip_find_get(int chip_num)
 			}
 		} while (chip_prev != chip_num);
 	} else {
-		chip = idr_find(&dev_nums_idr, chip_num);
-		if (chip && !tpm_try_get_ops(chip))
+		if (!tpm_try_get_ops(chip))
 			res = chip;
 	}
 
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index ebe0a1d36d8c..19f820f775b5 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -809,19 +809,20 @@ int tpm_pcr_read_dev(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
 }
 
 /**
- * tpm_is_tpm2 - is the chip a TPM2 chip?
- * @chip_num:	tpm idx # or ANY
+ * tpm_is_tpm2 - do we a have a TPM2 chip?
+ * @chip:	a &struct tpm_chip instance, %NULL for the default chip
  *
- * Returns < 0 on error, and 1 or 0 on success depending whether the chip
- * is a TPM2 chip.
+ * Return:
+ * 1 if we have a TPM2 chip.
+ * 0 if we don't have a TPM2 chip.
+ * A negative number for system errors (errno).
  */
-int tpm_is_tpm2(u32 chip_num)
+int tpm_is_tpm2(struct tpm_chip *chip)
 {
-	struct tpm_chip *chip;
 	int rc;
 
-	chip = tpm_chip_find_get(chip_num);
-	if (chip == NULL)
+	chip = tpm_chip_find_get(chip);
+	if (!chip)
 		return -ENODEV;
 
 	rc = (chip->flags & TPM_CHIP_FLAG_TPM2) != 0;
@@ -833,23 +834,19 @@ int tpm_is_tpm2(u32 chip_num)
 EXPORT_SYMBOL_GPL(tpm_is_tpm2);
 
 /**
- * tpm_pcr_read - read a pcr value
- * @chip_num:	tpm idx # or ANY
- * @pcr_idx:	pcr idx to retrieve
- * @res_buf:	TPM_PCR value
- *		size of res_buf is 20 bytes (or NULL if you don't care)
+ * tpm_pcr_read - read a PCR value from SHA1 bank
+ * @chip:	a &struct tpm_chip instance, %NULL for the default chip
+ * @pcr_idx:	the PCR to be retrieved
+ * @res_buf:	the value of the PCR
  *
- * The TPM driver should be built-in, but for whatever reason it
- * isn't, protect against the chip disappearing, by incrementing
- * the module usage count.
+ * Return: same as with tpm_transmit_cmd()
  */
-int tpm_pcr_read(u32 chip_num, int pcr_idx, u8 *res_buf)
+int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
 {
-	struct tpm_chip *chip;
 	int rc;
 
-	chip = tpm_chip_find_get(chip_num);
-	if (chip == NULL)
+	chip = tpm_chip_find_get(chip);
+	if (!chip)
 		return -ENODEV;
 	if (chip->flags & TPM_CHIP_FLAG_TPM2)
 		rc = tpm2_pcr_read(chip, pcr_idx, res_buf);
@@ -889,25 +886,26 @@ static int tpm1_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash,
 }
 
 /**
- * tpm_pcr_extend - extend pcr value with hash
- * @chip_num:	tpm idx # or AN&
- * @pcr_idx:	pcr idx to extend
- * @hash:	hash value used to extend pcr value
+ * tpm_pcr_extend - extend a PCR value in SHA1 bank.
+ * @chip:	a &struct tpm_chip instance, %NULL for the default chip
+ * @pcr_idx:	the PCR to be retrieved
+ * @hash:	the hash value used to extend the PCR value
  *
- * The TPM driver should be built-in, but for whatever reason it
- * isn't, protect against the chip disappearing, by incrementing
- * the module usage count.
+ * Note: with TPM 2.0 extends also those banks with a known digest size to the
+ * cryto subsystem in order to prevent malicious use of those PCR banks. In the
+ * future we should dynamically determine digest sizes.
+ *
+ * Return: same as with tpm_transmit_cmd()
  */
-int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
+int tpm_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash)
 {
 	int rc;
-	struct tpm_chip *chip;
 	struct tpm2_digest digest_list[ARRAY_SIZE(chip->active_banks)];
 	u32 count = 0;
 	int i;
 
-	chip = tpm_chip_find_get(chip_num);
-	if (chip == NULL)
+	chip = tpm_chip_find_get(chip);
+	if (!chip)
 		return -ENODEV;
 
 	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
@@ -1019,17 +1017,24 @@ out:
 	return rc;
 }
 
-int tpm_send(u32 chip_num, void *cmd, size_t buflen)
+/**
+ * tpm_send - send a TPM command
+ * @chip:	a &struct tpm_chip instance, %NULL for the default chip
+ * @cmd:	a TPM command buffer
+ * @buflen:	the length of the TPM command buffer
+ *
+ * Return: same as with tpm_transmit_cmd()
+ */
+int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen)
 {
-	struct tpm_chip *chip;
 	int rc;
 
-	chip = tpm_chip_find_get(chip_num);
-	if (chip == NULL)
+	chip = tpm_chip_find_get(chip);
+	if (!chip)
 		return -ENODEV;
 
 	rc = tpm_transmit_cmd(chip, NULL, cmd, buflen, 0, 0,
-			      "attempting tpm_cmd");
+			      "attempting to a send a command");
 	tpm_put_ops(chip);
 	return rc;
 }
@@ -1127,16 +1132,15 @@ static const struct tpm_input_header tpm_getrandom_header = {
 };
 
 /**
- * tpm_get_random() - Get random bytes from the tpm's RNG
- * @chip_num: A specific chip number for the request or TPM_ANY_NUM
- * @out: destination buffer for the random bytes
- * @max: the max number of bytes to write to @out
+ * tpm_get_random() - get random bytes from the TPM's RNG
+ * @chip:	a &struct tpm_chip instance, %NULL for the default chip
+ * @out:	destination buffer for the random bytes
+ * @max:	the max number of bytes to write to @out
  *
- * Returns < 0 on error and the number of bytes read on success
+ * Return: same as with tpm_transmit_cmd()
  */
-int tpm_get_random(u32 chip_num, u8 *out, size_t max)
+int tpm_get_random(struct tpm_chip *chip, u8 *out, size_t max)
 {
-	struct tpm_chip *chip;
 	struct tpm_cmd_t tpm_cmd;
 	u32 recd, num_bytes = min_t(u32, max, TPM_MAX_RNG_DATA), rlength;
 	int err, total = 0, retries = 5;
@@ -1145,8 +1149,8 @@ int tpm_get_random(u32 chip_num, u8 *out, size_t max)
 	if (!out || !num_bytes || max > TPM_MAX_RNG_DATA)
 		return -EINVAL;
 
-	chip = tpm_chip_find_get(chip_num);
-	if (chip == NULL)
+	chip = tpm_chip_find_get(chip);
+	if (!chip)
 		return -ENODEV;
 
 	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
@@ -1188,22 +1192,23 @@ int tpm_get_random(u32 chip_num, u8 *out, size_t max)
 EXPORT_SYMBOL_GPL(tpm_get_random);
 
 /**
- * tpm_seal_trusted() - seal a trusted key
- * @chip_num: A specific chip number for the request or TPM_ANY_NUM
- * @options: authentication values and other options
- * @payload: the key data in clear and encrypted form
+ * tpm_seal_trusted() - seal a trusted key payload
+ * @chip:	a &struct tpm_chip instance, %NULL for the default chip
+ * @options:	authentication values and other options
+ * @payload:	the key data in clear and encrypted form
+ *
+ * Note: only TPM 2.0 chip are supported. TPM 1.x implementation is located in
+ * the keyring subsystem.
  *
- * Returns < 0 on error and 0 on success. At the moment, only TPM 2.0 chips
- * are supported.
+ * Return: same as with tpm_transmit_cmd()
  */
-int tpm_seal_trusted(u32 chip_num, struct trusted_key_payload *payload,
+int tpm_seal_trusted(struct tpm_chip *chip, struct trusted_key_payload *payload,
 		     struct trusted_key_options *options)
 {
-	struct tpm_chip *chip;
 	int rc;
 
-	chip = tpm_chip_find_get(chip_num);
-	if (chip == NULL || !(chip->flags & TPM_CHIP_FLAG_TPM2))
+	chip = tpm_chip_find_get(chip);
+	if (!chip || !(chip->flags & TPM_CHIP_FLAG_TPM2))
 		return -ENODEV;
 
 	rc = tpm2_seal_trusted(chip, payload, options);
@@ -1215,21 +1220,23 @@ EXPORT_SYMBOL_GPL(tpm_seal_trusted);
 
 /**
  * tpm_unseal_trusted() - unseal a trusted key
- * @chip_num: A specific chip number for the request or TPM_ANY_NUM
- * @options: authentication values and other options
- * @payload: the key data in clear and encrypted form
+ * @chip:	a &struct tpm_chip instance, %NULL for the default chip
+ * @options:	authentication values and other options
+ * @payload:	the key data in clear and encrypted form
+ *
+ * Note: only TPM 2.0 chip are supported. TPM 1.x implementation is located in
+ * the keyring subsystem.
  *
- * Returns < 0 on error and 0 on success. At the moment, only TPM 2.0 chips
- * are supported.
+ * Return: same as with tpm_transmit_cmd()
  */
-int tpm_unseal_trusted(u32 chip_num, struct trusted_key_payload *payload,
+int tpm_unseal_trusted(struct tpm_chip *chip,
+		       struct trusted_key_payload *payload,
 		       struct trusted_key_options *options)
 {
-	struct tpm_chip *chip;
 	int rc;
 
-	chip = tpm_chip_find_get(chip_num);
-	if (chip == NULL || !(chip->flags & TPM_CHIP_FLAG_TPM2))
+	chip = tpm_chip_find_get(chip);
+	if (!chip || !(chip->flags & TPM_CHIP_FLAG_TPM2))
 		return -ENODEV;
 
 	rc = tpm2_unseal_trusted(chip, payload, options);
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index c1866cc02e30..6c189174c0d3 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -516,7 +516,7 @@ static inline void tpm_msleep(unsigned int delay_msec)
 		     delay_msec * 1000);
 };
 
-struct tpm_chip *tpm_chip_find_get(int chip_num);
+struct tpm_chip *tpm_chip_find_get(struct tpm_chip *chip);
 __must_check int tpm_try_get_ops(struct tpm_chip *chip);
 void tpm_put_ops(struct tpm_chip *chip);