[PATCH v3 6/7] tpm: Orchestrate TPM commands in tpm_get_random()

Jarkko Sakkinen
2025-12-10T14:40:18Z

tpm1_get_random() and tpm2_get_random() contain duplicate orchestration
code. Consolidate orchestration to tpm_get_random().

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
drivers/char/tpm/tpm-interface.c | 165 ++++++++++++++++++++++++++++---
drivers/char/tpm/tpm.h | 2 -
drivers/char/tpm/tpm1-cmd.c | 62 ------------
drivers/char/tpm/tpm2-cmd.c | 95 ------------------
4 files changed, 154 insertions(+), 170 deletions(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index f745a098908b..ab52a1cb0a78 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -26,7 +26,7 @@
#include <linux/suspend.h>
#include <linux/freezer.h>
#include <linux/tpm_eventlog.h>
-
+#include <linux/tpm_command.h>
#include "tpm.h"

/*
@@ -486,19 +486,143 @@ int tpm_pm_resume(struct device *dev)
}
EXPORT_SYMBOL_GPL(tpm_pm_resume);

+struct tpm1_get_random_out {
+ __be32 rng_data_len;
+ u8 rng_data[TPM_MAX_RNG_DATA];
+} __packed;
+
+static int tpm1_get_random(struct tpm_chip *chip, u8 *out, size_t max)
+{
+ struct tpm1_get_random_out *resp;
+ u32 recd;
+ int rc;
+
+ if (!out || !max || max > TPM_MAX_RNG_DATA)
+ return -EINVAL;
+
+ struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ tpm_buf_init(buf, TPM_BUFSIZE);
+ tpm_buf_reset(buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GETRANDOM);
+ tpm_buf_append_u32(buf, max);
+
+ rc = tpm_transmit_cmd(chip, buf, sizeof(resp->rng_data_len), "TPM_GetRandom");
+ if (rc) {
+ if (rc > 0)
+ rc = -EIO;
+ return rc;
+ }
+
+ resp = (struct tpm1_get_random_out *)&buf->data[TPM_HEADER_SIZE];
+
+ recd = be32_to_cpu(resp->rng_data_len);
+ if (recd > max)
+ return -EIO;
+
+ if (buf->length < TPM_HEADER_SIZE + sizeof(resp->rng_data_len) + recd)
+ return -EIO;
+
+ memcpy(out, resp->rng_data, recd);
+ return recd;
+}
+
+struct tpm2_get_random_out {
+ __be16 size;
+ u8 buffer[TPM_MAX_RNG_DATA];
+} __packed;
+
+static int tpm2_get_random(struct tpm_chip *chip, u8 *out, size_t max)
+{
+ struct tpm2_get_random_out *resp;
+ struct tpm_header *head;
+ off_t offset;
+ u32 recd;
+ int ret;
+
+ if (!out || !max || max > TPM_MAX_RNG_DATA)
+ return -EINVAL;
+
+ struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ tpm_buf_init(buf, TPM_BUFSIZE);
+ tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_GET_RANDOM);
+ if (tpm2_chip_auth(chip)) {
+ tpm_buf_append_hmac_session(chip, buf,
+ TPM2_SA_ENCRYPT | TPM2_SA_CONTINUE_SESSION,
+ NULL, 0);
+ } else {
+ head = (struct tpm_header *)buf->data;
+ head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
+ }
+ tpm_buf_append_u16(buf, max);
+
+ ret = tpm_buf_fill_hmac_session(chip, buf);
+ if (ret)
+ return ret;
+
+ ret = tpm_transmit_cmd(chip, buf, offsetof(struct tpm2_get_random_out, buffer),
+ "TPM2_GetRandom");
+
+ ret = tpm_buf_check_hmac_response(chip, buf, ret);
+ if (ret) {
+ if (ret > 0)
+ ret = -EIO;
+
+ goto out;
+ }
+
+ head = (struct tpm_header *)buf->data;
+ offset = TPM_HEADER_SIZE;
+
+ /* Skip the parameter size field: */
+ if (be16_to_cpu(head->tag) == TPM2_ST_SESSIONS)
+ offset += 4;
+
+ resp = (struct tpm2_get_random_out *)&buf->data[offset];
+ recd = min_t(u32, be16_to_cpu(resp->size), max);
+
+ if (tpm_buf_length(buf) <
+ TPM_HEADER_SIZE + offsetof(struct tpm2_get_random_out, buffer) + recd) {
+ ret = -EIO;
+ goto out;
+ }
+
+ memcpy(out, resp->buffer, recd);
+ return recd;
+
+out:
+ tpm2_end_auth_session(chip);
+ return ret;
+}
+
/**
- * 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
+ * tpm_get_random() - Get random bytes from the TPM's RNG
+ * @chip: A &tpm_chip instance. Whenset to %NULL, the default chip is used.
+ * @out: Destination buffer for the acquired random bytes.
+ * @max: The maximum number of bytes to write to @out.
*
- * Return: number of random bytes read or a negative error value.
+ * Iterates pulling more bytes from TPM up until all of the @max bytes have been
+ * received.
+ *
+ * Returns the number of random bytes read on success.
+ * Returns -EINVAL when @out is NULL, or @max is not between zero and
+ * %TPM_MAX_RNG_DATA.
+ * Returns tpm_transmit_cmd() error codes when the TPM command results an
+ * error.
*/
int tpm_get_random(struct tpm_chip *chip, u8 *out, size_t max)
{
+ u32 num_bytes = max;
+ u8 *out_ptr = out;
+ int retries = 5;
+ int total = 0;
int rc;

- if (!out || max > TPM_MAX_RNG_DATA)
+ if (!out || !max || max > TPM_MAX_RNG_DATA)
return -EINVAL;

if (!chip)
@@ -508,11 +632,30 @@ int tpm_get_random(struct tpm_chip *chip, u8 *out, size_t max)
if (rc)
return rc;

- if (chip->flags & TPM_CHIP_FLAG_TPM2)
- rc = tpm2_get_random(chip, out, max);
- else
- rc = tpm1_get_random(chip, out, max);
+ if (chip->flags & TPM_CHIP_FLAG_TPM2) {
+ rc = tpm2_start_auth_session(chip);
+ if (rc)
+ return rc;
+ }
+
+ do {
+ if (chip->flags & TPM_CHIP_FLAG_TPM2)
+ rc = tpm2_get_random(chip, out_ptr, num_bytes);
+ else
+ rc = tpm1_get_random(chip, out_ptr, num_bytes);
+
+ if (rc < 0)
+ goto err;
+
+ out_ptr += rc;
+ total += rc;
+ num_bytes -= rc;
+ } while (retries-- && total < max);
+
+ tpm_put_ops(chip);
+ return total ? total : -EIO;

+err:
tpm_put_ops(chip);
return rc;
}
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 5395927c62fc..c4bbd8f04605 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -250,7 +250,6 @@ int tpm1_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash,
int tpm1_pcr_read(struct tpm_chip *chip, u32 pcr_idx, u8 *res_buf);
ssize_t tpm1_getcap(struct tpm_chip *chip, u32 subcap_id, cap_t *cap,
const char *desc, size_t min_cap_length);
-int tpm1_get_random(struct tpm_chip *chip, u8 *out, size_t max);
int tpm1_get_pcr_allocation(struct tpm_chip *chip);
unsigned long tpm_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal);
int tpm_pm_suspend(struct device *dev);
@@ -290,7 +289,6 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
struct tpm_digest *digest, u16 *digest_size_ptr);
int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
struct tpm_digest *digests);
-int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max);
ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id,
u32 *value, const char *desc);

diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
index 11090053ef54..d8f16e66666b 100644
--- a/drivers/char/tpm/tpm1-cmd.c
+++ b/drivers/char/tpm/tpm1-cmd.c
@@ -502,68 +502,6 @@ ssize_t tpm1_getcap(struct tpm_chip *chip, u32 subcap_id, cap_t *cap,
}
EXPORT_SYMBOL_GPL(tpm1_getcap);

-#define TPM_ORD_GET_RANDOM 70
-struct tpm1_get_random_out {
- __be32 rng_data_len;
- u8 rng_data[TPM_MAX_RNG_DATA];
-} __packed;
-
-/**
- * tpm1_get_random() - get random bytes from the TPM's RNG
- * @chip: a &struct tpm_chip instance
- * @dest: destination buffer for the random bytes
- * @max: the maximum number of bytes to write to @dest
- *
- * Return:
- * * number of bytes read
- * * -errno (positive TPM return codes are masked to -EIO)
- */
-int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
-{
- struct tpm1_get_random_out *out;
- u32 num_bytes = min_t(u32, max, TPM_MAX_RNG_DATA);
- u32 total = 0;
- int retries = 5;
- u32 recd;
- int rc;
-
- struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
- if (!buf)
- return -ENOMEM;
-
- tpm_buf_init(buf, TPM_BUFSIZE);
- do {
- tpm_buf_reset(buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_RANDOM);
- tpm_buf_append_u32(buf, num_bytes);
-
- rc = tpm_transmit_cmd(chip, buf, sizeof(out->rng_data_len), "TPM_GetRandom");
- if (rc) {
- if (rc > 0)
- rc = -EIO;
- return rc;
- }
-
- out = (struct tpm1_get_random_out *)&buf->data[TPM_HEADER_SIZE];
-
- recd = be32_to_cpu(out->rng_data_len);
- if (recd > num_bytes)
- return -EFAULT;
-
- if (buf->length < TPM_HEADER_SIZE +
- sizeof(out->rng_data_len) + recd)
- return -EFAULT;
-
- memcpy(dest, out->rng_data, recd);
-
- dest += recd;
- total += recd;
- num_bytes -= recd;
- } while (retries-- && total < max);
-
- rc = total ? (int)total : -EIO;
- return rc;
-}
-
#define TPM_ORD_PCRREAD 21
int tpm1_pcr_read(struct tpm_chip *chip, u32 pcr_idx, u8 *res_buf)
{
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index bc50d6b734cf..f066efb54a2c 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -233,101 +233,6 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
return rc;
}

-struct tpm2_get_random_out {
- __be16 size;
- u8 buffer[TPM_MAX_RNG_DATA];
-} __packed;
-
-/**
- * tpm2_get_random() - get random bytes from the TPM RNG
- *
- * @chip: a &tpm_chip instance
- * @dest: destination buffer
- * @max: the max number of random bytes to pull
- *
- * Return:
- * size of the buffer on success,
- * -errno otherwise (positive TPM return codes are masked to -EIO)
- */
-int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
-{
- struct tpm2_get_random_out *out;
- struct tpm_header *head;
- u32 recd;
- u32 num_bytes = max;
- int err;
- int total = 0;
- int retries = 5;
- u8 *dest_ptr = dest;
- off_t offset;
-
- if (!num_bytes || max > TPM_MAX_RNG_DATA)
- return -EINVAL;
-
- struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
- if (!buf)
- return -ENOMEM;
-
- err = tpm2_start_auth_session(chip);
- if (err)
- return err;
-
- tpm_buf_init(buf, TPM_BUFSIZE);
- do {
- tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_GET_RANDOM);
- if (tpm2_chip_auth(chip)) {
- tpm_buf_append_hmac_session(chip, buf,
- TPM2_SA_ENCRYPT |
- TPM2_SA_CONTINUE_SESSION,
- NULL, 0);
- } else {
- head = (struct tpm_header *)buf->data;
- head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
- }
- tpm_buf_append_u16(buf, num_bytes);
- err = tpm_buf_fill_hmac_session(chip, buf);
- if (err)
- return err;
-
- err = tpm_transmit_cmd(chip, buf,
- offsetof(struct tpm2_get_random_out,
- buffer),
- "TPM2_GetRandom");
- err = tpm_buf_check_hmac_response(chip, buf, err);
- if (err) {
- if (err > 0)
- err = -EIO;
- goto out;
- }
-
- head = (struct tpm_header *)buf->data;
- offset = TPM_HEADER_SIZE;
- /* Skip the parameter size field: */
- if (be16_to_cpu(head->tag) == TPM2_ST_SESSIONS)
- offset += 4;
-
- out = (struct tpm2_get_random_out *)&buf->data[offset];
- recd = min_t(u32, be16_to_cpu(out->size), num_bytes);
- if (tpm_buf_length(buf) <
- TPM_HEADER_SIZE +
- offsetof(struct tpm2_get_random_out, buffer) +
- recd) {
- err = -EFAULT;
- goto out;
- }
- memcpy(dest_ptr, out->buffer, recd);
-
- dest_ptr += recd;
- total += recd;
- num_bytes -= recd;
- } while (retries-- && total < max);
-
- return total ? total : -EIO;
-out:
- tpm2_end_auth_session(chip);
- return err;
-}
-
/**
* tpm2_flush_context() - execute a TPM2_FlushContext command
* @chip: TPM chip to use
--
2.52.0