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Subject[PATCH v3 16/20] tpm: tpm1: rewrite tpm1_get_random() using tpm_buf structure
Date
1. Use tpm_buf in tpm1_get_random()
2. Fix comment in tpm_get_random() so it is clear that
the function is expected to return number of random bytes.

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
---
V3: new in the series
drivers/char/tpm/tpm-interface.c | 2 +-
drivers/char/tpm/tpm.h | 11 ------
drivers/char/tpm/tpm1-cmd.c | 85 +++++++++++++++++++++++-----------------
3 files changed, 50 insertions(+), 48 deletions(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 358ef5bd601e..e3206874be22 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -576,7 +576,7 @@ EXPORT_SYMBOL_GPL(tpm_pm_resume);
* @out: destination buffer for the random bytes
* @max: the max number of bytes to write to @out
*
- * Return: same as with tpm_transmit_cmd()
+ * Return: number of random bytes read or a negative error value.
*/
int tpm_get_random(struct tpm_chip *chip, u8 *out, size_t max)
{
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 4ccffbb56864..d6eca81a011a 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -396,20 +396,9 @@ struct tpm_pcrread_in {
* compiler warnings about stack frame size. */
#define TPM_MAX_RNG_DATA 128

-struct tpm_getrandom_out {
- __be32 rng_data_len;
- u8 rng_data[TPM_MAX_RNG_DATA];
-} __packed;
-
-struct tpm_getrandom_in {
- __be32 num_bytes;
-} __packed;
-
typedef union {
struct tpm_pcrread_in pcrread_in;
struct tpm_pcrread_out pcrread_out;
- struct tpm_getrandom_in getrandom_in;
- struct tpm_getrandom_out getrandom_out;
} tpm_cmd_params;

struct tpm_cmd_t {
diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
index 90e5bc1720ad..5708d4bf908f 100644
--- a/drivers/char/tpm/tpm1-cmd.c
+++ b/drivers/char/tpm/tpm1-cmd.c
@@ -507,58 +507,71 @@ 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
-#define TPM_GETRANDOM_RESULT_SIZE 18
-static const struct tpm_input_header tpm_getrandom_header = {
- .tag = cpu_to_be16(TPM_TAG_RQU_COMMAND),
- .length = cpu_to_be32(14),
- .ordinal = cpu_to_be32(TPM_ORD_GET_RANDOM)
-};
+struct tpm1_get_random_out {
+ __be32 rng_data_len;
+ u8 rng_data[TPM_MAX_RNG_DATA];
+} __packed;

-int tpm1_get_random(struct tpm_chip *chip, u8 *out, size_t max)
+/**
+ * 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 or a TPM return code otherwise
+ */
+int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
{
- struct tpm_cmd_t tpm_cmd;
+ struct tpm1_get_random_out *out;
+ u32 num_bytes = min_t(u32, max, TPM_MAX_RNG_DATA);
+ struct tpm_buf buf;
+ u32 total = 0;
+ int retries = 5;
u32 recd;
- u32 num_bytes = min_t(u32, max, TPM_MAX_RNG_DATA);
- u32 rlength;
- int err, total = 0, retries = 5;
- u8 *dest = out;
+ int rc;

- if (!out || !num_bytes || max > TPM_MAX_RNG_DATA)
- return -EINVAL;
+ rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_RANDOM);
+ if (rc)
+ return rc;

do {
- tpm_cmd.header.in = tpm_getrandom_header;
- tpm_cmd.params.getrandom_in.num_bytes = cpu_to_be32(num_bytes);
-
- err = tpm_transmit_cmd(chip, NULL, &tpm_cmd,
- TPM_GETRANDOM_RESULT_SIZE + num_bytes,
- offsetof(struct tpm_getrandom_out,
- rng_data),
- 0, "attempting get random");
- if (err)
- break;
+ tpm_buf_append_u32(&buf, num_bytes);
+
+ rc = tpm_transmit_cmd(chip, NULL, buf.data, PAGE_SIZE,
+ sizeof(out->rng_data_len), 0,
+ "attempting get random");
+ if (rc)
+ goto out;

- recd = be32_to_cpu(tpm_cmd.params.getrandom_out.rng_data_len);
+ out = (struct tpm1_get_random_out *)&buf.data[TPM_HEADER_SIZE];
+
+ recd = be32_to_cpu(out->rng_data_len);
if (recd > num_bytes) {
- total = -EFAULT;
- break;
+ rc = -EFAULT;
+ goto out;
}

- rlength = be32_to_cpu(tpm_cmd.header.out.length);
- if (rlength < TPM_HEADER_SIZE +
- offsetof(struct tpm_getrandom_out, rng_data) +
- recd) {
- total = -EFAULT;
- break;
+ if (tpm_buf_length(&buf) < TPM_HEADER_SIZE +
+ sizeof(out->rng_data_len) + recd) {
+ rc = -EFAULT;
+ goto out;
}
- memcpy(dest, tpm_cmd.params.getrandom_out.rng_data, recd);
+ memcpy(dest, out->rng_data, recd);

dest += recd;
total += recd;
num_bytes -= recd;
- } while (retries-- && (size_t)total < max);

- return total ? total : -EIO;
+ tpm_buf_reset(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_RANDOM);
+ } while (retries-- && total < max);
+
+ rc = total ? total : -EIO;
+out:
+ tpm_buf_destroy(&buf);
+ return rc;
}

#define TPM_ORDINAL_PCRREAD 21
--
2.14.4
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