[PATCH v10 3/4] tpm, tpm2-cmd: Use stack for trivial cases

Jarkko Sakkinen
2025-09-21T02:08:26Z

From: Jarkko Sakkinen <jarkko.sakkinen@opinsys.com>

Use stack allocation for trivial "low-hanging fruit" sites, which are often
also critical code paths associated with probing and power management.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@opinsys.com>
---
drivers/char/tpm/tpm2-cmd.c | 57 ++++++++++++++-----------------------
1 file changed, 22 insertions(+), 35 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 245c7c952e82..3c55f60ae4c2 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -382,14 +382,13 @@ EXPORT_SYMBOL_GPL(tpm2_get_tpm_pt);
*/
void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type)
{
- struct tpm_buf *buf __free(kfree) = kzalloc(PAGE_SIZE, GFP_KERNEL);
- if (!buf)
- return;
+ u8 buf_data[TPM_BUF_MIN_SIZE];
+ struct tpm_buf *buf = (struct tpm_buf *)buf_data;

- tpm_buf_init(buf, TPM_BUF_MAX_SIZE);
+ tpm_buf_init(buf, TPM_BUF_MIN_SIZE);
tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SHUTDOWN);
tpm_buf_append_u16(buf, shutdown_type);
- tpm_transmit_cmd(chip, buf, 0, "stopping the TPM");
+ tpm_transmit_cmd(chip, buf, 0, "TPM2_Shutdown");
}

/**
@@ -407,58 +406,49 @@ void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type)
*/
static int tpm2_do_selftest(struct tpm_chip *chip)
{
+ u8 buf_data[TPM_BUF_MIN_SIZE];
+ struct tpm_buf *buf = (struct tpm_buf *)buf_data;
int full;
int rc;

- struct tpm_buf *buf __free(kfree) = kzalloc(PAGE_SIZE, GFP_KERNEL);
- if (!buf)
- return -ENOMEM;
-
- tpm_buf_init(buf, TPM_BUF_MAX_SIZE);
- tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SELF_TEST);
+ tpm_buf_init(buf, TPM_BUF_MIN_SIZE);
for (full = 0; full < 2; full++) {
tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SELF_TEST);
tpm_buf_append_u8(buf, full);
- rc = tpm_transmit_cmd(chip, buf, 0,
- "attempting the self test");
-
+ rc = tpm_transmit_cmd(chip, buf, 0, "TPM2_SelfTest");
if (rc == TPM2_RC_TESTING)
rc = TPM2_RC_SUCCESS;
if (rc == TPM2_RC_INITIALIZE || rc == TPM2_RC_SUCCESS)
return rc;
}
-
return rc;
}

/**
- * tpm2_probe() - probe for the TPM 2.0 protocol
+ * tpm2_probe() - Probe for the TPM 2.0 protocol
* @chip: a &tpm_chip instance
*
- * Send an idempotent TPM 2.0 command and see whether there is TPM2 chip in the
- * other end based on the response tag. The flag TPM_CHIP_FLAG_TPM2 is set by
- * this function if this is the case.
+ * Sends an idempotent TPM 2.0 command, and based on the response tag deduces
+ * whether a functional TPM2 chip is on the other side. When the result is
+ * positive, TPM_CHIP_FLAG_TPM2 is append to the chip's flags.
*
* Return:
- * 0 on success,
- * -errno otherwise
+ * * 0 on success,
+ * * -errno otherwise
*/
int tpm2_probe(struct tpm_chip *chip)
{
+ u8 buf_data[TPM_BUF_MIN_SIZE];
+ struct tpm_buf *buf = (struct tpm_buf *)buf_data;
struct tpm_header *out;
int rc;

- struct tpm_buf *buf __free(kfree) = kzalloc(PAGE_SIZE, GFP_KERNEL);
- if (!buf)
- return -ENOMEM;
-
- tpm_buf_init(buf, TPM_BUF_MAX_SIZE);
+ tpm_buf_init(buf, TPM_BUF_MIN_SIZE);
tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
tpm_buf_append_u32(buf, TPM2_CAP_TPM_PROPERTIES);
tpm_buf_append_u32(buf, TPM_PT_TOTAL_COMMANDS);
tpm_buf_append_u32(buf, 1);
rc = tpm_transmit_cmd(chip, buf, 0, NULL);
- /* We ignore TPM return codes on purpose. */
if (rc >= 0) {
out = (struct tpm_header *)buf->data;
if (be16_to_cpu(out->tag) == TPM2_ST_NO_SESSIONS)
@@ -651,17 +641,14 @@ EXPORT_SYMBOL_GPL(tpm2_get_cc_attrs_tbl);

static int tpm2_startup(struct tpm_chip *chip)
{
- struct tpm_buf *buf __free(kfree) = kzalloc(PAGE_SIZE, GFP_KERNEL);
- if (!buf)
- return -ENOMEM;
-
- dev_info(&chip->dev, "starting up the TPM manually\n");
+ u8 buf_data[TPM_BUF_MIN_SIZE];
+ struct tpm_buf *buf = (struct tpm_buf *)buf_data;

- tpm_buf_init(buf, TPM_BUF_MAX_SIZE);
+ dev_info(&chip->dev, "TPM2_Startup\n");
+ tpm_buf_init(buf, TPM_BUF_MIN_SIZE);
tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_STARTUP);
tpm_buf_append_u16(buf, TPM2_SU_CLEAR);
-
- return tpm_transmit_cmd(chip, buf, 0, "attempting to start the TPM");
+ return tpm_transmit_cmd(chip, buf, 0, "TPM2_Startup");
}

/**
--
2.39.5