Re: [PATCH v2] tpm: tpm2-space: Resize session and context buffers dynamically

[Jerry Snitselaar <jsnitsel@redhat.com>]

On Thu Jun 25 20, Jarkko Sakkinen wrote:
>Re-allocate context and session buffers when needed. Scale them in page
>increments so that the reallocation is only seldomly required, and thus
>causes minimal stress to the system. Add a static maximum limit of four
>pages for buffer sizes.
>
>Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
>Suggested-by: Stefan Berger <stefanb@linux.ibm.com>
>Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
>---
>Tested only for compilation.
>v2: TPM2_SPACE_DEFAULT_BUFFER_SIZE
> drivers/char/tpm/tpm2-space.c | 87 ++++++++++++++++++++++++-----------
> include/linux/tpm.h           |  6 ++-
> 2 files changed, 64 insertions(+), 29 deletions(-)
>
>diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
>index 982d341d8837..b8ece01d6afb 100644
>--- a/drivers/char/tpm/tpm2-space.c
>+++ b/drivers/char/tpm/tpm2-space.c
>@@ -15,6 +15,9 @@
> #include <asm/unaligned.h>
> #include "tpm.h"
>
>+#define TPM2_SPACE_DEFAULT_BUFFER_SIZE	PAGE_SIZE
>+#define TPM2_SPACE_MAX_BUFFER_SIZE	(4 * PAGE_SIZE)
>+
> enum tpm2_handle_types {
> 	TPM2_HT_HMAC_SESSION	= 0x02000000,
> 	TPM2_HT_POLICY_SESSION	= 0x03000000,
>@@ -40,16 +43,21 @@ static void tpm2_flush_sessions(struct tpm_chip *chip, struct tpm_space *space)
>
> int tpm2_init_space(struct tpm_space *space)
> {
>-	space->context_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
>+	space->context_buf = kzalloc(TPM2_SPACE_DEFAULT_BUFFER_SIZE,
>+				     GFP_KERNEL);
> 	if (!space->context_buf)
> 		return -ENOMEM;
>
>-	space->session_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
>+	space->session_buf = kzalloc(TPM2_SPACE_DEFAULT_BUFFER_SIZE,
>+				     GFP_KERNEL);
> 	if (space->session_buf == NULL) {
> 		kfree(space->context_buf);
>+		space->context_buf = NULL;
> 		return -ENOMEM;
> 	}
>
>+	space->context_size = TPM2_SPACE_DEFAULT_BUFFER_SIZE;
>+	space->session_size = TPM2_SPACE_DEFAULT_BUFFER_SIZE;
> 	return 0;
> }
>
>@@ -116,11 +124,13 @@ static int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
> 	return 0;
> }
>
>-static int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 *buf,
>-			     unsigned int buf_size, unsigned int *offset)
>+static int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 **buf,
>+			     unsigned int *buf_size, unsigned int *offset)
> {
>-	struct tpm_buf tbuf;
>+	unsigned int new_buf_size;
> 	unsigned int body_size;
>+	struct tpm_buf tbuf;
>+	void *new_buf;
> 	int rc;
>
> 	rc = tpm_buf_init(&tbuf, TPM2_ST_NO_SESSIONS, TPM2_CC_CONTEXT_SAVE);
>@@ -131,31 +141,48 @@ static int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 *buf,
>
> 	rc = tpm_transmit_cmd(chip, &tbuf, 0, NULL);
> 	if (rc < 0) {
>-		dev_warn(&chip->dev, "%s: failed with a system error %d\n",
>-			 __func__, rc);
>-		tpm_buf_destroy(&tbuf);
>-		return -EFAULT;
>+		rc = -EFAULT;
>+		goto err;
> 	} else if (tpm2_rc_value(rc) == TPM2_RC_REFERENCE_H0) {
>-		tpm_buf_destroy(&tbuf);
>-		return -ENOENT;
>+		rc = -ENOENT;
>+		goto out;
> 	} else if (rc) {
>-		dev_warn(&chip->dev, "%s: failed with a TPM error 0x%04X\n",
>-			 __func__, rc);
>-		tpm_buf_destroy(&tbuf);
>-		return -EFAULT;
>+		rc = -EFAULT;
>+		goto err;
> 	}
>

Would it be worthwhile to still output something here since it is changing
the value of rc returned from tpm_transmit_cmd()? Wondering if it would
be useful for debugging to know what the returned error was. Other than
that question looks good to me pending what is decided on using PAGE_SIZE.

Regards,
Jerry

> 	body_size = tpm_buf_length(&tbuf) - TPM_HEADER_SIZE;
>-	if ((*offset + body_size) > buf_size) {
>-		dev_warn(&chip->dev, "%s: out of backing storage\n", __func__);
>-		tpm_buf_destroy(&tbuf);
>-		return -ENOMEM;
>+	/* We grow the buffer in page increments. */
>+	new_buf_size = PFN_UP(*offset + body_size);
>+
>+	if (new_buf_size > TPM2_SPACE_MAX_BUFFER_SIZE) {
>+		rc = -ENOMEM;
>+		goto err;
> 	}
>
>-	memcpy(&buf[*offset], &tbuf.data[TPM_HEADER_SIZE], body_size);
>+	if (new_buf_size > *buf_size) {
>+		new_buf = krealloc(*buf, new_buf_size, GFP_KERNEL);
>+		if (!new_buf) {
>+			rc = -ENOMEM;
>+			goto err;
>+		}
>+
>+		*buf = new_buf;
>+		*buf_size = new_buf_size;
>+	}
>+
>+	memcpy(*buf + *offset, &tbuf.data[TPM_HEADER_SIZE], body_size);
> 	*offset += body_size;
>+
>+out:
> 	tpm_buf_destroy(&tbuf);
>-	return 0;
>+	return rc;
>+
>+err:
>+	dev_warn(&chip->dev, "%s: ret=%d\n", __func__, rc);
>+
>+	tpm_buf_destroy(&tbuf);
>+	return rc;
> }
>
> void tpm2_flush_space(struct tpm_chip *chip)
>@@ -311,8 +338,10 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u8 *cmd,
> 	       sizeof(space->context_tbl));
> 	memcpy(&chip->work_space.session_tbl, &space->session_tbl,
> 	       sizeof(space->session_tbl));
>-	memcpy(chip->work_space.context_buf, space->context_buf, PAGE_SIZE);
>-	memcpy(chip->work_space.session_buf, space->session_buf, PAGE_SIZE);
>+	memcpy(chip->work_space.context_buf, space->context_buf,
>+	       space->context_size);
>+	memcpy(chip->work_space.session_buf, space->session_buf,
>+	       space->session_size);
>
> 	rc = tpm2_load_space(chip);
> 	if (rc) {
>@@ -492,7 +521,8 @@ static int tpm2_save_space(struct tpm_chip *chip)
> 			continue;
>
> 		rc = tpm2_save_context(chip, space->context_tbl[i],
>-				       space->context_buf, PAGE_SIZE,
>+				       &space->context_buf,
>+				       &space->context_size,
> 				       &offset);
> 		if (rc == -ENOENT) {
> 			space->context_tbl[i] = 0;
>@@ -509,7 +539,8 @@ static int tpm2_save_space(struct tpm_chip *chip)
> 			continue;
>
> 		rc = tpm2_save_context(chip, space->session_tbl[i],
>-				       space->session_buf, PAGE_SIZE,
>+				       &space->session_buf,
>+				       &space->session_size,
> 				       &offset);
>
> 		if (rc == -ENOENT) {
>@@ -557,8 +588,10 @@ int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space,
> 	       sizeof(space->context_tbl));
> 	memcpy(&space->session_tbl, &chip->work_space.session_tbl,
> 	       sizeof(space->session_tbl));
>-	memcpy(space->context_buf, chip->work_space.context_buf, PAGE_SIZE);
>-	memcpy(space->session_buf, chip->work_space.session_buf, PAGE_SIZE);
>+	memcpy(space->context_buf, chip->work_space.context_buf,
>+	       space->context_size);
>+	memcpy(space->session_buf, chip->work_space.session_buf,
>+	       space->session_size);
>
> 	return 0;
> out:
>diff --git a/include/linux/tpm.h b/include/linux/tpm.h
>index 03e9b184411b..9ea39e8f7162 100644
>--- a/include/linux/tpm.h
>+++ b/include/linux/tpm.h
>@@ -92,10 +92,12 @@ enum tpm_duration {
> #define TPM_PPI_VERSION_LEN		3
>
> struct tpm_space {
>+	u8  *context_buf;
>+	u8  *session_buf;
>+	u32 context_size;
>+	u32 session_size;
> 	u32 context_tbl[3];
>-	u8 *context_buf;
> 	u32 session_tbl[3];
>-	u8 *session_buf;
> };
>
> struct tpm_bios_log {
>-- 
>2.25.1
>