[PATCH V2] tpm_crb: Add support for CRB devices based on Pluton

* [PATCH V2] tpm_crb: Add support for CRB devices based on Pluton
@ 2022-12-31  9:14 Matthew Garrett
  2023-01-16  6:29 ` Jarkko Sakkinen
  0 siblings, 1 reply; 2+ messages in thread
From: Matthew Garrett @ 2022-12-31  9:14 UTC (permalink / raw)
  To: peterhuewe, jarkko, jgg, linux-integrity; +Cc: Matthew Garrett

Pluton is an integrated security processor present in some recent Ryzen
parts. If it's enabled, it presents two devices - an MSFT0101 ACPI device
that's broadly an implementation of a Command Response Buffer TPM2, and
an MSFT0200 ACPI device whose functionality I haven't examined in detail
yet. This patch only attempts to add support for the TPM device.

There's a few things that need to be handled here. The first is that the
TPM2 ACPI table uses a previously undefined start method identifier. The
table format appears to include 16 bytes of startup data, which corresponds
to one 64-bit address for a start message and one 64-bit address for a
completion response. The second is that the ACPI tables on the Thinkpad Z13
I'm testing this on don't define any memory windows in _CRS (or, more
accurately, there are two empty memory windows). This check doesn't seem
strictly necessary, so I've skipped that.

Finally, it seems like chip needs to be explicitly asked to transition into
ready status on every command. Failing to do this means that if two commands
are sent in succession without an idle/ready transition in between,
everything will appear to work fine but the response is simply the original
command. I'm working without any docs here, so I'm not sure if this is
actually the required behaviour or if I'm missing something somewhere else,
but doing this results in the chip working reliably.

Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
---

Updated with Jarkko's feedback

 drivers/char/tpm/tpm_crb.c | 102 +++++++++++++++++++++++++++++++++----
 include/acpi/actbl3.h      |   1 +
 2 files changed, 94 insertions(+), 9 deletions(-)

diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
index 7e9da671a0e8..1d7b27d57974 100644
--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c
@@ -98,6 +98,8 @@ struct crb_priv {
 	u8 __iomem *rsp;
 	u32 cmd_size;
 	u32 smc_func_id;
+	u32 __iomem *pluton_start_addr;
+	u32 __iomem *pluton_reply_addr;
 };
 
 struct tpm2_crb_smc {
@@ -108,6 +110,11 @@ struct tpm2_crb_smc {
 	u32 smc_func_id;
 };
 
+struct tpm2_crb_pluton {
+	u64 start_addr;
+	u64 reply_addr;
+};
+
 static bool crb_wait_for_reg_32(u32 __iomem *reg, u32 mask, u32 value,
 				unsigned long timeout)
 {
@@ -127,6 +134,25 @@ static bool crb_wait_for_reg_32(u32 __iomem *reg, u32 mask, u32 value,
 	return ((ioread32(reg) & mask) == value);
 }
 
+static int crb_try_pluton_doorbell(struct crb_priv *priv, bool wait_for_complete)
+{
+	if (priv->sm != ACPI_TPM2_COMMAND_BUFFER_WITH_PLUTON)
+		return 0;
+
+	if (!crb_wait_for_reg_32(priv->pluton_reply_addr, ~0, 1, TPM2_TIMEOUT_C))
+		return -ETIME;
+
+	iowrite32(1, priv->pluton_start_addr);
+	if (wait_for_complete == false)
+		return 0;
+
+	if (!crb_wait_for_reg_32(priv->pluton_start_addr,
+				 0xffffffff, 0, 200))
+		return -ETIME;
+
+	return 0;
+}
+
 /**
  * __crb_go_idle - request tpm crb device to go the idle state
  *
@@ -145,6 +171,8 @@ static bool crb_wait_for_reg_32(u32 __iomem *reg, u32 mask, u32 value,
  */
 static int __crb_go_idle(struct device *dev, struct crb_priv *priv)
 {
+	int rc;
+
 	if ((priv->sm == ACPI_TPM2_START_METHOD) ||
 	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
 	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
@@ -152,6 +180,11 @@ static int __crb_go_idle(struct device *dev, struct crb_priv *priv)
 
 	iowrite32(CRB_CTRL_REQ_GO_IDLE, &priv->regs_t->ctrl_req);
 
+	rc = crb_try_pluton_doorbell(priv, true);
+
+	if (rc)
+		return rc;
+
 	if (!crb_wait_for_reg_32(&priv->regs_t->ctrl_req,
 				 CRB_CTRL_REQ_GO_IDLE/* mask */,
 				 0, /* value */
@@ -188,12 +221,20 @@ static int crb_go_idle(struct tpm_chip *chip)
  */
 static int __crb_cmd_ready(struct device *dev, struct crb_priv *priv)
 {
+	int rc;
+
 	if ((priv->sm == ACPI_TPM2_START_METHOD) ||
 	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
 	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
 		return 0;
 
 	iowrite32(CRB_CTRL_REQ_CMD_READY, &priv->regs_t->ctrl_req);
+
+	rc = crb_try_pluton_doorbell(priv, true);
+
+	if (rc)
+		return rc;
+
 	if (!crb_wait_for_reg_32(&priv->regs_t->ctrl_req,
 				 CRB_CTRL_REQ_CMD_READY /* mask */,
 				 0, /* value */
@@ -371,6 +412,10 @@ static int crb_send(struct tpm_chip *chip, u8 *buf, size_t len)
 		return -E2BIG;
 	}
 
+	/* Seems to be necessary for every command */
+	if (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_PLUTON)
+		__crb_cmd_ready(&chip->dev, priv);
+
 	memcpy_toio(priv->cmd, buf, len);
 
 	/* Make sure that cmd is populated before issuing start. */
@@ -394,6 +439,11 @@ static int crb_send(struct tpm_chip *chip, u8 *buf, size_t len)
 		rc = tpm_crb_smc_start(&chip->dev, priv->smc_func_id);
 	}
 
+	if (rc)
+		return rc;
+
+	rc = crb_try_pluton_doorbell(priv, false);
+
 	return rc;
 }
 
@@ -524,15 +574,18 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
 		return ret;
 	acpi_dev_free_resource_list(&acpi_resource_list);
 
-	if (resource_type(iores_array) != IORESOURCE_MEM) {
-		dev_err(dev, FW_BUG "TPM2 ACPI table does not define a memory resource\n");
-		return -EINVAL;
-	} else if (resource_type(iores_array + TPM_CRB_MAX_RESOURCES) ==
-		IORESOURCE_MEM) {
-		dev_warn(dev, "TPM2 ACPI table defines too many memory resources\n");
-		memset(iores_array + TPM_CRB_MAX_RESOURCES,
-		       0, sizeof(*iores_array));
-		iores_array[TPM_CRB_MAX_RESOURCES].flags = 0;
+	/* Pluton doesn't appear to define ACPI memory regions */
+	if (priv->sm != ACPI_TPM2_COMMAND_BUFFER_WITH_PLUTON) {
+		if (resource_type(iores_array) != IORESOURCE_MEM) {
+			dev_err(dev, FW_BUG "TPM2 ACPI table does not define a memory resource\n");
+			return -EINVAL;
+		} else if (resource_type(iores_array + TPM_CRB_MAX_RESOURCES) ==
+			   IORESOURCE_MEM) {
+			dev_warn(dev, "TPM2 ACPI table defines too many memory resources\n");
+			memset(iores_array + TPM_CRB_MAX_RESOURCES,
+			       0, sizeof(*iores_array));
+			iores_array[TPM_CRB_MAX_RESOURCES].flags = 0;
+		}
 	}
 
 	iores = NULL;
@@ -656,6 +709,22 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
 	return ret;
 }
 
+static int crb_map_pluton(struct device *dev, struct crb_priv *priv,
+	       struct acpi_table_tpm2 *buf, struct tpm2_crb_pluton *crb_pluton)
+{
+	priv->pluton_start_addr = crb_map_res(dev, NULL, NULL,
+					      crb_pluton->start_addr, 4);
+	if (IS_ERR(priv->pluton_start_addr))
+		return PTR_ERR(priv->pluton_start_addr);
+
+	priv->pluton_reply_addr = crb_map_res(dev, NULL, NULL,
+					      crb_pluton->reply_addr, 4);
+	if (IS_ERR(priv->pluton_reply_addr))
+		return PTR_ERR(priv->pluton_reply_addr);
+
+	return 0;
+}
+
 static int crb_acpi_add(struct acpi_device *device)
 {
 	struct acpi_table_tpm2 *buf;
@@ -663,6 +732,7 @@ static int crb_acpi_add(struct acpi_device *device)
 	struct tpm_chip *chip;
 	struct device *dev = &device->dev;
 	struct tpm2_crb_smc *crb_smc;
+	struct tpm2_crb_pluton *crb_pluton;
 	acpi_status status;
 	u32 sm;
 	int rc;
@@ -700,6 +770,20 @@ static int crb_acpi_add(struct acpi_device *device)
 		priv->smc_func_id = crb_smc->smc_func_id;
 	}
 
+	if (sm == ACPI_TPM2_COMMAND_BUFFER_WITH_PLUTON) {
+		if (buf->header.length < (sizeof(*buf) + sizeof(*crb_pluton))) {
+			dev_err(dev,
+				FW_BUG "TPM2 ACPI table has wrong size %u for start method type %d\n",
+				buf->header.length,
+				ACPI_TPM2_COMMAND_BUFFER_WITH_PLUTON);
+			return -EINVAL;
+		}
+		crb_pluton = ACPI_ADD_PTR(struct tpm2_crb_pluton, buf, sizeof(*buf));
+		rc = crb_map_pluton(dev, priv, buf, crb_pluton);
+		if (rc)
+			return rc;
+	}
+
 	priv->sm = sm;
 	priv->hid = acpi_device_hid(device);
 
diff --git a/include/acpi/actbl3.h b/include/acpi/actbl3.h
index 7b9571e00cc4..832c6464f063 100644
--- a/include/acpi/actbl3.h
+++ b/include/acpi/actbl3.h
@@ -443,6 +443,7 @@ struct acpi_tpm2_phy {
 #define ACPI_TPM2_RESERVED10                        10
 #define ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC       11	/* V1.2 Rev 8 */
 #define ACPI_TPM2_RESERVED                          12
+#define ACPI_TPM2_COMMAND_BUFFER_WITH_PLUTON        13
 
 /* Optional trailer appears after any start_method subtables */
 
-- 
2.38.1


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