linux-kernel - [RFC PATCH v2 3/3] tpm: of: If available use linux,sml-log to get the log and its size

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Message-ID: <20240311132030.1103122-4-stefanb@linux.ibm.com>
Date: Mon, 11 Mar 2024 09:20:30 -0400
From: Stefan Berger <stefanb@...ux.ibm.com>
To: mpe@...erman.id.au, linux-integrity@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Cc: linux-kernel@...r.kernel.org, jarkko@...nel.org, rnsastry@...ux.ibm.com,
        peterhuewe@....de, viparash@...ibm.com, devicetree@...r.kernel.org,
        jsnitsel@...hat.com, Stefan Berger <stefanb@...ux.ibm.com>
Subject: [RFC PATCH v2 3/3] tpm: of: If available use linux,sml-log to get the log and its size

If linux,sml-log is available use it to get the TPM log rather than the
pointer found in linux,sml-base. This resolves an issue on PowerVM and KVM
on Power where after a kexec the memory pointed to by linux,sml-base may
have become inaccessible or corrupted. Also, linux,sml-log has replaced
linux,sml-base and linux,sml-size on these two platforms.

Keep the handling of linux,sml-base/sml-size for powernv platforms that
provide the two properties via skiboot.

Fixes: c5df39262dd5 ("drivers/char/tpm: Add securityfs support for event log")
Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
---
 drivers/char/tpm/eventlog/of.c | 36 +++++++++++-----------------------
 1 file changed, 11 insertions(+), 25 deletions(-)

diff --git a/drivers/char/tpm/eventlog/of.c b/drivers/char/tpm/eventlog/of.c
index 930fe43d5daf..dbd837d65264 100644
--- a/drivers/char/tpm/eventlog/of.c
+++ b/drivers/char/tpm/eventlog/of.c
@@ -54,8 +54,8 @@ int tpm_read_log_of(struct tpm_chip *chip)
 	const u32 *sizep;
 	const u64 *basep;
 	struct tpm_bios_log *log;
+	const void *logp;
 	u32 size;
-	u64 base;
 
 	log = &chip->log;
 	if (chip->dev.parent && chip->dev.parent->of_node)
@@ -66,37 +66,23 @@ int tpm_read_log_of(struct tpm_chip *chip)
 	if (of_property_read_bool(np, "powered-while-suspended"))
 		chip->flags |= TPM_CHIP_FLAG_ALWAYS_POWERED;
 
-	sizep = of_get_property(np, "linux,sml-size", NULL);
-	basep = of_get_property(np, "linux,sml-base", NULL);
-	if (sizep == NULL && basep == NULL)
-		return tpm_read_log_memory_region(chip);
-	if (sizep == NULL || basep == NULL)
-		return -EIO;
-
-	/*
-	 * For both vtpm/tpm, firmware has log addr and log size in big
-	 * endian format. But in case of vtpm, there is a method called
-	 * sml-handover which is run during kernel init even before
-	 * device tree is setup. This sml-handover function takes care
-	 * of endianness and writes to sml-base and sml-size in little
-	 * endian format. For this reason, vtpm doesn't need conversion
-	 * but physical tpm needs the conversion.
-	 */
-	if (of_property_match_string(np, "compatible", "IBM,vtpm") < 0 &&
-	    of_property_match_string(np, "compatible", "IBM,vtpm20") < 0) {
+	logp = of_get_property(np, "linux,sml-log", &size);
+	if (logp == NULL) {
+		sizep = of_get_property(np, "linux,sml-size", NULL);
+		basep = of_get_property(np, "linux,sml-base", NULL);
+		if (sizep == NULL && basep == NULL)
+			return tpm_read_log_memory_region(chip);
+		if (sizep == NULL || basep == NULL)
+			return -EIO;
 		size = be32_to_cpup((__force __be32 *)sizep);
-		base = be64_to_cpup((__force __be64 *)basep);
-	} else {
-		size = *sizep;
-		base = *basep;
+		logp = __va(be64_to_cpup((__force __be64 *)basep));
 	}
-
 	if (size == 0) {
 		dev_warn(&chip->dev, "%s: Event log area empty\n", __func__);
 		return -EIO;
 	}
 
-	log->bios_event_log = devm_kmemdup(&chip->dev, __va(base), size, GFP_KERNEL);
+	log->bios_event_log = devm_kmemdup(&chip->dev, logp, size, GFP_KERNEL);
 	if (!log->bios_event_log)
 		return -ENOMEM;
 
-- 
2.43.0