commit 8e7251c6257aa59fc73ae1f64c278341bfde4c95
author Subrata Banik <subratabanik@google.com> Tue Jan 02 23:28:49 2024 +0530
committer Subrata Banik <subratabanik@google.com> Fri Jan 05 09:24:01 2024 +0000
tree 87ff3f97b130f29720cf4126d32b6bcdb0617bda
parent c64be928de8421ea1bb2f575e32d74d58e41d659

vendorcode/google/chromeos: Use unsigned int for "factory_config"

This patch ensures `chromeos_get_factory_config()` returns an
unsigned integer value because factory config represents
bit-fields to determine the Chromebook Plus branding.

Additionally, introduced safety measures to catch future
"factory_config" bit-field exhaustion.

BUG=b:317880956
TEST=Able to verify that google/screebo is branded as
Chromebook Plus.

Change-Id: I3021b8646de4750b4c8e2a2981f42500894fa2d0
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79769
Reviewed-by: Kapil Porwal <kapilporwal@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <ericllai@google.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/vendorcode/google/chromeos/chromeos.h

diff --git a/src/vendorcode/google/chromeos/chromeos.h b/src/vendorcode/google/chromeos/chromeos.h
index 0c5e4f7..a4315c3 100644
--- a/src/vendorcode/google/chromeos/chromeos.h
+++ b/src/vendorcode/google/chromeos/chromeos.h
@@ -17,6 +17,8 @@
 static inline void reboot_from_watchdog(void) { return; }
 #endif /* CONFIG_CHROMEOS */
 
+#define UNDEFINED_FACTORY_CONFIG	~((uint64_t)0)
+
 /**
  * Perform any platform specific actions required prior to resetting the Cr50.
  * Defined as weak function in cr50_enable_update.c
@@ -29,9 +31,9 @@
 /*
  * The factory config space is a one-time programmable info page.
  * For the unprovisioned one, the read will be 0x0.
- * Return `-1` in case of error.
+ * Return "UNDEFINED_FACTORY_CONFIG" in case of error.
  */
-int64_t chromeos_get_factory_config(void);
+uint64_t chromeos_get_factory_config(void);
 /*
  * Determines whether a ChromeOS device is branded as a Chromebook Plus
  * based on specific bit flags:

src/vendorcode/google/chromeos/tpm_factory_config.c

diff --git a/src/vendorcode/google/chromeos/tpm_factory_config.c b/src/vendorcode/google/chromeos/tpm_factory_config.c
index 4f8801a..44fb9f0 100644
--- a/src/vendorcode/google/chromeos/tpm_factory_config.c
+++ b/src/vendorcode/google/chromeos/tpm_factory_config.c
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
+#include <assert.h>
 #include <console/console.h>
 #include <security/tpm/tss.h>
 #include <types.h>
@@ -9,11 +10,11 @@
 #define CHROMEBOOK_PLUS_SOFT_BRANDED BIT(0)
 #define CHROMEBOOK_PLUS_DEVICE (CHROMEBOOK_PLUS_HARD_BRANDED | CHROMEBOOK_PLUS_SOFT_BRANDED)
 
-int64_t chromeos_get_factory_config(void)
+uint64_t chromeos_get_factory_config(void)
 {
-	static int64_t factory_config = -1;
+	static uint64_t factory_config = UNDEFINED_FACTORY_CONFIG;
 
-	if (factory_config >= 0)
+	if (factory_config != UNDEFINED_FACTORY_CONFIG)
 		return factory_config;
 
 	/* Initialize TPM driver. */
@@ -21,17 +22,19 @@
 	if (rc != TPM_SUCCESS) {
 		printk(BIOS_ERR, "%s:%d - tlcl_lib_init() failed: %#x\n",
 		       __func__, __LINE__, rc);
-		return -1;
+		return UNDEFINED_FACTORY_CONFIG;
 	}
 
-	rc = tlcl_cr50_get_factory_config((uint64_t *)&factory_config);
+	rc = tlcl_cr50_get_factory_config(&factory_config);
 
 	if (rc != TPM_SUCCESS) {
 		printk(BIOS_ERR, "%s:%d - tlcl_cr50_get_factory_config() failed: %#x\n",
 		       __func__, __LINE__, rc);
-		return -1;
+		return UNDEFINED_FACTORY_CONFIG;
 	}
 
+	assert(factory_config != UNDEFINED_FACTORY_CONFIG);
+
 	return factory_config;
 }
 
@@ -48,9 +51,9 @@
  */
 bool chromeos_device_branded_plus(void)
 {
-	int64_t factory_config = chromeos_get_factory_config();
+	uint64_t factory_config = chromeos_get_factory_config();
 
-	if (factory_config < 0)
+	if (factory_config == UNDEFINED_FACTORY_CONFIG)
 		return false;
 
 	return factory_config & CHROMEBOOK_PLUS_DEVICE;