linux-kernel - [PATCH v3] ACPI: sysfs: Enable ACPI sysfs support for CCEL records

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Date:   Wed, 22 Mar 2023 12:13:13 -0700
From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Rafael J Wysocki <rafael@...nel.org>
Cc:     Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Subject: [PATCH v3] ACPI: sysfs: Enable ACPI sysfs support for CCEL records

The Confidential Computing Event Log (CCEL) table provides the address
and length of the CCEL records area in UEFI reserved memory.

To allow user space access to these records, expose a sysfs interface
similar to the BERT table.

More details about the CCEL table can be found in the ACPI specification
r6.5 [1], sec 5.2.34.

Link: https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#cc-event-log-acpi-table # [1]
Co-developed-by: Haibo Xu <haibo1.xu@...el.com>
Signed-off-by: Haibo Xu <haibo1.xu@...el.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
---

Changes since v2:
 * Fixed the commit log as per review suggestion.

Changes since v1:
 * Removed unnecessary parenthesis as per Rafael's suggestion.

 drivers/acpi/sysfs.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
index 7f4ff56c9d42..687524b50085 100644
--- a/drivers/acpi/sysfs.c
+++ b/drivers/acpi/sysfs.c
@@ -458,11 +458,28 @@ static int acpi_bert_data_init(void *th, struct acpi_data_attr *data_attr)
 	return sysfs_create_bin_file(tables_data_kobj, &data_attr->attr);
 }
 
+static int acpi_ccel_data_init(void *th, struct acpi_data_attr *data_attr)
+{
+	struct acpi_table_ccel *ccel = th;
+
+	if (ccel->header.length < sizeof(struct acpi_table_ccel) ||
+	    !ccel->log_area_start_address || !ccel->log_area_minimum_length) {
+		kfree(data_attr);
+		return -EINVAL;
+	}
+	data_attr->addr = ccel->log_area_start_address;
+	data_attr->attr.size = ccel->log_area_minimum_length;
+	data_attr->attr.attr.name = "CCEL";
+
+	return sysfs_create_bin_file(tables_data_kobj, &data_attr->attr);
+}
+
 static struct acpi_data_obj {
 	char *name;
 	int (*fn)(void *, struct acpi_data_attr *);
 } acpi_data_objs[] = {
 	{ ACPI_SIG_BERT, acpi_bert_data_init },
+	{ ACPI_SIG_CCEL, acpi_ccel_data_init },
 };
 
 #define NUM_ACPI_DATA_OBJS ARRAY_SIZE(acpi_data_objs)
-- 
2.34.1