ACPI/sysfs: Enable ACPI sysfs support for TDEL

Currently, all ACPI tables can be accessed via entries under
'/sys/firmware/acpi/tables/'. The TDEL(Trust Domain Event Log)[1]
table simply provide the address and length of the TDEL records
area in UEFI reserved memory. To access these records, userspace
can use /dev/mem to retrieve them. But '/dev/mem' is not enabled on
many systems for security reasons.

The ACPI driver has provided read only access to BERT records area
via '/sys/firmware/acpi/tables/data/BERT' in sysfs. So follow the same
way, this patch create a new file /sys/firmware/acpi/tables/data/TDEL
to enable read-only access to the TDEL records area.

[1] https://software.intel.com/content/dam/develop/external/us/en/
    documents/intel-tdx-guest-hypervisor-communication-interface-
    1.0-344426-002.pdf

Signed-off-by: Haibo Xu <[email protected]>

Author: xiaobo55x

drivers/acpi/sysfs.c

@@ -446,11 +446,28 @@ 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_tdel_data_init(void *th, struct acpi_data_attr *data_attr)
+{
+	struct acpi_table_tdel *tdel = th;
+
+	if (tdel->header.length < sizeof(struct acpi_table_tdel) ||
+	    !(tdel->log_area_address) || !(tdel->log_area_length)) {
+		kfree(data_attr);
+		return -EINVAL;
+	}
+	data_attr->addr = tdel->log_area_address;
+	data_attr->attr.size = tdel->log_area_length;
+	data_attr->attr.attr.name = "TDEL";
+
+	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_TDEL, acpi_tdel_data_init },
 };
 
 #define NUM_ACPI_DATA_OBJS ARRAY_SIZE(acpi_data_objs)

include/acpi/actbl3.h

@@ -42,6 +42,7 @@
 #define ACPI_SIG_WSMT           "WSMT"	/* Windows SMM Security Mitigations Table */
 #define ACPI_SIG_XENV           "XENV"	/* Xen Environment table */
 #define ACPI_SIG_XXXX           "XXXX"	/* Intermediate AML header for ASL/ASL+ converter */
+#define ACPI_SIG_TDEL           "TDEL"	/* Intel Trust Domain Event Log table */
 
 /*
  * All tables must be byte-packed to match the ACPI specification, since
@@ -469,6 +470,22 @@ struct acpi_tpm2_arm_smc {
 
 #define ACPI_TPM2_IDLE_SUPPORT          (1)
 
+/*******************************************************************************
+ *
+ * TDEL - Trust Domain Event Log Table
+ *
+ * Conforms to Intel TDX GHCI Specification
+ * Version 1, Sep 2021
+ *
+ ******************************************************************************/
+
+struct acpi_table_tdel {
+	struct acpi_table_header header;    /* Common ACPI table header */
+	u32 reserved;
+	u64 log_area_length;    /* Log area minimum length */
+	u64 log_area_address;   /* Log area start address */
+};
+
 /*******************************************************************************
  *
  * UEFI - UEFI Boot optimization Table