efi: Export Runtime Configuration Interface table to sysfs

System firmware advertises the address of the 'Runtime
Configuration Interface table version 2 (RCI2)' via
an EFI Configuration Table entry. This code retrieves the RCI2
table from the address and exports it to sysfs as a binary
attribute 'rci2' under /sys/firmware/efi/tables directory.
The approach adopted is similar to the attribute 'DMI' under
/sys/firmware/dmi/tables.

RCI2 table contains BIOS HII in XML format and is used to populate
BIOS setup page in Dell EMC OpenManage Server Administrator tool.
The BIOS setup page contains BIOS tokens which can be configured.

Signed-off-by: Narendra K <Narendra.K@dell.com>
Reviewed-by: Mario Limonciello <mario.limonciello@dell.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

4 files changed, 164 insertions, 0 deletions

diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index d4ea929e8b34..178ee8106828 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -180,6 +180,19 @@ config RESET_ATTACK_MITIGATION
 	  have been evicted, since otherwise it will trigger even on clean
 	  reboots.
 
+config EFI_RCI2_TABLE
+	bool "EFI Runtime Configuration Interface Table Version 2 Support"
+	help
+	  Displays the content of the Runtime Configuration Interface
+	  Table version 2 on Dell EMC PowerEdge systems as a binary
+	  attribute 'rci2' under /sys/firmware/efi/tables directory.
+
+	  RCI2 table contains BIOS HII in XML format and is used to populate
+	  BIOS setup page in Dell EMC OpenManage Server Administrator tool.
+	  The BIOS setup page contains BIOS tokens which can be configured.
+
+	  Say Y here for Dell EMC PowerEdge systems.
+
 endmenu
 
 config UEFI_CPER
diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
index d2d0d2030620..4ac2de4dfa72 100644
--- a/drivers/firmware/efi/Makefile
+++ b/drivers/firmware/efi/Makefile
@@ -25,6 +25,7 @@ obj-$(CONFIG_EFI_BOOTLOADER_CONTROL)	+= efibc.o
 obj-$(CONFIG_EFI_TEST)			+= test/
 obj-$(CONFIG_EFI_DEV_PATH_PARSER)	+= dev-path-parser.o
 obj-$(CONFIG_APPLE_PROPERTIES)		+= apple-properties.o
+obj-$(CONFIG_EFI_RCI2_TABLE)		+= rci2-table.o
 
 arm-obj-$(CONFIG_EFI)			:= arm-init.o arm-runtime.o
 obj-$(CONFIG_ARM)			+= $(arm-obj-y)
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 801925c5bcfb..8f1ab04f6743 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -465,6 +465,9 @@ static __initdata efi_config_table_type_t common_tables[] = {
 	{LINUX_EFI_TPM_EVENT_LOG_GUID, "TPMEventLog", &efi.tpm_log},
 	{LINUX_EFI_TPM_FINAL_LOG_GUID, "TPMFinalLog", &efi.tpm_final_log},
 	{LINUX_EFI_MEMRESERVE_TABLE_GUID, "MEMRESERVE", &efi.mem_reserve},
+#ifdef CONFIG_EFI_RCI2_TABLE
+	{DELLEMC_EFI_RCI2_TABLE_GUID, NULL, &rci2_table_phys},
+#endif
 	{NULL_GUID, NULL, NULL},
 };
 
diff --git a/drivers/firmware/efi/rci2-table.c b/drivers/firmware/efi/rci2-table.c
new file mode 100644
index 000000000000..3e290f96620a
--- /dev/null
+++ b/drivers/firmware/efi/rci2-table.c
@@ -0,0 +1,147 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Export Runtime Configuration Interface Table Version 2 (RCI2)
+ * to sysfs
+ *
+ * Copyright (C) 2019 Dell Inc
+ * by Narendra K <Narendra.K@dell.com>
+ *
+ * System firmware advertises the address of the RCI2 Table via
+ * an EFI Configuration Table entry. This code retrieves the RCI2
+ * table from the address and exports it to sysfs as a binary
+ * attribute 'rci2' under /sys/firmware/efi/tables directory.
+ */
+
+#include <linux/kobject.h>
+#include <linux/device.h>
+#include <linux/sysfs.h>
+#include <linux/efi.h>
+#include <linux/types.h>
+#include <linux/io.h>
+
+#define RCI_SIGNATURE	"_RC_"
+
+struct rci2_table_global_hdr {
+	u16 type;
+	u16 resvd0;
+	u16 hdr_len;
+	u8 rci2_sig[4];
+	u16 resvd1;
+	u32 resvd2;
+	u32 resvd3;
+	u8 major_rev;
+	u8 minor_rev;
+	u16 num_of_structs;
+	u32 rci2_len;
+	u16 rci2_chksum;
+} __packed;
+
+static u8 *rci2_base;
+static u32 rci2_table_len;
+unsigned long rci2_table_phys __ro_after_init = EFI_INVALID_TABLE_ADDR;
+
+static ssize_t raw_table_read(struct file *file, struct kobject *kobj,
+			      struct bin_attribute *attr, char *buf,
+			      loff_t pos, size_t count)
+{
+	memcpy(buf, attr->private + pos, count);
+	return count;
+}
+
+static BIN_ATTR(rci2, S_IRUSR, raw_table_read, NULL, 0);
+
+static u16 checksum(void)
+{
+	u8 len_is_odd = rci2_table_len % 2;
+	u32 chksum_len = rci2_table_len;
+	u16 *base = (u16 *)rci2_base;
+	u8 buf[2] = {0};
+	u32 offset = 0;
+	u16 chksum = 0;
+
+	if (len_is_odd)
+		chksum_len -= 1;
+
+	while (offset < chksum_len) {
+		chksum += *base;
+		offset += 2;
+		base++;
+	}
+
+	if (len_is_odd) {
+		buf[0] = *(u8 *)base;
+		chksum += *(u16 *)(buf);
+	}
+
+	return chksum;
+}
+
+int __init efi_rci2_sysfs_init(void)
+{
+	struct kobject *tables_kobj;
+	int ret = -ENOMEM;
+
+	rci2_base = memremap(rci2_table_phys,
+			     sizeof(struct rci2_table_global_hdr),
+			     MEMREMAP_WB);
+	if (!rci2_base) {
+		pr_debug("RCI2 table init failed - could not map RCI2 table\n");
+		goto err;
+	}
+
+	if (strncmp(rci2_base +
+		    offsetof(struct rci2_table_global_hdr, rci2_sig),
+		    RCI_SIGNATURE, 4)) {
+		pr_debug("RCI2 table init failed - incorrect signature\n");
+		ret = -ENODEV;
+		goto err_unmap;
+	}
+
+	rci2_table_len = *(u32 *)(rci2_base +
+				  offsetof(struct rci2_table_global_hdr,
+				  rci2_len));
+
+	memunmap(rci2_base);
+
+	if (!rci2_table_len) {
+		pr_debug("RCI2 table init failed - incorrect table length\n");
+		goto err;
+	}
+
+	rci2_base = memremap(rci2_table_phys, rci2_table_len, MEMREMAP_WB);
+	if (!rci2_base) {
+		pr_debug("RCI2 table - could not map RCI2 table\n");
+		goto err;
+	}
+
+	if (checksum() != 0) {
+		pr_debug("RCI2 table - incorrect checksum\n");
+		ret = -ENODEV;
+		goto err_unmap;
+	}
+
+	tables_kobj = kobject_create_and_add("tables", efi_kobj);
+	if (!tables_kobj) {
+		pr_debug("RCI2 table - tables_kobj creation failed\n");
+		goto err_unmap;
+	}
+
+	bin_attr_rci2.size = rci2_table_len;
+	bin_attr_rci2.private = rci2_base;
+	ret = sysfs_create_bin_file(tables_kobj, &bin_attr_rci2);
+	if (ret != 0) {
+		pr_debug("RCI2 table - rci2 sysfs bin file creation failed\n");
+		kobject_del(tables_kobj);
+		kobject_put(tables_kobj);
+		goto err_unmap;
+	}
+
+	return 0;
+
+ err_unmap:
+	memunmap(rci2_base);
+ err:
+	pr_debug("RCI2 table - sysfs initialization failed\n");
+	return ret;
+}
+late_initcall(efi_rci2_sysfs_init);