// 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 __ro_after_init BIN_ATTR_SIMPLE_ADMIN_RO(rci2);

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;
}

static int __init efi_rci2_sysfs_init(void)
{
        struct kobject *tables_kobj;
        int ret = -ENOMEM;

        if (rci2_table_phys == EFI_INVALID_TABLE_ADDR)
                return 0;

        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);