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// 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;
}
static 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);
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