diff options
Diffstat (limited to 'drivers/firmware/efi/rci2-table.c')
| -rw-r--r-- | drivers/firmware/efi/rci2-table.c | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/drivers/firmware/efi/rci2-table.c b/drivers/firmware/efi/rci2-table.c new file mode 100644 index 000000000..de1a9a1f9 --- /dev/null +++ b/drivers/firmware/efi/rci2-table.c @@ -0,0 +1,150 @@ +// 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; + + 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); |