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// SPDX-License-Identifier: GPL-2.0
/*
* Helpers for early access to EFI configuration table.
*
* Originally derived from arch/x86/boot/compressed/acpi.c
*/
#include "misc.h"
#include <linux/efi.h>
#include <asm/efi.h>
/**
* efi_get_type - Given a pointer to boot_params, determine the type of EFI environment.
*
* @bp: pointer to boot_params
*
* Return: EFI_TYPE_{32,64} for valid EFI environments, EFI_TYPE_NONE otherwise.
*/
enum efi_type efi_get_type(struct boot_params *bp)
{
struct efi_info *ei;
enum efi_type et;
const char *sig;
ei = &bp->efi_info;
sig = (char *)&ei->efi_loader_signature;
if (!strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) {
et = EFI_TYPE_64;
} else if (!strncmp(sig, EFI32_LOADER_SIGNATURE, 4)) {
et = EFI_TYPE_32;
} else {
debug_putstr("No EFI environment detected.\n");
et = EFI_TYPE_NONE;
}
#ifndef CONFIG_X86_64
/*
* Existing callers like acpi.c treat this case as an indicator to
* fall-through to non-EFI, rather than an error, so maintain that
* functionality here as well.
*/
if (ei->efi_systab_hi || ei->efi_memmap_hi) {
debug_putstr("EFI system table is located above 4GB and cannot be accessed.\n");
et = EFI_TYPE_NONE;
}
#endif
return et;
}
/**
* efi_get_system_table - Given a pointer to boot_params, retrieve the physical address
* of the EFI system table.
*
* @bp: pointer to boot_params
*
* Return: EFI system table address on success. On error, return 0.
*/
unsigned long efi_get_system_table(struct boot_params *bp)
{
unsigned long sys_tbl_pa;
struct efi_info *ei;
enum efi_type et;
/* Get systab from boot params. */
ei = &bp->efi_info;
#ifdef CONFIG_X86_64
sys_tbl_pa = ei->efi_systab | ((__u64)ei->efi_systab_hi << 32);
#else
sys_tbl_pa = ei->efi_systab;
#endif
if (!sys_tbl_pa) {
debug_putstr("EFI system table not found.");
return 0;
}
return sys_tbl_pa;
}
/**
* efi_get_conf_table - Given a pointer to boot_params, locate and return the physical
* address of EFI configuration table.
*
* @bp: pointer to boot_params
* @cfg_tbl_pa: location to store physical address of config table
* @cfg_tbl_len: location to store number of config table entries
*
* Return: 0 on success. On error, return params are left unchanged.
*/
int efi_get_conf_table(struct boot_params *bp, unsigned long *cfg_tbl_pa,
unsigned int *cfg_tbl_len)
{
unsigned long sys_tbl_pa;
enum efi_type et;
int ret;
if (!cfg_tbl_pa || !cfg_tbl_len)
return -EINVAL;
sys_tbl_pa = efi_get_system_table(bp);
if (!sys_tbl_pa)
return -EINVAL;
/* Handle EFI bitness properly */
et = efi_get_type(bp);
if (et == EFI_TYPE_64) {
efi_system_table_64_t *stbl = (efi_system_table_64_t *)sys_tbl_pa;
*cfg_tbl_pa = stbl->tables;
*cfg_tbl_len = stbl->nr_tables;
} else if (et == EFI_TYPE_32) {
efi_system_table_32_t *stbl = (efi_system_table_32_t *)sys_tbl_pa;
*cfg_tbl_pa = stbl->tables;
*cfg_tbl_len = stbl->nr_tables;
} else {
return -EINVAL;
}
return 0;
}
/* Get vendor table address/guid from EFI config table at the given index */
static int get_vendor_table(void *cfg_tbl, unsigned int idx,
unsigned long *vendor_tbl_pa,
efi_guid_t *vendor_tbl_guid,
enum efi_type et)
{
if (et == EFI_TYPE_64) {
efi_config_table_64_t *tbl_entry = (efi_config_table_64_t *)cfg_tbl + idx;
if (!IS_ENABLED(CONFIG_X86_64) && tbl_entry->table >> 32) {
debug_putstr("Error: EFI config table entry located above 4GB.\n");
return -EINVAL;
}
*vendor_tbl_pa = tbl_entry->table;
*vendor_tbl_guid = tbl_entry->guid;
} else if (et == EFI_TYPE_32) {
efi_config_table_32_t *tbl_entry = (efi_config_table_32_t *)cfg_tbl + idx;
*vendor_tbl_pa = tbl_entry->table;
*vendor_tbl_guid = tbl_entry->guid;
} else {
return -EINVAL;
}
return 0;
}
/**
* efi_find_vendor_table - Given EFI config table, search it for the physical
* address of the vendor table associated with GUID.
*
* @bp: pointer to boot_params
* @cfg_tbl_pa: pointer to EFI configuration table
* @cfg_tbl_len: number of entries in EFI configuration table
* @guid: GUID of vendor table
*
* Return: vendor table address on success. On error, return 0.
*/
unsigned long efi_find_vendor_table(struct boot_params *bp,
unsigned long cfg_tbl_pa,
unsigned int cfg_tbl_len,
efi_guid_t guid)
{
enum efi_type et;
unsigned int i;
et = efi_get_type(bp);
if (et == EFI_TYPE_NONE)
return 0;
for (i = 0; i < cfg_tbl_len; i++) {
unsigned long vendor_tbl_pa;
efi_guid_t vendor_tbl_guid;
int ret;
ret = get_vendor_table((void *)cfg_tbl_pa, i,
&vendor_tbl_pa,
&vendor_tbl_guid, et);
if (ret)
return 0;
if (!efi_guidcmp(guid, vendor_tbl_guid))
return vendor_tbl_pa;
}
return 0;
}
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