// 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 <asm/bootparam.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 config table address changes to virtual address after boot, which may
 * not be accessible for the kexec'd kernel. To address this, kexec provides
 * the initial physical address via a struct setup_data entry, which is
 * checked for here, along with some sanity checks.
 */
static struct efi_setup_data *get_kexec_setup_data(struct boot_params *bp,
                                                   enum efi_type et)
{
#ifdef CONFIG_X86_64
        struct efi_setup_data *esd = NULL;
        struct setup_data *data;
        u64 pa_data;

        pa_data = bp->hdr.setup_data;
        while (pa_data) {
                data = (struct setup_data *)pa_data;
                if (data->type == SETUP_EFI) {
                        esd = (struct efi_setup_data *)(pa_data + sizeof(struct setup_data));
                        break;
                }

                pa_data = data->next;
        }

        /*
         * Original ACPI code falls back to attempting normal EFI boot in these
         * cases, so maintain existing behavior by indicating non-kexec
         * environment to the caller, but print them for debugging.
         */
        if (esd && !esd->tables) {
                debug_putstr("kexec EFI environment missing valid configuration table.\n");
                return NULL;
        }

        return esd;
#endif
        return NULL;
}

/**
 * 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;
                struct efi_setup_data *esd;

                /* kexec provides an alternative EFI conf table, check for it. */
                esd = get_kexec_setup_data(bp, et);

                *cfg_tbl_pa = esd ? esd->tables : 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;
}