treewide: remove redundant IS_ERR() before error code check

[linux/fpc-iii.git] / arch / x86 / platform / efi / quirks.c

// SPDX-License-Identifier: GPL-2.0-only
#define pr_fmt(fmt) "efi: " fmt

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/time.h>
#include <linux/types.h>
#include <linux/efi.h>
#include <linux/slab.h>
#include <linux/memblock.h>
#include <linux/acpi.h>
#include <linux/dmi.h>

#include <asm/e820/api.h>
#include <asm/efi.h>
#include <asm/uv/uv.h>
#include <asm/cpu_device_id.h>
#include <asm/realmode.h>
#include <asm/reboot.h>

#define EFI_MIN_RESERVE 5120

#define EFI_DUMMY_GUID \
        EFI_GUID(0x4424ac57, 0xbe4b, 0x47dd, 0x9e, 0x97, 0xed, 0x50, 0xf0, 0x9f, 0x92, 0xa9)

#define QUARK_CSH_SIGNATURE             0x5f435348      /* _CSH */
#define QUARK_SECURITY_HEADER_SIZE      0x400

/*
 * Header prepended to the standard EFI capsule on Quark systems the are based
 * on Intel firmware BSP.
 * @csh_signature:      Unique identifier to sanity check signed module
 *                      presence ("_CSH").
 * @version:            Current version of CSH used. Should be one for Quark A0.
 * @modulesize:         Size of the entire module including the module header
 *                      and payload.
 * @security_version_number_index: Index of SVN to use for validation of signed
 *                      module.
 * @security_version_number: Used to prevent against roll back of modules.
 * @rsvd_module_id:     Currently unused for Clanton (Quark).
 * @rsvd_module_vendor: Vendor Identifier. For Intel products value is
 *                      0x00008086.
 * @rsvd_date:          BCD representation of build date as yyyymmdd, where
 *                      yyyy=4 digit year, mm=1-12, dd=1-31.
 * @headersize:         Total length of the header including including any
 *                      padding optionally added by the signing tool.
 * @hash_algo:          What Hash is used in the module signing.
 * @cryp_algo:          What Crypto is used in the module signing.
 * @keysize:            Total length of the key data including including any
 *                      padding optionally added by the signing tool.
 * @signaturesize:      Total length of the signature including including any
 *                      padding optionally added by the signing tool.
 * @rsvd_next_header:   32-bit pointer to the next Secure Boot Module in the
 *                      chain, if there is a next header.
 * @rsvd:               Reserved, padding structure to required size.
 *
 * See also QuartSecurityHeader_t in
 * Quark_EDKII_v1.2.1.1/QuarkPlatformPkg/Include/QuarkBootRom.h
 * from https://downloadcenter.intel.com/download/23197/Intel-Quark-SoC-X1000-Board-Support-Package-BSP
 */
struct quark_security_header {
        u32 csh_signature;
        u32 version;
        u32 modulesize;
        u32 security_version_number_index;
        u32 security_version_number;
        u32 rsvd_module_id;
        u32 rsvd_module_vendor;
        u32 rsvd_date;
        u32 headersize;
        u32 hash_algo;
        u32 cryp_algo;
        u32 keysize;
        u32 signaturesize;
        u32 rsvd_next_header;
        u32 rsvd[2];
};

static const efi_char16_t efi_dummy_name[] = L"DUMMY";

static bool efi_no_storage_paranoia;

/*
 * Some firmware implementations refuse to boot if there's insufficient
 * space in the variable store. The implementation of garbage collection
 * in some FW versions causes stale (deleted) variables to take up space
 * longer than intended and space is only freed once the store becomes
 * almost completely full.
 *
 * Enabling this option disables the space checks in
 * efi_query_variable_store() and forces garbage collection.
 *
 * Only enable this option if deleting EFI variables does not free up
 * space in your variable store, e.g. if despite deleting variables
 * you're unable to create new ones.
 */
static int __init setup_storage_paranoia(char *arg)
{
        efi_no_storage_paranoia = true;
        return 0;
}
early_param("efi_no_storage_paranoia", setup_storage_paranoia);

/*
 * Deleting the dummy variable which kicks off garbage collection
*/
void efi_delete_dummy_variable(void)
{
        efi.set_variable_nonblocking((efi_char16_t *)efi_dummy_name,
                                     &EFI_DUMMY_GUID,
                                     EFI_VARIABLE_NON_VOLATILE |
                                     EFI_VARIABLE_BOOTSERVICE_ACCESS |
                                     EFI_VARIABLE_RUNTIME_ACCESS, 0, NULL);
}

/*
 * In the nonblocking case we do not attempt to perform garbage
 * collection if we do not have enough free space. Rather, we do the
 * bare minimum check and give up immediately if the available space
 * is below EFI_MIN_RESERVE.
 *
 * This function is intended to be small and simple because it is
 * invoked from crash handler paths.
 */
static efi_status_t
query_variable_store_nonblocking(u32 attributes, unsigned long size)
{
        efi_status_t status;
        u64 storage_size, remaining_size, max_size;

        status = efi.query_variable_info_nonblocking(attributes, &storage_size,
                                                     &remaining_size,
                                                     &max_size);
        if (status != EFI_SUCCESS)
                return status;

        if (remaining_size - size < EFI_MIN_RESERVE)
                return EFI_OUT_OF_RESOURCES;

        return EFI_SUCCESS;
}

/*
 * Some firmware implementations refuse to boot if there's insufficient space
 * in the variable store. Ensure that we never use more than a safe limit.
 *
 * Return EFI_SUCCESS if it is safe to write 'size' bytes to the variable
 * store.
 */
efi_status_t efi_query_variable_store(u32 attributes, unsigned long size,
                                      bool nonblocking)
{
        efi_status_t status;
        u64 storage_size, remaining_size, max_size;

        if (!(attributes & EFI_VARIABLE_NON_VOLATILE))
                return 0;

        if (nonblocking)
                return query_variable_store_nonblocking(attributes, size);

        status = efi.query_variable_info(attributes, &storage_size,
                                         &remaining_size, &max_size);
        if (status != EFI_SUCCESS)
                return status;

        /*
         * We account for that by refusing the write if permitting it would
         * reduce the available space to under 5KB. This figure was provided by
         * Samsung, so should be safe.
         */
        if ((remaining_size - size < EFI_MIN_RESERVE) &&
                !efi_no_storage_paranoia) {

                /*
                 * Triggering garbage collection may require that the firmware
                 * generate a real EFI_OUT_OF_RESOURCES error. We can force
                 * that by attempting to use more space than is available.
                 */
                unsigned long dummy_size = remaining_size + 1024;
                void *dummy = kzalloc(dummy_size, GFP_KERNEL);

                if (!dummy)
                        return EFI_OUT_OF_RESOURCES;

                status = efi.set_variable((efi_char16_t *)efi_dummy_name,
                                          &EFI_DUMMY_GUID,
                                          EFI_VARIABLE_NON_VOLATILE |
                                          EFI_VARIABLE_BOOTSERVICE_ACCESS |
                                          EFI_VARIABLE_RUNTIME_ACCESS,
                                          dummy_size, dummy);

                if (status == EFI_SUCCESS) {
                        /*
                         * This should have failed, so if it didn't make sure
                         * that we delete it...
                         */
                        efi_delete_dummy_variable();
                }

                kfree(dummy);

                /*
                 * The runtime code may now have triggered a garbage collection
                 * run, so check the variable info again
                 */
                status = efi.query_variable_info(attributes, &storage_size,
                                                 &remaining_size, &max_size);

                if (status != EFI_SUCCESS)
                        return status;

                /*
                 * There still isn't enough room, so return an error
                 */
                if (remaining_size - size < EFI_MIN_RESERVE)
                        return EFI_OUT_OF_RESOURCES;
        }

        return EFI_SUCCESS;
}
EXPORT_SYMBOL_GPL(efi_query_variable_store);

/*
 * The UEFI specification makes it clear that the operating system is
 * free to do whatever it wants with boot services code after
 * ExitBootServices() has been called. Ignoring this recommendation a
 * significant bunch of EFI implementations continue calling into boot
 * services code (SetVirtualAddressMap). In order to work around such
 * buggy implementations we reserve boot services region during EFI
 * init and make sure it stays executable. Then, after
 * SetVirtualAddressMap(), it is discarded.
 *
 * However, some boot services regions contain data that is required
 * by drivers, so we need to track which memory ranges can never be
 * freed. This is done by tagging those regions with the
 * EFI_MEMORY_RUNTIME attribute.
 *
 * Any driver that wants to mark a region as reserved must use
 * efi_mem_reserve() which will insert a new EFI memory descriptor
 * into efi.memmap (splitting existing regions if necessary) and tag
 * it with EFI_MEMORY_RUNTIME.
 */
void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size)
{
        struct efi_memory_map_data data = { 0 };
        struct efi_mem_range mr;
        efi_memory_desc_t md;
        int num_entries;
        void *new;

        if (efi_mem_desc_lookup(addr, &md) ||
            md.type != EFI_BOOT_SERVICES_DATA) {
                pr_err("Failed to lookup EFI memory descriptor for %pa\n", &addr);
                return;
        }

        if (addr + size > md.phys_addr + (md.num_pages << EFI_PAGE_SHIFT)) {
                pr_err("Region spans EFI memory descriptors, %pa\n", &addr);
                return;
        }

        size += addr % EFI_PAGE_SIZE;
        size = round_up(size, EFI_PAGE_SIZE);
        addr = round_down(addr, EFI_PAGE_SIZE);

        mr.range.start = addr;
        mr.range.end = addr + size - 1;
        mr.attribute = md.attribute | EFI_MEMORY_RUNTIME;

        num_entries = efi_memmap_split_count(&md, &mr.range);
        num_entries += efi.memmap.nr_map;

        if (efi_memmap_alloc(num_entries, &data) != 0) {
                pr_err("Could not allocate boot services memmap\n");
                return;
        }

        new = early_memremap(data.phys_map, data.size);
        if (!new) {
                pr_err("Failed to map new boot services memmap\n");
                return;
        }

        efi_memmap_insert(&efi.memmap, new, &mr);
        early_memunmap(new, data.size);

        efi_memmap_install(&data);
        e820__range_update(addr, size, E820_TYPE_RAM, E820_TYPE_RESERVED);
        e820__update_table(e820_table);
}

/*
 * Helper function for efi_reserve_boot_services() to figure out if we
 * can free regions in efi_free_boot_services().
 *
 * Use this function to ensure we do not free regions owned by somebody
 * else. We must only reserve (and then free) regions:
 *
 * - Not within any part of the kernel
 * - Not the BIOS reserved area (E820_TYPE_RESERVED, E820_TYPE_NVS, etc)
 */
static __init bool can_free_region(u64 start, u64 size)
{
        if (start + size > __pa_symbol(_text) && start <= __pa_symbol(_end))
                return false;

        if (!e820__mapped_all(start, start+size, E820_TYPE_RAM))
                return false;

        return true;
}

void __init efi_reserve_boot_services(void)
{
        efi_memory_desc_t *md;

        if (!efi_enabled(EFI_MEMMAP))
                return;

        for_each_efi_memory_desc(md) {
                u64 start = md->phys_addr;
                u64 size = md->num_pages << EFI_PAGE_SHIFT;
                bool already_reserved;

                if (md->type != EFI_BOOT_SERVICES_CODE &&
                    md->type != EFI_BOOT_SERVICES_DATA)
                        continue;

                already_reserved = memblock_is_region_reserved(start, size);

                /*
                 * Because the following memblock_reserve() is paired
                 * with memblock_free_late() for this region in
                 * efi_free_boot_services(), we must be extremely
                 * careful not to reserve, and subsequently free,
                 * critical regions of memory (like the kernel image) or
                 * those regions that somebody else has already
                 * reserved.
                 *
                 * A good example of a critical region that must not be
                 * freed is page zero (first 4Kb of memory), which may
                 * contain boot services code/data but is marked
                 * E820_TYPE_RESERVED by trim_bios_range().
                 */
                if (!already_reserved) {
                        memblock_reserve(start, size);

                        /*
                         * If we are the first to reserve the region, no
                         * one else cares about it. We own it and can
                         * free it later.
                         */
                        if (can_free_region(start, size))
                                continue;
                }

                /*
                 * We don't own the region. We must not free it.
                 *
                 * Setting this bit for a boot services region really
                 * doesn't make sense as far as the firmware is
                 * concerned, but it does provide us with a way to tag
                 * those regions that must not be paired with
                 * memblock_free_late().
                 */
                md->attribute |= EFI_MEMORY_RUNTIME;
        }
}

/*
 * Apart from having VA mappings for EFI boot services code/data regions,
 * (duplicate) 1:1 mappings were also created as a quirk for buggy firmware. So,
 * unmap both 1:1 and VA mappings.
 */
static void __init efi_unmap_pages(efi_memory_desc_t *md)
{
        pgd_t *pgd = efi_mm.pgd;
        u64 pa = md->phys_addr;
        u64 va = md->virt_addr;

        /*
         * To Do: Remove this check after adding functionality to unmap EFI boot
         * services code/data regions from direct mapping area because the UV1
         * memory map maps EFI regions in swapper_pg_dir.
         */
        if (efi_have_uv1_memmap())
                return;

        /*
         * EFI mixed mode has all RAM mapped to access arguments while making
         * EFI runtime calls, hence don't unmap EFI boot services code/data
         * regions.
         */
        if (efi_is_mixed())
                return;

        if (kernel_unmap_pages_in_pgd(pgd, pa, md->num_pages))
                pr_err("Failed to unmap 1:1 mapping for 0x%llx\n", pa);

        if (kernel_unmap_pages_in_pgd(pgd, va, md->num_pages))
                pr_err("Failed to unmap VA mapping for 0x%llx\n", va);
}

void __init efi_free_boot_services(void)
{
        struct efi_memory_map_data data = { 0 };
        efi_memory_desc_t *md;
        int num_entries = 0;
        void *new, *new_md;

        for_each_efi_memory_desc(md) {
                unsigned long long start = md->phys_addr;
                unsigned long long size = md->num_pages << EFI_PAGE_SHIFT;
                size_t rm_size;

                if (md->type != EFI_BOOT_SERVICES_CODE &&
                    md->type != EFI_BOOT_SERVICES_DATA) {
                        num_entries++;
                        continue;
                }

                /* Do not free, someone else owns it: */
                if (md->attribute & EFI_MEMORY_RUNTIME) {
                        num_entries++;
                        continue;
                }

                /*
                 * Before calling set_virtual_address_map(), EFI boot services
                 * code/data regions were mapped as a quirk for buggy firmware.
                 * Unmap them from efi_pgd before freeing them up.
                 */
                efi_unmap_pages(md);

                /*
                 * Nasty quirk: if all sub-1MB memory is used for boot
                 * services, we can get here without having allocated the
                 * real mode trampoline.  It's too late to hand boot services
                 * memory back to the memblock allocator, so instead
                 * try to manually allocate the trampoline if needed.
                 *
                 * I've seen this on a Dell XPS 13 9350 with firmware
                 * 1.4.4 with SGX enabled booting Linux via Fedora 24's
                 * grub2-efi on a hard disk.  (And no, I don't know why
                 * this happened, but Linux should still try to boot rather
                 * panicing early.)
                 */
                rm_size = real_mode_size_needed();
                if (rm_size && (start + rm_size) < (1<<20) && size >= rm_size) {
                        set_real_mode_mem(start);
                        start += rm_size;
                        size -= rm_size;
                }

                memblock_free_late(start, size);
        }

        if (!num_entries)
                return;

        if (efi_memmap_alloc(num_entries, &data) != 0) {
                pr_err("Failed to allocate new EFI memmap\n");
                return;
        }

        new = memremap(data.phys_map, data.size, MEMREMAP_WB);
        if (!new) {
                pr_err("Failed to map new EFI memmap\n");
                return;
        }

        /*
         * Build a new EFI memmap that excludes any boot services
         * regions that are not tagged EFI_MEMORY_RUNTIME, since those
         * regions have now been freed.
         */
        new_md = new;
        for_each_efi_memory_desc(md) {
                if (!(md->attribute & EFI_MEMORY_RUNTIME) &&
                    (md->type == EFI_BOOT_SERVICES_CODE ||
                     md->type == EFI_BOOT_SERVICES_DATA))
                        continue;

                memcpy(new_md, md, efi.memmap.desc_size);
                new_md += efi.memmap.desc_size;
        }

        memunmap(new);

        if (efi_memmap_install(&data) != 0) {
                pr_err("Could not install new EFI memmap\n");
                return;
        }
}

/*
 * A number of config table entries get remapped to virtual addresses
 * after entering EFI virtual mode. However, the kexec kernel requires
 * their physical addresses therefore we pass them via setup_data and
 * correct those entries to their respective physical addresses here.
 *
 * Currently only handles smbios which is necessary for some firmware
 * implementation.
 */
int __init efi_reuse_config(u64 tables, int nr_tables)
{
        int i, sz, ret = 0;
        void *p, *tablep;
        struct efi_setup_data *data;

        if (nr_tables == 0)
                return 0;

        if (!efi_setup)
                return 0;

        if (!efi_enabled(EFI_64BIT))
                return 0;

        data = early_memremap(efi_setup, sizeof(*data));
        if (!data) {
                ret = -ENOMEM;
                goto out;
        }

        if (!data->smbios)
                goto out_memremap;

        sz = sizeof(efi_config_table_64_t);

        p = tablep = early_memremap(tables, nr_tables * sz);
        if (!p) {
                pr_err("Could not map Configuration table!\n");
                ret = -ENOMEM;
                goto out_memremap;
        }

        for (i = 0; i < efi.systab->nr_tables; i++) {
                efi_guid_t guid;

                guid = ((efi_config_table_64_t *)p)->guid;

                if (!efi_guidcmp(guid, SMBIOS_TABLE_GUID))
                        ((efi_config_table_64_t *)p)->table = data->smbios;
                p += sz;
        }
        early_memunmap(tablep, nr_tables * sz);

out_memremap:
        early_memunmap(data, sizeof(*data));
out:
        return ret;
}

static const struct dmi_system_id sgi_uv1_dmi[] __initconst = {
        { NULL, "SGI UV1",
                {       DMI_MATCH(DMI_PRODUCT_NAME,     "Stoutland Platform"),
                        DMI_MATCH(DMI_PRODUCT_VERSION,  "1.0"),
                        DMI_MATCH(DMI_BIOS_VENDOR,      "SGI.COM"),
                }
        },
        { } /* NULL entry stops DMI scanning */
};

void __init efi_apply_memmap_quirks(void)
{
        /*
         * Once setup is done earlier, unmap the EFI memory map on mismatched
         * firmware/kernel architectures since there is no support for runtime
         * services.
         */
        if (!efi_runtime_supported()) {
                pr_info("Setup done, disabling due to 32/64-bit mismatch\n");
                efi_memmap_unmap();
        }

        /* UV2+ BIOS has a fix for this issue.  UV1 still needs the quirk. */
        if (dmi_check_system(sgi_uv1_dmi)) {
                if (IS_ENABLED(CONFIG_X86_UV)) {
                        set_bit(EFI_UV1_MEMMAP, &efi.flags);
                } else {
                        pr_warn("EFI runtime disabled, needs CONFIG_X86_UV=y on UV1\n");
                        clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
                        efi_memmap_unmap();
                }
        }
}

/*
 * For most modern platforms the preferred method of powering off is via
 * ACPI. However, there are some that are known to require the use of
 * EFI runtime services and for which ACPI does not work at all.
 *
 * Using EFI is a last resort, to be used only if no other option
 * exists.
 */
bool efi_reboot_required(void)
{
        if (!acpi_gbl_reduced_hardware)
                return false;

        efi_reboot_quirk_mode = EFI_RESET_WARM;
        return true;
}

bool efi_poweroff_required(void)
{
        return acpi_gbl_reduced_hardware || acpi_no_s5;
}

#ifdef CONFIG_EFI_CAPSULE_QUIRK_QUARK_CSH

static int qrk_capsule_setup_info(struct capsule_info *cap_info, void **pkbuff,
                                  size_t hdr_bytes)
{
        struct quark_security_header *csh = *pkbuff;

        /* Only process data block that is larger than the security header */
        if (hdr_bytes < sizeof(struct quark_security_header))
                return 0;

        if (csh->csh_signature != QUARK_CSH_SIGNATURE ||
            csh->headersize != QUARK_SECURITY_HEADER_SIZE)
                return 1;

        /* Only process data block if EFI header is included */
        if (hdr_bytes < QUARK_SECURITY_HEADER_SIZE +
                        sizeof(efi_capsule_header_t))
                return 0;

        pr_debug("Quark security header detected\n");

        if (csh->rsvd_next_header != 0) {
                pr_err("multiple Quark security headers not supported\n");
                return -EINVAL;
        }

        *pkbuff += csh->headersize;
        cap_info->total_size = csh->headersize;

        /*
         * Update the first page pointer to skip over the CSH header.
         */
        cap_info->phys[0] += csh->headersize;

        /*
         * cap_info->capsule should point at a virtual mapping of the entire
         * capsule, starting at the capsule header. Our image has the Quark
         * security header prepended, so we cannot rely on the default vmap()
         * mapping created by the generic capsule code.
         * Given that the Quark firmware does not appear to care about the
         * virtual mapping, let's just point cap_info->capsule at our copy
         * of the capsule header.
         */
        cap_info->capsule = &cap_info->header;

        return 1;
}

#define ICPU(family, model, quirk_handler) \
        { X86_VENDOR_INTEL, family, model, X86_FEATURE_ANY, \
          (unsigned long)&quirk_handler }

static const struct x86_cpu_id efi_capsule_quirk_ids[] = {
        ICPU(5, 9, qrk_capsule_setup_info),     /* Intel Quark X1000 */
        { }
};

int efi_capsule_setup_info(struct capsule_info *cap_info, void *kbuff,
                           size_t hdr_bytes)
{
        int (*quirk_handler)(struct capsule_info *, void **, size_t);
        const struct x86_cpu_id *id;
        int ret;

        if (hdr_bytes < sizeof(efi_capsule_header_t))
                return 0;

        cap_info->total_size = 0;

        id = x86_match_cpu(efi_capsule_quirk_ids);
        if (id) {
                /*
                 * The quirk handler is supposed to return
                 *  - a value > 0 if the setup should continue, after advancing
                 *    kbuff as needed
                 *  - 0 if not enough hdr_bytes are available yet
                 *  - a negative error code otherwise
                 */
                quirk_handler = (typeof(quirk_handler))id->driver_data;
                ret = quirk_handler(cap_info, &kbuff, hdr_bytes);
                if (ret <= 0)
                        return ret;
        }

        memcpy(&cap_info->header, kbuff, sizeof(cap_info->header));

        cap_info->total_size += cap_info->header.imagesize;

        return __efi_capsule_setup_info(cap_info);
}

#endif

/*
 * If any access by any efi runtime service causes a page fault, then,
 * 1. If it's efi_reset_system(), reboot through BIOS.
 * 2. If any other efi runtime service, then
 *    a. Return error status to the efi caller process.
 *    b. Disable EFI Runtime Services forever and
 *    c. Freeze efi_rts_wq and schedule new process.
 *
 * @return: Returns, if the page fault is not handled. This function
 * will never return if the page fault is handled successfully.
 */
void efi_recover_from_page_fault(unsigned long phys_addr)
{
        if (!IS_ENABLED(CONFIG_X86_64))
                return;

        /*
         * Make sure that an efi runtime service caused the page fault.
         * "efi_mm" cannot be used to check if the page fault had occurred
         * in the firmware context because the UV1 memmap doesn't use efi_pgd.
         */
        if (efi_rts_work.efi_rts_id == EFI_NONE)
                return;

        /*
         * Address range 0x0000 - 0x0fff is always mapped in the efi_pgd, so
         * page faulting on these addresses isn't expected.
         */
        if (phys_addr <= 0x0fff)
                return;

        /*
         * Print stack trace as it might be useful to know which EFI Runtime
         * Service is buggy.
         */
        WARN(1, FW_BUG "Page fault caused by firmware at PA: 0x%lx\n",
             phys_addr);

        /*
         * Buggy efi_reset_system() is handled differently from other EFI
         * Runtime Services as it doesn't use efi_rts_wq. Although,
         * native_machine_emergency_restart() says that machine_real_restart()
         * could fail, it's better not to compilcate this fault handler
         * because this case occurs *very* rarely and hence could be improved
         * on a need by basis.
         */
        if (efi_rts_work.efi_rts_id == EFI_RESET_SYSTEM) {
                pr_info("efi_reset_system() buggy! Reboot through BIOS\n");
                machine_real_restart(MRR_BIOS);
                return;
        }

        /*
         * Before calling EFI Runtime Service, the kernel has switched the
         * calling process to efi_mm. Hence, switch back to task_mm.
         */
        arch_efi_call_virt_teardown();

        /* Signal error status to the efi caller process */
        efi_rts_work.status = EFI_ABORTED;
        complete(&efi_rts_work.efi_rts_comp);

        clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
        pr_info("Froze efi_rts_wq and disabled EFI Runtime Services\n");

        /*
         * Call schedule() in an infinite loop, so that any spurious wake ups
         * will never run efi_rts_wq again.
         */
        for (;;) {
                set_current_state(TASK_IDLE);
                schedule();
        }

        return;
}