// SPDX-License-Identifier: GPL-2.0
/*
 * Helper functions used by the EFI stub on multiple
 * architectures. This should be #included by the EFI stub
 * implementation files.
 *
 * Copyright 2011 Intel Corporation; author Matt Fleming
 */

#include <linux/stdarg.h>

#include <linux/efi.h>
#include <linux/kernel.h>
#include <linux/overflow.h>
#include <asm/efi.h>
#include <asm/setup.h>

#include "efistub.h"

bool efi_nochunk;
bool efi_nokaslr = !IS_ENABLED(CONFIG_RANDOMIZE_BASE);
bool efi_novamap;

static bool efi_noinitrd;
static bool efi_nosoftreserve;
static bool efi_disable_pci_dma = IS_ENABLED(CONFIG_EFI_DISABLE_PCI_DMA);

int efi_mem_encrypt;

bool __pure __efi_soft_reserve_enabled(void)
{
        return !efi_nosoftreserve;
}

/**
 * efi_parse_options() - Parse EFI command line options
 * @cmdline:    kernel command line
 *
 * Parse the ASCII string @cmdline for EFI options, denoted by the efi=
 * option, e.g. efi=nochunk.
 *
 * It should be noted that efi= is parsed in two very different
 * environments, first in the early boot environment of the EFI boot
 * stub, and subsequently during the kernel boot.
 *
 * Return:      status code
 */
efi_status_t efi_parse_options(char const *cmdline)
{
        char *buf __free(efi_pool) = NULL;
        efi_status_t status;
        size_t len;
        char *str;

        if (!cmdline)
                return EFI_SUCCESS;

        len = strnlen(cmdline, COMMAND_LINE_SIZE - 1) + 1;
        status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, len, (void **)&buf);
        if (status != EFI_SUCCESS)
                return status;

        memcpy(buf, cmdline, len - 1);
        buf[len - 1] = '\0';
        str = skip_spaces(buf);

        while (*str) {
                char *param, *val;

                str = next_arg(str, &param, &val);
                if (!val && !strcmp(param, "--"))
                        break;

                if (!strcmp(param, "nokaslr")) {
                        efi_nokaslr = true;
                } else if (!strcmp(param, "quiet")) {
                        efi_loglevel = CONSOLE_LOGLEVEL_QUIET;
                } else if (!strcmp(param, "noinitrd")) {
                        efi_noinitrd = true;
                } else if (IS_ENABLED(CONFIG_X86_64) && !strcmp(param, "no5lvl")) {
                        efi_no5lvl = true;
                } else if (IS_ENABLED(CONFIG_ARCH_HAS_MEM_ENCRYPT) &&
                           !strcmp(param, "mem_encrypt") && val) {
                        if (parse_option_str(val, "on"))
                                efi_mem_encrypt = 1;
                        else if (parse_option_str(val, "off"))
                                efi_mem_encrypt = -1;
                } else if (!strcmp(param, "efi") && val) {
                        efi_nochunk = parse_option_str(val, "nochunk");
                        efi_novamap |= parse_option_str(val, "novamap");

                        efi_nosoftreserve = IS_ENABLED(CONFIG_EFI_SOFT_RESERVE) &&
                                            parse_option_str(val, "nosoftreserve");

                        if (parse_option_str(val, "disable_early_pci_dma"))
                                efi_disable_pci_dma = true;
                        if (parse_option_str(val, "no_disable_early_pci_dma"))
                                efi_disable_pci_dma = false;
                        if (parse_option_str(val, "debug"))
                                efi_loglevel = CONSOLE_LOGLEVEL_DEBUG;
                } else if (!strcmp(param, "video") &&
                           val && strstarts(val, "efifb:")) {
                        efi_parse_option_graphics(val + strlen("efifb:"));
                }
        }
        return EFI_SUCCESS;
}

/*
 * The EFI_LOAD_OPTION descriptor has the following layout:
 *      u32 Attributes;
 *      u16 FilePathListLength;
 *      u16 Description[];
 *      efi_device_path_protocol_t FilePathList[];
 *      u8 OptionalData[];
 *
 * This function validates and unpacks the variable-size data fields.
 */
static
bool efi_load_option_unpack(efi_load_option_unpacked_t *dest,
                            const efi_load_option_t *src, size_t size)
{
        const void *pos;
        u16 c;
        efi_device_path_protocol_t header;
        const efi_char16_t *description;
        const efi_device_path_protocol_t *file_path_list;

        if (size < offsetof(efi_load_option_t, variable_data))
                return false;
        pos = src->variable_data;
        size -= offsetof(efi_load_option_t, variable_data);

        if ((src->attributes & ~EFI_LOAD_OPTION_MASK) != 0)
                return false;

        /* Scan description. */
        description = pos;
        do {
                if (size < sizeof(c))
                        return false;
                c = *(const u16 *)pos;
                pos += sizeof(c);
                size -= sizeof(c);
        } while (c != L'\0');

        /* Scan file_path_list. */
        file_path_list = pos;
        do {
                if (size < sizeof(header))
                        return false;
                header = *(const efi_device_path_protocol_t *)pos;
                if (header.length < sizeof(header))
                        return false;
                if (size < header.length)
                        return false;
                pos += header.length;
                size -= header.length;
        } while ((header.type != EFI_DEV_END_PATH && header.type != EFI_DEV_END_PATH2) ||
                 (header.sub_type != EFI_DEV_END_ENTIRE));
        if (pos != (const void *)file_path_list + src->file_path_list_length)
                return false;

        dest->attributes = src->attributes;
        dest->file_path_list_length = src->file_path_list_length;
        dest->description = description;
        dest->file_path_list = file_path_list;
        dest->optional_data_size = size;
        dest->optional_data = size ? pos : NULL;

        return true;
}

/*
 * At least some versions of Dell firmware pass the entire contents of the
 * Boot#### variable, i.e. the EFI_LOAD_OPTION descriptor, rather than just the
 * OptionalData field.
 *
 * Detect this case and extract OptionalData.
 */
void efi_apply_loadoptions_quirk(const void **load_options, u32 *load_options_size)
{
        const efi_load_option_t *load_option = *load_options;
        efi_load_option_unpacked_t load_option_unpacked;

        if (!IS_ENABLED(CONFIG_X86))
                return;
        if (!load_option)
                return;
        if (*load_options_size < sizeof(*load_option))
                return;
        if ((load_option->attributes & ~EFI_LOAD_OPTION_BOOT_MASK) != 0)
                return;

        if (!efi_load_option_unpack(&load_option_unpacked, load_option, *load_options_size))
                return;

        efi_warn_once(FW_BUG "LoadOptions is an EFI_LOAD_OPTION descriptor\n");
        efi_warn_once(FW_BUG "Using OptionalData as a workaround\n");

        *load_options = load_option_unpacked.optional_data;
        *load_options_size = load_option_unpacked.optional_data_size;
}

enum efistub_event_type {
        EFISTUB_EVT_INITRD,
        EFISTUB_EVT_LOAD_OPTIONS,
        EFISTUB_EVT_COUNT,
};

#define STR_WITH_SIZE(s)        sizeof(s), s

static const struct {
        u32             pcr_index;
        u32             event_id;
        u32             event_data_len;
        u8              event_data[52];
} events[] = {
        [EFISTUB_EVT_INITRD] = {
                9,
                INITRD_EVENT_TAG_ID,
                STR_WITH_SIZE("Linux initrd")
        },
        [EFISTUB_EVT_LOAD_OPTIONS] = {
                9,
                LOAD_OPTIONS_EVENT_TAG_ID,
                STR_WITH_SIZE("LOADED_IMAGE::LoadOptions")
        },
};

static_assert(sizeof(efi_tcg2_event_t) == sizeof(efi_cc_event_t));

union efistub_event {
        efi_tcg2_event_t        tcg2_data;
        efi_cc_event_t          cc_data;
};

struct efistub_measured_event {
        union efistub_event     event_data;
        TCG_PCClientTaggedEvent tagged_event __packed;
};

static efi_status_t efi_measure_tagged_event(unsigned long load_addr,
                                             unsigned long load_size,
                                             enum efistub_event_type event)
{
        union {
                efi_status_t
                (__efiapi *hash_log_extend_event)(void *, u64, efi_physical_addr_t,
                                                  u64, const union efistub_event *);
                struct { u32 hash_log_extend_event; } mixed_mode;
        } method;
        struct efistub_measured_event *evt __free(efi_pool) = NULL;
        int size = struct_size(evt, tagged_event.tagged_event_data,
                               events[event].event_data_len);
        efi_guid_t tcg2_guid = EFI_TCG2_PROTOCOL_GUID;
        efi_tcg2_protocol_t *tcg2 = NULL;
        union efistub_event ev;
        efi_status_t status;
        void *protocol;

        efi_bs_call(locate_protocol, &tcg2_guid, NULL, (void **)&tcg2);
        if (tcg2) {
                ev.tcg2_data = (struct efi_tcg2_event){
                        .event_size                     = size,
                        .event_header.header_size       = sizeof(ev.tcg2_data.event_header),
                        .event_header.header_version    = EFI_TCG2_EVENT_HEADER_VERSION,
                        .event_header.pcr_index         = events[event].pcr_index,
                        .event_header.event_type        = EV_EVENT_TAG,
                };
                protocol = tcg2;
                method.hash_log_extend_event =
                        (void *)efi_table_attr(tcg2, hash_log_extend_event);
        } else {
                efi_guid_t cc_guid = EFI_CC_MEASUREMENT_PROTOCOL_GUID;
                efi_cc_protocol_t *cc = NULL;

                efi_bs_call(locate_protocol, &cc_guid, NULL, (void **)&cc);
                if (!cc)
                        return EFI_UNSUPPORTED;

                ev.cc_data = (struct efi_cc_event){
                        .event_size                     = size,
                        .event_header.header_size       = sizeof(ev.cc_data.event_header),
                        .event_header.header_version    = EFI_CC_EVENT_HEADER_VERSION,
                        .event_header.event_type        = EV_EVENT_TAG,
                };

                status = efi_call_proto(cc, map_pcr_to_mr_index,
                                        events[event].pcr_index,
                                        &ev.cc_data.event_header.mr_index);
                if (status != EFI_SUCCESS)
                        goto fail;

                protocol = cc;
                method.hash_log_extend_event =
                        (void *)efi_table_attr(cc, hash_log_extend_event);
        }

        status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, size, (void **)&evt);
        if (status != EFI_SUCCESS)
                goto fail;

        *evt = (struct efistub_measured_event) {
                .event_data                          = ev,
                .tagged_event.tagged_event_id        = events[event].event_id,
                .tagged_event.tagged_event_data_size = events[event].event_data_len,
        };

        memcpy(evt->tagged_event.tagged_event_data, events[event].event_data,
               events[event].event_data_len);

        status = efi_fn_call(&method, hash_log_extend_event, protocol, 0,
                             load_addr, load_size, &evt->event_data);

        if (status == EFI_SUCCESS)
                return EFI_SUCCESS;

fail:
        efi_warn("Failed to measure data for event %d: 0x%lx\n", event, status);
        return status;
}

/*
 * Convert the unicode UEFI command line to ASCII to pass to kernel.
 * Size of memory allocated return in *cmd_line_len.
 * Returns NULL on error.
 */
char *efi_convert_cmdline(efi_loaded_image_t *image)
{
        const efi_char16_t *options = efi_table_attr(image, load_options);
        u32 options_size = efi_table_attr(image, load_options_size);
        int options_bytes = 0, safe_options_bytes = 0;  /* UTF-8 bytes */
        unsigned long cmdline_addr = 0;
        const efi_char16_t *s2;
        bool in_quote = false;
        efi_status_t status;
        u32 options_chars;

        if (options_size > 0)
                efi_measure_tagged_event((unsigned long)options, options_size,
                                         EFISTUB_EVT_LOAD_OPTIONS);

        efi_apply_loadoptions_quirk((const void **)&options, &options_size);
        options_chars = options_size / sizeof(efi_char16_t);

        if (options) {
                s2 = options;
                while (options_bytes < COMMAND_LINE_SIZE && options_chars--) {
                        efi_char16_t c = *s2++;

                        if (c < 0x80) {
                                if (c == L'\0' || c == L'\n')
                                        break;
                                if (c == L'"')
                                        in_quote = !in_quote;
                                else if (!in_quote && isspace((char)c))
                                        safe_options_bytes = options_bytes;

                                options_bytes++;
                                continue;
                        }

                        /*
                         * Get the number of UTF-8 bytes corresponding to a
                         * UTF-16 character.
                         * The first part handles everything in the BMP.
                         */
                        options_bytes += 2 + (c >= 0x800);
                        /*
                         * Add one more byte for valid surrogate pairs. Invalid
                         * surrogates will be replaced with 0xfffd and take up
                         * only 3 bytes.
                         */
                        if ((c & 0xfc00) == 0xd800) {
                                /*
                                 * If the very last word is a high surrogate,
                                 * we must ignore it since we can't access the
                                 * low surrogate.
                                 */
                                if (!options_chars) {
                                        options_bytes -= 3;
                                } else if ((*s2 & 0xfc00) == 0xdc00) {
                                        options_bytes++;
                                        options_chars--;
                                        s2++;
                                }
                        }
                }
                if (options_bytes >= COMMAND_LINE_SIZE) {
                        options_bytes = safe_options_bytes;
                        efi_err("Command line is too long: truncated to %d bytes\n",
                                options_bytes);
                }
        }

        options_bytes++;        /* NUL termination */

        status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, options_bytes,
                             (void **)&cmdline_addr);
        if (status != EFI_SUCCESS)
                return NULL;

        snprintf((char *)cmdline_addr, options_bytes, "%.*ls",
                 options_bytes - 1, options);

        return (char *)cmdline_addr;
}

/**
 * efi_exit_boot_services() - Exit boot services
 * @handle:     handle of the exiting image
 * @priv:       argument to be passed to @priv_func
 * @priv_func:  function to process the memory map before exiting boot services
 *
 * Handle calling ExitBootServices according to the requirements set out by the
 * spec.  Obtains the current memory map, and returns that info after calling
 * ExitBootServices.  The client must specify a function to perform any
 * processing of the memory map data prior to ExitBootServices.  A client
 * specific structure may be passed to the function via priv.  The client
 * function may be called multiple times.
 *
 * Return:      status code
 */
efi_status_t efi_exit_boot_services(void *handle, void *priv,
                                    efi_exit_boot_map_processing priv_func)
{
        struct efi_boot_memmap *map;
        efi_status_t status;

        if (efi_disable_pci_dma)
                efi_pci_disable_bridge_busmaster();

        status = efi_get_memory_map(&map, true);
        if (status != EFI_SUCCESS)
                return status;

        status = priv_func(map, priv);
        if (status != EFI_SUCCESS) {
                efi_bs_call(free_pool, map);
                return status;
        }

        status = efi_bs_call(exit_boot_services, handle, map->map_key);

        if (status == EFI_INVALID_PARAMETER) {
                /*
                 * The memory map changed between efi_get_memory_map() and
                 * exit_boot_services().  Per the UEFI Spec v2.6, Section 6.4:
                 * EFI_BOOT_SERVICES.ExitBootServices we need to get the
                 * updated map, and try again.  The spec implies one retry
                 * should be sufficent, which is confirmed against the EDK2
                 * implementation.  Per the spec, we can only invoke
                 * get_memory_map() and exit_boot_services() - we cannot alloc
                 * so efi_get_memory_map() cannot be used, and we must reuse
                 * the buffer.  For all practical purposes, the headroom in the
                 * buffer should account for any changes in the map so the call
                 * to get_memory_map() is expected to succeed here.
                 */
                map->map_size = map->buff_size;
                status = efi_bs_call(get_memory_map,
                                     &map->map_size,
                                     &map->map,
                                     &map->map_key,
                                     &map->desc_size,
                                     &map->desc_ver);

                /* exit_boot_services() was called, thus cannot free */
                if (status != EFI_SUCCESS)
                        return status;

                status = priv_func(map, priv);
                /* exit_boot_services() was called, thus cannot free */
                if (status != EFI_SUCCESS)
                        return status;

                status = efi_bs_call(exit_boot_services, handle, map->map_key);
        }

        return status;
}

/**
 * get_efi_config_table() - retrieve UEFI configuration table
 * @guid:       GUID of the configuration table to be retrieved
 * Return:      pointer to the configuration table or NULL
 */
void *get_efi_config_table(efi_guid_t guid)
{
        unsigned long tables = efi_table_attr(efi_system_table, tables);
        int nr_tables = efi_table_attr(efi_system_table, nr_tables);
        int i;

        for (i = 0; i < nr_tables; i++) {
                efi_config_table_t *t = (void *)tables;

                if (efi_guidcmp(t->guid, guid) == 0)
                        return efi_table_attr(t, table);

                tables += efi_is_native() ? sizeof(efi_config_table_t)
                                          : sizeof(efi_config_table_32_t);
        }
        return NULL;
}

/*
 * The LINUX_EFI_INITRD_MEDIA_GUID vendor media device path below provides a way
 * for the firmware or bootloader to expose the initrd data directly to the stub
 * via the trivial LoadFile2 protocol, which is defined in the UEFI spec, and is
 * very easy to implement. It is a simple Linux initrd specific conduit between
 * kernel and firmware, allowing us to put the EFI stub (being part of the
 * kernel) in charge of where and when to load the initrd, while leaving it up
 * to the firmware to decide whether it needs to expose its filesystem hierarchy
 * via EFI protocols.
 */
static const struct {
        struct efi_vendor_dev_path      vendor;
        struct efi_generic_dev_path     end;
} __packed initrd_dev_path = {
        {
                {
                        EFI_DEV_MEDIA,
                        EFI_DEV_MEDIA_VENDOR,
                        sizeof(struct efi_vendor_dev_path),
                },
                LINUX_EFI_INITRD_MEDIA_GUID
        }, {
                EFI_DEV_END_PATH,
                EFI_DEV_END_ENTIRE,
                sizeof(struct efi_generic_dev_path)
        }
};

/**
 * efi_load_initrd_dev_path() - load the initrd from the Linux initrd device path
 * @initrd:     pointer of struct to store the address where the initrd was loaded
 *              and the size of the loaded initrd
 * @max:        upper limit for the initrd memory allocation
 *
 * Return:
 * * %EFI_SUCCESS if the initrd was loaded successfully, in which
 *   case @load_addr and @load_size are assigned accordingly
 * * %EFI_NOT_FOUND if no LoadFile2 protocol exists on the initrd device path
 * * %EFI_OUT_OF_RESOURCES if memory allocation failed
 * * %EFI_LOAD_ERROR in all other cases
 */
static
efi_status_t efi_load_initrd_dev_path(struct linux_efi_initrd *initrd,
                                      unsigned long max)
{
        efi_guid_t lf2_proto_guid = EFI_LOAD_FILE2_PROTOCOL_GUID;
        efi_device_path_protocol_t *dp;
        efi_load_file2_protocol_t *lf2;
        efi_handle_t handle;
        efi_status_t status;

        dp = (efi_device_path_protocol_t *)&initrd_dev_path;
        status = efi_bs_call(locate_device_path, &lf2_proto_guid, &dp, &handle);
        if (status != EFI_SUCCESS)
                return status;

        status = efi_bs_call(handle_protocol, handle, &lf2_proto_guid,
                             (void **)&lf2);
        if (status != EFI_SUCCESS)
                return status;

        initrd->size = 0;
        status = efi_call_proto(lf2, load_file, dp, false, &initrd->size, NULL);
        if (status != EFI_BUFFER_TOO_SMALL)
                return EFI_LOAD_ERROR;

        status = efi_allocate_pages(initrd->size, &initrd->base, max);
        if (status != EFI_SUCCESS)
                return status;

        status = efi_call_proto(lf2, load_file, dp, false, &initrd->size,
                                (void *)initrd->base);
        if (status != EFI_SUCCESS) {
                efi_free(initrd->size, initrd->base);
                return EFI_LOAD_ERROR;
        }
        return EFI_SUCCESS;
}

static
efi_status_t efi_load_initrd_cmdline(efi_loaded_image_t *image,
                                     struct linux_efi_initrd *initrd,
                                     unsigned long soft_limit,
                                     unsigned long hard_limit)
{
        if (image == NULL)
                return EFI_UNSUPPORTED;

        return handle_cmdline_files(image, L"initrd=", sizeof(L"initrd=") - 2,
                                    soft_limit, hard_limit,
                                    &initrd->base, &initrd->size);
}

/**
 * efi_load_initrd() - Load initial RAM disk
 * @image:      EFI loaded image protocol
 * @soft_limit: preferred address for loading the initrd
 * @hard_limit: upper limit address for loading the initrd
 * @out:        pointer to store the address of the initrd table
 *
 * Return:      status code
 */
efi_status_t efi_load_initrd(efi_loaded_image_t *image,
                             unsigned long soft_limit,
                             unsigned long hard_limit,
                             const struct linux_efi_initrd **out)
{
        efi_guid_t tbl_guid = LINUX_EFI_INITRD_MEDIA_GUID;
        efi_status_t status = EFI_SUCCESS;
        struct linux_efi_initrd initrd, *tbl;

        if (!IS_ENABLED(CONFIG_BLK_DEV_INITRD) || efi_noinitrd)
                return EFI_SUCCESS;

        status = efi_load_initrd_dev_path(&initrd, hard_limit);
        if (status == EFI_SUCCESS) {
                efi_info("Loaded initrd from LINUX_EFI_INITRD_MEDIA_GUID device path\n");
        } else if (status == EFI_NOT_FOUND) {
                status = efi_load_initrd_cmdline(image, &initrd, soft_limit,
                                                 hard_limit);
                /* command line loader disabled or no initrd= passed? */
                if (status == EFI_UNSUPPORTED || status == EFI_NOT_READY)
                        return EFI_SUCCESS;
                if (status == EFI_SUCCESS)
                        efi_info("Loaded initrd from command line option\n");
        }
        if (status != EFI_SUCCESS)
                goto failed;

        if (initrd.size > 0 &&
            efi_measure_tagged_event(initrd.base, initrd.size,
                                     EFISTUB_EVT_INITRD) == EFI_SUCCESS)
                efi_info("Measured initrd data into PCR 9\n");

        status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, sizeof(initrd),
                             (void **)&tbl);
        if (status != EFI_SUCCESS)
                goto free_initrd;

        *tbl = initrd;
        status = efi_bs_call(install_configuration_table, &tbl_guid, tbl);
        if (status != EFI_SUCCESS)
                goto free_tbl;

        if (out)
                *out = tbl;
        return EFI_SUCCESS;

free_tbl:
        efi_bs_call(free_pool, tbl);
free_initrd:
        efi_free(initrd.size, initrd.base);
failed:
        efi_err("Failed to load initrd: 0x%lx\n", status);
        return status;
}

/**
 * efi_wait_for_key() - Wait for key stroke
 * @usec:       number of microseconds to wait for key stroke
 * @key:        key entered
 *
 * Wait for up to @usec microseconds for a key stroke.
 *
 * Return:      status code, EFI_SUCCESS if key received
 */
efi_status_t efi_wait_for_key(unsigned long usec, efi_input_key_t *key)
{
        efi_event_t events[2], timer;
        unsigned long index;
        efi_simple_text_input_protocol_t *con_in;
        efi_status_t status;

        con_in = efi_table_attr(efi_system_table, con_in);
        if (!con_in)
                return EFI_UNSUPPORTED;
        efi_set_event_at(events, 0, efi_table_attr(con_in, wait_for_key));

        status = efi_bs_call(create_event, EFI_EVT_TIMER, 0, NULL, NULL, &timer);
        if (status != EFI_SUCCESS)
                return status;

        status = efi_bs_call(set_timer, timer, EfiTimerRelative,
                             EFI_100NSEC_PER_USEC * usec);
        if (status != EFI_SUCCESS)
                return status;
        efi_set_event_at(events, 1, timer);

        status = efi_bs_call(wait_for_event, 2, events, &index);
        if (status == EFI_SUCCESS) {
                if (index == 0)
                        status = efi_call_proto(con_in, read_keystroke, key);
                else
                        status = EFI_TIMEOUT;
        }

        efi_bs_call(close_event, timer);

        return status;
}

/**
 * efi_remap_image - Remap a loaded image with the appropriate permissions
 *                   for code and data
 *
 * @image_base: the base of the image in memory
 * @alloc_size: the size of the area in memory occupied by the image
 * @code_size:  the size of the leading part of the image containing code
 *              and read-only data
 *
 * efi_remap_image() uses the EFI memory attribute protocol to remap the code
 * region of the loaded image read-only/executable, and the remainder
 * read-write/non-executable. The code region is assumed to start at the base
 * of the image, and will therefore cover the PE/COFF header as well.
 */
void efi_remap_image(unsigned long image_base, unsigned alloc_size,
                     unsigned long code_size)
{
        efi_guid_t guid = EFI_MEMORY_ATTRIBUTE_PROTOCOL_GUID;
        efi_memory_attribute_protocol_t *memattr;
        efi_status_t status;
        u64 attr;

        /*
         * If the firmware implements the EFI_MEMORY_ATTRIBUTE_PROTOCOL, let's
         * invoke it to remap the text/rodata region of the decompressed image
         * as read-only and the data/bss region as non-executable.
         */
        status = efi_bs_call(locate_protocol, &guid, NULL, (void **)&memattr);
        if (status != EFI_SUCCESS)
                return;

        // Get the current attributes for the entire region
        status = memattr->get_memory_attributes(memattr, image_base,
                                                alloc_size, &attr);
        if (status != EFI_SUCCESS) {
                efi_warn("Failed to retrieve memory attributes for image region: 0x%lx\n",
                         status);
                return;
        }

        // Mark the code region as read-only
        status = memattr->set_memory_attributes(memattr, image_base, code_size,
                                                EFI_MEMORY_RO);
        if (status != EFI_SUCCESS) {
                efi_warn("Failed to remap code region read-only\n");
                return;
        }

        // If the entire region was already mapped as non-exec, clear the
        // attribute from the code region. Otherwise, set it on the data
        // region.
        if (attr & EFI_MEMORY_XP) {
                status = memattr->clear_memory_attributes(memattr, image_base,
                                                          code_size,
                                                          EFI_MEMORY_XP);
                if (status != EFI_SUCCESS)
                        efi_warn("Failed to remap code region executable\n");
        } else {
                status = memattr->set_memory_attributes(memattr,
                                                        image_base + code_size,
                                                        alloc_size - code_size,
                                                        EFI_MEMORY_XP);
                if (status != EFI_SUCCESS)
                        efi_warn("Failed to remap data region non-executable\n");
        }
}