Linux 4.18.10

[linux/fpc-iii.git] / drivers / firmware / efi / libstub / efi-stub-helper.c

/*
 * 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
 *
 * This file is part of the Linux kernel, and is made available
 * under the terms of the GNU General Public License version 2.
 *
 */

#include <linux/efi.h>
#include <asm/efi.h>

#include "efistub.h"

/*
 * Some firmware implementations have problems reading files in one go.
 * A read chunk size of 1MB seems to work for most platforms.
 *
 * Unfortunately, reading files in chunks triggers *other* bugs on some
 * platforms, so we provide a way to disable this workaround, which can
 * be done by passing "efi=nochunk" on the EFI boot stub command line.
 *
 * If you experience issues with initrd images being corrupt it's worth
 * trying efi=nochunk, but chunking is enabled by default because there
 * are far more machines that require the workaround than those that
 * break with it enabled.
 */
#define EFI_READ_CHUNK_SIZE     (1024 * 1024)

static unsigned long __chunk_size = EFI_READ_CHUNK_SIZE;

static int __section(.data) __nokaslr;
static int __section(.data) __quiet;

int __pure nokaslr(void)
{
        return __nokaslr;
}
int __pure is_quiet(void)
{
        return __quiet;
}

#define EFI_MMAP_NR_SLACK_SLOTS 8

struct file_info {
        efi_file_handle_t *handle;
        u64 size;
};

void efi_printk(efi_system_table_t *sys_table_arg, char *str)
{
        char *s8;

        for (s8 = str; *s8; s8++) {
                efi_char16_t ch[2] = { 0 };

                ch[0] = *s8;
                if (*s8 == '\n') {
                        efi_char16_t nl[2] = { '\r', 0 };
                        efi_char16_printk(sys_table_arg, nl);
                }

                efi_char16_printk(sys_table_arg, ch);
        }
}

static inline bool mmap_has_headroom(unsigned long buff_size,
                                     unsigned long map_size,
                                     unsigned long desc_size)
{
        unsigned long slack = buff_size - map_size;

        return slack / desc_size >= EFI_MMAP_NR_SLACK_SLOTS;
}

efi_status_t efi_get_memory_map(efi_system_table_t *sys_table_arg,
                                struct efi_boot_memmap *map)
{
        efi_memory_desc_t *m = NULL;
        efi_status_t status;
        unsigned long key;
        u32 desc_version;

        *map->desc_size =       sizeof(*m);
        *map->map_size =        *map->desc_size * 32;
        *map->buff_size =       *map->map_size;
again:
        status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
                                *map->map_size, (void **)&m);
        if (status != EFI_SUCCESS)
                goto fail;

        *map->desc_size = 0;
        key = 0;
        status = efi_call_early(get_memory_map, map->map_size, m,
                                &key, map->desc_size, &desc_version);
        if (status == EFI_BUFFER_TOO_SMALL ||
            !mmap_has_headroom(*map->buff_size, *map->map_size,
                               *map->desc_size)) {
                efi_call_early(free_pool, m);
                /*
                 * Make sure there is some entries of headroom so that the
                 * buffer can be reused for a new map after allocations are
                 * no longer permitted.  Its unlikely that the map will grow to
                 * exceed this headroom once we are ready to trigger
                 * ExitBootServices()
                 */
                *map->map_size += *map->desc_size * EFI_MMAP_NR_SLACK_SLOTS;
                *map->buff_size = *map->map_size;
                goto again;
        }

        if (status != EFI_SUCCESS)
                efi_call_early(free_pool, m);

        if (map->key_ptr && status == EFI_SUCCESS)
                *map->key_ptr = key;
        if (map->desc_ver && status == EFI_SUCCESS)
                *map->desc_ver = desc_version;

fail:
        *map->map = m;
        return status;
}


unsigned long get_dram_base(efi_system_table_t *sys_table_arg)
{
        efi_status_t status;
        unsigned long map_size, buff_size;
        unsigned long membase  = EFI_ERROR;
        struct efi_memory_map map;
        efi_memory_desc_t *md;
        struct efi_boot_memmap boot_map;

        boot_map.map =          (efi_memory_desc_t **)&map.map;
        boot_map.map_size =     &map_size;
        boot_map.desc_size =    &map.desc_size;
        boot_map.desc_ver =     NULL;
        boot_map.key_ptr =      NULL;
        boot_map.buff_size =    &buff_size;

        status = efi_get_memory_map(sys_table_arg, &boot_map);
        if (status != EFI_SUCCESS)
                return membase;

        map.map_end = map.map + map_size;

        for_each_efi_memory_desc_in_map(&map, md) {
                if (md->attribute & EFI_MEMORY_WB) {
                        if (membase > md->phys_addr)
                                membase = md->phys_addr;
                }
        }

        efi_call_early(free_pool, map.map);

        return membase;
}

/*
 * Allocate at the highest possible address that is not above 'max'.
 */
efi_status_t efi_high_alloc(efi_system_table_t *sys_table_arg,
                            unsigned long size, unsigned long align,
                            unsigned long *addr, unsigned long max)
{
        unsigned long map_size, desc_size, buff_size;
        efi_memory_desc_t *map;
        efi_status_t status;
        unsigned long nr_pages;
        u64 max_addr = 0;
        int i;
        struct efi_boot_memmap boot_map;

        boot_map.map =          &map;
        boot_map.map_size =     &map_size;
        boot_map.desc_size =    &desc_size;
        boot_map.desc_ver =     NULL;
        boot_map.key_ptr =      NULL;
        boot_map.buff_size =    &buff_size;

        status = efi_get_memory_map(sys_table_arg, &boot_map);
        if (status != EFI_SUCCESS)
                goto fail;

        /*
         * Enforce minimum alignment that EFI or Linux requires when
         * requesting a specific address.  We are doing page-based (or
         * larger) allocations, and both the address and size must meet
         * alignment constraints.
         */
        if (align < EFI_ALLOC_ALIGN)
                align = EFI_ALLOC_ALIGN;

        size = round_up(size, EFI_ALLOC_ALIGN);
        nr_pages = size / EFI_PAGE_SIZE;
again:
        for (i = 0; i < map_size / desc_size; i++) {
                efi_memory_desc_t *desc;
                unsigned long m = (unsigned long)map;
                u64 start, end;

                desc = efi_early_memdesc_ptr(m, desc_size, i);
                if (desc->type != EFI_CONVENTIONAL_MEMORY)
                        continue;

                if (desc->num_pages < nr_pages)
                        continue;

                start = desc->phys_addr;
                end = start + desc->num_pages * EFI_PAGE_SIZE;

                if (end > max)
                        end = max;

                if ((start + size) > end)
                        continue;

                if (round_down(end - size, align) < start)
                        continue;

                start = round_down(end - size, align);

                /*
                 * Don't allocate at 0x0. It will confuse code that
                 * checks pointers against NULL.
                 */
                if (start == 0x0)
                        continue;

                if (start > max_addr)
                        max_addr = start;
        }

        if (!max_addr)
                status = EFI_NOT_FOUND;
        else {
                status = efi_call_early(allocate_pages,
                                        EFI_ALLOCATE_ADDRESS, EFI_LOADER_DATA,
                                        nr_pages, &max_addr);
                if (status != EFI_SUCCESS) {
                        max = max_addr;
                        max_addr = 0;
                        goto again;
                }

                *addr = max_addr;
        }

        efi_call_early(free_pool, map);
fail:
        return status;
}

/*
 * Allocate at the lowest possible address.
 */
efi_status_t efi_low_alloc(efi_system_table_t *sys_table_arg,
                           unsigned long size, unsigned long align,
                           unsigned long *addr)
{
        unsigned long map_size, desc_size, buff_size;
        efi_memory_desc_t *map;
        efi_status_t status;
        unsigned long nr_pages;
        int i;
        struct efi_boot_memmap boot_map;

        boot_map.map =          &map;
        boot_map.map_size =     &map_size;
        boot_map.desc_size =    &desc_size;
        boot_map.desc_ver =     NULL;
        boot_map.key_ptr =      NULL;
        boot_map.buff_size =    &buff_size;

        status = efi_get_memory_map(sys_table_arg, &boot_map);
        if (status != EFI_SUCCESS)
                goto fail;

        /*
         * Enforce minimum alignment that EFI or Linux requires when
         * requesting a specific address.  We are doing page-based (or
         * larger) allocations, and both the address and size must meet
         * alignment constraints.
         */
        if (align < EFI_ALLOC_ALIGN)
                align = EFI_ALLOC_ALIGN;

        size = round_up(size, EFI_ALLOC_ALIGN);
        nr_pages = size / EFI_PAGE_SIZE;
        for (i = 0; i < map_size / desc_size; i++) {
                efi_memory_desc_t *desc;
                unsigned long m = (unsigned long)map;
                u64 start, end;

                desc = efi_early_memdesc_ptr(m, desc_size, i);

                if (desc->type != EFI_CONVENTIONAL_MEMORY)
                        continue;

                if (desc->num_pages < nr_pages)
                        continue;

                start = desc->phys_addr;
                end = start + desc->num_pages * EFI_PAGE_SIZE;

                /*
                 * Don't allocate at 0x0. It will confuse code that
                 * checks pointers against NULL. Skip the first 8
                 * bytes so we start at a nice even number.
                 */
                if (start == 0x0)
                        start += 8;

                start = round_up(start, align);
                if ((start + size) > end)
                        continue;

                status = efi_call_early(allocate_pages,
                                        EFI_ALLOCATE_ADDRESS, EFI_LOADER_DATA,
                                        nr_pages, &start);
                if (status == EFI_SUCCESS) {
                        *addr = start;
                        break;
                }
        }

        if (i == map_size / desc_size)
                status = EFI_NOT_FOUND;

        efi_call_early(free_pool, map);
fail:
        return status;
}

void efi_free(efi_system_table_t *sys_table_arg, unsigned long size,
              unsigned long addr)
{
        unsigned long nr_pages;

        if (!size)
                return;

        nr_pages = round_up(size, EFI_ALLOC_ALIGN) / EFI_PAGE_SIZE;
        efi_call_early(free_pages, addr, nr_pages);
}

static efi_status_t efi_file_size(efi_system_table_t *sys_table_arg, void *__fh,
                                  efi_char16_t *filename_16, void **handle,
                                  u64 *file_sz)
{
        efi_file_handle_t *h, *fh = __fh;
        efi_file_info_t *info;
        efi_status_t status;
        efi_guid_t info_guid = EFI_FILE_INFO_ID;
        unsigned long info_sz;

        status = efi_call_proto(efi_file_handle, open, fh, &h, filename_16,
                                EFI_FILE_MODE_READ, (u64)0);
        if (status != EFI_SUCCESS) {
                efi_printk(sys_table_arg, "Failed to open file: ");
                efi_char16_printk(sys_table_arg, filename_16);
                efi_printk(sys_table_arg, "\n");
                return status;
        }

        *handle = h;

        info_sz = 0;
        status = efi_call_proto(efi_file_handle, get_info, h, &info_guid,
                                &info_sz, NULL);
        if (status != EFI_BUFFER_TOO_SMALL) {
                efi_printk(sys_table_arg, "Failed to get file info size\n");
                return status;
        }

grow:
        status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
                                info_sz, (void **)&info);
        if (status != EFI_SUCCESS) {
                efi_printk(sys_table_arg, "Failed to alloc mem for file info\n");
                return status;
        }

        status = efi_call_proto(efi_file_handle, get_info, h, &info_guid,
                                &info_sz, info);
        if (status == EFI_BUFFER_TOO_SMALL) {
                efi_call_early(free_pool, info);
                goto grow;
        }

        *file_sz = info->file_size;
        efi_call_early(free_pool, info);

        if (status != EFI_SUCCESS)
                efi_printk(sys_table_arg, "Failed to get initrd info\n");

        return status;
}

static efi_status_t efi_file_read(void *handle, unsigned long *size, void *addr)
{
        return efi_call_proto(efi_file_handle, read, handle, size, addr);
}

static efi_status_t efi_file_close(void *handle)
{
        return efi_call_proto(efi_file_handle, close, handle);
}

/*
 * 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.
 */
efi_status_t efi_parse_options(char const *cmdline)
{
        char *str;

        str = strstr(cmdline, "nokaslr");
        if (str == cmdline || (str && str > cmdline && *(str - 1) == ' '))
                __nokaslr = 1;

        str = strstr(cmdline, "quiet");
        if (str == cmdline || (str && str > cmdline && *(str - 1) == ' '))
                __quiet = 1;

        /*
         * If no EFI parameters were specified on the cmdline we've got
         * nothing to do.
         */
        str = strstr(cmdline, "efi=");
        if (!str)
                return EFI_SUCCESS;

        /* Skip ahead to first argument */
        str += strlen("efi=");

        /*
         * Remember, because efi= is also used by the kernel we need to
         * skip over arguments we don't understand.
         */
        while (*str && *str != ' ') {
                if (!strncmp(str, "nochunk", 7)) {
                        str += strlen("nochunk");
                        __chunk_size = -1UL;
                }

                /* Group words together, delimited by "," */
                while (*str && *str != ' ' && *str != ',')
                        str++;

                if (*str == ',')
                        str++;
        }

        return EFI_SUCCESS;
}

/*
 * Check the cmdline for a LILO-style file= arguments.
 *
 * We only support loading a file from the same filesystem as
 * the kernel image.
 */
efi_status_t handle_cmdline_files(efi_system_table_t *sys_table_arg,
                                  efi_loaded_image_t *image,
                                  char *cmd_line, char *option_string,
                                  unsigned long max_addr,
                                  unsigned long *load_addr,
                                  unsigned long *load_size)
{
        struct file_info *files;
        unsigned long file_addr;
        u64 file_size_total;
        efi_file_handle_t *fh = NULL;
        efi_status_t status;
        int nr_files;
        char *str;
        int i, j, k;

        file_addr = 0;
        file_size_total = 0;

        str = cmd_line;

        j = 0;                  /* See close_handles */

        if (!load_addr || !load_size)
                return EFI_INVALID_PARAMETER;

        *load_addr = 0;
        *load_size = 0;

        if (!str || !*str)
                return EFI_SUCCESS;

        for (nr_files = 0; *str; nr_files++) {
                str = strstr(str, option_string);
                if (!str)
                        break;

                str += strlen(option_string);

                /* Skip any leading slashes */
                while (*str == '/' || *str == '\\')
                        str++;

                while (*str && *str != ' ' && *str != '\n')
                        str++;
        }

        if (!nr_files)
                return EFI_SUCCESS;

        status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
                                nr_files * sizeof(*files), (void **)&files);
        if (status != EFI_SUCCESS) {
                pr_efi_err(sys_table_arg, "Failed to alloc mem for file handle list\n");
                goto fail;
        }

        str = cmd_line;
        for (i = 0; i < nr_files; i++) {
                struct file_info *file;
                efi_char16_t filename_16[256];
                efi_char16_t *p;

                str = strstr(str, option_string);
                if (!str)
                        break;

                str += strlen(option_string);

                file = &files[i];
                p = filename_16;

                /* Skip any leading slashes */
                while (*str == '/' || *str == '\\')
                        str++;

                while (*str && *str != ' ' && *str != '\n') {
                        if ((u8 *)p >= (u8 *)filename_16 + sizeof(filename_16))
                                break;

                        if (*str == '/') {
                                *p++ = '\\';
                                str++;
                        } else {
                                *p++ = *str++;
                        }
                }

                *p = '\0';

                /* Only open the volume once. */
                if (!i) {
                        status = efi_open_volume(sys_table_arg, image,
                                                 (void **)&fh);
                        if (status != EFI_SUCCESS)
                                goto free_files;
                }

                status = efi_file_size(sys_table_arg, fh, filename_16,
                                       (void **)&file->handle, &file->size);
                if (status != EFI_SUCCESS)
                        goto close_handles;

                file_size_total += file->size;
        }

        if (file_size_total) {
                unsigned long addr;

                /*
                 * Multiple files need to be at consecutive addresses in memory,
                 * so allocate enough memory for all the files.  This is used
                 * for loading multiple files.
                 */
                status = efi_high_alloc(sys_table_arg, file_size_total, 0x1000,
                                    &file_addr, max_addr);
                if (status != EFI_SUCCESS) {
                        pr_efi_err(sys_table_arg, "Failed to alloc highmem for files\n");
                        goto close_handles;
                }

                /* We've run out of free low memory. */
                if (file_addr > max_addr) {
                        pr_efi_err(sys_table_arg, "We've run out of free low memory\n");
                        status = EFI_INVALID_PARAMETER;
                        goto free_file_total;
                }

                addr = file_addr;
                for (j = 0; j < nr_files; j++) {
                        unsigned long size;

                        size = files[j].size;
                        while (size) {
                                unsigned long chunksize;

                                if (IS_ENABLED(CONFIG_X86) && size > __chunk_size)
                                        chunksize = __chunk_size;
                                else
                                        chunksize = size;

                                status = efi_file_read(files[j].handle,
                                                       &chunksize,
                                                       (void *)addr);
                                if (status != EFI_SUCCESS) {
                                        pr_efi_err(sys_table_arg, "Failed to read file\n");
                                        goto free_file_total;
                                }
                                addr += chunksize;
                                size -= chunksize;
                        }

                        efi_file_close(files[j].handle);
                }

        }

        efi_call_early(free_pool, files);

        *load_addr = file_addr;
        *load_size = file_size_total;

        return status;

free_file_total:
        efi_free(sys_table_arg, file_size_total, file_addr);

close_handles:
        for (k = j; k < i; k++)
                efi_file_close(files[k].handle);
free_files:
        efi_call_early(free_pool, files);
fail:
        *load_addr = 0;
        *load_size = 0;

        return status;
}
/*
 * Relocate a kernel image, either compressed or uncompressed.
 * In the ARM64 case, all kernel images are currently
 * uncompressed, and as such when we relocate it we need to
 * allocate additional space for the BSS segment. Any low
 * memory that this function should avoid needs to be
 * unavailable in the EFI memory map, as if the preferred
 * address is not available the lowest available address will
 * be used.
 */
efi_status_t efi_relocate_kernel(efi_system_table_t *sys_table_arg,
                                 unsigned long *image_addr,
                                 unsigned long image_size,
                                 unsigned long alloc_size,
                                 unsigned long preferred_addr,
                                 unsigned long alignment)
{
        unsigned long cur_image_addr;
        unsigned long new_addr = 0;
        efi_status_t status;
        unsigned long nr_pages;
        efi_physical_addr_t efi_addr = preferred_addr;

        if (!image_addr || !image_size || !alloc_size)
                return EFI_INVALID_PARAMETER;
        if (alloc_size < image_size)
                return EFI_INVALID_PARAMETER;

        cur_image_addr = *image_addr;

        /*
         * The EFI firmware loader could have placed the kernel image
         * anywhere in memory, but the kernel has restrictions on the
         * max physical address it can run at.  Some architectures
         * also have a prefered address, so first try to relocate
         * to the preferred address.  If that fails, allocate as low
         * as possible while respecting the required alignment.
         */
        nr_pages = round_up(alloc_size, EFI_ALLOC_ALIGN) / EFI_PAGE_SIZE;
        status = efi_call_early(allocate_pages,
                                EFI_ALLOCATE_ADDRESS, EFI_LOADER_DATA,
                                nr_pages, &efi_addr);
        new_addr = efi_addr;
        /*
         * If preferred address allocation failed allocate as low as
         * possible.
         */
        if (status != EFI_SUCCESS) {
                status = efi_low_alloc(sys_table_arg, alloc_size, alignment,
                                       &new_addr);
        }
        if (status != EFI_SUCCESS) {
                pr_efi_err(sys_table_arg, "Failed to allocate usable memory for kernel.\n");
                return status;
        }

        /*
         * We know source/dest won't overlap since both memory ranges
         * have been allocated by UEFI, so we can safely use memcpy.
         */
        memcpy((void *)new_addr, (void *)cur_image_addr, image_size);

        /* Return the new address of the relocated image. */
        *image_addr = new_addr;

        return status;
}

/*
 * Get the number of UTF-8 bytes corresponding to an UTF-16 character.
 * This overestimates for surrogates, but that is okay.
 */
static int efi_utf8_bytes(u16 c)
{
        return 1 + (c >= 0x80) + (c >= 0x800);
}

/*
 * Convert an UTF-16 string, not necessarily null terminated, to UTF-8.
 */
static u8 *efi_utf16_to_utf8(u8 *dst, const u16 *src, int n)
{
        unsigned int c;

        while (n--) {
                c = *src++;
                if (n && c >= 0xd800 && c <= 0xdbff &&
                    *src >= 0xdc00 && *src <= 0xdfff) {
                        c = 0x10000 + ((c & 0x3ff) << 10) + (*src & 0x3ff);
                        src++;
                        n--;
                }
                if (c >= 0xd800 && c <= 0xdfff)
                        c = 0xfffd; /* Unmatched surrogate */
                if (c < 0x80) {
                        *dst++ = c;
                        continue;
                }
                if (c < 0x800) {
                        *dst++ = 0xc0 + (c >> 6);
                        goto t1;
                }
                if (c < 0x10000) {
                        *dst++ = 0xe0 + (c >> 12);
                        goto t2;
                }
                *dst++ = 0xf0 + (c >> 18);
                *dst++ = 0x80 + ((c >> 12) & 0x3f);
        t2:
                *dst++ = 0x80 + ((c >> 6) & 0x3f);
        t1:
                *dst++ = 0x80 + (c & 0x3f);
        }

        return dst;
}

#ifndef MAX_CMDLINE_ADDRESS
#define MAX_CMDLINE_ADDRESS     ULONG_MAX
#endif

/*
 * 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_system_table_t *sys_table_arg,
                          efi_loaded_image_t *image,
                          int *cmd_line_len)
{
        const u16 *s2;
        u8 *s1 = NULL;
        unsigned long cmdline_addr = 0;
        int load_options_chars = image->load_options_size / 2; /* UTF-16 */
        const u16 *options = image->load_options;
        int options_bytes = 0;  /* UTF-8 bytes */
        int options_chars = 0;  /* UTF-16 chars */
        efi_status_t status;
        u16 zero = 0;

        if (options) {
                s2 = options;
                while (*s2 && *s2 != '\n'
                       && options_chars < load_options_chars) {
                        options_bytes += efi_utf8_bytes(*s2++);
                        options_chars++;
                }
        }

        if (!options_chars) {
                /* No command line options, so return empty string*/
                options = &zero;
        }

        options_bytes++;        /* NUL termination */

        status = efi_high_alloc(sys_table_arg, options_bytes, 0,
                                &cmdline_addr, MAX_CMDLINE_ADDRESS);
        if (status != EFI_SUCCESS)
                return NULL;

        s1 = (u8 *)cmdline_addr;
        s2 = (const u16 *)options;

        s1 = efi_utf16_to_utf8(s1, s2, options_chars);
        *s1 = '\0';

        *cmd_line_len = options_bytes;
        return (char *)cmdline_addr;
}

/*
 * 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.
 */
efi_status_t efi_exit_boot_services(efi_system_table_t *sys_table_arg,
                                    void *handle,
                                    struct efi_boot_memmap *map,
                                    void *priv,
                                    efi_exit_boot_map_processing priv_func)
{
        efi_status_t status;

        status = efi_get_memory_map(sys_table_arg, map);

        if (status != EFI_SUCCESS)
                goto fail;

        status = priv_func(sys_table_arg, map, priv);
        if (status != EFI_SUCCESS)
                goto free_map;

        status = efi_call_early(exit_boot_services, handle, *map->key_ptr);

        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_call_early(get_memory_map,
                                        map->map_size,
                                        *map->map,
                                        map->key_ptr,
                                        map->desc_size,
                                        map->desc_ver);

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

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

                status = efi_call_early(exit_boot_services, handle, *map->key_ptr);
        }

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

        return EFI_SUCCESS;

free_map:
        efi_call_early(free_pool, *map->map);
fail:
        return status;
}