elfloader-tool/src/binaries/efi/efi_init.c

/*
 * Copyright 2020, Data61, CSIRO (ABN 41 687 119 230)
 *
 * SPDX-License-Identifier: GPL-2.0-only
 */

#include <binaries/efi/efi.h>
#include <elfloader_common.h>

void *__application_handle = NULL;             // current efi application handler
efi_system_table_t *__efi_system_table = NULL; // current efi system table

extern void _start(void);
unsigned int efi_main(uintptr_t application_handle, uintptr_t efi_system_table)
{
    clear_bss();
    __application_handle = (void *)application_handle;
    __efi_system_table = (efi_system_table_t *)efi_system_table;
    _start();
    return 0;
}

void *efi_get_fdt(void)
{
    efi_guid_t fdt_guid = make_efi_guid(0xb1b621d5, 0xf19c, 0x41a5,  0x83, 0x0b, 0xd9, 0x15, 0x2c, 0x69, 0xaa, 0xe0);
    efi_config_table_t *tables = (efi_config_table_t *)__efi_system_table->tables;

    for (uint32_t i = 0; i < __efi_system_table->nr_tables; i++) {
        if (!efi_guideq(fdt_guid, tables[i].guid))
            continue;

        return (void *)tables[i].table;
    }

    return NULL;
}

/* Before starting the kernel we should notify the UEFI firmware about it
 * otherwise the internal watchdog may reboot us after 5 min.
 *
 * This means boot time services are not available anymore. We should store
 * system information e.g. current memory map and pass them to kernel.
 */
unsigned long efi_exit_boot_services(void)
{
    unsigned long status;
    efi_memory_desc_t *memory_map;
    unsigned long map_size;
    unsigned long desc_size, key;
    uint32_t desc_version;

    efi_boot_services_t *bts = get_efi_boot_services();

    /*
     * As the number of existing memeory segments are unknown,
     * we need to resort to a trial and error to guess that.
     * We start from 32 and increase it by one until get a valid value.
     */
    map_size = sizeof(*memory_map) * 32;

again:
    status = bts->allocate_pool(EFI_LOADER_DATA, map_size, (void **)&memory_map);

    if (status != EFI_SUCCESS)
        return status;

    status = bts->get_memory_map(&map_size, memory_map, &key, &desc_size, &desc_version);
    if (status == EFI_BUFFER_TOO_SMALL) {
        bts->free_pool(memory_map);

        map_size += sizeof(*memory_map);
        goto again;
    }

    if (status != EFI_SUCCESS){
        bts->free_pool(memory_map);
        return status;
    }

    status = bts->exit_boot_services(__application_handle, key);
    return status;
}