RISC-V Linux 内核 UEFI 启动过程分析（Part2）：内核侧 UEFI 支持

// include/linux/efi.h : 547

struct efi_memory_map_data {
        phys_addr_t phys_map;
        unsigned long size;
        unsigned long desc_version;
        unsigned long desc_size;
        unsigned long flags;
};

struct efi_memory_map {
        phys_addr_t phys_map;
        void *map;
        void *map_end;
        int nr_map;
        unsigned long desc_version;
        unsigned long desc_size;
        unsigned long flags;
};

// drivers/firmware/efi/fdtparams.c : 35

static __initconst const struct {
        const char      path[17];
        u8              paravirt;
        const char      params[PARAMCOUNT][26];
} dt_params[] = {

                .path = "/chosen",
                .params = {     //  <-----------26----------->
                        [SYSTAB] = "linux,uefi-system-table",
                        [MMBASE] = "linux,uefi-mmap-start",
                        [MMSIZE] = "linux,uefi-mmap-size",
                        [DCSIZE] = "linux,uefi-mmap-desc-size",
                        [DCVERS] = "linux,uefi-mmap-desc-ver",
                }
}

// drivers/firmware/efi/efi-init.c :199

efi_init()
  // Grab UEFI information placed in FDT by stub
  efi_system_table = efi_get_fdt_params(&data); // struct efi_memory_map_data * data
      return systab;

  efi_memmap_init_early(&data)
    struct efi_memory_map map;
    map.map = early_memremap(data->phys_map, data->size); // 内存映射表的虚拟地址
    set_bit(EFI_MEMMAP, &efi.flags); // we use EFI memory map
    efi.memmap = map

efi_init()
  // drivers/firmware/efi/efi-init.c : 78
  uefi_init(efi_system_table)
    systab = early_memremap_ro(efi_system_table // remap systable
    set_bit(EFI_BOOT, &efi.flags);
    set_bit(EFI_64BIT, &efi.flags);

    efi.runtime = systab->runtime;

    config_tables = early_memremap_ro(efi_to_phys(systab->tables), table_size); // remap conftable
    efi_config_parse_tables(config_tables, systab->nr_tables, efi_arch_tables);
      match_config_table(guid, table, common_tables) // 解析 common_tables (ACPI/SMBIOS/ESRT/INITRD/MEMRESERVE)
      set_bit(EFI_CONFIG_TABLES, &efi.flags);

      // 处理 efi_rng_seed mem_reserve rt_prop initrd ...

      // set the reserved memory in the memblock.reserved
      memblock_reserve(prsv, struct_size(rsv, entry, rsv->size));

static const efi_config_table_type_t common_tables[] __initconst = {
        {ACPI_20_TABLE_GUID,                    &efi.acpi20,            "ACPI 2.0"      },
        {ACPI_TABLE_GUID,                       &efi.acpi,              "ACPI"          },
        {SMBIOS_TABLE_GUID,                     &efi.smbios,            "SMBIOS"        },
        {SMBIOS3_TABLE_GUID,                    &efi.smbios3,           "SMBIOS 3.0"    },
        {EFI_SYSTEM_RESOURCE_TABLE_GUID,        &efi.esrt,              "ESRT"          },
        {EFI_MEMORY_ATTRIBUTES_TABLE_GUID,      &efi_mem_attr_table,    "MEMATTR"       },
        {LINUX_EFI_RANDOM_SEED_TABLE_GUID,      &efi_rng_seed,          "RNG"           },
        // ...
        {LINUX_EFI_MEMRESERVE_TABLE_GUID,       &mem_reserve,           "MEMRESERVE"    },
        {LINUX_EFI_INITRD_MEDIA_GUID,           &initrd,                "INITRD"        },
        {EFI_RT_PROPERTIES_TABLE_GUID,          &rt_prop,               "RTPROP"        },
        // ...
}

efi_init()
  //drivers/firmware/efi/efi-init.c : 155

  reserve_regions()
    // discard memblock which originated from memory nodes in the DT
    memblock_dump_all(); && memblock_remove(0, PHYS_ADDR_MAX);

    for_each_efi_memory_desc(md)
      early_init_dt_add_memory_arch()
        memblock_add(md->phys_addr, size);
      !is_usable_memory(md) && memblock_mark_nomap()  // nomap some ram

  early_init_dt_check_for_usable_mem_range() // 处理 linux,usable-memory-range
  efi_find_mirror()  // 处理高可靠内存 EFI_MEMORY_MORE_RELIABLE
  efi_esrt_init()  // Reserving ESRT space in memblock.reserved
  efi_mokvar_table_init(); // 处理 EFI MOK config table
  memblock_reserve(data.phys_map & PAGE_MASK, PAGE_ALIGN(data.size + (data.phys_map & ~PAGE_MASK))); // 设置 UEFI 内存映射表到 memblock.reserved
  init_screen_info() // 处理 screen_info_table

// drivers/firmware/efi/riscv-runtime.c : 66

early_initcall(riscv_enable_runtime_services);

riscv_enable_runtime_services()

  efi_memmap_unmap();
    early_memunmap(efi.memmap.map, size); // clear the early EFI memmap
    efi.memmap.map = NULL;
    clear_bit(EFI_MEMMAP, &efi.flags);

  // EFI map 有两个初始化
  // 早期初始化（efi_init/efi_memmap_init_early -> early_memremap）使用稀缺的 fixmap 空间
  // 后期初始化（efi_memmap_init_late -> memremap）使用 vmalloc 空间
  efi_memmap_init_late(efi.memmap.phys_map, mapsize)

  // Remapping and enabling EFI services
  efi_virtmap_init()

    efi_mm.pgd = pgd_alloc(&efi_mm);
    for_each_efi_memory_desc(md)
      if (md->attribute & EFI_MEMORY_RUNTIME)  efi_create_mapping(&efi_mm, md);
        for (i = 0; i < md->num_pages; i++)
          create_pgd_mapping(mm->pgd, md->virt_addr + i * PAGE_SIZE, md->phys_addr + i * PAGE_SIZE, PAGE_SIZE, prot);

    efi_memattr_apply_permissions(&efi_mm, efi_set_mapping_permissions)
      tbl = memremap(efi_mem_attr_table, tbl_size, MEMREMAP_WB); // 映射内存属性表
      efi_set_mapping_permissions(mm, &md, has_bti);       // print EFI memmap attr table
        apply_to_page_range(mm, md->virt_addr, md->num_pages << EFI_PAGE_SHIFT, set_permissions, md); // 对 vm 设置权限，底层实现为设置 pte_val(pte)

  efi_native_runtime_setup() // efi.get_time = virt_efi_get_time // efi.reset_system = virt_efi_reset_system
  set_bit(EFI_RUNTIME_SERVICES, &efi.flags);

// include/linux/efi.h : 1249

struct efi_runtime_work {
        void *arg1;
        void *arg2;
        void *arg3;
        void *arg4;
        void *arg5;
        efi_status_t status;
        struct work_struct work;
        enum efi_rts_ids efi_rts_id;
        struct completion efi_rts_comp;
};

// drivers/firmware/efi/runtime-wrappers.c : 253

static efi_status_t virt_efi_get_time(efi_time_t *tm, efi_time_cap_t *tc)
  status = efi_queue_work(EFI_GET_TIME, tm, tc, NULL, NULL, NULL); //
    init_completion(&efi_rts_work.efi_rts_comp);
    INIT_WORK(&efi_rts_work.work, efi_call_rts);
    efi_rts_work.arg1 = _arg1;
    //...
    efi_rts_work.efi_rts_id = _rts;
    if (queue_work(efi_rts_wq, &efi_rts_work.work))
      wait_for_completion(&efi_rts_work.efi_rts_comp);

// drivers/firmware/efi/runtime-wrappers.c : 174

void efi_call_rts(struct work_struct *work)

  switch (efi_rts_work.efi_rts_id) {
    case EFI_GET_TIME:
      status = efi_call_virt(get_time, (efi_time_t *)arg1, (efi_time_cap_t *)arg2);
        efi_call_virt_pointer(efi.runtime, f, args)

          arch_efi_call_virt_setup()
            sync_kernel_mappings(efi_mm.pgd);
            efi_virtmap_load(); // switch_mm

          arch_efi_call_virt(efi.runtime,f,args)
            // call efi.runtime.get_time
          arch_efi_call_virt_teardown()