On Tue, 11 Dec 2018 at 10:04, Pankaj Bansal <pankaj.bansal@xxxxxxx> wrote:
>
> Bootloader may need to fixup the device tree before OS can use it.
>
> Therefore, install fdt used by OS in configuration tables and associate it
> with device tree guid.
>
> UEFI/DXE drivers can fixup this device tree in their respective
> ExitBootServices events.
>
> Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> Cc: linux-efi@xxxxxxxxxxxxxxx
> Signed-off-by: Pankaj Bansal <pankaj.bansal@xxxxxxx>
I still think this is a bad idea. The firmware is closely tied to the
platform, so it should provide the DT instead of the kernel.
> ---
>
> Notes:
> V2:
> - Add a check while installing fdt in configuration table, that
> new_fdt would only be installed in configuration table if it
> has been generated using fdt already present in configuration table.
>
> drivers/firmware/efi/libstub/fdt.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
> index 45cded5b5d5c..dc228c05d0cd 100644
> --- a/drivers/firmware/efi/libstub/fdt.c
> +++ b/drivers/firmware/efi/libstub/fdt.c
> @@ -269,6 +269,9 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table_arg,
> int runtime_entry_count = 0;
> struct efi_boot_memmap map;
> struct exit_boot_struct priv;
> + efi_guid_t fdt_guid = DEVICE_TREE_GUID;
> + unsigned long fdt_config_table_addr = 0;
> + unsigned long fdt_config_table_size = 0;
>
> map.map = &runtime_map;
> map.map_size = &map_size;
> @@ -318,6 +321,23 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table_arg,
> goto fail_free_new_fdt;
> }
>
> + /* Determine if the fdt_addr is obtained from uefi configuration
> + * table or not? if yes, then install the new_fdt_addr in configuration
> + * table in its place, as the UEFI firmware may need to modify it
> + * as part of exit_boot_services routine
> + */
> + fdt_config_table_addr = (uintptr_t)get_fdt(sys_table_arg,
> + &fdt_config_table_size);
> + if ((fdt_config_table_size == fdt_size) &&
> + (fdt_config_table_addr == fdt_addr)) {
> + status = efi_call_early(install_configuration_table, &fdt_guid,
> + (void *)*new_fdt_addr);
> + if (status != EFI_SUCCESS) {
> + pr_efi_err(sys_table_arg, "Unable to install new device tree.\n");
> + goto fail_free_new_fdt;
> + }
> + }
> +
> priv.runtime_map = runtime_map;
> priv.runtime_entry_count = &runtime_entry_count;
> priv.new_fdt_addr = (void *)*new_fdt_addr;
> --
> 2.17.1
>
