Re: [PATCH 3/8] efi: implemented LoadFile2 initrd loading protocol for Linux

[Heinrich Schuchardt <xypron.glpk@gmx.de>]

On 5/28/21 3:04 PM, Nikita Ermakov wrote:
> From: Ard Biesheuvel <ard.biesheuvel@arm.com>
>
> Recent Linux kernels will invoke the LoadFile2 protocol installed on
> a well-known vendor media path to load the initrd if it is exposed by
> the firmware. Using this method is preferred for two reasons:
> - the Linux kernel is in charge of allocating the memory, and so it can
>    implement any placement policy it wants (given that these tend to
>    change between kernel versions),
> - it is no longer necessary to modify the device tree provided by the
>    firmware.
>
> So let's install this protocol when handling the 'initrd' command if
> such a recent kernel was detected (based on the PE/COFF image version),
> and defer loading the initrd contents until the point where the kernel
> invokes the LoadFile2 protocol.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> ---
>   grub-core/loader/arm64/linux.c | 117 ++++++++++++++++++++++++++++++++-
>   1 file changed, 116 insertions(+), 1 deletion(-)
>
> diff --git a/grub-core/loader/arm64/linux.c b/grub-core/loader/arm64/linux.c
> index ef3e9f944..285422c7b 100644
> --- a/grub-core/loader/arm64/linux.c
> +++ b/grub-core/loader/arm64/linux.c
> @@ -48,9 +48,16 @@ static grub_uint32_t cmdline_size;
>   static grub_addr_t initrd_start;
>   static grub_addr_t initrd_end;
>
> +static struct grub_linux_initrd_context initrd_ctx = { 0, 0, 0 };
> +static grub_efi_handle_t initrd_lf2_handle;
> +static int initrd_use_loadfile2;
> +
>   grub_err_t
>   grub_arch_efi_linux_check_image (struct linux_arch_kernel_header * lh)
>   {
> +  struct grub_pe32_coff_header *coff_header;
> +  struct grub_pe32_optional_header *optional_header;
> +
>     if (lh->magic != GRUB_LINUX_ARMXX_MAGIC_SIGNATURE)
>       return grub_error(GRUB_ERR_BAD_OS, "invalid magic number");
>
> @@ -61,6 +68,21 @@ grub_arch_efi_linux_check_image (struct linux_arch_kernel_header * lh)
>     grub_dprintf ("linux", "UEFI stub kernel:\n");
>     grub_dprintf ("linux", "PE/COFF header @ %08x\n", lh->hdr_offset);
>
> +  coff_header = (struct grub_pe32_coff_header *)((unsigned long)lh + lh->hdr_offset);
> +  optional_header = (struct grub_pe32_optional_header *)(coff_header + 1);
> +
> +  /*
> +   * Linux kernels built for any architecture are guaranteed to support the
> +   * LoadFile2 based initrd loading protocol if the image version is >= 1.
> +   */
> +  if (optional_header->major_image_version >= 1)
> +    initrd_use_loadfile2 = 1;
> +   else
> +    initrd_use_loadfile2 = 0;
> +
> +  grub_dprintf ("linux", "LoadFile2 initrd loading %sabled\n",
> +		initrd_use_loadfile2 ? "en" : "dis");
> +
>     return GRUB_ERR_NONE;
>   }
>
> @@ -230,13 +252,88 @@ allocate_initrd_mem (int initrd_pages)
>   				       GRUB_EFI_LOADER_DATA);
>   }
>
> +struct initrd_media_device_path {
> +  grub_efi_vendor_media_device_path_t	vendor;
> +  grub_efi_device_path_t		end;
> +} GRUB_PACKED;
> +
> +#define LINUX_EFI_INITRD_MEDIA_GUID  \
> +  { 0x5568e427, 0x68fc, 0x4f3d, \
> +    { 0xac, 0x74, 0xca, 0x55, 0x52, 0x31, 0xcc, 0x68 } \
> +  }
> +
> +static struct initrd_media_device_path initrd_lf2_device_path = {
> +  {
> +    {
> +      GRUB_EFI_MEDIA_DEVICE_PATH_TYPE,
> +      GRUB_EFI_VENDOR_MEDIA_DEVICE_PATH_SUBTYPE,
> +      sizeof(grub_efi_vendor_media_device_path_t),
> +    },
> +    LINUX_EFI_INITRD_MEDIA_GUID
> +  }, {
> +    GRUB_EFI_END_DEVICE_PATH_TYPE,
> +    GRUB_EFI_END_ENTIRE_DEVICE_PATH_SUBTYPE,
> +    sizeof(grub_efi_device_path_t)
> +  }
> +};
> +
> +static grub_efi_status_t
> +grub_efi_initrd_load_file2(grub_efi_load_file2_t *this,
> +                           grub_efi_device_path_t *device_path,
> +                           grub_efi_boolean_t boot_policy,
> +                           grub_efi_uintn_t *buffer_size,
> +                           void *buffer);
> +
> +static grub_efi_load_file2_t initrd_lf2 = {
> +  grub_efi_initrd_load_file2
> +};
> +
> +static grub_efi_status_t
> +grub_efi_initrd_load_file2(grub_efi_load_file2_t *this,
> +			   grub_efi_device_path_t *device_path,
> +			   grub_efi_boolean_t boot_policy,
> +			   grub_efi_uintn_t *buffer_size,
> +			   void *buffer)
> +{
> +  grub_efi_status_t status = GRUB_EFI_SUCCESS;
> +  grub_efi_uintn_t initrd_size;
> +
> +  if (!this || this != &initrd_lf2 || !buffer_size)
> +    return GRUB_EFI_INVALID_PARAMETER;
> +
> +  if (device_path->type != GRUB_EFI_END_DEVICE_PATH_TYPE ||
> +      device_path->subtype != GRUB_EFI_END_ENTIRE_DEVICE_PATH_SUBTYPE)
> +    return GRUB_EFI_NOT_FOUND;
> +
> +  if (boot_policy)
> +    return GRUB_EFI_UNSUPPORTED;
> +
> +  initrd_size = grub_get_initrd_size (&initrd_ctx);
> +  if (!buffer || *buffer_size < initrd_size)
> +    {
> +      *buffer_size = initrd_size;
> +      return GRUB_EFI_BUFFER_TOO_SMALL;
> +    }
> +
> +  grub_dprintf ("linux", "Loading initrd via LOAD_FILE2_PROTOCOL\n");

GRUB is not loading anything via the EFI_LOAD_FILE2_PROTOCOL. The
message text should be:

	"Providing initrd via LOAD_FILE2_PROTOCOL\n"

Otherwise looks good.

Best regards

Heinrich

> +
> +  if (grub_initrd_load (&initrd_ctx, NULL, buffer))
> +    status = GRUB_EFI_LOAD_ERROR;
> +
> +  grub_initrd_close (&initrd_ctx);
> +  return status;
> +}
> +
>   static grub_err_t
>   grub_cmd_initrd (grub_command_t cmd __attribute__ ((unused)),
>   		 int argc, char *argv[])
>   {
> -  struct grub_linux_initrd_context initrd_ctx = { 0, 0, 0 };
>     int initrd_size, initrd_pages;
>     void *initrd_mem = NULL;
> +  grub_efi_guid_t load_file2_guid = GRUB_EFI_LOAD_FILE2_PROTOCOL_GUID;
> +  grub_efi_guid_t device_path_guid = GRUB_EFI_DEVICE_PATH_GUID;
> +  grub_efi_boot_services_t *b;
> +  grub_efi_status_t status;
>
>     if (argc == 0)
>       {
> @@ -254,6 +351,24 @@ grub_cmd_initrd (grub_command_t cmd __attribute__ ((unused)),
>     if (grub_initrd_init (argc, argv, &initrd_ctx))
>       goto fail;
>
> +  if (initrd_use_loadfile2 && !initrd_lf2_handle)
> +    {
> +      b = grub_efi_system_table->boot_services;
> +      status = b->install_multiple_protocol_interfaces (&initrd_lf2_handle,
> +							&load_file2_guid,
> +							&initrd_lf2,
> +							&device_path_guid,
> +							&initrd_lf2_device_path,
> +							NULL);
> +      if (status == GRUB_EFI_OUT_OF_RESOURCES)
> +        {
> +	  grub_error (GRUB_ERR_OUT_OF_MEMORY, N_("out of memory"));
> +	  return grub_errno;
> +	}
> +      grub_dprintf ("linux", "LoadFile2 initrd loading protocol installed\n");
> +      return GRUB_ERR_NONE;
> +    }
> +
>     initrd_size = grub_get_initrd_size (&initrd_ctx);
>     grub_dprintf ("linux", "Loading initrd\n");
>
>