Re: [PATCH v3 3/7] efi: implemented LoadFile2 initrd loading protocol for Linux

[Daniel Kiper]

On Thu, Oct 28, 2021 at 11:31:16PM +0300, 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>
> Signed-off-by: Nikita Ermakov <arei@altlinux.org>
> ---
>  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 aed7a200b..6b03455d1 100644
> --- a/grub-core/loader/arm64/linux.c
> +++ b/grub-core/loader/arm64/linux.c
> @@ -48,9 +48,18 @@ 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;

Please explicitly initialize these two variables.

> +static grub_efi_guid_t load_file2_guid = GRUB_EFI_LOAD_FILE2_PROTOCOL_GUID;
> +static grub_efi_guid_t device_path_guid = GRUB_EFI_DEVICE_PATH_GUID;
> +
>  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 +70,21 @@ 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);

coff_header = (struct grub_pe32_coff_header *) ((grub_addr_t) lh + 
lh->hdr_offset);

... please note missing spaces too.

> +  optional_header = (struct grub_pe32_optional_header *)(coff_header + 1);

(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 +254,86 @@ 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;

typedef struct initrd_media_device_path initrd_media_device_path_t;

And please use initrd_media_device_path_t instead of "struct 
initrd_media_device_path".

> +
> +#define LINUX_EFI_INITRD_MEDIA_GUID  \
> +  { 0x5568e427, 0x68fc, 0x4f3d, \
> +    { 0xac, 0x74, 0xca, 0x55, 0x52, 0x31, 0xcc, 0x68 } \
> +  }

Please move struct initrd_media_device_path and
LINUX_EFI_INITRD_MEDIA_GUID definitions to the include/grub/efi/api.h file.

> +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)
> +  }
> +};

This declaration/initialization should be behind device_path_guid declaration.

> +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);

Please drop this...

> +
> +static grub_efi_load_file2_t initrd_lf2 = {
> +  grub_efi_initrd_load_file2
> +};

... and move this behind grub_efi_initrd_load_file2() definition.

> +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)

This works only because UEFI RISC-V/ARM and "normal" RISC-V/ARM calling
conventions are the same. This will not work on x86_64. So, we have to
introduce something like __grub_efi_api macro. It should be empty for
at least for RISC-V and ARM but it should be "__attribute__ ((ms_abi))"
for at least for x86_64. I think the __grub_efi_api macro should be
defined in include/grub/efi/api.h next to efi_call_* definitions.

> +{
> +  grub_efi_status_t status = GRUB_EFI_SUCCESS;
> +  grub_efi_uintn_t initrd_size;
> +
> +  if (!this || this != &initrd_lf2 || !buffer_size)

if (this == NULL || this != &initrd_lf2 || buffer_size == NULL)

Please use NULL explicitly below too...

> +    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", "Providing initrd via LOAD_FILE2_PROTOCOL\n");

s/LOAD_FILE2_PROTOCOL/EFI_LOAD_FILE2_PROTOCOL/

> +  if (grub_initrd_load (&initrd_ctx, buffer))

if (grub_initrd_load (&initrd_ctx, buffer) != GRUB_ERR_NONE))

> +    status = GRUB_EFI_LOAD_ERROR;

According to the UEFI spec this should be GRUB_EFI_DEVICE_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_boot_services_t *b;

grub_efi_boot_services_t *b = grub_efi_system_table->boot_services;

> +  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;

... then you can drop this.

> +      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;

s/return grub_errno/goto fail/ otherwise your are leaking memory.

Or you can move protocols installation to the beginning of the function
and return immediately in case of error.

> +     }

I think we should not ignore the other UEFI errors here.

> +      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");

Daniel