Re: [PATCH v2 7/8] efi: implement LoadFile2 initrd loading protocol for Linux

[Ard Biesheuvel]

On Mon, 26 Oct 2020 at 22:38, Atish Patra <atishp@atishpatra.org> wrote:
>
> On Sun, Oct 25, 2020 at 6:50 AM Ard Biesheuvel <ard.biesheuvel@arm.com> wrote:
> >
> > Recent Linux kernels will invoke the LoadFile2 protocol installed on a
> > well-known vendor media devicepath 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.
> >
>
> Thanks for adding the support for LoadFile2 protocol. This was one of
> the blockers for full RISC-V support.
> How do you prefer to proceed with RISC-V support ?
>

I'll defer to Daniel and Leif for the answer to that question.

> For RISC-V, we just need to move the arm64 loader to a common file so
> that both RISC-V/ARM64 can use it apart from
> few header file fixes. During the last attempt[1], I moved it to
> loader/efi/linux.c.
>

That seems the most logical to me. Given that it is shared between ARM
and arm64 today, it doesn't belong in grub-core/loader/arm64/linux.c
to begin with.

As I understand it, Daniel is doing a release imminently. Once that is
out of the way, I'm happy to proceed whichever way the maintainers
prefer.

> I am happy to test it on Qemu/hardware, if you want to send the series
> either part of this one or a separate series.
> I can rebase my previous series on top of this series as well. Please
> let me know your preference.
>

That would be a good start in any case, to ensure that the PE/COFF
image loading and LoadFile2 handling works as expected. And perhaps
simply merging the changes in that order is the most straight-forward.



> [1] https://www.mail-archive.com/grub-devel@gnu.org/msg30107.html
>
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> > ---
> >  grub-core/loader/arm64/linux.c | 109 +++++++++++++++++++-
> >  1 file changed, 108 insertions(+), 1 deletion(-)
> >
> > diff --git a/grub-core/loader/arm64/linux.c b/grub-core/loader/arm64/linux.c
> > index 28ff8584a3b5..c6a95e1f0c43 100644
> > --- a/grub-core/loader/arm64/linux.c
> > +++ b/grub-core/loader/arm64/linux.c
> > @@ -48,6 +48,10 @@ 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_load_image_header (grub_file_t file,
> >                                        struct linux_arch_kernel_header * lh)
> > @@ -81,6 +85,18 @@ grub_arch_efi_linux_load_image_header (grub_file_t file,
> >         return grub_error(GRUB_ERR_FILE_READ_ERROR, "failed to read COFF 
> > image header");
> >      }
> >
> > +  /*
> > +   * Linux kernels built for any architecture are guaranteed to support the
> > +   * LoadFile2 based initrd loading protocol if the image version is >= 1.
> > +   */
> > +  if (lh->coff_image_header.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;
> >  }
> >
> > @@ -250,13 +266,86 @@ 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;
> > +
> > +#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 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 = {
> > +  initrd_load_file2
> > +};
> > +
> > +static grub_efi_status_t 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");
> > +
> > +  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)
> >      {
> > @@ -274,6 +363,24 @@ grub_cmd_initrd (grub_command_t cmd __attribute__ 
> > ((unused)),
> >    if (grub_initrd_init (argc, argv, &initrd_ctx))
> >      goto fail;
> >
> > +  if (initrd_use_loadfile2)
> > +    {
> > +      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");
> >
> > --
> > 2.17.1
> >
>
>
> --
> Regards,
> Atish