linux-kernel - Re: [PATCH v3 2/5] efi: Introduce EFI_FIRMWARE_MANAGEMENT_CAPSULE

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Date:   Mon, 27 Sep 2021 19:33:15 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <len.brown@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Aubrey Li <aubrey.li@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Mike Rapoport <rppt@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [PATCH v3 2/5] efi: Introduce EFI_FIRMWARE_MANAGEMENT_CAPSULE_HEADER
 and corresponding structures

On Thu, Sep 16, 2021 at 5:54 PM Chen Yu <yu.c.chen@...el.com> wrote:
>
> Platform Firmware Runtime Update image starts with UEFI headers, and the
> headers are defined in UEFI specification, but some of them have not been
> defined in the kernel yet.
>
> For example, the header layout of a capsule file looks like this:
>
> EFI_CAPSULE_HEADER
> EFI_FIRMWARE_MANAGEMENT_CAPSULE_HEADER
> EFI_FIRMWARE_MANAGEMENT_CAPSULE_IMAGE_HEADER
> EFI_FIRMWARE_IMAGE_AUTHENTICATION
>
> These structures would be used by the Platform Firmware Runtime Update
> driver to parse the format of capsule file to verify if the corresponding
> version number is valid. The EFI_CAPSULE_HEADER has been defined in the
> kernel, however the rest are not, thus introduce corresponding UEFI
> structures accordingly.
>
> The reason why efi_manage_capsule_header_t and
> efi_manage_capsule_image_header_t are packedi might be that:
> According to the uefi spec,
> [Figure 23-6 Firmware Management and Firmware Image Management headers]
> EFI_FIRMWARE_MANAGEMENT_CAPSULE_HEADER is located at the lowest offset
> within the body of the capsule. And this structure is designed to be
> unaligned to save space, because in this way the adjacent drivers and
> binary payload elements could start on byte boundary with no padding.
> And the EFI_FIRMWARE_MANAGEMENT_CAPSULE_IMAGE_HEADER is at the head of
> each payload, so packing this structure also makes room for more data.

IMO it would be sufficient to say that both
EFI_FIRMWARE_MANAGEMENT_CAPSULE_HEADER and
EFI_FIRMWARE_MANAGEMENT_CAPSULE_IMAGE_HEADER need not be aligned and
so the corresponding data types should be packed.

>
> Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> ---
>  include/linux/efi.h | 50 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 50 insertions(+)
>
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index 6b5d36babfcc..19ff834e1388 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -148,6 +148,56 @@ typedef struct {
>         u32 imagesize;
>  } efi_capsule_header_t;
>
> +#pragma pack(1)
> +
> +/* EFI_FIRMWARE_MANAGEMENT_CAPSULE_HEADER */
> +typedef struct {
> +       u32     ver;
> +       u16     emb_drv_cnt;
> +       u16     payload_cnt;
> +       /*
> +        * Variable array indicated by number of
> +        * (emb_drv_cnt + payload_cnt)
> +        */
> +       u64     offset_list[];
> +} efi_manage_capsule_header_t;
> +
> +/* EFI_FIRMWARE_MANAGEMENT_CAPSULE_IMAGE_HEADER */
> +typedef struct {
> +       u32     ver;
> +       guid_t  image_type_id;
> +       u8      image_index;
> +       u8      reserved_bytes[3];
> +       u32     image_size;
> +       u32     vendor_code_size;
> +       /* ver = 2. */
> +       u64     hw_ins;
> +       /* ver = v3. */
> +       u64     capsule_support;
> +} efi_manage_capsule_image_header_t;
> +
> +#pragma pack()
> +
> +/* WIN_CERTIFICATE */
> +typedef struct {
> +       u32     len;
> +       u16     rev;
> +       u16     cert_type;
> +} win_cert_t;
> +
> +/* WIN_CERTIFICATE_UEFI_GUID */
> +typedef struct {
> +       win_cert_t      hdr;
> +       guid_t          cert_type;
> +       u8              cert_data[];
> +} win_cert_uefi_guid_t;
> +
> +/* EFI_FIRMWARE_IMAGE_AUTHENTICATIO */
> +typedef struct {
> +       u64                             mon_count;
> +       win_cert_uefi_guid_t            auth_info;
> +} efi_image_auth_t;
> +
>  /*
>   * EFI capsule flags
>   */
> --
> 2.25.1
>