linux-kernel - Re: [PATCH v6 1/4] efi: Introduce EFI_FIRMWARE_MANAGEMENT_CAPSULE

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Message-ID: <YXZSMCaODRPw0Zlj@kroah.com>
Date:   Mon, 25 Oct 2021 08:44:00 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Chen Yu <yu.c.chen@...el.com>
Cc:     linux-acpi@...r.kernel.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>, Len Brown <lenb@...nel.org>,
        Ashok Raj <ashok.raj@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Mike Rapoport <rppt@...nel.org>,
        Aubrey Li <aubrey.li@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/4] efi: Introduce
 EFI_FIRMWARE_MANAGEMENT_CAPSULE_HEADER and corresponding structures

On Mon, Oct 25, 2021 at 02:25:04PM +0800, Chen Yu 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. Besides, 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>
> ---
> v6: No change since v5.
> v5: No change since v4.
> v4: Revise the commit log to make it more clear. (Rafael J. Wysocki) 
> ---
>  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)

Why is this pragma suddenly needed now in this file?

If you really need this for a specific structure, use the "__packed"
attribute please.

thanks,

greg k-h