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

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Date:   Mon, 25 Oct 2021 19:45:19 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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 08:44:00AM +0200, Greg Kroah-Hartman wrote:
> 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.
>
These two structures are required to be packed in the uefi spec, I'll change
them to "__packed".

thanks,
Chenyu
> thanks,
> 
> greg k-h