linux-kernel - Re: [PATCH v2 2/3] efi/libstub: Add support for loading the initrd from a device path

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Message-ID: <20200217110906.GA147685@apalos.home>
Date:   Mon, 17 Feb 2020 13:09:06 +0200
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Laszlo Ersek <lersek@...hat.com>,
        linux-efi <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Leif Lindholm <leif@...iainc.com>,
        Peter Jones <pjones@...hat.com>,
        Matthew Garrett <mjg59@...gle.com>,
        Alexander Graf <agraf@...raf.de>,
        Heinrich Schuchardt <xypron.glpk@....de>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH v2 2/3] efi/libstub: Add support for loading the initrd
 from a device path

Hi Ard,

[...]
> > > > +             return EFI_INVALID_PARAMETER;
> > >
> > > Doesn't return EFI_LOAD_ERROR.
> > >
> > > > +
> > > > +     dp = (efi_device_path_protocol_t *)&initrd_dev_path;
> > > > +     status = efi_bs_call(locate_device_path, &lf2_proto_guid, &dp, &handle);
> > > > +     if (status != EFI_SUCCESS)
> > > > +             return status;
> > >
> > > Seems safe (the only plausible error could be EFI_NOT_FOUND).
> > >
> > > > +
> > > > +     status = efi_bs_call(handle_protocol, handle, &lf2_proto_guid,
> > > > +                          (void **)&lf2);
> > > > +     if (status != EFI_SUCCESS)
> > > > +             return status;
> > >
> > > Interesting case; this should never fail... but note, if it does, it
> > > returns EFI_UNSUPPORTED, not EFI_NOT_FOUND (if the protocol is missing
> > > from the handle).
> > >
> > > > +
> > > > +     status = efi_call_proto(lf2, load_file, dp, false, &initrd_size, NULL);
> > > > +     if (status != EFI_BUFFER_TOO_SMALL)
> > > > +             return EFI_LOAD_ERROR;
> > > > +
> > > > +     status = efi_allocate_pages(initrd_size, &initrd_addr, max);
> > > > +     if (status != EFI_SUCCESS)
> > > > +             return status;
> > >
> > > Not sure about the efi_allocate_pages() wrapper (?); the UEFI service
> > > could return EFI_OUT_OF_RESOURCES.
> > >
> >
> > Hmm, guess I was a bit sloppy with the return codes. The important
> > thing is that EFI_NOT_FOUND is only returned in the one specifically
> > defined case.
> >
> 
> For the record [in case no respin+resend is needed for other reasons],
> I intend to update the comment block as below, and keep the code as
> is:
> 

Yes i think this makes more sense the return codes are already correct and the
fallback is properly triggered.

For what it's worth 

Tested-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>

> 
>   * @load_addr: pointer to store the address where the initrd was loaded
>   * @load_size: pointer to store the size of the loaded initrd
>   * @max:       upper limit for the initrd memory allocation
> - * @return:    %EFI_SUCCESS if the initrd was loaded successfully, in
> which case
> - *             @load_addr and @load_size are assigned accordingly
> - *             %EFI_NOT_FOUND if no LoadFile2 protocol exists on the initrd
> - *             device path
> + * @return:    %EFI_SUCCESS if the initrd was loaded successfully, in which
> + *             case @load_addr and @load_size are assigned accordingly
> + *             %EFI_NOT_FOUND if no LoadFile2 protocol exists on the initrd
> + *             device path
> + *             %EFI_INVALID_PARAMETER if load_addr == NULL or load_size == NULL
> + *             %EFI_OUT_OF_RESOURCES if memory allocation failed
>   *             %EFI_LOAD_ERROR in all other cases

Regards
/Ilias