linux-kernel - Re: [PATCH 2/2] efi: Add embedded peripheral firmware support

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Message-ID: <20180403195332.tezh6alee26aic2s@redhat.com>
Date:   Tue, 3 Apr 2018 12:53:34 -0700
From:   Peter Jones <pjones@...hat.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "Luis R . Rodriguez" <mcgrof@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Dave Olsthoorn <dave@...aar.me>, x86@...nel.org,
        linux-efi@...r.kernel.org
Subject: Re: [PATCH 2/2] efi: Add embedded peripheral firmware support

On Sat, Mar 31, 2018 at 02:19:44PM +0200, Hans de Goede wrote:
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index fddc5f706fd2..1a5ea950f58f 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -455,6 +455,7 @@ int __init efi_mem_desc_lookup(u64 phys_addr, efi_memory_desc_t *out_md)
>  		u64 end;
>  
>  		if (!(md->attribute & EFI_MEMORY_RUNTIME) &&
> +		    md->type != EFI_BOOT_SERVICES_CODE &&
>  		    md->type != EFI_BOOT_SERVICES_DATA &&
>  		    md->type != EFI_RUNTIME_SERVICES_DATA) {
>  			continue;

Might be worth adding a comment here to ensure nobody comes along later
and adds something like EFI_BOOT_LOADER_DATA or other stuff that's
allocated later here.  I don't want to accidentally patch our way into
having the ability to stumble across a firmware blob somebody dumped
into the middle of a grub config file, especially since you only need to
collide crc32 (within the same length) to pre-alias a match.

...
> +static int __init efi_check_md_for_embedded_firmware(
> +	efi_memory_desc_t *md, const struct embedded_fw_desc *desc)
> +{
...
> +	if (found_fw_count >= MAX_EMBEDDED_FIRMWARES) {
> +		pr_err("Error already have %d embedded firmwares\n",
> +		       MAX_EMBEDDED_FIRMWARES);
> +		return -ENOSPC;
> +	}

Doesn't seem like this needs to be pr_err(); after all we have already
found a valid match, so the firmware vendor has done something
moderately stupid, but we have a firmware that will probably work.  Of
course it still needs to return != 0, but pr_warn() or even pr_info()
seems more reasonable.

Aside from those nits, looks good to me.

Reviewed-by: Peter Jones <pjones@...hat.com>

-- 
  Peter