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[84.106.84.65]) by smtp.gmail.com with ESMTPSA id z4sm6280823wmf.36.2019.11.14.03.27.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 Nov 2019 03:27:02 -0800 (PST) Subject: Re: [PATCH v7 2/8] efi: Add embedded peripheral firmware support To: Luis Chamberlain Cc: Ard Biesheuvel , Darren Hart , Andy Shevchenko , Greg Kroah-Hartman , "Rafael J . Wysocki" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , Jonathan Corbet , Dmitry Torokhov , Peter Jones , Dave Olsthoorn , x86@kernel.org, platform-driver-x86@vger.kernel.org, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-input@vger.kernel.org References: <20191004145056.43267-1-hdegoede@redhat.com> <20191004145056.43267-3-hdegoede@redhat.com> <20191011144834.GL16384@42.do-not-panic.com> From: Hans de Goede Message-ID: Date: Thu, 14 Nov 2019 12:27:01 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: <20191011144834.GL16384@42.do-not-panic.com> Content-Language: en-US X-MC-Unique: FJcM29aRPAKx9fSLIfdTVQ-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Luis, Thank you for the reviews and sorry for being a bit slow to respind. On 11-10-2019 16:48, Luis Chamberlain wrote: > On Fri, Oct 04, 2019 at 04:50:50PM +0200, Hans de Goede wrote: >> +static int __init efi_check_md_for_embedded_firmware( >> +=09efi_memory_desc_t *md, const struct efi_embedded_fw_desc *desc) >> +{ >> +=09const u64 prefix =3D *((u64 *)desc->prefix); >> +=09struct sha256_state sctx; >> +=09struct embedded_fw *fw; >> +=09u8 sha256[32]; >> +=09u64 i, size; >> +=09void *map; >> + >> +=09size =3D md->num_pages << EFI_PAGE_SHIFT; >> +=09map =3D memremap(md->phys_addr, size, MEMREMAP_WB); >=20 > Since our limitaiton is the init process must have mostly finished, > it implies early x86 boot code cannot use this, what measures can we > take to prevent / check for such conditions to be detected and > gracefully errored out? As with all (EFI) early boot code, there simply is a certain order in which things need to be done. This needs to happen after the basic mm is setup, but before efi_free_boot_services() gets called, there isn't really a way to check for all these conditions. As with all early boot code, people making changes need to be careful to not break stuff. >=20 >> +=09if (!map) { >> +=09=09pr_err("Error mapping EFI mem at %#llx\n", md->phys_addr); >> +=09=09return -ENOMEM; >> +=09} >> + >> +=09size -=3D desc->length; >=20 > Remind me again, why we decrement the size here? Basically this is another way of writing: =09for (i =3D 0; (i + desc->length) < size; i +=3D 8) { > I was going to ask if we didn't need a: >=20 > if (desc->length > size) { > =09memunmap(map); > =09return -EINVAL; > } That is a good point, unlikely but still a good point, so I guess that writing: =09for (i =3D 0; (i + desc->length) < size; i +=3D 8) { Instead would better as that avoids the need for that check. I will fix this for the next version. Regards, Hans >=20 >> +=09for (i =3D 0; i < size; i +=3D 8) { >> +=09=09u64 *mem =3D map + i; >> + >> +=09=09if (*mem !=3D prefix) >> +=09=09=09continue; >> + >> +=09=09sha256_init(&sctx); >> +=09=09sha256_update(&sctx, map + i, desc->length); >> +=09=09sha256_final(&sctx, sha256); >> +=09=09if (memcmp(sha256, desc->sha256, 32) =3D=3D 0) >> +=09=09=09break; >> +=09} >> +=09if (i >=3D size) { >> +=09=09memunmap(map); >> +=09=09return -ENOENT; >> +=09} >> + >> +=09pr_info("Found EFI embedded fw '%s'\n", desc->name); >=20 > Otherwise looks good. >=20 > Luis >=20