From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Rutland Subject: Re: [PATCH 1/4] efi/libstub: Allocate headspace in efi_get_memory_map() Date: Mon, 18 Jul 2016 12:00:02 +0100 Message-ID: <20160718110001.GC10069@leverpostej> References: <1468788362-3962-1-git-send-email-jhugo@codeaurora.org> <1468788362-3962-2-git-send-email-jhugo@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1468788362-3962-2-git-send-email-jhugo-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jeffrey Hugo Cc: matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org, linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, timur-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org, leif.lindholm-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org List-Id: linux-efi@vger.kernel.org Hi, On Sun, Jul 17, 2016 at 02:45:59PM -0600, Jeffrey Hugo wrote: > + if (status == EFI_BUFFER_TOO_SMALL || > + (*buff_size - *map_size) / sizeof(*m) < 8) { > efi_call_early(free_pool, m); > + /* > + * Make sure there is 8 entries worth of headroom so that the > + * buffer can be reused for a new map after allocations are > + * no longer permitted. Its unlikely that the map will grow to > + * exceed this headroom once we are ready to trigger > + * ExitBootServices() > + */ > + *map_size += sizeof(*m) * 8; It's probably worth having something like... #define EFI_MMAP_NR_SLACK_SLOTS 8 ... at the top of the file, and changing the comment here to not refer to the specific value. That way we avoid duplicating the value, and making it easier to modify / backport in future. As a general note, it's a shame that we don't know desc_size first time through. If descs grow, 8 * sizeof(*m) might be too small. That's an existing problem though, so I guess it makes sense to be consistent and use sizeof(*m) here. Otherwise, this looks fine to me. Thanks, Mark.