From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Vasut Date: Tue, 27 Nov 2018 14:09:53 +0100 Subject: [U-Boot] [PATCH] ARM: rmobile: Convert to bootm_size In-Reply-To: References: <20181127001054.29623-1-marek.vasut+renesas@gmail.com> <8cd3e7ee-f5dd-61f3-082c-feec2777141f@gmail.com> Message-ID: <97181119-9bd1-8f37-7b1e-0624d077e571@gmail.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 11/27/2018 01:33 PM, Simon Goldschmidt wrote: > On Tue, Nov 27, 2018 at 1:25 PM Marek Vasut wrote: >> >> On 11/27/2018 08:03 AM, Simon Goldschmidt wrote: >>> On Tue, Nov 27, 2018 at 1:11 AM Marek Vasut wrote: >>>> >>>> Convert all Renesas R-Car boards to bootm_size of 256 MiB and drop both >>>> fdt_high and initrd_high. This change implies that the FDT and initrd >>>> will always be copied into the first 256 MiB of RAM instead of being >>>> used in place, which can cause various kinds of inobvious problems. >>>> >>>> The simpler problems include FDT or initrd being overwritten or being >>>> used from unaligned addresses, especially on ARM64. The overhead of >>>> copying the FDT to aligned location is negligible and these problems >>>> go away, so the benefit is significant. >>>> >>>> Regarding alignment problems with fitImage. The alignment of DT properties >>>> is always 32 bits, which implies that the alignment of the "data" property >>>> in fitImage is also 32 bits. The /incbin/ syntax plays no role here. The >>>> kernel expects all elements, including DT and initrd, to be aligned to >>>> 64 bits on ARM64, thus using them in place may not be possible. Using the >>>> bootm_size assures correct alignment, again with negligible overhead. >>> >>> In my opinion, all of these raw addresses defined in scripts or config >>> should be removed: They are probably vulnerable to overwriting >>> themselves as they only provide an address, not a range. >> >> This is not an address, it's size. And this one at least assures that >> the first 256 MiB are reserved for the kernel/FDT/initrd during bootm time. > > Sorry I did not express myself clear enough. I meant that "fdt_high" > and "initrd_high" are bad because they contain an address only, not a > range. The 'bootm_size' thing is much better! Well the fdt_high and intrd_high can also contain a special ~0 value, which says "use the fdt/initrd in place", which is dangerous. >>> Just out of curiosity: is it required to put fdt and initrd into the >>> first 256 MiB or is this just some 'random' limit to ensure we use lmb >>> but don't overwrite U-Boot (text, heap, stack, etc)? Because if so, my >>> series to fix the recent CVE issues improves lmb to not overwrite >>> U-Boot and other reserved addresses and you might be able to remove >>> 'bootm_size', too. The improved lmb code would just allocate an >>> aligned address somewhere in the available RAM. >> >> It's just the first 256 MiB from the beginning, so there's enough space >> between that and U-Boot on all these boards. > > Of course. I wanted to know if it would be good enough if U-Boot would > just put it somewhere without overwriting things or do you really need > them in the first 256 MiB? Because the revised lmb code would make > sure there's nothing overwritten, so there would be no need to trim at > 256 MiB. You can put them anywhere, you just need to meet the alignment requirements. Can the new LMB code help somehow with that ? And if so, how ? -- Best regards, Marek Vasut