From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Vasut Date: Fri, 8 May 2020 21:00:02 +0200 Subject: [PATCH V2] mkimage: fit: Do not tail-pad fitImage with external data In-Reply-To: <20200508184748.GQ12564@bill-the-cat> References: <04cb1a3b-ec71-9ce1-f0cd-9d4ddae57010@denx.de> <20200506160447.GO12564@bill-the-cat> <2ed78efa-9ef2-06f5-20c3-767e9113603f@denx.de> <20200506163334.GP12564@bill-the-cat> <20200506170248.GQ12564@bill-the-cat> <4c10945e-8cc2-bd0b-8501-4c8c0c9faf87@sholland.org> <97d1a603-951a-2750-bc08-63bd3177070c@denx.de> <20200508184748.GQ12564@bill-the-cat> Message-ID: <65a1d328-f5f6-f77f-5d9b-15bf4c6dba1b@denx.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 5/8/20 8:47 PM, Tom Rini wrote: > On Fri, May 08, 2020 at 03:37:01AM +0200, Marek Vasut wrote: >> On 5/7/20 10:46 PM, Samuel Holland wrote: >>> On 5/6/20 12:02 PM, trini at konsulko.com (Tom Rini) wrote: >>>>>>>> I'm not sure that it is. Can we easily/safely memmove the data to be >>>>>>>> aligned? Is that really a better option in this case than ensuring >>>>>>>> alignment within the file? >>>>>>> >>>>>>> Can't we use the new mkimage -B option to enforce the alignment IFF and >>>>>>> only IFF it is required ? >>>>>> >>>>>> Perhaps. But.. >>>>>> >>>>>>> Then we can enforce it separately for 32bit >>>>>>> and 64bit platforms to 4 and 8 bytes respectively even. >>>>>> >>>>>> It's 8 bytes for both. It's possible that Linux doesn't hard fail if >>>>>> you only do 4 byte alignment but the documented requirement is 8, for >>>>>> arm32. >>>>> >>>>> With Linux you usually need to move the kernel anyway, no ? It's 2 MiB >>>>> for arm64 for example. >>>> >>>> For arm64 you have to move it to where text_offset says it needs to be. >>>> For arm32 the common (always, practically?) case is you're firing off >>>> the zImage which does what's needed. But.. >>>> >>>>> And what you usually parse in-place would be the DT then. >>>> >>>> Yes, the practical case is that it's a DT and that needs 8 byte >>>> alignment. And we should just get back to aligning that correctly. >>>> Going back to the v1 thread, it turns out the answer to "why do we even >>>> have this padding?" is "we need the DT to be aligned". >>> >>> This change broke SPL booting for me on MACH_SUN50I as well. One thing that I >>> haven't seen brought up yet is that SPL FIT code assumes exactly a 4-byte >>> alignment of external data after the FIT. In spl_load_simple_fit(): >>> >>> /* >>> * For FIT with external data, figure out where the external images >>> * start. This is the base for the data-offset properties in each >>> * image. >>> */ >>> size = fdt_totalsize(fit); >>> size = (size + 3) & ~3; >>> size = board_spl_fit_size_align(size); >>> base_offset = (size + 3) & ~3; >> >> Somehow this doesn't match the 8-byte alignment Tom was suggesting. >> And that only leads me to believe that we can either make assumptions >> about alignment, which would very likely fail one way or the other OR we >> can say that for SPL as a special case, we enforce some alignment. > > It's likely the case that on arm32 as there's no natural alignment > problem, even tho the kernel says 8 byte, 4 byte doesn't lead to failure > and is rarely if ever given 4-but-not-8-byte-aligned addresses of the > DTB. Which is why we should probably move the alignment here to 8 bytes > instead of 4. > >> But that in turn fails for fitImage with embedded data, where the >> embedded data are always aligned to 4 bytes, because that's how DTC >> aligns properties. > > I think the answer is that the use-case you're talking about is simply > going to require data to be relocated. I have a feeling that no matter how much you try to pad when generating fitImage from U-Boot, there will always be a case where that will fail. I listed at least two: - fitImage with embedded data, 4byte alignment due to DTC - Older fitImages, 4byte alignment, fails on arm64 - Someone can generate signed fitImage with older mkimage => fail So that relocation logic or at least warning or something should be in there, no matter what.