On Wed, May 06, 2020 at 04:33:37PM +0200, Marek Vasut wrote: > On 5/6/20 4:27 PM, Tom Rini wrote: > > On Wed, May 06, 2020 at 04:17:35PM +0200, Marek Vasut wrote: > >> On 5/6/20 3:48 PM, Tom Rini wrote: > >>> On Tue, May 05, 2020 at 11:17:19PM +0200, Michael Walle wrote: > >>>> Hi all, > >>>> > >>>> Am 2020-05-05 20:41, schrieb Simon Glass: > >>>>> Hi Tom, > >>>>> > >>>>> On Tue, 5 May 2020 at 11:50, Tom Rini <tr...@konsulko.com> wrote: > >>>>>> > >>>>>> On Tue, May 05, 2020 at 06:39:58PM +0200, Marek Vasut wrote: > >>>>>>> On 5/5/20 6:37 PM, Alex Kiernan wrote: > >>>>>>>> On Tue, May 5, 2020 at 2:28 PM Marek Vasut <ma...@denx.de> wrote: > >>>>>>>>> > >>>>>>>>> On 5/5/20 3:22 PM, Alex Kiernan wrote: > >>>>>>>>>> On Mon, May 4, 2020 at 12:28 PM Tom Rini <tr...@konsulko.com> > >>>>>>>>>> wrote: > >>>>>>>>>>> > >>>>>>>>>>> On Fri, May 01, 2020 at 05:40:25PM +0200, Marek Vasut wrote: > >>>>>>>>>>> > >>>>>>>>>>>> There is no reason to tail-pad fitImage with external data to > >>>>>>>>>>>> 4-bytes, > >>>>>>>>>>>> while fitImage without external data does not have any such > >>>>>>>>>>>> padding and > >>>>>>>>>>>> is often unaligned. DT spec also does not mandate any such > >>>>>>>>>>>> padding. > >>>>>>>>>>>> > >>>>>>>>>>>> Moreover, the tail-pad fills the last few bytes with > >>>>>>>>>>>> uninitialized data, > >>>>>>>>>>>> which could lead to a potential information leak. > >>>>>>>>>>>> > >>>>>>>>>>>> $ echo -n xy > /tmp/data ; \ > >>>>>>>>>>>> ./tools/mkimage -E -f auto -d /tmp/data /tmp/fitImage ; \ > >>>>>>>>>>>> hexdump -vC /tmp/fitImage | tail -n 3 > >>>>>>>>>>>> > >>>>>>>>>>>> before: > >>>>>>>>>>>> 00000260 61 2d 6f 66 66 73 65 74 00 64 61 74 61 2d 73 69 > >>>>>>>>>>>> |a-offset.data-si| > >>>>>>>>>>>> 00000270 7a 65 00 00 78 79 64 64 > >>>>>>>>>>>> |ze..xydd| > >>>>>>>>>>>> ^^ ^^ ^^ > >>>>>>>>>>>> after: > >>>>>>>>>>>> 00000260 61 2d 6f 66 66 73 65 74 00 64 61 74 61 2d 73 69 > >>>>>>>>>>>> |a-offset.data-si| > >>>>>>>>>>>> 00000270 7a 65 00 78 79 > >>>>>>>>>>>> |ze.xy| > >>>>>>>>>>>> > >>>>>>>>>>>> Signed-off-by: Marek Vasut <ma...@denx.de> > >>>>>>>>>>>> Reviewed-by: Simon Glass <s...@chromium.org> > >>>>>>>>>>>> Cc: Heinrich Schuchardt <xypron.g...@gmx.de> > >>>>>>>>>>>> Cc: Tom Rini <tr...@konsulko.com> > >>>>>>>>>>> > >>>>>>>>>>> Applied to u-boot/master, thanks! > >>>>>>>>>>> > >>>>>>>>>> > >>>>>>>>>> This breaks booting on my board (am3352, eMMC boot, FIT u-boot, > >>>>>>>>>> CONFIG_SPL_LOAD_FIT). Not got any useful diagnostics - if I boot it > >>>>>>>>>> from eMMC I get nothing at all on the console, if I boot over > >>>>>>>>>> ymodem > >>>>>>>>>> it stalls at 420k, before continuing to 460k. My guess is there's > >>>>>>>>>> some > >>>>>>>>>> error going to the console at the 420k mark, but obviously it's > >>>>>>>>>> lost > >>>>>>>>>> in the ymodem... I have two DTBs in the FIT image, 420k would about > >>>>>>>>>> align to the point between them. > >>>>>>>>> > >>>>>>>>> My bet would be on some padding / unaligned access problem that this > >>>>>>>>> patch uncovered. Can you take a look ? > >>>>>>>> > >>>>>>>> Seems plausible. With this change my external data starts at 0x483 > >>>>>>>> and > >>>>>>>> everything after it is non-aligned: > >>>>>>> > >>>>>>> Should the beginning of external data be aligned ? > >>>>>> > >>>>>> If in U-Boot we revert e8c2d25845c72c7202a628a97d45e31beea40668 does > >>>>>> the > >>>>>> problem go away? If so, that's not a fix outright, it means we need > >>>>>> to > >>>>>> dig back in to the libfdt thread and find the "make this work without > >>>>>> killing performance everywhere all the time" option. > >>>>> > >>>>> If it is a device tree, it must be 32-bit aligned. > >>>> > >>>> This commit actually breaks my board too (which I was just about to send > >>>> upstream, but realized it was broken). > >>>> > >>>> Said board uses SPL and main U-Boot. SPL runs fine and main u-boot > >>>> doesn't > >>>> output anything. The only difference which I found is that fit-dtb.blob > >>>> is > >>>> 2 bytes shorter. And the content is shifted by one byte although > >>>> data-offset is the same. Strange. In the non-working case, the inner > >>>> FDT magic isn't 4 byte aligned. > >>>> > >>>> You can find the two fit-dtb.blobs here: > >>>> > >>>> https://walle.cc/u-boot/fit-dtb.blob.working > >>>> https://walle.cc/u-boot/fit-dtb.blob.non-working > >>>> > >>>> > >>>> Reverting e8c2d25845c72c7202a628a97d45e31beea40668 doesn't help (I might > >>>> reverted it the wrong way, there is actually a conflict). > >>>> > >>>> I'll dig deeper into that tomorrow, but maybe you have some pointers > >>>> where > >>>> to look. > >>>> > >>>> For reference you can find the current patch here: > >>>> https://github.com/mwalle/u-boot/tree/sl28-upstream > >>> > >>> I think we have a few things to fix here. Marek's patch is breaking > >>> things and needs to be reverted. But it's showing a few underlying > >>> problems that need to be fixed too: > >>> - fit_extract_data() needs to use calloc() not malloc() so that we don't > >>> leak random data. > >>> - We need to 8-byte alignment on the external data. That's the > >>> requirement for Linux for device trees on both 32 and 64bit arm. > >>> Atish, does RISC-V require more than that? I don't see it in Linux's > >>> Documentation/riscv/boot-image-header.rst (and there's no booting.rst > >>> file like arm/arm64). > >> > >> Why 8-byte alignment ? The external data are copied into the target > >> location, so why do they need to be padded in any way? > > > > The start of the external data needs the alignment, to be clearer. > > Why ?
Given that things which end up in external data have alignment requirements, we need to align and meet those requirements. And I noted why 8 above. > >> If the external data are used in place, then it's the same problem as > >> arm64 fitImage with fdt_high=-1, which fails because the DT is aligned > >> to 4 bytes and arm64 expects it at 8byte offset. > > > > Except we're talking about cases where we can't relocate the data or it > > doesn't make any sense to. > > Which cases? This really needs to be spelled out. > > > That said, if you think the answer is that we need to ensure that when > > we use external data we first align it, please show us how that looks. > > I would like to understand the problem space first. Then please re-read this thread and come up with an alternative solution to the problem you're trying to solve, thanks! -- Tom
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