[U-Boot] [PATCH v2 3/3] usb: gadget: f_sdp: Allow SPL to load and boot FIT via SDP

[Breno Matheus Lima]

Hi Sjoerd,

Em seg, 17 de jun de 2019 às 11:26, Sjoerd Simons
<sjoerd.simons at collabora.co.uk> escreveu:
>
> On Tue, 2019-06-04 at 18:56 -0300, Fabio Estevam wrote:
> > On Tue, Jun 4, 2019 at 5:41 PM Sjoerd Simons
> > <sjoerd.simons at collabora.co.uk> wrote:
>
> > We have been using imx_usb_loader for a long time. After DM / fit
> > comvesion the IVT piece is not added into the final .img.
> >
> > From the main Makefile:
> >
> > ifdef CONFIG_SPL_LOAD_FIT
> > MKIMAGEFLAGS_u-boot.img = -f auto -A $(ARCH) -T firmware -C none -O
> > u-boot \
> > -a $(CONFIG_SYS_TEXT_BASE) -e $(CONFIG_SYS_UBOOT_START) \
> > -n "U-Boot $(UBOOTRELEASE) for $(BOARD) board" -E \
> > $(patsubst %,-b arch/$(ARCH)/dts/%.dtb,$(subst ",,$(CONFIG_OF_LIST)))
> > else
> > MKIMAGEFLAGS_u-boot.img = -A $(ARCH) -T firmware -C none -O u-boot \
> > -a $(CONFIG_SYS_TEXT_BASE) -e $(CONFIG_SYS_UBOOT_START) \
> > -n "U-Boot $(UBOOTRELEASE) for $(BOARD) board"
> > MKIMAGEFLAGS_u-boot-ivt.img = -A $(ARCH) -T firmware_ivt -C none -O
> > u-boot \
> > -a $(CONFIG_SYS_TEXT_BASE) -e $(CONFIG_SYS_UBOOT_START) \
> > -n "U-Boot $(UBOOTRELEASE) for $(BOARD) board"
> > u-boot-ivt.img: MKIMAGEOUTPUT = u-boot-ivt.img.log
> > CLEAN_FILES += u-boot-ivt.img.log u-boot-dtb.imx.log SPL.log u-
> > boot.imx.log
> > endif
> >
> > we  can see that the ivt is not added for the CONFIG_SPL_LOAD_FIT
> > case.
> >
> > I tried to change this logic, but so far was not able to make it
> > work.
>
> So when looking through how secure boot can work from the SPL i can
> accross e246bfcfe. Which explains the u-boot SPL expect a signed fit
> image with roughly the following layout:
>
> --------------------------------------------------
> |     |     |     |   |           |     |        |
> | FIT | FIT | FIT |   | U-BOOT    | ATF | U-BOOT |
> | FDT | IVT | CSF |   | nodtb.bin |     |   DTB  |
> |     |     |     |   |           |     |        |
> --------------------------------------------------
>
> The code aligns the IVT at 0x1000 and the standard CSF size is
> 0x2000. So one has to set CONFIG_FIT_EXTERNAL_OFFSET=0x3000 (assuming the FIT FDT <= 0x1000 bytes) to make CONFIG_SECURE_BOOT work in this setup (even if HAB is off and the image isn't signed). Otherwise the SPL won't pick up the correct location for all the external data.
>
> Seems a bit ugly that the start offset of the external data can't be
> introspected from the fdt blob, but oh well.
>
> The way this seems to work for i.mx8 is that the SECOND_LOADER command
> sticks in a IVT header into the fit image. I assume some other tooling
> can then stick the CSF data in the appropriate place (anyone have a
> pointer?).
>

Thanks for looking at this issue.

We are using similar structure in NXP U-Boot for i.MX8M devices, you
can use dd tool as explained in document below:
https://source.codeaurora.org/external/imx/uboot-imx/tree/doc/imx/habv4/guides/mx8m_mx8mm_secure_boot.txt?h=imx_v2018.03_4.14.98_2.0.0_ga#n301

> Now i guess the first question becomes whether the i.mx6 should follow
> the same layout. And if so how to integrate it properly (teach mkimage
> about handling firmware_ivt for fit images?).
>

IMHO we should follow the same layout as in i.MX8M, as far as I know
in NXP BSP this is handled by imx-mkimage tool:
https://source.codeaurora.org/external/imx/imx-mkimage/?h=imx_4.14.98_2.0.0_ga

Perhaps we can try similar with mkimage tool included in upstream U-Boot?

> Relatedly i was looking for a good description of using HAB for loading
> the OS in FIT images, but failed to find a good document. pointers
> welcome.
>

For HAB API usage you can take a look in HABv4 RVT Guidelines and
Recommendations application note:
https://www.nxp.com/docs/en/application-note/AN12263.pdf

The U-Boot docs in NXP BSP U-Boot also provides an overview:
https://source.codeaurora.org/external/imx/uboot-imx/tree/doc/imx/habv4?h=imx_v2018.03_4.14.98_2.0.0_ga

Thanks,
Breno Lima