Document the image and load structure for i.MX6 and i.MX8MQ. Signed-off-by: Rouven Czerwinski <r.czerwinski@xxxxxxxxxxxxxx> --- Documentation/boards/imx.rst | 69 ++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+) diff --git a/Documentation/boards/imx.rst b/Documentation/boards/imx.rst index 71cc6bb09a..7110492eba 100644 --- a/Documentation/boards/imx.rst +++ b/Documentation/boards/imx.rst @@ -142,6 +142,75 @@ It must be included in the board's flash header: Analogous to HABv4 options and a template exist for HABv3. +Secure Boot on i.MX6 +-------------------- + +The secure boot process on i.MX6 consist of the following image constellation:: + + 0x0 +---------------------------------+ + | Barebox Header | + 0x400 +---------------------------------+ - + | i.MX IVT Header | | + | Boot Data +--+ | + | CSF Pointer +--|-+ | Signed Area + +---------------------------------+ | | | + | Device Configuration Data (DCD) | | | | + 0x1000 +---------------------------------+ | | | + | Barebox Prebootloader (PBL) |<-+ | | + +---------------------------------+ | | + | Piggydata (Main Barebox Binary) | | | + +---------------------------------+ | - + | Command Sequence File (CSF) |<---+ + +---------------------------------+ + +Here the Command Sequence File signs the complete Header, PBL and piggy data +file. This ensures that the whole barebox binary is authenticated. This is +possible since the DDR RAM is configured using the DCD and the whole DDR memory +area can be used to load data onto the device for authentication. +The boot ROM loads the CSF area and barebox into memory and uses the CSF to +verify the complete barebox binary. + +Secure Boot on i.MX8MQ +---------------------- + +For i.MX8MQ the image has the following design:: + + 0x0 +---------------------------------+ + | Barebox Header | + +---------------------------------+ + | i.MX IVT Header | + | HDMI Firmware (Signed by NXP) | + +---------------------------------+ - + | i.MX IVT Header | | + | Boot Data +--+ | + | CSF Pointer +--|-+ | + +---------------------------------+ | | | Signed Area + | Device Configuration Data (DCD) | | | | + +---------------------------------+ | | | + | Barebox Prebootloader (PBL) |<-+ | | + | Piggydata Hash (SHA256) +----|-+ | + +---------------------------------+ | | - + | Command Sequence File (CSF) |<---+ | + +---------------------------------+ | - + | Piggydata (Main Barebox Binary) |<-----+ | Hashed Area + +---------------------------------+ - + +In contrast to i.MX6, for the i.MX8MQ the piggydata can not be signed together +with the PBL binary. The DDR memory is initialized during the start of the PBL, +previous to this no access to the DDR memory is possible. Since the Tightly +Coupled Memory used for early startup on i.MX8MQ has only 256Kib, the whole +barebox can't be loaded and verified at once, since the complete barebox with +firmware has a size of ~500Kib. + +The bootrom loads the HDMI firmware unconditionally, since it is signed by NXP. +Afterwards the Prebootloader (PBL) is loaded into SRAM and the bootrom proceeds +to verify the PBL according to the Command Sequence File (CSF). The verified +PBL initializes the ARM Trusted Firmware (TF-A) and DDR RAM. It subsequently +loads the piggydata from the SD card and calculates the sha256sum of the +piggydata. This is compared to the sha256sum built into the PBL during compile +time, the PBL will only continue to boot if the sha256sum matches the builtin +sha256sum. + Using GPT on i.MX ^^^^^^^^^^^^^^^^^ -- 2.23.0 _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
