This patch series is derived from an earlier RFC [1] with (most of the) feedback implemented that was provided by Simon, Tom, and Lokesh (see change log at the end). There are still some loose ends namely affecting the make process (see discussion here [2], maybe Yamada-san has some inputs?) as well as the conversion of the "weak" post-process function call to a Kconfig option. We did experiment with a few options regarding the Kconfig conversion but couldn't really settle on a good way. Simon or Tom- if you could provide a tiny bit of additional direction here we will be happy to re-visit this and change the current implementation.
Here's again the high-level summary of what we are trying to achieve:
A method is introduced that uses a "weak" post-process function call that's injected into the SPL FIT loading process after each blob has been extracted (U-Boot firmware, selected DTB) which is populated with a platform specific function. In case of TI high-security (HS) device variants a ROM API call is performed (via SMC) that transparently handles authentication and optional decryption. This essentially allows authenticating (and optionally decrypting) U-Boot from SPL. The post-processing injection is implemented such to enable a more universal use of this feature by other platforms or for other purposes.
Furthermore the build process has been modified to automatically invoke a TI blob signing/encryption tool through the $TI_SECURE_DEV_PKG env variable already introduced into U-Boot. This singing/encryption step happens for each artifact that gets bundled into the final u-boot.img FIT blob.
Why do we need this for our platforms if some generic form of verified boot already exists in U-Boot? The approach proposed here provides support for decryption which is currently not available in U-Boot (and may not be easily implementable generically for example due to the need for keeping symmetric keys secure). Furthermore it allows for a consistent build as well as runtime flow no matter authentication and/or decryption is used (as opposed to using existing U-Boot verified boot for authentication and an additional TI-specific ROM API call for decryption for example). It also allows for a faster and more efficient boot process (auth and decryption can be performed in a single step by the ROM APIs also utilizing crypto HW accelerators in a completely transparent fashion). However anyone can still use the standard U-Boot verified boot scheme from U-Boot onwards if they so chose and only need authentication.
I also just re-rested the patch series on actual AM437x HS, DRA7 HS, DRA72 HS, and AM57 HS device variants by building and running SPL/U-Boot. I've also build-tested the corresponding non-HS device variant configurations to make sure nothing is broken there.
Changes RFC->PATCH: - Update of README.ti-secure - Unification of some of the secure ROM API call stuff between AM43xx and OMAP5-based platforms by moving those into common files - Replacement of puts() with printf() - Minor build simplification/cleanup - Addition of "Reviewed-by:" comments for files that were pretty much carried over from the RFC as-is - Addition of AM437x HS device build support (was missing in RFC) - Removal of some redundant conditional compile directives - Rebased on upstream U-Boot commit "Prepare v2016.07-rc2"
Regards, Andreas Dannenberg
[1] https://www.mail-archive.com/u-boot@lists.denx.de/msg216299.html [2] https://www.mail-archive.com/u-boot@lists.denx.de/msg216298.html
Andreas Dannenberg (4): arm: omap-common: add secure rom call API for secure devices arm: omap-common: secure ROM signature verify API arm: omap-common: Update to generate secure U-Boot FIT blob arm: omap5: add U-Boot FIT signing and SPL image post-processing
Daniel Allred (4): arm: cache: add missing dummy functions for when dcache disabled spl: fit: add support for post-processing of images arm: omap-common: add secure smc entry doc: Update info on using secure devices from TI
Madan Srinivas (1): arm: am4x: add U-Boot FIT signing and SPL image post-processing
arch/arm/cpu/armv7/am33xx/config.mk | 1 + arch/arm/cpu/armv7/cache_v7.c | 8 ++ arch/arm/cpu/armv7/omap-common/Makefile | 2 + arch/arm/cpu/armv7/omap-common/config_secure.mk | 57 +++++++- arch/arm/cpu/armv7/omap-common/lowlevel_init.S | 45 +++++-- arch/arm/cpu/armv7/omap-common/sec-common.c | 125 +++++++++++++++++ arch/arm/cpu/armv7/omap5/config.mk | 3 + arch/arm/include/asm/omap_common.h | 22 +++ board/ti/am43xx/board.c | 7 + board/ti/am57xx/board.c | 7 + board/ti/dra7xx/evm.c | 7 + common/spl/spl_fit.c | 21 ++- doc/README.ti-secure | 170 ++++++++++++++++-------- include/image.h | 15 +++ 14 files changed, 420 insertions(+), 70 deletions(-) create mode 100644 arch/arm/cpu/armv7/omap-common/sec-common.c