On 01/22/2016 03:10 AM, Aneesh Bansal wrote:
There are two phases in Secure Boot
- ISBC: In BootROM, validate the BootLoader (U-Boot).
- ESBC: In U-Boot, continuing the Chain of Trust by validating and booting LINUX.
For ESBC phase, there is no difference in SoC's based on ARM or PowerPC cores.
But the exit conditions after ISBC phase i.e. entry conditions for U-Boot are different for ARM and PowerPC. PowerPC: ======== If Secure Boot is executed, a separate U-Boot target is required which must be compiled with a diffrent Text Base as compared to Non-Secure Boot. There are some LAW and TLB settings which are required specifically for Secure Boot scenario.
ARM:
ARM based SoC's have a fixed memory map and exit conditions from BootROM are same irrespective of boot mode (Secure or Non-Secure).
Thus the current Secure Boot functionlity has been split into two parts:
CONFIG_CHAIN_OF_TRUST
This will have the following functionality as part of U-Boot:
- Enable commands like esbc_validate, esbc_halt
- Change the environment settings based on bootmode (determined at run time):
- If bootmode is non-secure, no change
- If bootmode is secure, set the following:
- bootdelay = 0 (Don't give boot prompt)
- bootcmd = Validate and execute the bootscript.
CONFIG_SECURE_BOOT
This is defined only for creating a different compile time target for secure boot.
Traditionally, both these functionalities were defined under CONFIG_SECURE_BOOT This patch is aimed at removing the requirement for a separate Secure Boot target for ARM based SoC's. CONFIG_CHAIN_OF_TRUST will be defined and boot mode will be determine at run time.
Another Security Requirement for running CHAIN_OF_TRUST is that U-Boot environemnt must not be picked from flash/external memory. This cannot be done based on bootmode at run time in current U-Boot architecture. Once this dependency is resolved, no separate SECURE_BOOT target will be required for ARM based SoC's.
Currently, the only code under CONFIG_SECURE_BOOT for ARM SoC's is defining CONFIG_ENV_IS_NOWHERE
Signed-off-by: Aneesh Bansal aneesh.bansal@nxp.com
Changes in v3: None
Changes in v2: CONFIG_ENV_IS_NOWHERE is defined for Secure Boot
arch/arm/include/asm/fsl_secure_boot.h | 16 ++-- arch/powerpc/include/asm/fsl_secure_boot.h | 41 +++++----- include/config_fsl_chain_trust.h | 101 +++++++++++++++++++++++++ include/config_fsl_secboot.h | 116 ----------------------------- 4 files changed, 135 insertions(+), 139 deletions(-) create mode 100644 include/config_fsl_chain_trust.h delete mode 100644 include/config_fsl_secboot.h
Change subject prefix to "secure_boot:". Slightly reformat commit message. Applied to u-boot-fsl-qoriq master. Awaiting upstream.
Thanks.
York