• Aneesh Bansal's avatar
    secure_boot: split the secure boot functionality in two parts · bdc22074
    Aneesh Bansal authored
    There are two phases in Secure Boot
    1. ISBC: In BootROM, validate the BootLoader (U-Boot).
    2. 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:
    1. Enable commands like esbc_validate, esbc_halt
    2. 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: default avatarAneesh Bansal <aneesh.bansal@nxp.com>
    Acked-by: default avatarRuchika Gupta <ruchika.gupta@nxp.com>
    Reviewed-by: default avatarYork Sun <york.sun@nxp.com>
    bdc22074
config_fsl_chain_trust.h 2.75 KB