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  • Eugeniy Paltsev's avatar
    ARC: u-boot args: check that magic number is correct · 8232cdfd
    Eugeniy Paltsev authored
    [ Upstream commit edb64bca
    
     ]
    
    In case of devboards we really often disable bootloader and load
    Linux image in memory via JTAG. Even if kernel tries to verify
    uboot_tag and uboot_arg there is sill a chance that we treat some
    garbage in registers as valid u-boot arguments in JTAG case.
    E.g. it is enough to have '1' in r0 to treat any value in r2 as
    a boot command line.
    
    So check that magic number passed from u-boot is correct and drop
    u-boot arguments otherwise. That helps to reduce the possibility
    of using garbage as u-boot arguments in JTAG case.
    
    We can safely check U-boot magic value (0x0) in linux passed via
    r1 register as U-boot pass it from the beginning. So there is no
    backward-compatibility issues.
    
    Signed-off-by: default avatarEugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
    Signed-off-by: default avatarVineet Gupta <vgupta@synopsys.com>
    Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
    8232cdfd