• Mark Rutland's avatar
    arm64: alternative: add auto-nop infrastructure · 792d4737
    Mark Rutland authored
    In some cases, one side of an alternative sequence is simply a number of
    NOPs used to balance the other side. Keeping track of this manually is
    tedious, and the presence of large chains of NOPs makes the code more
    painful to read than necessary.
    
    To ameliorate matters, this patch adds a new alternative_else_nop_endif,
    which automatically balances an alternative sequence with a trivial NOP
    sled.
    
    In many cases, we would like a NOP-sled in the default case, and
    instructions patched in in the presence of a feature. To enable the NOPs
    to be generated automatically for this case, this patch also adds a new
    alternative_if, and updates alternative_else and alternative_endif to
    work with either alternative_if or alternative_endif.
    
    Cc: Andre Przywara <andre.przywara@arm.com>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Dave Martin <dave.martin@arm.com>
    Cc: James Morse <james.morse@arm.com>
    Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
    [will: use new nops macro to generate nop sequences]
    Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
    792d4737
alternative.h 6.5 KB