• Mark Rutland's avatar
    arm64: head.S: use memset to clear BSS · 2a803c4d
    Mark Rutland authored
    Currently we use an open-coded memzero to clear the BSS. As it is a
    trivial implementation, it is sub-optimal.
    Our optimised memset doesn't use the stack, is position-independent, and
    for the memzero case can use of DC ZVA to clear large blocks
    efficiently. In __mmap_switched the MMU is on and there are no live
    caller-saved registers, so we can safely call an uninstrumented memset.
    This patch changes __mmap_switched to use memset when clearing the BSS.
    We use the __pi_memset alias so as to avoid any instrumentation in all
    kernel configurations.
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Marc Zyngier <marc.zyngier@arm.com>
    Reviewed-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
    Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
    Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
head.S 18 KB