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    arm64: Abstract syscallno manipulation · 17c28958
    Dave Martin 提交于
    The -1 "no syscall" value is written in various ways, shared with
    the user ABI in some places, and generally obscure.
    
    This patch attempts to make things a little more consistent and
    readable by replacing all these uses with a single #define.  A
    couple of symbolic helpers are provided to clarify the intent
    further.
    
    Because the in-syscall check in do_signal() is changed from >= 0 to
    != NO_SYSCALL by this patch, different behaviour may be observable
    if syscallno is set to values less than -1 by a tracer.  However,
    this is not different from the behaviour that is already observable
    if a tracer sets syscallno to a value >= __NR_(compat_)syscalls.
    
    It appears that this can cause spurious syscall restarting, but
    that is not a new behaviour either, and does not appear harmful.
    Signed-off-by: NDave Martin <Dave.Martin@arm.com>
    Acked-by: NWill Deacon <will.deacon@arm.com>
    Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
    17c28958
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