Tweak arm64's cpu_fetch_syscall_args()

[trasz]

Summary

Tweak arm64's cpu_fetch_syscall_args(). This should make it possible
for the compiler to inline the memcpy().

[trasz]

Try to make it more buildable.

[andrew]

sys/arm64/arm64/trap.c

139

What does dst_ap point at?

[trasz]

Sigh, initialize dst_ap.

sys/arm64/arm64/trap.c

139

Let's leave this review alone until I both tinderbox _and_ test it.

[trasz]

Fix tinderbox.

[trasz]

I've tested it, it works and is ready for review.

[andrew]

sys/arm64/arm64/trap.c

147–151

Won't this be wrong in the SYS_syscall an SYS___syscall cases?

[trasz]

sys/arm64/arm64/trap.c

147–151

I don't think so; in both cases - when calling through syscall(2), and when calling the "destination" syscall directly - the number of arguments to put into sa->args is the same; it's just the layout in the registers (or trapframe) that differs; this is taken care of a few lines above.