>
> I'm thinking there of the silly fadvise64_64 syscall, where ARM was forced
> into having a different argument ordering from everything else through
> zero discussion.
>
> So, what would your scripts do with the fadvise64_64 syscall on an
> architecture requiring natural alignment of the 64-bit args in 32-bit
> regs?
>
It depends on the exact rules: in most cases, it doesn't have to do
anything, because the calling convention on the user side and on the
kernel side simply cancel out. This was lesson #1 while implementing
klibc (which does all system calls that aren't totally ad hoc via
autogenerated stubs.) If, however, it is needed, the scripts I have can
handle arbitrary weirdness, including stuff like needing manual splitting
and even passing 64-bit arguments by reference.
The important bit here is consistent rules, but ad hoc rules that are per
system call (as opposed to a set of *per platform* rules that are adhered
to) is just a disaster -- and one from which we can never recover with any
kind of automation. Inconsistencies here hurt everything that involves
the system call interface: all libcs, the kernel itself, strace etc.
-hpa
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