Re: Linux emulation

[Robert Swindells <rjs%fdy2.co.uk@localhost>]

Matt Thomas wrote:
>On Apr 3, 2014, at 2:30 PM, Dennis Ferguson 
><dennis.c.ferguson%gmail.com@localhost> wrote:
>
>> I think it can be enabled unconditionally.  I think the ABI the
>> kernel was compiled for doesn't matter, it is the ABI the Linux
>> binary was compiled for which causes things to change.  The executive
>> decision would be whether the emulation code should run with Linux
>> binaries of either ABI or whether just picking one ABI is sufficient.
>
>Almost right.  non-EABI has a maximal alignment of 4 (long long have
>an alignment of 4) while on EABI has a maximal alignment of 8.  This
>causes structures to have different layouts which is why there is 
>COMPAT_NETBSD32 support (for the other alignment). 

With the Linux EABI, a syscall with arguments of (32, 64, 32) will
put them in (r1, r3&r4, r5).

I think that I can do something similar to mips to detect any syscalls
with 64 bit arguments.