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Re: converting SWIs to pass swi number in a register.

On 7/3/08, Chris Gilbert <chris%dokein.co.uk@localhost> wrote:
> Richard Earnshaw wrote:
>  > On Wed, 2008-07-02 at 22:41 -0700, Matt Thomas wrote:
>  >> One question is how do we know we are using ip?  Think binary
>  >> compat with older binaries...
>  >
>  > Use 0 in the SWI # field (as linux does).  You only need to look in the
>  > SWI field if you have a relevant COMPAT_.. enabled.
>  And if we find 0 look at the register?

But if you always have to check for SWI  0 before looking in the
register, then you have to inspect the instruction stream with a data
access for every SWI anyway and lose the whole point of doing this!
  Linux does this for "old-abi compatability under EABI mode", but you
lose the syscall speed advantage - which seems to be the only reason
for making this change in BSD.



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