ABI choice in adding new syscall

[Valdis.Kletnieks at vt.edu]

On Thu, 20 Nov 2014 16:44:25 -0200, Marcelo Silva Freitas said:

> I am studing how to add new syscall to the kernel.
> When editing the file syscall_64.tlb there are 3 choices for the ABI: 64,
> common, x32
> I have read about and I don't found clearly the meaning and effect of
> 'common' choice.
> In what imply this choice?

I'm pretty sure it means "this ABI works for both 32 and 64 bit invocations",
which is a good design feature to have if you can do it.  That way, your syscall
code doesn't have to jump through ugly hoops depending on whether the
userspace program was in 32 or 64 bit mode - we've had a *lot* of bugs
relating to that.
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