Linux powerpc new system call instruction and ABI
segher at kernel.crashing.org
Thu May 20 01:22:05 AEST 2021
On Wed, May 19, 2021 at 03:06:49PM +0000, Joakim Tjernlund wrote:
> On Wed, 2021-05-19 at 09:38 -0500, Segher Boessenkool wrote:
> > On Wed, May 19, 2021 at 06:42:40PM +1000, Nicholas Piggin wrote:
> > > Excerpts from Joakim Tjernlund's message of May 19, 2021 6:08 pm:
> > > > I always figured the ppc way was superior. It begs the question if not the other archs should
> > > > change instead?
> > >
> > > It is superior in some ways, not enough to be worth being different.
> > The PowerPC syscall ABI *requires* using cr0.3 for indicating errors,
> > you will have to do that whether you conflate the concepts of return
> > code and error indicator or not!
> > > Other archs are unlikely to change because it would be painful for
> > > not much benefit.
> > Other archs cannot easily change for much the same reason :-)
> Really? I figured you could just add extra error indication in kernel syscall I/F.
> Eventually user space could migrate to the new indication.
You seem to assume all user space uses glibc, or *any* libc even? This
is false. Some programs do system calls directly. Do not break the
kernel ABI :-)
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