[PATCH 07/24] arm64: ilp32: add documentation on the ILP32 ABI for ARM64

Yury Norov
2018-05-24T12:15:24Z

Hi Pavel,

On Wed, May 23, 2018 at 04:06:20PM +0200, Pavel Machek wrote:
> On Wed 2018-05-16 11:18:52, Yury Norov wrote:
> > Based on Andrew Pinski's patch-series.
> >
> > Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
>
> So Andrew's signoff should be here?

Yes it should, but it lost since v4. I'll restore it.

> > ---
> > Documentation/arm64/ilp32.txt | 45 +++++++++++++++++++++++++++++++++++
> > 1 file changed, 45 insertions(+)
> > create mode 100644 Documentation/arm64/ilp32.txt
> >
> > diff --git a/Documentation/arm64/ilp32.txt b/Documentation/arm64/ilp32.txt
> > new file mode 100644
> > index 000000000000..d0fd5109c4b2
> > --- /dev/null
> > +++ b/Documentation/arm64/ilp32.txt
> > @@ -0,0 +1,45 @@
> > +ILP32 AARCH64 SYSCALL ABI
> > +=========================
> > +
> > +This document describes the ILP32 syscall ABI and where it differs
> > +from the generic compat linux syscall interface.
>
> I was hoping to learn what ILP32 is / what is it good for, but no,
> this does not tell me... it would be good to do a short explanation
> here, and maybe reference it from cover letter of the series...
> Pavel

ILP32 is ABI acronym that means "Integers, Longs and Pointers are 32-bit".
And LP64 means "Longs and Pointers are 64-bit".

There's AN490 - "ILP32 for AArch64 Whitepaper" from ARM which covers
the topic:
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dai0490a/ar01s01.html

And some talks:
http://connect.linaro.org/resource/bkk16/bkk16-305b/

Briefly, ILP32 is 32-bit ABI that works with AARCH64 instruction set. It looks
better in some performance tests, and is useful for compatibility with 32-bit
legacy code.

If you're more familiar with x86 terminology, in ARM world LP64 corresponds
to x86_64, AARCH32_EL0 corresponds to x86_32, and ILP32 corresponds to x32
ABI.

I'll add link to AN490 in next submission.

Yury

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