linux-kernel - Re: [PATCH 02/18] arm64: ilp32: add documentation on the ILP32 ABI for ARM64

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Date:   Thu, 27 Oct 2016 12:40:07 +0300
From:   Yury Norov <ynorov@...iumnetworks.com>
To:     Chris Metcalf <cmetcalf@...lanox.com>
CC:     <arnd@...db.de>, <catalin.marinas@....com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-arch@...r.kernel.org>, <schwidefsky@...ibm.com>,
        <heiko.carstens@...ibm.com>, <pinskia@...il.com>,
        <broonie@...nel.org>, <joseph@...esourcery.com>,
        <christoph.muellner@...obroma-systems.com>,
        <bamvor.zhangjian@...wei.com>, <szabolcs.nagy@....com>,
        <klimov.linux@...il.com>, <Nathan_Lynch@...tor.com>,
        <agraf@...e.de>, <Prasun.Kapoor@...iumnetworks.com>,
        <kilobyte@...band.pl>, <geert@...ux-m68k.org>,
        <philipp.tomsich@...obroma-systems.com>,
        <manuel.montezelo@...il.com>, <linyongting@...wei.com>,
        <maxim.kuvyrkov@...aro.org>, <davem@...emloft.net>,
        <zhouchengming1@...wei.com>
Subject: Re: [PATCH 02/18] arm64: ilp32: add documentation on the ILP32 ABI
 for ARM64

Hi Chris,

Thank you for comments

On Mon, Oct 24, 2016 at 12:36:27PM -0400, Chris Metcalf wrote:
> On 10/21/2016 4:33 PM, Yury Norov wrote:
> >Based on Andrew Pinski's patch-series.
> >
> >Signed-off-by: Yury Norov <ynorov@...iumnetworks.com>
> >---
> >  Documentation/arm64/ilp32.txt | 46 +++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 46 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 0000000..b96c18f
> >--- /dev/null
> >+++ b/Documentation/arm64/ilp32.txt
> >@@ -0,0 +1,46 @@
> >+ILP32 AARCH64 SYSCALL ABI
> >+=========================
> >+
> >+This document describes the ILP32 syscall ABI and where it differs
> >+from the generic compat linux syscall interface.
> >+
> >+AARCH64/ILP32 userspace can potentially access top halves of registers that
> >+are passed as syscall arguments, so such registers (w0-w7) are deloused.
> 
> I'm not sure what "potentially access" here means: I think what you want to say
> is that userspace can pass garbage in the top half, but you should be clearer about
> what you mean here. 

Yes. Will change.

> Also, you shouldn't use "deloused" here, since it's not a term
> that's defined elsewhere in the kernel, even though it's been used colloquially on LKML.
> Provide an actual implementation definition, like "have their top 32 bits zeroed".

Agree.
In fact 'delouse' is used in the name of corresponding macro in
include/linux/compat.h:
29 #ifndef __SC_DELOUSE
30 #define __SC_DELOUSE(t,v) ((t)(unsigned long)(v))
31 #endif

But it's not for documentation.

> 
> >+AARCH64/ILP32 provides next types turned to 64-bit (comparing to AARCH32):
> 
> What does "turned" mean here?  And I "next types" isn't standard English; you want
> to say something like "the following types".  Likewise later with "next syscalls".

Thanks, will change.

Yury