Re: [gentoo-dev] [PATCH] Profile-enforced big-endian USE flag

[James Le Cuirot]

On Thu, 29 Jun 2017 14:37:49 -0700
Matt Turner  wrote:

> On Thu, Jun 29, 2017 at 2:19 PM, James Le Cuirot  wrote:
> > On Wed, 28 Jun 2017 23:29:03 +0100
> > James Le Cuirot  wrote:
> >  
> >> > On Tue, Jun 27, 2017 at 6:44 PM, James Le Cuirot  
> >> > wrote:  
> >> > > I am therefore proposing a new global big-endian flag. This could be
> >> > > masked by default and unmasked + forced in the relevant profiles under
> >> > > arch. I will apply this according to the mapping defined in tc-endian 
> >> > > of
> >> > > toolchain-funcs.eclass.  
> >>
> >> I've just been putting the patch together. I made it slightly simpler
> >> by masking *and* forcing it by default so that it only needs to be
> >> unmasked were necessary.  
> >
> > Feedback seems positive so here is the patch. I'll apply it late next
> > week as I don't need it immediately and I will be away until then.
> >
> > ---
> >
> > diff --git a/profiles/arch/alpha/use.mask b/profiles/arch/alpha/use.mask
> > index d488fe8a09f4..b17afe9d9d4d 100644
> > --- a/profiles/arch/alpha/use.mask
> > +++ b/profiles/arch/alpha/use.mask
> > @@ -1,6 +1,10 @@
> >  # Copyright 1999-2017 Gentoo Foundation.
> >  # Distributed under the terms of the GNU General Public License, v2
> >
> > +# James Le Cuirot  (29 Jun 2017)
> > +# Unmask as this profile is big endian.
> > +-big-endian  
> 
> No. Alpha is little endian.

Wikipedia says it is bi. tc-native() reports alpha* as big so I guess
that's the only variant we support? Then again, this page says it is
usually little. Is tc-native() wrong?

https://kernelnewbies.org/EndianIssues

> > --- /dev/null
> > +++ b/profiles/arch/mips/mipsel/use.mask
> > @@ -0,0 +1,6 @@
> > +# Copyright 1999-2017 Gentoo Foundation
> > +# Distributed under the terms of the GNU General Public License v2
> > +
> > +# James Le Cuirot  (29 Jun 2017)
> > +# Remask as this profile is little endian.
> > +big-endian
> > diff --git a/profiles/arch/mips/use.mask b/profiles/arch/mips/use.mask
> > index 09ac8ca4b2cc..6caff81617cb 100644
> > --- a/profiles/arch/mips/use.mask
> > +++ b/profiles/arch/mips/use.mask
> > @@ -4,6 +4,10 @@
> >  # Unmask the flag which corresponds to ARCH.
> >  -mips
> >
> > +# James Le Cuirot  (29 Jun 2017)
> > +# Unmask as this profile is big endian.
> > +-big-endian  
> 
> I'm not sure if this one is correct. arch/mips/mipsel's 'parent' file
> contains '..'
> 
> I think if you re-mask big-endian in arch/mips/mipsel it'll work, and
> that seems like the best way to solve it.

That's what I did?


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Description: OpenPGP digital signature

Re: [gentoo-dev] [PATCH] Profile-enforced big-endian USE flag

[Matt Turner]

On Thu, Jun 29, 2017 at 2:19 PM, James Le Cuirot  wrote:
> On Wed, 28 Jun 2017 23:29:03 +0100
> James Le Cuirot  wrote:
>
>> > On Tue, Jun 27, 2017 at 6:44 PM, James Le Cuirot  wrote:
>> > > I am therefore proposing a new global big-endian flag. This could be
>> > > masked by default and unmasked + forced in the relevant profiles under
>> > > arch. I will apply this according to the mapping defined in tc-endian of
>> > > toolchain-funcs.eclass.
>>
>> I've just been putting the patch together. I made it slightly simpler
>> by masking *and* forcing it by default so that it only needs to be
>> unmasked were necessary.
>
> Feedback seems positive so here is the patch. I'll apply it late next
> week as I don't need it immediately and I will be away until then.
>
> ---
>
> From e6aaee518b5e7eab735116a2ea57d538a8e26c19 Mon Sep 17 00:00:00 2001
> From: James Le Cuirot 
> Date: Thu, 29 Jun 2017 22:11:49 +0100
> Subject: [PATCH] profiles: Add profile-enforced global big-endian USE flag
>
> The flag is forced and masked by default and then unmasked where
> necessary. Note that there are some big endian host values listed in
> tc-endian() that we do not have profiles for.
> ---
>  profiles/arch/alpha/use.mask  | 4 
>  profiles/arch/arm64/big-endian/use.mask   | 6 ++
>  profiles/arch/base/use.force  | 6 ++
>  profiles/arch/base/use.mask   | 4 
>  profiles/arch/hppa/use.mask   | 4 
>  profiles/arch/m68k/use.mask   | 7 +++
>  profiles/arch/mips/mipsel/use.mask| 6 ++
>  profiles/arch/mips/use.mask   | 4 
>  profiles/arch/powerpc/ppc64/64le/use.mask | 4 
>  profiles/arch/powerpc/use.mask| 7 +++
>  profiles/arch/s390/use.mask   | 7 +++
>  profiles/arch/sparc/use.mask  | 4 
>  profiles/use.desc | 3 ++-
>  13 files changed, 65 insertions(+), 1 deletion(-)
>  create mode 100644 profiles/arch/arm64/big-endian/use.mask
>  create mode 100644 profiles/arch/base/use.force
>  create mode 100644 profiles/arch/mips/mipsel/use.mask
>
> diff --git a/profiles/arch/alpha/use.mask b/profiles/arch/alpha/use.mask
> index d488fe8a09f4..b17afe9d9d4d 100644
> --- a/profiles/arch/alpha/use.mask
> +++ b/profiles/arch/alpha/use.mask
> @@ -1,6 +1,10 @@
>  # Copyright 1999-2017 Gentoo Foundation.
>  # Distributed under the terms of the GNU General Public License, v2
>
> +# James Le Cuirot  (29 Jun 2017)
> +# Unmask as this profile is big endian.
> +-big-endian

No. Alpha is little endian.

> +
>  # Tobias Klausmann  (03 March 2017)
>  # There is no luajit support on alpha. Bugs #554376, #608322.
>  luajit
> diff --git a/profiles/arch/arm64/big-endian/use.mask 
> b/profiles/arch/arm64/big-endian/use.mask
> new file mode 100644
> index ..0a4af0711f5c
> --- /dev/null
> +++ b/profiles/arch/arm64/big-endian/use.mask
> @@ -0,0 +1,6 @@
> +# Copyright 1999-2017 Gentoo Foundation.
> +# Distributed under the terms of the GNU General Public License, v2
> +
> +# James Le Cuirot  (29 Jun 2017)
> +# Unmask as this profile is big endian.
> +-big-endian
> diff --git a/profiles/arch/base/use.force b/profiles/arch/base/use.force
> new file mode 100644
> index ..7f213b9dd017
> --- /dev/null
> +++ b/profiles/arch/base/use.force
> @@ -0,0 +1,6 @@
> +# Copyright 1999-2017 Gentoo Foundation
> +# Distributed under the terms of the GNU General Public License v2
> +
> +# James Le Cuirot  (29 Jun 2017)
> +# Forced and masked by default. Unmask where necessary.
> +big-endian
> diff --git a/profiles/arch/base/use.mask b/profiles/arch/base/use.mask
> index 1a4a39cefc13..2ea1fb3d89fa 100644
> --- a/profiles/arch/base/use.mask
> +++ b/profiles/arch/base/use.mask
> @@ -1,6 +1,10 @@
>  # Copyright 1999-2017 Gentoo Foundation
>  # Distributed under the terms of the GNU General Public License v2
>
> +# James Le Cuirot  (29 Jun 2017)
> +# Forced and masked by default. Unmask where necessary.
> +big-endian
> +
>  # Sven Wegener  (31 May 2017)
>  # libvirt is only supported on specific architectures
>  libvirt
> diff --git a/profiles/arch/hppa/use.mask b/profiles/arch/hppa/use.mask
> index 7361e2c52af2..bd158162a449 100644
> --- a/profiles/arch/hppa/use.mask
> +++ b/profiles/arch/hppa/use.mask
> @@ -3,6 +3,10 @@
>  # NOTE: When masking a USE flag due to missing keywords, please file a 
> keyword
>  # request bug for the hppa arch.
>
> +# James Le Cuirot  (29 Jun 2017)
> +# Unmask as this profile is big endian.
> +-big-endian
> +
>  # Andreas Sturmlechner  (25 Feb 2017)
>  # kwallet integration split from kde to distinct flag
>  kwallet
> diff --git a/profiles/arch/m68k/use.mask b/profiles/arch/m68k/use.mask
> index aac0e46e97c2..646567111d56 100644
> --- 

Re: [gentoo-dev] Profile-enforced big-endian USE flag

[Joshua Kinard]

On 06/28/2017 18:29, James Le Cuirot wrote:
> On Wed, 28 Jun 2017 17:52:26 -0400
> Mike Gilbert  wrote:
> 
>> On Tue, Jun 27, 2017 at 6:44 PM, James Le Cuirot  wrote:
>>> I am therefore proposing a new global big-endian flag. This could be
>>> masked by default and unmasked + forced in the relevant profiles under
>>> arch. I will apply this according to the mapping defined in tc-endian of
>>> toolchain-funcs.eclass.  
> 
> I've just been putting the patch together. I made it slightly simpler
> by masking *and* forcing it by default so that it only needs to be
> unmasked were necessary.
> 
>> A possible alternative would be to create a new USE_EXPAND variable
>> for this. That would allow for easier expansion in case we ever
>> support something other than big/little endian machines.
> 
> That way madness lies? Wikipedia talks about middle-endian as being the
> catch all for other random orderings that have appeared over the years
> but I don't think any of them were used on a system-wide basis. I can't
> imagine Linux ever supporting such a thing. Unless you're talking about
> dealing with soft vs hard float here too?

As far as I know, Linux only supports big-endian and little-endian systems,
along with supporting a fairly-wide variety of platforms and architectures,
beaten really only by NetBSD.  If NetBSD lacks anything for middle-endian, then
it's probably safe to ignore it.

That said, Wikipedia doesn't offer much on the nature of middle-endian (which
is called "PDP-endian"), except to state that "The ARM architecture can also
produce this format when writing a 32-bit word to an address 2 bytes from a
32-bit word alignment."
https://en.wikipedia.org/wiki/Endianness#Middle

And this resource:
http://unixpapa.com/incnote/byteorder.html

Recommends to ignore middle-endian, as it believes no processor was ever
implemented that stored integers in middle-endian format.

-- 
Joshua Kinard
Gentoo/MIPS
ku...@gentoo.org
6144R/F5C6C943 2015-04-27
177C 1972 1FB8 F254 BAD0 3E72 5C63 F4E3 F5C6 C943

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