Arm AArch64 port - search for interested people

Arm AArch64 port - search for interested people

[Bortis Kevin]

Is someone interessted to help out with a musl ARM Aarch64 port? I got
the message, that I will receive a dev board Q2/2014 for a new project,
so I hope to have a working musl toolchain by then :)

I have started a wiki page where I gather all Information needed for the
port. First step will be, learn A64 assembler/registers and get the ARM
Foundation Model running with a Linux distribution. I also hope that the
musl documentation with information on musl internals and porting will
be finished by then ;)

http://wiki.musl-libc.org/wiki/Porting/AArch64

  Kevin

Re: Arm AArch64 port - search for interested people

[Szabolcs Nagy]

* Bortis Kevin <Kevin.Bortis@ruf.ch> [2013-09-11 13:38:03 +0200]:
> Is someone interessted to help out with a musl ARM Aarch64 port? I got
> the message, that I will receive a dev board Q2/2014 for a new project,
> so I hope to have a working musl toolchain by then :)
> 
> I have started a wiki page where I gather all Information needed for the
> port. First step will be, learn A64 assembler/registers and get the ARM
> Foundation Model running with a Linux distribution. I also hope that the
> musl documentation with information on musl internals and porting will
> be finished by then ;)
> 
> http://wiki.musl-libc.org/wiki/Porting/AArch64

it seems long double is IEEE binary128 in the abi,
but there are no quad precision fp instructions..

so good that i did not remove the ld128 code from libm,
however complete support will take some time.. and it will
depend on the soft-float implementation in gcc which has
fenv issues

Re: Arm AArch64 port - search for interested people

[Rich Felker]

On Wed, Sep 11, 2013 at 02:58:51PM +0200, Szabolcs Nagy wrote:
> * Bortis Kevin <Kevin.Bortis@ruf.ch> [2013-09-11 13:38:03 +0200]:
> > Is someone interessted to help out with a musl ARM Aarch64 port? I got
> > the message, that I will receive a dev board Q2/2014 for a new project,
> > so I hope to have a working musl toolchain by then :)
> > 
> > I have started a wiki page where I gather all Information needed for the
> > port. First step will be, learn A64 assembler/registers and get the ARM
> > Foundation Model running with a Linux distribution. I also hope that the
> > musl documentation with information on musl internals and porting will
> > be finished by then ;)
> > 
> > http://wiki.musl-libc.org/wiki/Porting/AArch64
> 
> it seems long double is IEEE binary128 in the abi,
> but there are no quad precision fp instructions..

It's really unfortunate that AArch64 does not have instructions for
ld128; even if they were unimplemented, they could be emulated to
avoid the hideousness of softfloat.

> so good that i did not remove the ld128 code from libm,
> however complete support will take some time.. and it will
> depend on the soft-float implementation in gcc which has
> fenv issues

I would hope on archs with hardfloat but where long double is
implemented with softfloat, gcc is smart enough to do something with
the fpu to raise the appropriate flags. Any idea if this is the case,
or if the AArch64 ABI mentions the issue at all?

Rich

Re: Arm AArch64 port - search for interested people

[Szabolcs Nagy]

* Rich Felker <dalias@aerifal.cx> [2013-09-11 12:51:29 -0400]:
> > however complete support will take some time.. and it will
> > depend on the soft-float implementation in gcc which has
> > fenv issues
> 
> I would hope on archs with hardfloat but where long double is
> implemented with softfloat, gcc is smart enough to do something with
> the fpu to raise the appropriate flags. Any idea if this is the case,
> or if the AArch64 ABI mentions the issue at all?

yes, i was wrong, gcc seems to use the fpu fenv in such cases

(libgcc uses inline asm fp arithmetics to raise the exceptions..
they don't trust themselfs about incorrectly optimizing away
fp operations in c code)

Re: Arm AArch64 port - search for interested people

[Strake]

On 11/09/2013, Bortis Kevin <Kevin.Bortis@ruf.ch> wrote:
> get the ARM Foundation Model running with a Linux distribution

Which? Have you one in mind?

Re: Arm AArch64 port - search for interested people

[Strake]

On 11/09/2013, Bortis Kevin <Kevin.Bortis@ruf.ch> wrote:
> Is someone interessted to help out with a musl ARM Aarch64 port? I got
> the message, that I will receive a dev board Q2/2014 for a new project,
> so I hope to have a working musl toolchain by then :)

I am interested. I shall ask an AMD A-series dev board sample when
available. I can likely start hacking this significantly next term,
from May. Is the status at
http://wiki.musl-libc.org/wiki/Porting/AArch64 accurate now?

Re: Arm AArch64 port - search for interested people

[Szabolcs Nagy]

* Strake <strake888@gmail.com> [2014-02-24 12:22:22 -0500]:
> On 11/09/2013, Bortis Kevin <Kevin.Bortis@ruf.ch> wrote:
> > Is someone interessted to help out with a musl ARM Aarch64 port? I got
> > the message, that I will receive a dev board Q2/2014 for a new project,
> > so I hope to have a working musl toolchain by then :)
> 
> I am interested. I shall ask an AMD A-series dev board sample when
> available. I can likely start hacking this significantly next term,
> from May. Is the status at
> http://wiki.musl-libc.org/wiki/Porting/AArch64 accurate now?

i've added some links to armv8 resources

until you get the hw, there are some simulators: the official
closed one from arm, gem5 (full-system) and qemu (userspace only)

floating-point will need some work because of the IEEE binary128
long double, some code may not compile in math/ immediately

Re: Arm AArch64 port - search for interested people

[Rich Felker]

On Mon, Feb 24, 2014 at 12:22:22PM -0500, Strake wrote:
> On 11/09/2013, Bortis Kevin <Kevin.Bortis@ruf.ch> wrote:
> > Is someone interessted to help out with a musl ARM Aarch64 port? I got
> > the message, that I will receive a dev board Q2/2014 for a new project,
> > so I hope to have a working musl toolchain by then :)
> 
> I am interested. I shall ask an AMD A-series dev board sample when
> available. I can likely start hacking this significantly next term,
> from May. Is the status at
> http://wiki.musl-libc.org/wiki/Porting/AArch64 accurate now?

I haven't followed efforts to port to aarch64, so I can't answer
whether it's accurate. I just spent a few minutes looking at the
partial port linker from the wiki
(https://github.com/wermut/musl-aarch64) and it looks like a good bit
of the work has been done and it might be fairly easy to finish it up.
Either way, it would be great to have someone working on it again!

Rich

Re: Arm AArch64 port - search for interested people

[Richard Pennington]

On 02/24/2014 12:32 PM, Rich Felker wrote:
> On Mon, Feb 24, 2014 at 12:22:22PM -0500, Strake wrote:
>> On 11/09/2013, Bortis Kevin <Kevin.Bortis@ruf.ch> wrote:
>>> Is someone interessted to help out with a musl ARM Aarch64 port? I got
>>> the message, that I will receive a dev board Q2/2014 for a new project,
>>> so I hope to have a working musl toolchain by then :)
>> I am interested. I shall ask an AMD A-series dev board sample when
>> available. I can likely start hacking this significantly next term,
>> from May. Is the status at
>> http://wiki.musl-libc.org/wiki/Porting/AArch64 accurate now?
> I haven't followed efforts to port to aarch64, so I can't answer
> whether it's accurate. I just spent a few minutes looking at the
> partial port linker from the wiki
> (https://github.com/wermut/musl-aarch64) and it looks like a good bit
> of the work has been done and it might be fairly easy to finish it up.
> Either way, it would be great to have someone working on it again!
>
> Rich
I'm also interested in the aarch64. Over the weekend I added binutils, 
GDB, and QEMU support for it to the ELLCC build.

-Rich

Re: Arm AArch64 port - search for interested people

[Rich Felker]

On Mon, Feb 24, 2014 at 01:32:42PM -0500, Rich Felker wrote:
> On Mon, Feb 24, 2014 at 12:22:22PM -0500, Strake wrote:
> > On 11/09/2013, Bortis Kevin <Kevin.Bortis@ruf.ch> wrote:
> > > Is someone interessted to help out with a musl ARM Aarch64 port? I got
> > > the message, that I will receive a dev board Q2/2014 for a new project,
> > > so I hope to have a working musl toolchain by then :)
> > 
> > I am interested. I shall ask an AMD A-series dev board sample when
> > available. I can likely start hacking this significantly next term,
> > from May. Is the status at
> > http://wiki.musl-libc.org/wiki/Porting/AArch64 accurate now?
> 
> I haven't followed efforts to port to aarch64, so I can't answer
> whether it's accurate. I just spent a few minutes looking at the
> partial port linker from the wiki
> (https://github.com/wermut/musl-aarch64) and it looks like a good bit
> of the work has been done and it might be fairly easy to finish it up.
> Either way, it would be great to have someone working on it again!

One thing to note: there seems to be some fishy stuff in the bits
headers we should check out, like whether blksize_t really needs to be
"int" (it's long on other systems), explicit use of "unsigned int"
instead of nlink_t without defining nlink_t to match, possibly-wrong
sysvipc structures (it looks like the legacy ones are being used
instead of the "64" ones, but I may be wrong), namespace issues in
bits/signal.h, ...

Rich