[Buildroot] Custom C Libraries for RISC-V 32-bit Support

[Buildroot] Custom C Libraries for RISC-V 32-bit Support

[Mark Corbin]

Hello

I've been asked by a few people about adding RISC-V 32-bit support to
Buildroot.

This would require the ability to select custom git repositories for C
libraries. There is a glibc repository based on v2.26 that works for
riscv32 and there is also a musl repository for riscv32/riscv64 that I'd
like to test.

I'm happy to add support for custom C libraries, but was wondering what
everybody's thoughts were on this?

Thanks

Mark

-- 
Mark Corbin
Embecosm Ltd.
https://www.embecosm.com

[Buildroot] Custom C Libraries for RISC-V 32-bit Support

[Baruch Siach]

Hi Mark,

On Wed, Oct 03, 2018 at 11:26:53AM +0100, Mark Corbin wrote:
> I've been asked by a few people about adding RISC-V 32-bit support to
> Buildroot.
> 
> This would require the ability to select custom git repositories for C
> libraries. There is a glibc repository based on v2.26 that works for
> riscv32 and there is also a musl repository for riscv32/riscv64 that I'd
> like to test.
> 
> I'm happy to add support for custom C libraries, but was wondering what
> everybody's thoughts were on this?

We already support a custom version of glibc for the ARC architecture. See 
package/glibc/glibc.mk. Is there a plan to push upstream musl/glibc support 
for RISC-V 32-bit?

baruch

-- 
     http://baruch.siach.name/blog/                  ~. .~   Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
   - baruch at tkos.co.il - tel: +972.2.679.5364, http://www.tkos.co.il -

[Buildroot] Custom C Libraries for RISC-V 32-bit Support

[Mark Corbin]

Hello Baruch

On 03/10/18 11:40, Baruch Siach wrote:
> Hi Mark,
>
> On Wed, Oct 03, 2018 at 11:26:53AM +0100, Mark Corbin wrote:
>> I've been asked by a few people about adding RISC-V 32-bit support to
>> Buildroot.
>>
>> This would require the ability to select custom git repositories for C
>> libraries. There is a glibc repository based on v2.26 that works for
>> riscv32 and there is also a musl repository for riscv32/riscv64 that I'd
>> like to test.
>>
>> I'm happy to add support for custom C libraries, but was wondering what
>> everybody's thoughts were on this?
> We already support a custom version of glibc for the ARC architecture. See 
> package/glibc/glibc.mk. Is there a plan to push upstream musl/glibc support 
> for RISC-V 32-bit?
It looks like the musl patches have been submitted for review[1]. I'm
not sure about the status of glibc 32-bit support.

I could add custom library support as per the ARC architecture, or I
could add a generic way to specify a git repository like the kernel, or
I could try to produce some patch sets against the latest C library
versions. I'm open to suggestions.

Regards

Mark

[1] https://www.openwall.com/lists/musl/2018/09/28/1
>
> baruch
>

-- 

*Mark Corbin*
Embedded Operating Systems Lead
Phone: +44 1590 610184?????Mobile: +44 7765 703479
Email: mark.corbin at embecosm.com
<mailto:mark.corbin@embecosm.com>?????Web: https://www.embecosm.com

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[Buildroot] Custom C Libraries for RISC-V 32-bit Support

[Baruch Siach]

Hi Mark,

On Wed, Oct 03, 2018 at 11:53:54AM +0100, Mark Corbin wrote:
> On 03/10/18 11:40, Baruch Siach wrote:
> > On Wed, Oct 03, 2018 at 11:26:53AM +0100, Mark Corbin wrote:
> >> I've been asked by a few people about adding RISC-V 32-bit support to
> >> Buildroot.
> >>
> >> This would require the ability to select custom git repositories for C
> >> libraries. There is a glibc repository based on v2.26 that works for
> >> riscv32 and there is also a musl repository for riscv32/riscv64 that I'd
> >> like to test.
> >>
> >> I'm happy to add support for custom C libraries, but was wondering what
> >> everybody's thoughts were on this?
> > We already support a custom version of glibc for the ARC architecture. See 
> > package/glibc/glibc.mk. Is there a plan to push upstream musl/glibc support 
> > for RISC-V 32-bit?
> It looks like the musl patches have been submitted for review[1]. I'm
> not sure about the status of glibc 32-bit support.
> 
> I could add custom library support as per the ARC architecture, or I
> could add a generic way to specify a git repository like the kernel, or
> I could try to produce some patch sets against the latest C library
> versions. I'm open to suggestions.

The kernel way is definitely not the way to go. The kernel and U-Boot are 
special because people tend to use per target source trees. I think that 
something like what ARC is doing would be easier. A patch set might be 
problematic because we'll need to forward port the patches whenever we bump 
glibc version. But I guess Buildroot maintainers would like to see a clear 
upstream path before committing to accept a riscv32 specific glibc version.

> [1] https://www.openwall.com/lists/musl/2018/09/28/1

baruch

-- 
     http://baruch.siach.name/blog/                  ~. .~   Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
   - baruch at tkos.co.il - tel: +972.2.679.5364, http://www.tkos.co.il -

[Buildroot] Custom C Libraries for RISC-V 32-bit Support

[Thomas Petazzoni]

Hello,

On Wed, 3 Oct 2018 14:41:45 +0300, Baruch Siach wrote:

> The kernel way is definitely not the way to go. The kernel and U-Boot are 
> special because people tend to use per target source trees. I think that 
> something like what ARC is doing would be easier. A patch set might be 
> problematic because we'll need to forward port the patches whenever we bump 
> glibc version.

I agree with Baruch, I'd prefer to see something similar to what we do
for glibc on ARC, i.e the musl/glibc package automatically chose a
different repo/version when building for RISC-V 32 (glibc) or RISC-V
32/64 (musl).

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com