Re: [musl] Support for musl libc in OpenWrt

[Florian Fainelli <florian@openwrt.org>]

Le samedi 24 novembre 2012 07:15:33, Isaac Dunham a écrit :
> On Fri, 23 Nov 2012 21:10:33 +0100
> 
> Florian Fainelli <florian@openwrt.org> wrote:
> > Hi All,
> > 
> > Support for musl libc in OpenWrt has been added in revision r34314,
> 
> Glad to hear it!
> 
> > Note that the following issues are known:
> > 
> > - unable to complete libstdc++ build due to some missing declarations
> > (WIP)
> 
> Are you using the default "linux-gnu" libstdc++, or the "generic" target?
> Only the latter is known to work at this point.

It is the linux-gnu libstdc++, we do not support building the "generic" one 
yet, might be worth supporting it now.

> 
> > - MIPS and MIPSel ports are not functionnal (details below)
> > 
> > --
> > MIPS and MIPSel specific issues:
> > 
> > using qemu's binary emulation (qemu-mips[el]) against a statically
> > linked binary works, a dynamic binary makes my host qemu segv. Using
> > qemu-system-mips[el], the binary segfaults while being executed by the
> > kernel. So far I have not had the time to debug this further.
> 
> There are likely other issues, but are you using a hardfloat-compatible
> kernel (FPU emulation enabled)? 

No, we have patched the kernel do disable the hardware FPU emulation, which 
was actually the issue, because musl setjmp MIPS-specific code tried to access 
Cop1 registers. After patching setjmp not to access these it works flawlessly 
on MIPS (big-endian) but MIPS (little-endian) still segfaults while being 
executed either from the kernel or qemu-mipsel.

> At present, musl/mips relies on certain
> instructions that the kernel  ordinarily emulates when they aren't
> supported.

You mean ll/sc right? I build for MIPS32r2 so this should not be an issue.
-- 
Florian