Re: Support for musl libc in OpenWrt

[Szabolcs Nagy <nsz@port70.net>]

* Isaac Dunham <idunham@lavabit.com> [2012-11-23 22:15:33 -0800]:
> On Fri, 23 Nov 2012 21:10:33 +0100
> Florian Fainelli <florian@openwrt.org> wrote:
> > 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)?
> At present, musl/mips relies on certain instructions that the kernel  ordinarily emulates when they aren't supported.
> 

the fpu issue should not cause segfault,
iirc it infinite loops at the fp instruction

it's a dynamic linking related issue

i've already ran cross compiled, dynlinked
mips binaries on an openwrt router using
musl based toolchain[1] (although that was
about a month ago)

i would guess it's some build issue (wrong
thing gets linked, or -fPIC fails,..)
or something in the runtime environment is
different from what musl expects

maybe try to run the loader in 'ldd' mode:
musl's libc.so is the loader itself and
can be invoked as

 pathto/libc.so executable

which runs the dynlinked executable (so the
musl dynamic loader can be straced) or

 ln -s pathto/libc.so pathto/ldd
 pathto/ldd executable

which prints the opened dso paths during
loading and then quits

[1] https://bitbucket.org/GregorR/musl-cross/downloads