Re: [Qemu-devel] [qemu-s390x] linux-user: s390x issue on Fedora 30 (dynamic library loader?)

[David Hildenbrand]

On 19.08.19 14:11, Peter Maydell wrote:
> On Sat, 17 Aug 2019 at 17:14, David Hildenbrand <address@hidden> wrote:
>>
>> On 17.08.19 17:59, David Hildenbrand wrote:
>>> Hi everybody,
>>>
>>> I was just trying to run qemu-s390x (linux-user) with a very simple
>>> binary (gzip + lib/ld64.so.1, compiled under Fedora 27). This used to
>>> work just fine a while ago (especially when I was working on vector
>>> instructions using QEMU v3.1). However, now I can't get past a SEGFAULT
>>> in the dynamic library loader (I assume it is trying to locate glibc). I
>>> tried a couple of other binaries that definitely used to work (from
>>> Fedora 30).
>>>
>>> I checked QEMU v4.1, v4.0 and v3.1. All are broken for me. Which is
>>> weird - because it used to work :/
>>>
>>> I remember that I was running Fedora 29 the last time I had it running,
>>> so my gut feeling is that this is related to some other system library
>>> (but which?). I am running on an up-to-date Fedora 30 x86-64 now.
>>>
>>> Any ideas? Has this been reported already? (not sure if this is a Fedora
>>> 30 issue)
> 
> I'm pretty sure the problem you've run into is a long standing
> bug in the glibc dynamic loader. It cannot cope with the ld.so.cache
> being for the wrong endianness. (Correct endianness but incorrect
> architecture it correctly detects and ignores). The result is that
> running a linux-user QEMU dynamic binary for big-endian on little-endian
> like this will crash in the dynamic loader unless you arrange that it can't
> find the host's ld.so.cache somehow, eg:
>  (a) run inside a chroot
>  (b) create an empty /etc/ld.so.cache file inside the -L directory
> 
> The ideal fix would be if somebody cared enough to track down
> and fix the ld.so bug.
> 
> Compare:
> https://bugs.launchpad.net/qemu/+bug/1701798
> https://bugs.launchpad.net/qemu/+bug/1835693
> 
> thanks
> -- PMM
> 

Thanks, running

"ldconfig -c etc/ld.so.cache -r ."

Seems to fix the issue for me. So you are sure the bug resides in glic
and not in the qemu-user pieces of the library loader?

-- 

Thanks,

David / dhildenb