Re: [Qemu-discuss] s390x user-mode working example

[Alex Kashchenko]

On 11/24/2017 10:14 AM, Peter Maydell wrote:
> On 23 November 2017 at 21:00, Alex Kashchenko <address@hidden> wrote:
> > Hi,
> >
> > I am trying to build qemu-s390x-user static binary to run a hello-world
> > program cross-compiled with gcc-s390x-linux-gnu on linux_x86_64.
> >
> > I am building qemu with:
> >
> > ./configure --static --disable-werror --target-list=s390x-linux-user
> > make
> >
> > and running example with:
> >
> > QEMU_STRACE=1 ./s390x-linux-user/qemu-s390x path/to/s390x-hello
> >
> > I tried latest git and a number of v2.x releases without success. Can see
> > either hang (on first brk call) or various errors for newer versions and
> > "Illegal instruction" for older ones. Tried on ubuntu 16.04 and 17.10
> > without success.
> >
> > The same steps worked for me for ppc64le hello-world.
> >
> > Any help on this is highly appreciated.
>
> Is your target binary statically linked? If not you'll need
> to tell QEMU where the libraries are, or run it in a chroot
> with the s390x libraries etc.

No, it is not statically linked, on ubuntu I am installing multiarch 
packet libc6:s390x (goes to /lib/s390x-linux-gnu/libc.so.6 ) for it as a 
dependency.

> (You'll also need to make sure
> it doesn't pick up the x86 /etc/ld.so.cache, because a glibc
> bug means a bigendian dynamic linker crashes when it finds
> a littleendian ld.so.cache, whereas same-endian-wrong-arch
> just ignores it.)

That was it, on a git master build:

$ QEMU_STRACE=1 ./qemu/s390x-linux-user/qemu-s390x ./a.out
4654 brk(NULL) = 0x0000004000003000
4654 uname(0x4000803102) = 0
4654 access("/etc/ld.so.nohwcap",F_OK) = -1 errno=2 (No such file or 
directory)
4654 
mmap(0x00000040008030e8,8192,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANONYMOUS,-1,0x82a168) 
= 0x000000400082b000
4654 access("/etc/ld.so.preload",R_OK) = -1 errno=2 (No such file or 
directory)
4654 open("/etc/ld.so.cache",O_RDONLY|O_CLOEXEC) = 3
4654 fstat(3,0x00000040008027d0) = 0
4654 mmap(0x00000040008026f8,25873,PROT_READ,MAP_PRIVATE,3,0x829098) = 
0x000000400082d000
4654 close(3) = 0
--- SIGSEGV {si_signo=SIGSEGV, si_code=1, si_addr=0x000000409088d000} ---
Segmentation fault (core dumped)


Simple example now works fine for me if I delete /etc/ld.so.cache before 
running it.

Thanks for your help!

--
-Alex