Re: [Qemu-devel] qemu-x86_64 on i386 host: SIGSEGV

[Peter Maydell]

On 24 March 2013 10:43, Michael Tokarev <address@hidden> wrote:
> $ ./x86_64-linux-user/qemu-x86_64 bash64
> qemu: uncaught target signal 11 (Segmentation fault) - core dumped
> Segmentation Fault

Are 64 bit linux-user guests on 32 bit hosts supposed to work?
I would expect them to be at best pretty unreliable.

> $ gdb x86_64-linux-user/qemu-x86_64
> (gdb) ru bash64
> Program received signal SIGSEGV, Segmentation fault.
> disas_insn (address@hidden, pc_start=18446744073699066880)
>     at target-i386/translate.c:4107
> 4107        b = ldub_code(s->pc);
> (gdb) p *s
> $1 = {override = -1, prefix = 1484501952, aflag = 1, dflag = 1484503884,
>   pc = 18446744073699066880, is_jmp = 0, cs_base = 0, pe = 1, code32 = 1,

PC is FFFFFFFFFF600400 so either we've messed it up already or this
is just "64 bit address space doesn't fit in a 32 bit one".

> Some binaries works - for example, gzip (it prints "qemu: Unsupported syscall:
> 202" on the way which is a different issue).

Yes. That is just the usual "x86 linux-user isn't really supported":
202 is TARGET_NR_futex, which works on other target archs but
won't on x86 until somebody actually fixes support for threaded
guests in x86 to at least the level it is for other targets.

-- PMM