Re: [Qemu-devel] [PATCH] cpu-exec(): also reload CPUClass *cc after longjmp return

[Juergen Lock]

On Fri, Oct 04, 2013 at 09:15:37AM +0200, Jan Kiszka wrote:
> On 2013-10-03 18:05, Peter Maydell wrote:
> > On 3 October 2013 23:09, Juergen Lock <address@hidden> wrote:
> >> Local variable CPUClass *cc needs to be reloaded after return from longjmp
> >> too.  (This fixes the mips-softmmu crash observed on FreeBSD when qemu is
> >> built with clang.)
> >>
> >> Signed-off-by: Juergen Lock <address@hidden>
> >> Found-by: Dimitry Andric <address@hidden>
> >>
> >> --- a/cpu-exec.c
> >> +++ b/cpu-exec.c
> >> @@ -681,6 +681,10 @@ int cpu_exec(CPUArchState *env)
> >>               * local variables as longjmp is marked 'noreturn'. */
> >>              cpu = current_cpu;
> >>              env = cpu->env_ptr;
> >> +#if !(defined(CONFIG_USER_ONLY) && \
> >> +      (defined(TARGET_M68K) || defined(TARGET_PPC) || 
> >> defined(TARGET_S390X)))
> >> +            cc = CPU_GET_CLASS(cpu);
> >> +#endif
> > 
> > This is a c compiler or libc bug -- the C standard says that this
> > local variable should not be trashed by the longjmp. We were
> > actually discussing removing the current workarounds there...
> 
> But we didn't decide if we should stop supporting the affected compiler
> versions.
> 
> Does this issue also exist with the latest clang version available for
> your platform?
> 
It happens with up to date clang as it's in FreeBSD 10.0-current
which is due for a release soon.  I think the clang folks are looking
into this issue but I don't know if a fix will make it into the
release...  (For now I've added the workaround to the FreeBSD
qemu-devel port.)

 Thanx,
        Juergen