Re: Missing backtrace information on aarch64

[Phil Reid]

On 19/03/2020 08:57, Stephen Hemminger wrote:
> On Thu, 19 Mar 2020 08:34:35 +0800
> Phil Reid <address@hidden> wrote:
>
> > On 19/03/2020 01:45, Stephen Hemminger wrote:
> > > Trying to use libunwind on Arm64 and discovered that it is not working
> > > as expected. Only one function is printed.
> > >
> > > On x86 Debian 10 (1.2.1-9)
> > > $ ./bt
> > > ^\Signal Quit recevied
> > > #0 0x5640deb47308 (sigquit+0x29)
> > > #1 0x7f4337b8587f (killpg+0x40)
> > > #2 0x7f4337c146f4 (nanosleep+0x14)
> > > #3 0x7f4337c1462a (sleep+0x3a)
> > > #4 0x5640deb4732c (main+0x1f)
> > > #5 0x7f4337b7209b (__libc_start_main+0xeb)
> > > #6 0x564
> > >
> > >
> > > On Arm64
> > >
> > > # /tmp/bt
> > > ^\Signal Quit recevied
> > > #0 0xab9f2f927bf0 (sigquit+0x34)
> > > Aborted (core dumped)
> > >    
> >
> > I patched gcc libs with the following for an 32bit arm system to get more 
> > complete backtraces.
> >
> >
> > diff -Naur a/libsupc++/eh_terminate.cc b/libsupc++/eh_terminate.cc
> > --- a/libstdc++-v3/libsupc++/eh_terminate.cc    2019-02-28 14:31:50.951261183 
> > +0800
> > +++ b/libstdc++-v3/libsupc++/eh_terminate.cc    2019-02-28 14:32:42.040396849 
> > +0800
> > @@ -40,7 +40,7 @@
> >    using namespace __cxxabiv1;
> >
> >    void
> > -__cxxabiv1::__terminate (std::terminate_handler handler) throw ()
> > +__cxxabiv1::__terminate (std::terminate_handler handler)
> >    {
> >      __try
> >        {
> > diff -Naur a/libsupc++/unwind-cxx.h b/libsupc++/unwind-cxx.h
> > --- a/libstdc++-v3/libsupc++/unwind-cxx.h       2019-02-28 14:31:50.949253953 
> > +0800
> > +++ b/libstdc++-v3/libsupc++/unwind-cxx.h       2019-02-28 14:32:53.073426806 
> > +0800
> > @@ -189,8 +189,7 @@
> >
> >    // Invokes given handler, dying appropriately if the user handler was
> >    // so inconsiderate as to return.
> > -extern void __terminate(std::terminate_handler) throw ()
> > -  __attribute__((__noreturn__));
> > +extern void __terminate(std::terminate_handler);
> >    extern void __unexpected(std::unexpected_handler)
> >      __attribute__((__noreturn__));
>
> But gcc backtrace already works on this platform, I am confused.

Do you me gdb backtrace or the gcc builtin functions?
gdb worked for me ok as well before the patch.

Any which way that's what I had to do.
I think the noreutrn attribute results in something getting
missed thats required for libunwind.



--
Regards
Phil Reid