cross-compiling & debugging embedded-linux apps

[Alan Mimms]

You know about the ldd command?  Do 'ldd bjs1-shared' to see what 
libraries you need for your shared executable and make sure they're 
there and built with no floating point.  When you compile and link, 
you're using '-mcpu=860' or '-msoft-float', right?  That also could be 
a problem for you.

I think the seg fault is what Dan's kernel maps the floating point 
handler's exception to - it's really a floating point exception.  I 
COULD be wrong about this.  It's one fo the things I have been meaning 
to look into but haven't yet had the chance.

(Caveat emptor on the above - I'm just a beginner myself.)

a

>>>>>>>>>>>>>>>>>> Original Message <<<<<<<<<<<<<<<<<<

On 12/30/99, 8:50:29 PM, Brendan J Simon <Brendan.Simon at ctam.com.au> 
wrote regarding cross-compiling & debugging embedded-linux apps:


> I have a powerpc embedded system (MPC860, 4MB Flash, 16MB RAM, 
ethernet,
> rs232).  I have compiled the kernel and can boot it using a root
> filesystem via initrd or nfs.  The root filesystem is a minimal one 
that
> was on the linuxppc-embedded ftp site.  It basically has /bin/sh,
> /bin/ls and a few libraries in /lib.

> I NEED to be able to compile apps from the sources.  I have managed to
> cross-compile ncurses and bash.  I can't get bash to run at all (even 
a
> statically compiled version).  I get segmentaion faults.  I'm 
currently
> using SASH which I have cross-compiled as a static binary.  I compiled 
a
> test app (bjs1.c) which outputs a string every second.  It is compiled
> as a static binary (bjs1-static) and a shared binary (bjs1-shared).  
The
> static binary works but the shared one does not.  I assume it is some
> library problem but I can't figure out what.  The output of the sash
> session is below.

> Stand-alone shell (version 1.0)
> > ./bjs1-static
> BJS1: Brendan was here
> BJS1: Brendan was here
> BJS1: Brendan was here
> pid 7: killed (signal 2)
> >
> > ./bjs1-shared
> pid 8: killed (signal 11)
> >

> I have all the libraries on the root filesystem.  The rpc.nfsd daemon
> seems to read the entire file but sash says the process is killed with
> signal 11 (segmentation fault).  I have no idea how to debug this.  I
> don't think there is a simulator for the mpc860 as part of gdb.  Is
> there a way of debugging this on the target with powerpc-gdb and an
> ethernet or serial connection ?

> How does the kernel know where to look for libraries ?  I assume there
> are some default locations like /lib.  I haven't got an ld.so.conf 
setup
> nor do I have ldconfig.

> It can't be that hard to get a simple 10 line program to execute as a
> shared binary.  It must be something really simple that I am missing.

> Thanks for any help,
> Brendan Simon.


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