ARM FDPIC port

Pedro Alves palves@redhat.com
Wed Dec 12 16:21:00 GMT 2018


Hi!

I believe that Rick Felker [added] was working on fdpic for yet another port too
a few months ago?  It'd be very nice if a single solib-fdpic.c worked
for everyone.

Thanks,
Pedro Alves

On 12/06/2018 02:47 PM, Christophe Lyon wrote:
> Hi!
> 
> 
> Some of you may have noticed that I am in the process of upstreaming the ARM-FDPIC toolchain we developed a few years ago.
> 
> As a reminder, FDPIC is used to run Linux on MMU-less systems.
> 
> A major difference with the existing Linux port is that functions are referred to by a function descriptor (FD) consisting of 2 words: the function address, and the address of the GOT associated with the shared object executing the function.
> 
> 
> So far, QEMU, binutils and uclibc-ng patches have been merged, and while I'm waiting for review of the GCC patches, I thought I could give a look at the GDB patches :-)
> 
> 
> GDB supports FDPIC on FRV, but I'm not sure how well maintained it is?
> 
> 
> Since I haven't contributed to GDB for several years, I'd like some guidance on how to proceed to update our patches. The main change is the addition of solib-fdpic.c, which has a lot of similarities with solib-frv.c. I'm wondering whether I should first remove FRV dependencies in solib-frv.c, probably rename it into solib-fdpic.c and make the ARM port use it with the appropriate hooks, or if I should rather add our new solib-fdpic.c file after updating it to the new C++ coding style GDB has adopted since we worked on it?
> I've noticed that solib-frv.c has some dependencies in frv-tdep.c, which I don't understand why they aren't in frv-linux-tdep.c instead?
> 
> Another thing I'm considering is that since the Linux kernel is able to load FDPIC binaries (if configured to do so) even on MMU-enabled systems, should I make arm-linux-gnueabi-gdb able to handle FDPIC binaries, or restrict that possibility to arm-uclinuxfdpiceabi-gdb ? Is it possible/desirable to link solib-svr4.c and solib-fdpic.c into the GDB executable at the same time?
> 
> For reference, our old branch is available on github: https://github.com/mickael-guene/gdb/commits/gdb-7.5.1-fdpic-m
> 
> Thanks,
> 
> Christophe
> 



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