[uClibc] thumb toolchain

[Dave Hylands]

Hi David,

There were a couple of patches posted recently (around Feb 22-24, 2004)
on the linux-arm-kernel list
http://www.arm.uk.linux.org/armlinux/mailinglists.php
which had some kernel patches relating to running thumb code.

I think that the thread starts here:
http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2004-February/0
19765.html

Make sure you read the entire thread.

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/

> -----Original Message-----
> From: uclibc-bounces at uclibc.org 
> [mailto:uclibc-bounces at uclibc.org] On Behalf Of David Muse
> Sent: Wednesday, March 03, 2004 3:46 PM
> To: uclibc at uclibc.org
> Subject: [uClibc] thumb toolchain
> 
> 
> Hello,
> 
> I've been hacking for a few days, trying to put together a 
> thumb-linux-uclibc toolchain.  That is, a uclibc toolchain 
> for linux where the tools generate thumb code and the 
> libraries are thumb code.
> 
> First, is anyone else working on this?
> 
> Second, I've been having a little trouble... I'm running a 
> montavista linux 2.4.18 kernel which alledges to have support 
> for thumb system calls but I can't even get very simple 
> assembly programs (that don't even make system calls) to run 
> without segfaulting.  I'm not terribly experienced with raw 
> assembly, so I may be doing something dumb, but does anyone 
> out there know of any thumb-related problems with that kernel 
> or other kernels?  Can anyone recommend a kernel where thumb 
> code is known or believed to run?
> 
> As far as hacking on the toolchain, here's what I've done so far:
> 
> binutils:
> 	nothing, when compiled for an arm target, as can 
> allegedly create thumb code when passed -mthumb
> 
> gcc:
> 	in gcc/config/arm/t-linux:
> 		added a MULTILIBS definition for mthumb, to 
> build mthumb versions of libgcc,crtbegin,crtend
> 		added a lib1asm functions that thumb code 
> requires to the LIBASM1FUNCS
> 
> uclibc:
> 	added new system call semantics for thumb: the system 
> call number is passed in r7 instead of in the swi parameter
> 	add #if defined(__thumb__) in most places where #if 
> defined(__arm__) is called
> 
> gcc and uclibc:
> 	add #ifdef __thumb__'s and (presumed) equivalent 
> thumb-specific code for wherever arm assembly code is used
> 
> 
> I've had moderate success getting everything to build so far. 
>  I still get some undefined symbols when trying to link 
> libc.so and a few complaints about arm calls to thumb 
> functions, but hopefully I'll be able to work through those 
> issues soon.
> 
> Am I on the right track?  I'm I missing anything signifigant?
> 
> Does anyone know of a good arm/thumb emulator/debugger that 
> can run on x86 linux?
> 
> Thanks,
> 
> David Muse
> dmuse at 4accesscommunications.com
>