Re: Running "eprommed" code

["Frank Ch. Eigler" <fche at redhat dot com>]

Hi -

On Thu, Apr 24, 2003 at 03:01:02PM -0400, Brandon Warhurst wrote:
> I asked a question a while back about running "precompiled" (aka, only 
> binary image, no source) code.  You gave me a good answer.  I finally 
> got sid up and running.  The question is: how do I point SID to the 
> first instruction to execute?  Is that where the insn-count option comes 
> in?  I have scoured the documentation to no avail on this point.  I've 
> only found a reference to setting the !run pin.  Am I going to have to 
> compile some sort of startup program?  

This is tricky.  In the hardware, presumably the ROM sits in a memory
range that includes the powerup-reset PC address.  If you do the same
with sid, it should just work.  If on the other hand your ROM is
not complete, you indeed need to find a way of jumping into whatever
entry point the ROM has.  A related problem is just how much
initialization does your ROM thingie assume to have taken place?


> (This may be a problem seeing as 
> I can't seem to compile a cross-compiler to save my life.  It ALWAYS 
> fails for one reason or another.  Especially the arm-elf target.  It 
> seems to not find the correct assembler (which I apparently can 
> compile).  I cannot force it through any configure options to locate the 
> assembler it should use once it has built xgcc.  Actually, if I remember 
> correctly, after stage1, it shouldn't even build stage 2 because stage 2 
> is built with stage 1 meaning I couldn't even run it anyway.  But for 
> some reason it wishes to build stage 2.

You can try building out of the sources.redhat.com "uberbaum", which
contains an integrated source tree for gcc, binutils, the lot.  The
stage2/3 thing shouldn't occur if you configured the build tree with
the usual "--target=arm-elf" option.


> Anyway, I think I'm much closer if I can just figure out how to start 
> SID running the code and get GDB in there, I'll get exactly what I want. 

With GDB, this is possible without extra startup binaries.  Start sid as
before, but add the "--gdb=PORT#" argument, and connect an arm-elf-gdb
instance there.  SID will just sit there, before startup.  Then you can
issue a PC change from within GDB, as in something like:

   (gdb) jump * 0xdeadbeef


- FChE