[ECOS] eCos / Redboot network sharing questions

[Barry Wealand <barry dot wealand at lmco dot com>]

Hi -

We're working with eCos and Redboot on a MIPS-like target.  Redboot is 
set up to be able to use an ethernet port, and most of our applications 
are built against a kernel that's been configured for network use as 
well.  While attempting to diagnose some difficulties with remote GDB 
operation, I observed that after the application starts up, Redboot 
performs all of its ethernet operations using the application's device 
driver.  Further investigation has shown that this sharing takes place 
via virtual vector 19.  I just spent some time browsing this mailing 
list, and it seems like this is the expected behavior.

That said, I have a couple of questions.

(1) It looks like this sharing continues to take place even after the 
application has exited and returned to Redboot (via 
CYGACC_CALL_IF_MONITOR_RETURN(0)), i.e., Redboot continues to use the 
application's device driver.  Is this also the expected behavior?  If 
so, then how does one go about reloading the same application, or 
loading another one (via TFTP)?  When we attempt to reload the same 
application (an S-record download), everything goes fine up until the 
initialized data associated with the appication's device driver gets 
rewritten by the download, at which point the driver dies (and so does 
the download and Redboot).  And of course, loading another application 
would be even worse, as the driver code (text) would get trashed during 
the download.  Is this normal?  Does this sharing of device drivers ever 
get shut down (short of maybe a "reset" command)?

(2) When I use GDB, I can connect to the target, download the program, 
set breakpoints, dump memory, etc., just fine initially.  I can even 
single-step through some of the early startup code in the program.  But 
if I try to, say, set a breakpoint within the program itself, and run to 
that breakpoint, GDB loses touch with the target.  I'm guessing that 
this happens when this driver sharing begins (presumably somewhere in 
the startup code).  Since it seems that this sharing of the driver is 
normal, I'll assume that we have some other bug to fix here.  (As 
another data point, if I build the same program against an eCos kernel 
with no network stack, I can use GDB to load that program, set 
breakpoints wherever I wish, and everything works fine.)

Thanks in advance for any assistance you can provide.

Barry Wealand
barry.wealand@lmco.com



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