Fwd: configuring memory size

[gregory.menke at gsfc.nasa.gov]

Its not hard to override the linkscript supplied by the bsp.  One
starting point is to copy linkcmds from the installed RTEMS tree &
modify it as required, then adjust the link step to use it instead.  Or,
just rename the old one and put the new one in its place.  That presents
a CM problem of course but it might save you from tedious makefile judo.

Regards,

Greg



D. Peter Siddons writes:
 > Thanks everyone for your input. I had no idea I was opening such a can 
 > of worms :) My initial hope was that a simple declaration somewhere in 
 > my application code or build system could override the linkcmds 
 > definitions in RTEMS; that would have been perfect. It seems not to be 
 > possible. Oh well...
 > Pete.
 > 
 > 
 > gregory.menke at gsfc.nasa.gov wrote:
 > 
 > >That approach presents problems when there are very tight & specific
 > >requirements on how an application is laid out in memory.  Further, its
 > >not unreasonable for memory mapped peripherals or missing regions of
 > >memory space to be in the way and if thats the case, memory detection
 > >algorithms might well cause a good deal of trouble.
 > >
 > >That said, any such provision for bizarre link scripts and memory sizing
 > >should probably be made by the user project and not be built into the
 > >RTEMS kernel.  So a reasonable compromise might be to arrange a default
 > >linker script and memory map, which the user can override.  But I would
 > >strongly disagree that mandatory automatic memory detection should be
 > >encouraged unless its particularly suited to a given architecture.
 > >
 > >Greg
 > >
 > >
 > >
 > >Ed Sutter writes:
 > > > Can't disagree there!
 > > > :-)
 > > > Ed
 > > > 
 > > > Till Straumann wrote:
 > > > 
 > > > > Sorry for the urge I feel to repeat myself.
 > > > > IMO, the whole approach of creating multiple linker scripts and binaries,
 > > > > one for each memory / board configuration is bad.
 > > > > A single instance should perform a run-time check and configure the
 > > > > workspace and heap according to the amount of memory detected.
 > > > > 
 > > > > T.
 > > > > 
 > > > > Ed Sutter wrote:
 > > > > 
 > > > >> Peter,
 > > > >> If you're looking for alternatives, then I also have a homegrown tool
 > > > >> that I use for this.  Very trivial, but does what I want, essentially
 > > > >> replacing a few sed/awk script with something that keeps everything to 
 > > > >> one
 > > > >> simple command line.
 > > > >> The purpose is slightly different than Thomas's, so you'll have several
 > > > >> options!  The purpose is to maintain the address information for the 
 > > > >> linker
 > > > >> file in my makefile as a variable.  Then the variable can be included in
 > > > >> CFLAGS if needed, along with being used as input to a template that 
 > > > >> creates
 > > > >> the final linker command file.
 > > > >> Anyway, the tool (called vsub) is included in the MicroMonitor source 
 > > > >> distribution
 > > > >> at http://www.microcross.com/html/micromonitor.html, or I can just send
 > > > >> you the source for that alone.
 > > > >> Lemme know if you want it.
 > > > >> Ed
 > > > >>
 > > > >> Thomas Doerfler wrote:
 > > > >>
 > > > >>> Hi,
 > > > >>>
 > > > >>> just as an additional idea: Some years ago I used the C preprocessor 
 > > > >>> to generate linker command files from a template. The benefit was, 
 > > > >>> that I could have ONE header file defining address/size information 
 > > > >>> for the C compiler and for the linker.
 > > > >>>
 > > > >>> Maybe this would also be convenient for Peter?
 > > > >>>
 > > > >>> wkr,
 > > > >>> Thomas.
 > > > >>>
 > > > >>>
 > > > >>> D. Peter Siddons wrote:
 > > > >>>
 > > > >>>> Hi Till,
 > > > >>>> The bsp is very similar to the uC5282. _M68k_Ramsize is copied from 
 > > > >>>> the linker value (_Ramsize) in bsp_start() (part of bspstart.c). I 
 > > > >>>> could easily check for the two possibilities here. Is that early 
 > > > >>>> enough?
 > > > >>>> Pete.
 > > > >>>>
 > > > >>>> Till Straumann wrote:
 > > > >>>>
 > > > >>>>> Eric Norum wrote:
 > > > >>>>>
 > > > >>>>>>>
 > > > >>>>>>> Looks like what I suggested won't work.   The linker complains 
 > > > >>>>>>> if  the expressions in the  ORIGIN/LENGTH contain symbols even if 
 > > > >>>>>>> those  symbols have been defined before the assignment.
 > > > >>>>>>>
 > > > >>>>>>> I guess that you'll need to have two separate linkcmds files and  
 > > > >>>>>>> use something like
 > > > >>>>>>>     -Wl,-TlinkcmdsFor4MFlash
 > > > >>>>>>> or
 > > > >>>>>>>     -Wl,-TlinkcmdsFor16MFlash
 > > > >>>>>>
 > > > >>>>>>
 > > > >>>>>>
 > > > >>>>>>
 > > > >>>>>>
 > > > >>>>>>
 > > > >>>>> A much better solution would be enhancing the BSP so it does
 > > > >>>>> auto-detection. This has to be performed early enough,though.
 > > > >>>>>
 > > > >>>>> If an early detection is too cumbersome, then you can limit
 > > > >>>>> the initial size to a minimum, let's say 4M and increase the
 > > > >>>>> size later. In order to make the additional ram available to
 > > > >>>>> RTEMS (i.e., after the malloc heap/libc have been initialized)
 > > > >>>>> you have to implement a trivial 'sbrk()'. The only constraint
 > > > >>>>> is that the 'late ram'-portion of the heap to be added by sbrk()
 > > > >>>>> must be contiguous to the initial heap.
 > > > >>>>>
 > > > >>>>> You can look at powerpc/shared/bspstart which uses the
 > > > >>>>> two-staged heap approach for different reasons.
 > > > >>>>>
 > > > >>>>> HTH
 > > > >>>>> T.
 > > > >>>>>
 > > > >>>>>>>
 > > > >>>>>>>
 > > > >>>>>>>>
 > > > >>>>>>>> Eric Norum wrote:
 > > > >>>>>>>>
 > > > >>>>>>>>>> You need to pass the --defsym option to the linker.
 > > > >>>>>>>>>>
 > > > >>>>>>>>>> On the compile line, add something like
 > > > >>>>>>>>>>     -Wl,--defsym,_RamSize=0x10000000
 > > > >>>>>>>>>>
 > > > >>>>>>>>>> On Dec 2, 2005, at 10:50 PM, D. Peter Siddons wrote:
 > > > >>>>>>>>>>
 > > > >>>>>>>>>>> I have two boards which are identical except for the amounts  
 > > > >>>>>>>>>>> of  flash and RAM. The linkcmds file has definitions for 
 > > > >>>>>>>>>>> these   parameters like:
 > > > >>>>>>>>>>> _RamSize = DEFINED(_RamSize) ? _RamSize : 0x7f0000;
 > > > >>>>>>>>>>>
 > > > >>>>>>>>>>> so my question is, can I invoke a definition somewhere in 
 > > > >>>>>>>>>>> the   application make process to override the one in 
 > > > >>>>>>>>>>> linkcmds? If  so,  how and/or where?
 > > > >>>>>>>>>>>
 > > > >>>>>>>>>>> Pete.
 > > > >>>>>>>>>>
 > > > >>>>>>>>>>
 > > > >>>>>>>>>>
 > > > >>>>>>>>>>
 > > > >>>>>>>>>>
 > > > >>>>>>>>>>
 > > > >>>>>>>>>>
 > > > >>>>>>>>>>
 > > > >>>>>>>
 > > > >>>>>>> -- 
 > > > >>>>>>> Eric Norum <norume at aps.anl.gov>
 > > > >>>>>>> Advanced Photon Source
 > > > >>>>>>> Argonne National Laboratory
 > > > >>>>>>> (630) 252-4793
 > > > >>>>>>>
 > > > >>>>>>>
 > > > >>>>>>
 > > > >>>>>
 > > > >>>>>
 > > > >>>
 > > > >>>
 > > > > 
 > > > 
 > >
 > >
 > >  
 > >
 >