Stack area - Load and Run (Linker Command File)

Hi,

I have an application whose DataMemory clashes with the DataMemory of
my Bootloader.
So, I have thought of shifting the Applications Datamemory mapping.
Now, i have rempped it.  But, When my application starts, the the MMU
is disabled & The MMU is enabled inside the application only. So, there

is a situation that my stack will be pointing to one location when the
MMU is disabled and will get pointed to another location when i enable
the MMU inside my application for my requirements.


So, i have thought of using 'load' and 'run' facilities in the CMD
file(Linker command file) . Now, as long as my application has not
enabled the MMU, it will be pointing to the physical area (Load area),
and as soon as my application enables the MMU, it will be pointing to
the virtual memory area(Run Area) .

After the changes, i find that the application behaves abnormally. So,
i suspect
if the stack has some issues.

Can i assign Stack area as 'load' and 'run' type in CMD
file(Linker command File) ? Will my application be able to retreive the

proper values when it gets switched between the 'MMU Enabled' and 'MMU
Disabled' modes ?    Any problems if i implement Stack in that manner ?


Thx in advans, 
Karthik Balaguru

karthikbg wrote:
> Hi,
>
> I have an application whose DataMemory clashes with the DataMemory of
> my Bootloader.
> So, I have thought of shifting the Applications Datamemory mapping.
> Now, i have rempped it.  But, When my application starts, the the MMU
> is disabled & The MMU is enabled inside the application only. So, there
>
> is a situation that my stack will be pointing to one location when the
> MMU is disabled and will get pointed to another location when i enable
> the MMU inside my application for my requirements.
>
>
> So, i have thought of using 'load' and 'run' facilities in the CMD
> file(Linker command file) . Now, as long as my application has not
> enabled the MMU, it will be pointing to the physical area (Load area),
> and as soon as my application enables the MMU, it will be pointing to
> the virtual memory area(Run Area) .
>
> After the changes, i find that the application behaves abnormally. So,
> i suspect
> if the stack has some issues.
>
> Can i assign Stack area as 'load' and 'run' type in CMD
> file(Linker command File) ? Will my application be able to retreive the
>
> proper values when it gets switched between the 'MMU Enabled' and 'MMU
> Disabled' modes ?    Any problems if i implement Stack in that manner ?
>
>
> Thx in advans,
> Karthik Balaguru

Hi,
I got some special tricks for the Linker Scripts for a non-contiguous
memory map in which
i can distribute code or data among more than one memory area.

MEMORY
   {
      PR_MEM1: origin = 0a000h, length = 0500h;
      PR_MEM2: origin = 0d000h, length = 0300h;
   }

   SECTIONS
   {
      .text_1: { test1.obj(.text), test2.obj(.text), test3.obj(.text) }
> PR_MEM1
      .text_2: { test4.obj(.text), test5.obj(.text) } > PR_MEM2
   }

Another trick of splitting the output sections among multiple memory
areas to automatically achieve an efficient allocation of the output
section among several memory areas as below :

SECTIONS
   {
      .text: { *(.text) } >> PR_MEM1 | PR_MEM2
   }


But, i have many other queries.  Consider the below scenario.
Application 'A' gets loaded first and starts running.
After application 'A' starts to run, Application 'B' gets loaded and
starts running.

Consider that application 'A' has for following memory map
Data_Mem -> 0x20001000 to 0x20006000  (Though so much is allocated,
this application 'A'  actually uses only upto 0x20002000 in runtime -
This info, i collected from MAP file) ( Has the
bss,stack,bss,data,idata )

Application 'B'  has the following memory map.
Data_Mem -> 0x20001000 to 0x20006000  (This uses only upto 0x20004000
in runtime).( Has the bss,stack,bss,data,idata )

Though both application A and Application B point to same memory area
w.r.t Data_Mem,
from the above it is clear that there is some memory area unused by
application A that can be used by application B.
How to tell the Application B to take the unused memory space of the
Application A. ?

Is there any feature for doing that in Linker Scripts ?
If we allocate certain regions via Linker Scripts, is it not possible
to allocate some part of that region to other module ?

I thought 'Load' and 'Run' feature can be used. But, i find that they
both allocate separate memory blocks and so result in wastage of usable
area.

In short, How to do Dynamic Memory Usage using Linker Script
Programming ?

Thx in advans,
Karthik Balaguru