Hello All,
I have recently been working on adding both data and instruction scratch Pad
(SPM) in GEM5 FS simulation. I was able to add both of them alongside with
having L1-I and L1-D cache. The memory system now looks as in figure at
https://imgur.com/a/wUtUX
Since I am using FS mode, I can access the D-SPM and I-SPM using
open("/dev/mem") and mmap(). I-SPM is connected to both the instruction as well
as data port, so that we can write the program to it through data port and
execute and read through instruction port.
To test this, I compiled a helloworld program as a library which does not print
anything, but just returns an integer value. We access this library through
dlopen and the function in the library through dlsym. Then through function
pointer we copied the function to the I-SPM. Finally we jumped to the function
in I-SPM through a function pointer call. After this the program gets stuck and
does not proceed.
In the stats file I can see the write accesses (to copy the function to) the
SPM issued by cpu.data, but I don't see any read cpu.inst access to I-SPM. Can
someone suggest why the CPU does not read the I-SPM when I jump to the function
in it ?
NOTE: When using mmap() I do enable PROT_EXEC to mark I-SPM as executable
memory region.
Regards
Yasir
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