anjiahao1 commented on PR #19536:
URL: https://github.com/apache/nuttx/pull/19536#issuecomment-5100614395

   > > @anjiahao1 already add ELF XIP last year, but deploy only on ROMFS and 
LROFS (Lightweight Read-Optimized writable FS): 
https://github.com/open-vela/nuttx/tree/dev/fs/lrofs lrofs has the same idea as 
xipfs, but lrofs disk layout is binary compatible with ROMFS.
   > 
   > I didn't know about that repo, I could have used LROFS then. I will 
investigate and compare.
   > 
   > @anjiahao1 can you run multiple (independent) instances of the same ELF 
PIC module (with XIP) in a no-MMU system? Do they share .text, but have 
separate .data?
   > 
   > > Let wait you comparing the difference between FDPIC ELF and XIP ELF.
   > 
   > If standard ELF PIC works with XIP on non-MMU systems, then I think we 
don't need FDPIC ELF. The code is done already so I will open the PR soon.
   > 
   > > OK, it's fine to merge this pr first, and work on XIP ELF and FDPIC ELF 
next.
   > 
   > Thank you!
   
   Yes, the current ELF PIC implementation targets no-MMU systems. In 
mps3-an547:picostest, ostest is compiled as a PIC ELF executable. On the 
MPS3-AN547 (an Arm Cortex-M platform without an MMU), r10 is used as the GOT 
base register for data accesses. This enables multiple instances to share a 
single .text section while each instance maintains its own .data section.


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