Placing a global variable at a constant address

[Alexandre Dang]

Hello everyone,

I'm currently implementing my own version of SFI derived from nacl.
For that I need to have a global variable which address is

1. known at compile time.
2. aligned on its size (for masking purpose)

I have some ideas for that but I don't know if they are possible:

• Use a linker script to create a new section and put my global variable in this fixed address section.
  However I use sel_ldr, so I guess I need to do this step in sel_ldr code which might be a bit complex.
• Introduce some padding to have my section .data at a desired location.
  Section .data is preceded by the sections:
  
  1. .note.gnu.build-id (constant size and start at a fix address)
  2. .rodata
  3. .eh_frame (constant size?)
  4. .tdata
  5. .init_array (constant size in most cases I think)
     
  6. .fini_array (constant size in most cases I think)
  7. .got.plt (constant size)
  8. .data
     

  Hence I would put some extra data in the .tdata section to create a padding. However I don't really know the purpose of this section,
  I only know that in the disassembly it contains a variable called "impure_data".
  

Are my ideas possible or is there any simpler solution?

Thanks