load-time ELF relocation

Question

I am writing a simple user-space ELF loader under Linux (why? for \'fun\'). My loader at the moment is quite simple and is designed to load only statically-linked ELF files con

Answer 1

I don't see any way you can do that, unless you emulate the kernel-provided virtual address space completely, and run the code inside that virtual space. When you mmap the data section from the file, you are intrinsically relocating it to an unknown address of the virtual address space of your ELF interpreter, and your code will not be able to reference to it in any way.

Glad to be proven wrong. There's something very cool to learn here.

Answer 2

If you modify the absolute addresses available in the .got section, (global offset table) your program should work. Make sure to modify the absolute address calculation to cater for the new distance between .text and .data, I'm afraid you need to figure out where this information comes from, for your architecture.

See this: Global Offset Table (Processor-Specific)

Good luck.