ELF Format

I am working on a assembler and linker (c++) for a specific microprocessor. I am using ELF format ( Executable and linking Format). I have very little documentation for the linker/assembler. I am having problem handling global variables in multiple obj file. i.e. the variable is defined in one file and can be used in other files. While assembler have scope of only one file how will the linker will know, in which file this global symbol is used.

I will be very thankful if some body supply me with some useful information

Regards!

nydhami