When the linker evaluates an expression, the result is either absolute or relative to some section. A relative expression is expressed as a fixed offset from the base of a section.
The position of the expression within the linker script determines whether it is absolute or relative. An expression which appears within an output section definition is relative to the base of the output section. An expression which appears elsewhere will be absolute.
A symbol set to a relative expression will be relocatable if you request relocatable output using the -r option. That means that a further link operation may change the value of the symbol. The symbol's section will be the section of the relative expression.
A symbol set to an absolute expression will retain the same value through any further link operation. The symbol will be absolute, and will not have any particular associated section.
You can use the builtin function ABSOLUTE to force an expression
to be absolute when it would otherwise be relative. For example, to
create an absolute symbol set to the address of the end of the output
section .data:
SECTIONS
{
.data : { *(.data) _edata = ABSOLUTE(.); }
}
If ABSOLUTE were not used, _edata would be relative to the .data section.