[parisc-linux] -fPIC position independent code on parisc
Randolph Chung <email@example.com>
Sun, 27 Apr 2003 13:12:19 -0700
> but what exactly is position independent code?
it's exactly what it says, it will work no matter at what position
the code is loaded.
> 18 ldil LR'.LC0,%r19
> 19 ldo RR'.LC0(%r19),%r26
> 20 bl printf,%r2
This loads the address of .LC0 (your string) relative to a fixed address
into r26 (arg0). The address is resolved statically at link time, so
if the code is moved to a different starting address, the address will
> 21 addil LT'.LC0,%r19
> 22 ldw RT'.LC0(%r1),%r1
> 23 copy %r1,%r26
> 24 bl printf,%r2
This calculates the offset of .LC0 relative to the linkage table pointer
(r19) by creating a GOT entry. The linkage table pointer is assigned
value at runtime based on where the dynamic loader loads the code into
memory, so the load will always point to the the right place wherever
it is loaded.
When you have a shared library, different programs that are linked
against the library may load it at different offsets, so the code must
be position independent for it to work.
Debian GNU/Linux Developer, hppa/ia64 ports