Re: No .got section in ELF

[Andrew Haley <aph@redhat.com>]

yunfeng zhang wrote:
> The idea I got is about removing .got section in ELF format totally.
> 
> Before we go, let's see the limitation on the idea
> 1) It must be deployed on aligned segment model, such as Linux, which cs.start
> = ds.start.
> 2) Currently, I only know how to do on x86 ELF.
> 
> Here is a typical sample in PIC model (shared library) when library want to
> access its global data
>     ...
>     // Later code snippet template is used by gcc in almost all shared function
>     // to imitate `mov %ip, %ebx'.
>     call next:
> next:
>     pop %ebx // << A.
>     ...
>     movl new_offset(%ebx), %eax // << B. load global variable foo to eax.
>     ...
>     .global foo // << C.
> OK!, to ld, offsetof(C - A) is const, and to gcc offsetof(B - A) is also
> const, so to aligned segment model, new_offset = offset(C - A) - offset(B - A),
> right?

Surely not, because in a shared library the address of the data varies.  There
are in theory many copies of the library, each one with its r/w data in a different
place.

Andrew.