Re: [Tinycc-devel] x86_64 static link fix

[Michael Matz]

Hi,

On Wed, 9 Jan 2019, Kurt Nalty wrote:

> After firing up gdb, and tracing through a few combinations of static and 
> dynamically linked object files, I have determined that the segfaults were due 
> to usage of procedure linking tables
> (.plt) with the statically linked process. The plt addresses are not corrected  
> when static loaded, but are corrected during dynamic linking. File 
> x86_64-gen.c, lines
> 630-634 were
>
> #ifdef TCC_TARGET_PE
>            greloca(cur_text_section, vtop->sym, ind + 1, R_X86_64_PC32, 
> (int)(vtop->c.i-4));
> #else
>            greloca(cur_text_section, vtop->sym, ind + 1, R_X86_64_PLT32, 
> (int)(vtop->c.i-4));
> #endif
>
> and are replaced by
>            greloca(cur_text_section, vtop->sym, ind + 1, R_X86_64_PC32, 
> (int)(vtop->c.i-4));
>
> This restores correct static linking in uClibc-0-9.30 and musl 
> environments. Dynamic linking is unaffected, and continues to use 
> procedure link table jumps and calls.

It's still wrong.  The relocation to use really should be PLT32, even 
though it doesn't often make a difference (*).

I've now found time to look into this, i.e. static linking with uClibc.  I 
fixed some problems in mob and reverted your patch again.  A simple hello 
world now works statically with uClibc.  Would be nice if you can retry 
(and maybe with bigger examples :) ).


Ciao,
Michael.
* it's a historic mistake of the initial x86-64 psABI implementations that 
PC32 relocs are sometimes used in place of PLT32 relocs (or from a 
different point of view, that both relocations exist, and not only PC32).