Re: ld generates static relocations in shared library

[Thomas Schmid <scth2000 at yahoo dot de>]

Hi,

does anyone have an idea on this?
Is there any documentation which describes, which relocations have to be handled by the loader?


Regards,
Tom


binutils-owner@sourceware.org wrote:

> Von: Thomas Schmid <scth2000@yahoo.de>
> An: "binutils@sourceware.org" <binutils@sourceware.org>
> Datum: 25.07.2013 16:54
> Betreff: ld generates static relocations in shared library
> Gesendet von: binutils-owner@sourceware.org
> 
> Hi, 
> I have a question concerning the relocations
generated by the linker:
> 
> If I compile the example code at the bottom with
> 
>     arm-elf-gcc init.c -o lib.so -Wl,-shared -nostdlib
> 
> I get a shared library with some relocations (readelf lib.so -r):
> 
>     0000032c  00000d02 R_ARM_ABS32       000004b8   plpv1
>     00000330  00001302 R_ARM_ABS32       00000000   lpv2
>     000004b8  00000b02 R_ARM_ABS32       00000000   lpv1
> 
> Till now I believed, that the linker resolves all static relocations
> and generates dynamic relocations (to be handled by the loader), 
> where it is necessary. 
> Why are there static relocations left in the linker output? 
> The document "ELF for the ARM Architecture"
at
> http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044e/IHI0044E_aaelf.pdf
> says, R_ARM_ABS32 is a static relocation and also:
> 
> > Static relocations are processed by a static linker; they are 
> normally either fully resolved or used to produce dynamic relocations 
> 
> > for processing by a post-linking step or a dynamic loader. A well 
> formed image will have no static relocations after static linking 
> 
> > is complete, so a post-linker or dynamic loader will normally only
> haveto deal with dynamic relocations.
> 
> BTW, this can also be reproduced using i386-elf-gcc, the static 
> relocation used there is R_386_32.
> 
> Can anyone tell me, why and tell me, which relocations should really
> be handled in the loader? 
> In the meantime, I was told to use the option "-fPIC" - which in 
> fact doesn't help, also
after that a static relocation (R_ARM_ABS32)
> is left in the library. 
> 
> Thanks in advance!
> 
> 
> Example code:
> 
>     extern unsigned char lpv1;
>     extern unsigned char lpv2;
> 
>     unsigned char* plpv1 = &lpv1;
> 
>     void func(void)
>     {
>         lpv2 = *plpv1;
>     }