[LLVMdev] [lld] TBSS wrong size

[Shankar Easwaram]

Are you saying it generates wrong section size?  Tbss is very special and I checked the behavior on X86_64 to model it. It does not account for virtual address increase as libc allocates it.


> On Jun 2, 2015, at 17:20, Adhemerval Zanella <adhemerval.zanella at linaro.org> wrote:
> 
> Hi,
> 
> I am tracking some TLS issues with lld and found that it is
> generating wrong tbss size for case where multiple modules
> have non initialized threads variables.  For instance:
> 
> -- t0.c --
> 
> __thread int x0;
> __thread int x1;
> __thread int x2;
> 
> extern __thread int e0;
> extern __thread int e1;
> extern __thread int e2;
> extern __thread int e3;
> 
> int foo0 ()
> {
>  return x0;
> }
> 
> int main ()
> {
>  return x0;
> }
> 
> -- t1.c --
> 
> __thread int e0;
> __thread int e1;
> __thread int e2;
> __thread int e3;
> 
> ---
> 
> lld is generating (for aarch64):
> 
>  [14] .tbss             NOBITS           0000000000401000  00001000
>       0000000000000010  0000000000000000 WAT       0     0     4
> 
> Where is just taking in consideration the largest tbss segment, not all
> from all objects.  ld generates a correct output:
> 
>  [17] .tbss             NOBITS           0000000000410dec  00000dec
>       000000000000001c  0000000000000000 WAT       0     0     4
> 
> My initial idea is that 'lib/ReaderWriter/ELF/SegmentChunks.cpp' / 
> Segment<ELFT>::assignVirtualAddress is setting wrong slice values, however
> playing with this I could not find a correct logic to handle the TBSS.
> 
> Any ideas where lld is possible messing the TBSS segments sizes?