foss-for-synopsys-dwc-arc-processors/embarc_osp

GNU build sets GP to _f_sdata instead of __SDATA_BEGIN__

iguryanov opened this issue · 0 comments

iguryanov commented

Issue Summary

  • Type: Bug
  • Category: Library
  • Priority: Low
  • Release Version: 2019.06

Bug

Development Environment

  • HOST OS
    All OS

  • TOOLCHAIN
    ARC GNU 2020.03=9.

  • BOARD
    Customer's board, irrelevant.

  • ARC CORE
    EM9D.

Bug Description

gcc builds use linker scripts with both _f_sdata and __SDATA_BEGIN__.
Normally they are the same in our scripts.
Native GNU toolchain startup uses __SDATA_BEGIN__ to configure %GP register.
But embARC startup sticks to MWDT agreement and uses _f_sdata.

This works ok until user decides to put __SDATA_BEGIN__ in the middle of the section to extend it's range.
(GP-based offset is signed). And linker uses __SDATA_BEGIN__ to calculate relocations and actual offsets.

So when user changes related line in the script to something like this - __SDATA_BEGIN__ = . + 0x100;
small data access becomes wrong. Runtime offsets will be 0x100 less (easily driving into negative zone),
while startup still sets %GP to the beginning of small data section.

Question

Is it possible to change arc_startup.s in a way that for GCC builds it will choose __SDATA_BEGIN__ for GP?