[libunwind] Add an interface for dynamic .eh_frame registration

The libgcc runtime library provides __register_frame and
__deregister_frame functions, which can be used by dynamic code
generators to register an .eh_frame section, which contains one or
more Call Frame Information records, each consisting of a Common
Information Entry record followed by one or more Frame Description
Entry records. This libunwind library also provides __register_frame
and __deregister_frame functions, but they are aliases for
__unw_add_dynamic_fde and __unw_remove_dynamic_fde and thus can only
take a single FDE.

This patch adds __unw_add_dynamic_eh_frame_section and
__unw_remove_dynamic_eh_frame_section functions which explicitly use
the .eh_frame format. Clients such as the ORCv2 platform and runtime
can check for these functions and use them if unwinding is being
provided by libunwind, or fall back to __register_frame and
__deregister_frame if unwinding is provided by libgcc.

Reviewed By: lhames

Differential Revision: https://reviews.llvm.org/D111863

GitOrigin-RevId: bab39816085d715e52c2131fa249ccd10178764b
3 files changed
tree: f958a05fc96830a33b032109b3434f03b187f96c
  1. .clang-format
  2. CMakeLists.txt
  3. LICENSE.TXT
  4. cmake/
  5. docs/
  6. include/
  7. src/
  8. test/