[libunwind] Add proper support for DWARF unwind on bare metal.
Right now, ARM EHABI unwind on bare metal expects to find the symbols
__exidx_start and __exidx_end defined, and uses those to locate
the EH tables. However, DWARF unwind on bare metal expects to find
dl_iterate_phdr, which, although possible to provide, is inconvenient
and mildly absurd.
This commit provides feature parity with ARM EHABI unwind by looking
for symbols __eh_frame_start, __eh_frame_end, __eh_frame_hdr_start
and __eh_frame_hdr_end, denoting the start and end of the sections
with corresponding names. As far as I know, there is no de jure or
de facto ABI providing any such names, so I chose the obvious ones.
The .eh_frame_hdr support is optional for maximum flexibility and
possible space savings (e.g. if libunwind is only used to provide
backtraces when a device crashes, providing the .eh_frame_hdr, which
is an index for rapid access to EH tables, would be a waste.)
The support for .eh_frame_hdr/DWARF index in the first place is
conditional on defined(_LIBUNWIND_SUPPORT_DWARF_INDEX), although
right now config.h will always define this macro.
The support for DWARF unwind on bare metal has been validated within
the ARTIQ environment[1].
[1]: https://m-labs.hk/artiq/
git-svn-id: https://llvm.org/svn/llvm-project/libunwind/trunk@321445 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed
