1. Extend MAX_BACKTRACE_FRAMES to 256, as we can have callchains
with length near 256 when recording Android applications.
2. .eh_frame and .ARM.exidx doesn't know how to unwind from instructions
setting up or destroying stack frames. It can lead to wrong callchains,
which may contain pcs outside executable mapping areas. Stop unwinding
once this is detected.
3. Some CIE entries in .eh_frame/.debug_frame suggest unwinder reading
personality routine from memory. However, that is not available in
offline unwinding, and leads to ACCESS_MEM_FAILED error. Work around
this by returning all zero data when failed to read data for some
addresses.
4. Some libraries have empty .eh_frame_hdr but valid .eh_frame.
Work around this by building eh_frame_hdr manually.
5. Prefer to use .debug_frame than .eh_frame. Because the former
can unwind instructions setting up and destroying stack frames.
Bug: http://b/69383534
Test: run backtrace_test.
Test: run simpleperf on some apps.
Change-Id: I62dddda3865dd567c6be150ce5527dc2d3516256
9879137720