tree a4de300723718b8bfac81cff5a0ab7caa4b76b4a
parent 255c43cd050f5202e96483430684c19b7ce916ff
author Christopher Ferris <cferris@google.com> 1512697278 -0800
committer Christopher Ferris <cferris@google.com> 1512702000 -0800

Add method to detect remote read function to use.

The process_vm_read function is much faster than ptrace, but sometimes
that will not work on a remote process. Modify the libunwindstack
MemoryRemote object to figure out which one it can use.

Wrote new unit test to verify this checking behavior.

Modify libbacktrace so that the read from libunwind is used instead of
using the default ptrace calls.

Add some benchmarks to libbacktrace to compare the two different methods.

Test: Ran unit tests libbacktrace/libunwindstack/debuggerd.
Test: Ran debuggerd -b <SYSTEM_SERVER_PID>
Test: Ran debuggerd -b <MEDIACODEC PID>
Test: Ran debuggerd -b <RANDOM_PID>
Test: Used crasher to create tombstones and verified stack data is
Test: dumped properly.
Change-Id: If75ca238289532dd8e1de430d569cabb2523380a