commit a3502b504d3c4868bd8716e00dd649101bbe3cb3
author Primiano Tucci <primiano@google.com> Mon Jun 29 11:28:58 2020 +0100
committer Primiano Tucci <primiano@google.com> Mon Jun 29 18:51:40 2020 +0100
tree d9ecb9020b67dd91f7e83f6149a047e5b2a015fe
parent ee1ad0698bf61f55a1da4a0bb4f84f8705f4c041

ftrace: fix pointer stability of events_ vector

This fixes an extremely subtle bug which causes traced_probes to
crash when tracing on some specific devices.
The root cause of the bug is the fact that in rare cirumstances
the events_ vector can be resized after construction, after some
Event* poitners have been handed out, hence invalidating them.
The rare circumstance is:
- The trace config ends up hitting a "generic event" path, i.e.
  the ftrace event is not known at compile time but exists on the
  target device (note this is not that unlikely because the expansion
  of some atrace categories in ftrace_config_muxer.cc can end up
  adding events like sde/sde_cmd_release_bw which are not in the
  compile-time list.
- The ftrace event ID of the generic event above is > than the
  max(ID of events known at compile time)
- The vector resize() ends up hitting the unhappy realloc() path
  which changes the data() pointer and mem-copies everything,
  invalidating all pointers.

Fix: use std::deque, which guarantees pointer stability.

Bug: 159998308
Change-Id: Id21fabf0c940fd0e5302518c0170686d61aaf847
Merged-In: Id21fabf0c940fd0e5302518c0170686d61aaf847
(cherry picked from commit bd3e8ecca937a76318c68ec8e8da72cb5c0239ba)
(cherry picked from commit 5cceb8adf772f3638577dea0d255b8bef3a743e5)