From 2f9bb95303904c77bed2e427c3149c96f7fc86cd Mon Sep 17 00:00:00 2001
From: Colin Cross <ccross@android.com>
Date: Thu, 20 Apr 2023 11:49:48 -0700
Subject: Order events returned by fdevent_epoll

The events returned by fdevent_epoll are ordered by
installed_fdevents_, which is an unordered map.  This causes
the order to be non-determinsitic, but generally stable within a
process.  Switch installed_fdevents_ to an ordered map, which will
return the events ordered by fd number.  This will make tests more
deterministic and allow writing a test that depends on event handling
order.

Bug: 268740023
Test: adb_test
Ignore-AOSP-First: Resolution for potential security exploit.
Change-Id: I65bef05d4edd6057bf9b2cebc4952b2f1e14b4d1
---
 fdevent/fdevent.h         |  4 ++--
 fdevent/fdevent_epoll.cpp | 28 +++++++++++++++++-----------
 2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/fdevent/fdevent.h b/fdevent/fdevent.h
index ff86f1fe..84d086b6 100644
--- a/fdevent/fdevent.h
+++ b/fdevent/fdevent.h
@@ -24,9 +24,9 @@
 #include <chrono>
 #include <deque>
 #include <functional>
+#include <map>
 #include <mutex>
 #include <optional>
-#include <unordered_map>
 #include <variant>
 
 #include <android-base/thread_annotations.h>
@@ -125,7 +125,7 @@ struct fdevent_context {
     std::optional<uint64_t> looper_thread_id_ = std::nullopt;
     std::atomic<bool> terminate_loop_ = false;
 
-    std::unordered_map<int, fdevent> installed_fdevents_;
+    std::map<int, fdevent> installed_fdevents_;
 
   private:
     uint64_t fdevent_id_ = 0;
diff --git a/fdevent/fdevent_epoll.cpp b/fdevent/fdevent_epoll.cpp
index d5d4d668..147913a5 100644
--- a/fdevent/fdevent_epoll.cpp
+++ b/fdevent/fdevent_epoll.cpp
@@ -108,14 +108,18 @@ void fdevent_context_epoll::Loop() {
     looper_thread_id_ = android::base::GetThreadId();
 
     std::vector<fdevent_event> fde_events;
+    std::unordered_map<fdevent*, fdevent_event*> event_map;
     std::vector<epoll_event> epoll_events;
-    epoll_events.resize(this->installed_fdevents_.size());
 
     while (true) {
         if (terminate_loop_) {
             break;
         }
 
+        if (epoll_events.size() < this->installed_fdevents_.size()) {
+            epoll_events.resize(this->installed_fdevents_.size());
+        }
+
         int rc = -1;
         while (rc == -1) {
             std::optional<std::chrono::milliseconds> timeout = CalculatePollDuration();
@@ -133,7 +137,10 @@ void fdevent_context_epoll::Loop() {
         }
 
         auto post_poll = std::chrono::steady_clock::now();
-        std::unordered_map<fdevent*, unsigned> event_map;
+        fde_events.reserve(installed_fdevents_.size());
+        fde_events.clear();
+        event_map.clear();
+
         for (int i = 0; i < rc; ++i) {
             fdevent* fde = static_cast<fdevent*>(epoll_events[i].data.ptr);
 
@@ -152,13 +159,16 @@ void fdevent_context_epoll::Loop() {
                 events |= FDE_READ | FDE_ERROR;
             }
 
-            event_map[fde] = events;
+            LOG(DEBUG) << dump_fde(fde) << " got events " << std::hex << std::showbase << events;
+            auto& fde_event = fde_events.emplace_back(fde, events);
+            event_map[fde] = &fde_event;
+            fde->last_active = post_poll;
         }
 
         for (auto& [fd, fde] : installed_fdevents_) {
             unsigned events = 0;
             if (auto it = event_map.find(&fde); it != event_map.end()) {
-                events = it->second;
+                events = it->second->events;
             }
 
             if (events == 0) {
@@ -166,16 +176,12 @@ void fdevent_context_epoll::Loop() {
                     auto deadline = fde.last_active + *fde.timeout;
                     if (deadline < post_poll) {
                         events |= FDE_TIMEOUT;
+                        LOG(DEBUG) << dump_fde(&fde) << " timed out";
+                        fde_events.emplace_back(&fde, events);
+                        fde.last_active = post_poll;
                     }
                 }
             }
-
-            if (events != 0) {
-                LOG(DEBUG) << dump_fde(&fde) << " got events " << std::hex << std::showbase
-                           << events;
-                fde_events.push_back({&fde, events});
-                fde.last_active = post_poll;
-            }
         }
         this->HandleEvents(fde_events);
         fde_events.clear();
-- 
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