From cc5885f92b7693a5b660313ec8e978c6dc002af8 Mon Sep 17 00:00:00 2001
From: Pete Gillin <peteg@google.com>
Date: Thu, 15 Feb 2018 17:17:27 +0000
Subject: [PATCH] Add new 'explicit GC' policy to StrictMode.

This change adds the policy but offers no public way to enable it. A
follow-up change will expose the detect/permit methods in the API and
change detectAll to enable it.

This new policy can only be triggered through the libcore BlockGuard API.

Bug: 3400644
Test: cts-tradefed run cts-dev -m CtsLibcoreTestCases
Test: cts-tradefed run cts-dev -m CtsOsTestCases
Change-Id: I2e7f34ce010c78d6a5a7ac85512c045bfb13d204
Merged-In: Ieebe4db747902246968d6382bbc9cee0e539af85
---
 core/java/android/os/StrictMode.java | 53 ++++++++++++++++++++++++++--
 1 file changed, 51 insertions(+), 2 deletions(-)

diff --git a/core/java/android/os/StrictMode.java b/core/java/android/os/StrictMode.java
index 3b6df5df13aa8..0789afddad59d 100644
--- a/core/java/android/os/StrictMode.java
+++ b/core/java/android/os/StrictMode.java
@@ -196,9 +196,14 @@ public final class StrictMode {
      */
     public static final int DETECT_UNBUFFERED_IO = 0x20;  // for ThreadPolicy
 
+    /**
+     * @hide
+     */
+    public static final int DETECT_EXPLICIT_GC = 0x40;  // for ThreadPolicy
+
     private static final int ALL_THREAD_DETECT_BITS =
             DETECT_DISK_WRITE | DETECT_DISK_READ | DETECT_NETWORK | DETECT_CUSTOM |
-            DETECT_RESOURCE_MISMATCH | DETECT_UNBUFFERED_IO;
+            DETECT_RESOURCE_MISMATCH | DETECT_UNBUFFERED_IO | DETECT_EXPLICIT_GC;
 
     // Byte 2: Process-policy
 
@@ -556,6 +561,27 @@ public final class StrictMode {
                 return disable(DETECT_DISK_WRITE);
             }
 
+            /**
+             * Detect explicit GC requests, i.e. calls to Runtime.gc().
+             *
+             * @hide
+             */
+            public Builder detectExplicitGc() {
+                // TODO(b/3400644): Un-hide this for next API update
+                // TODO(b/3400644): Call this from detectAll in next API update
+                return enable(DETECT_EXPLICIT_GC);
+            }
+
+            /**
+             * Disable detection of explicit GC requests, i.e. calls to Runtime.gc().
+             *
+             * @hide
+             */
+            public Builder permitExplicitGc() {
+                // TODO(b/3400644): Un-hide this for next API update
+                return disable(DETECT_EXPLICIT_GC);
+            }
+
             /**
              * Show an annoying dialog to the developer on detected
              * violations, rate-limited to be only a little annoying.
@@ -1093,6 +1119,15 @@ public final class StrictMode {
         }
     }
 
+    /**
+     * @hide
+     */
+    private static class StrictModeExplicitGcViolation extends StrictModeViolation {
+        StrictModeExplicitGcViolation(int policyMask) {
+            super(policyMask, DETECT_EXPLICIT_GC, null);
+        }
+    }
+
     /**
      * Returns the bitmask of the current thread's policy.
      *
@@ -1414,7 +1449,7 @@ public final class StrictMode {
             startHandlingViolationException(e);
         }
 
-        // Part of BlockGuard.Policy; just part of StrictMode:
+        // Part of BlockGuard.Policy interface:
         public void onUnbufferedIO() {
             if ((mPolicyMask & DETECT_UNBUFFERED_IO) == 0) {
                 return;
@@ -1457,6 +1492,20 @@ public final class StrictMode {
             startHandlingViolationException(e);
         }
 
+        // Part of BlockGuard.Policy interface:
+        public void onExplicitGc() {
+            if ((mPolicyMask & DETECT_EXPLICIT_GC) == 0) {
+                return;
+            }
+            if (tooManyViolationsThisLoop()) {
+                return;
+            }
+            BlockGuard.BlockGuardPolicyException e =
+                    new StrictModeExplicitGcViolation(mPolicyMask);
+            e.fillInStackTrace();
+            startHandlingViolationException(e);
+        }
+
         public void setPolicyMask(int policyMask) {
             mPolicyMask = policyMask;
         }