Handle accidental null arguments to Trace APIs.

We have @NonNull annotations, but not everyone is watching the warning
messages related to them.  Make the implementation a bit more robust
by swapping in the "(null)" literal when someone accidentally leaks
one through.

Bug: 249325721
Test: atest FrameworksCoreTests:TraceTest
Change-Id: Ic0f5a0236fbce88e086f3d68b2e5c6ed6b0aa33c

core/java/android/os/Trace.java

@@ -340,9 +340,6 @@ public final class Trace {
      * @hide
      */
     public static void instant(long traceTag, String methodName) {
-        if (methodName == null) {
-            throw new IllegalArgumentException("methodName cannot be null");
-        }
         if (isTagEnabled(traceTag)) {
             nativeInstant(traceTag, methodName);
         }
@@ -357,12 +354,6 @@ public final class Trace {
      * @hide
      */
     public static void instantForTrack(long traceTag, String trackName, String methodName) {
-        if (trackName == null) {
-            throw new IllegalArgumentException("trackName cannot be null");
-        }
-        if (methodName == null) {
-            throw new IllegalArgumentException("methodName cannot be null");
-        }
         if (isTagEnabled(traceTag)) {
             nativeInstantForTrack(traceTag, trackName, methodName);
         }

core/jni/android_os_Trace.cpp

@@ -22,6 +22,8 @@
 
 #include <array>
 
+static constexpr const char* kNullReplacement = "(null)";
+
 namespace android {
 
 inline static void sanitizeString(char* str) {
@@ -36,6 +38,11 @@ inline static void sanitizeString(char* str) {
 
 template<typename F>
 inline static void withString(JNIEnv* env, jstring jstr, F callback) {
+    if (CC_UNLIKELY(jstr == nullptr)) {
+        callback(kNullReplacement);
+        return;
+    }
+
     // We need to handle the worst case of 1 character -> 4 bytes
     // So make a buffer of size 4097 and let it hold a string with a maximum length
     // of 1024. The extra last byte for the null terminator.
@@ -52,14 +59,14 @@ inline static void withString(JNIEnv* env, jstring jstr, F callback) {
 
 static void android_os_Trace_nativeTraceCounter(JNIEnv* env, jclass,
         jlong tag, jstring nameStr, jlong value) {
-    withString(env, nameStr, [tag, value](char* str) {
+    withString(env, nameStr, [tag, value](const char* str) {
         atrace_int64(tag, str, value);
     });
 }
 
 static void android_os_Trace_nativeTraceBegin(JNIEnv* env, jclass,
         jlong tag, jstring nameStr) {
-    withString(env, nameStr, [tag](char* str) {
+    withString(env, nameStr, [tag](const char* str) {
         atrace_begin(tag, str);
     });
 }
@@ -70,22 +77,22 @@ static void android_os_Trace_nativeTraceEnd(JNIEnv*, jclass, jlong tag) {
 
 static void android_os_Trace_nativeAsyncTraceBegin(JNIEnv* env, jclass,
         jlong tag, jstring nameStr, jint cookie) {
-    withString(env, nameStr, [tag, cookie](char* str) {
+    withString(env, nameStr, [tag, cookie](const char* str) {
         atrace_async_begin(tag, str, cookie);
     });
 }
 
 static void android_os_Trace_nativeAsyncTraceEnd(JNIEnv* env, jclass,
         jlong tag, jstring nameStr, jint cookie) {
-    withString(env, nameStr, [tag, cookie](char* str) {
+    withString(env, nameStr, [tag, cookie](const char* str) {
         atrace_async_end(tag, str, cookie);
     });
 }
 
 static void android_os_Trace_nativeAsyncTraceForTrackBegin(JNIEnv* env, jclass,
         jlong tag, jstring trackStr, jstring nameStr, jint cookie) {
-    withString(env, trackStr, [env, tag, nameStr, cookie](char* track) {
-        withString(env, nameStr, [tag, track, cookie](char* name) {
+    withString(env, trackStr, [env, tag, nameStr, cookie](const char* track) {
+        withString(env, nameStr, [tag, track, cookie](const char* name) {
             atrace_async_for_track_begin(tag, track, name, cookie);
         });
     });
@@ -93,7 +100,7 @@ static void android_os_Trace_nativeAsyncTraceForTrackBegin(JNIEnv* env, jclass,
 
 static void android_os_Trace_nativeAsyncTraceForTrackEnd(JNIEnv* env, jclass,
         jlong tag, jstring trackStr, jint cookie) {
-    withString(env, trackStr, [tag, cookie](char* track) {
+    withString(env, trackStr, [tag, cookie](const char* track) {
         atrace_async_for_track_end(tag, track, cookie);
     });
 }
@@ -108,15 +115,15 @@ static void android_os_Trace_nativeSetTracingEnabled(JNIEnv*, jclass, jboolean e
 
 static void android_os_Trace_nativeInstant(JNIEnv* env, jclass,
         jlong tag, jstring nameStr) {
-    withString(env, nameStr, [tag](char* str) {
+    withString(env, nameStr, [tag](const char* str) {
         atrace_instant(tag, str);
     });
 }
 
 static void android_os_Trace_nativeInstantForTrack(JNIEnv* env, jclass,
         jlong tag, jstring trackStr, jstring nameStr) {
-    withString(env, trackStr, [env, tag, nameStr](char* track) {
-        withString(env, nameStr, [tag, track](char* name) {
+    withString(env, trackStr, [env, tag, nameStr](const char* track) {
+        withString(env, nameStr, [tag, track](const char* name) {
             atrace_instant_for_track(tag, track, name);
         });
     });

core/tests/coretests/src/android/os/TraceTest.java

@@ -33,7 +33,21 @@ public class TraceTest extends AndroidTestCase
     private int eMethodCalls = 0;
     private int fMethodCalls = 0;
     private int gMethodCalls = 0;
-    
+
+    public void testNullStrings() {
+        Trace.traceCounter(Trace.TRACE_TAG_ACTIVITY_MANAGER, null, 42);
+        Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, null);
+
+        Trace.asyncTraceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, null, 42);
+        Trace.asyncTraceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER, null, 42);
+
+        Trace.asyncTraceForTrackBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, null, null, 42);
+        Trace.asyncTraceForTrackEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER, null, 42);
+
+        Trace.instant(Trace.TRACE_TAG_ACTIVITY_MANAGER, null);
+        Trace.instantForTrack(Trace.TRACE_TAG_ACTIVITY_MANAGER, null, null);
+    }
+
     @SmallTest
     public void testNativeTracingFromJava()
     {