commit 6e69d65a3c575969e0461558d2496c3b2d877871
author Steven Moreland <smoreland@google.com> Wed Jul 10 14:17:55 2019 -0700
committer Steven Moreland <smoreland@google.com> Fri Jul 12 20:40:41 2019 +0000
tree d17961c1f394c709a1d8e733bfd904f3533fe0b4
parent add824adfe02d6c2e710d5f94ea5597f165ee1fa

libbinder: empty ping transaction

It came up recently that the libbinder ping transaction uses 4-bytes in
the reply header, but it really only needs to use the binder return
code (how servicemanager did it before when written in C).

Fixes: 137203409
Test: TH
Change-Id: I4555fdba0f80263caa3f3727ef5c5458d160a585

libs/binder/Binder.cpp

diff --git a/libs/binder/Binder.cpp b/libs/binder/Binder.cpp
index 96ee295..1729d6a 100644
--- a/libs/binder/Binder.cpp
+++ b/libs/binder/Binder.cpp
@@ -128,7 +128,7 @@
     status_t err = NO_ERROR;
     switch (code) {
         case PING_TRANSACTION:
-            reply->writeInt32(pingBinder());
+            err = pingBinder();
             break;
         default:
             err = onTransact(code, data, reply, flags);

libs/binder/BpBinder.cpp

diff --git a/libs/binder/BpBinder.cpp b/libs/binder/BpBinder.cpp
index 67f968a..f35803c 100644
--- a/libs/binder/BpBinder.cpp
+++ b/libs/binder/BpBinder.cpp
@@ -186,10 +186,7 @@
 {
     Parcel send;
     Parcel reply;
-    status_t err = transact(PING_TRANSACTION, send, &reply);
-    if (err != NO_ERROR) return err;
-    if (reply.dataSize() < sizeof(status_t)) return NOT_ENOUGH_DATA;
-    return (status_t)reply.readInt32();
+    return transact(PING_TRANSACTION, send, &reply);
 }
 
 status_t BpBinder::dump(int fd, const Vector<String16>& args)

libs/binder/tests/binderDriverInterfaceTest.cpp

diff --git a/libs/binder/tests/binderDriverInterfaceTest.cpp b/libs/binder/tests/binderDriverInterfaceTest.cpp
index 6508bb1..77ebac8 100644
--- a/libs/binder/tests/binderDriverInterfaceTest.cpp
+++ b/libs/binder/tests/binderDriverInterfaceTest.cpp
@@ -286,13 +286,7 @@
         EXPECT_EQ(0u, br.arg2.cookie);
         EXPECT_EQ(0u, br.arg2.code);
         EXPECT_EQ(0u, br.arg2.flags);
-
-        // ping returns a 4 byte header in libbinder, but the original
-        // C implementation of servicemanager returns a 0 byte header
-        if (br.arg2.data_size != 0 && br.arg2.data_size != 4) {
-            ADD_FAILURE() << br.arg2.data_size << " is expected to be 0 or 4";
-        }
-
+        EXPECT_EQ(0u, br.arg2.data_size);
         EXPECT_EQ(0u, br.arg2.offsets_size);
 
         SCOPED_TRACE("3rd WriteRead");