From 6bb3114246f6f6aa406e65452dbaa12b135029ea Mon Sep 17 00:00:00 2001
From: Adrian Roos <roosa@google.com>
Date: Thu, 22 Oct 2015 16:46:12 -0700
Subject: [PATCH] Maintain Parcel ABI

Makes sure we don't change the memory layout of the Parcel class
to maintain binary compatibility with prebuilts linking against
libbinder.

Bug: 25004154
Change-Id: I656687497f08bb85cefda796aafa2341e601e30a
---
 include/binder/Parcel.h |  6 +++---
 libs/binder/Parcel.cpp  | 46 +++++++++++++++++++++++++++--------------
 2 files changed, 34 insertions(+), 18 deletions(-)

diff --git a/include/binder/Parcel.h b/include/binder/Parcel.h
index 220a9353f..16cd6cf67 100644
--- a/include/binder/Parcel.h
+++ b/include/binder/Parcel.h
@@ -341,10 +341,10 @@ public:
     };
 
 private:
-    size_t mBlobAshmemSize;
     size_t mOpenAshmemSize;
 
 public:
+    // TODO: Remove once ABI can be changed.
     size_t getBlobAshmemSize() const;
     size_t getOpenAshmemSize() const;
 };
@@ -414,9 +414,9 @@ inline TextOutput& operator<<(TextOutput& to, const Parcel& parcel)
 
 // Generic acquire and release of objects.
 void acquire_object(const sp<ProcessState>& proc,
-                    const flat_binder_object& obj, const void* who, size_t* outAshmemSize);
+                    const flat_binder_object& obj, const void* who);
 void release_object(const sp<ProcessState>& proc,
-                    const flat_binder_object& obj, const void* who, size_t* outAshmemSize);
+                    const flat_binder_object& obj, const void* who);
 
 void flatten_binder(const sp<ProcessState>& proc,
                     const sp<IBinder>& binder, flat_binder_object* out);
diff --git a/libs/binder/Parcel.cpp b/libs/binder/Parcel.cpp
index 1c0358518..22d7ef36c 100644
--- a/libs/binder/Parcel.cpp
+++ b/libs/binder/Parcel.cpp
@@ -124,10 +124,12 @@ void acquire_object(const sp<ProcessState>& proc,
         }
         case BINDER_TYPE_FD: {
             if (obj.cookie != 0) {
-                // If we own an ashmem fd, keep track of how much memory it refers to.
-                int size = ashmem_get_size_region(obj.handle);
-                if (size > 0) {
-                    *outAshmemSize += size;
+                if (outAshmemSize != NULL) {
+                    // If we own an ashmem fd, keep track of how much memory it refers to.
+                    int size = ashmem_get_size_region(obj.handle);
+                    if (size > 0) {
+                        *outAshmemSize += size;
+                    }
                 }
             }
             return;
@@ -137,7 +139,13 @@ void acquire_object(const sp<ProcessState>& proc,
     ALOGD("Invalid object type 0x%08x", obj.type);
 }
 
-void release_object(const sp<ProcessState>& proc,
+void acquire_object(const sp<ProcessState>& proc,
+    const flat_binder_object& obj, const void* who)
+{
+    acquire_object(proc, obj, who, NULL);
+}
+
+static void release_object(const sp<ProcessState>& proc,
     const flat_binder_object& obj, const void* who, size_t* outAshmemSize)
 {
     switch (obj.type) {
@@ -165,13 +173,15 @@ void release_object(const sp<ProcessState>& proc,
             return;
         }
         case BINDER_TYPE_FD: {
-            if (obj.cookie != 0) {
-                int size = ashmem_get_size_region(obj.handle);
-                if (size > 0) {
-                    *outAshmemSize -= size;
-                }
+            if (outAshmemSize != NULL) {
+                if (obj.cookie != 0) {
+                    int size = ashmem_get_size_region(obj.handle);
+                    if (size > 0) {
+                        *outAshmemSize -= size;
+                    }
 
-                close(obj.handle);
+                    close(obj.handle);
+                }
             }
             return;
         }
@@ -180,6 +190,12 @@ void release_object(const sp<ProcessState>& proc,
     ALOGE("Invalid object type 0x%08x", obj.type);
 }
 
+void release_object(const sp<ProcessState>& proc,
+    const flat_binder_object& obj, const void* who)
+{
+    release_object(proc, obj, who, NULL);
+}
+
 inline static status_t finish_flatten_binder(
     const sp<IBinder>& /*binder*/, const flat_binder_object& flat, Parcel* out)
 {
@@ -935,8 +951,6 @@ status_t Parcel::writeBlob(size_t len, bool mutableCopy, WritableBlob* outBlob)
     int fd = ashmem_create_region("Parcel Blob", len);
     if (fd < 0) return NO_MEMORY;
 
-    mBlobAshmemSize += len;
-
     int result = ashmem_set_prot_region(fd, PROT_READ | PROT_WRITE);
     if (result < 0) {
         status = result;
@@ -1902,7 +1916,6 @@ void Parcel::initState()
     mFdsKnown = true;
     mAllowFds = true;
     mOwner = NULL;
-    mBlobAshmemSize = 0;
     mOpenAshmemSize = 0;
 }
 
@@ -1923,7 +1936,10 @@ void Parcel::scanForFds() const
 
 size_t Parcel::getBlobAshmemSize() const
 {
-    return mBlobAshmemSize;
+    // This used to return the size of all blobs that were written to ashmem, now we're returning
+    // the ashmem currently referenced by this Parcel, which should be equivalent.
+    // TODO: Remove method once ABI can be changed.
+    return mOpenAshmemSize;
 }
 
 size_t Parcel::getOpenAshmemSize() const