SharedMemory API changes
Hides getFd & getFileDescriptor due to lifecycle concenrs.
Adds ASharedMemory_dupFromJava to allow sharing a shared
memory region between Java & Native as safe as possible.
Mis-use results in an FD leak instead of double-close.
Bug: 64394076
Test: SharedMemory CTS tests
Change-Id: I01a5eb978fc4e99559a79baac75754c32f13bdc4
diff --git a/native/android/sharedmem.cpp b/native/android/sharedmem.cpp
index 9d029dfa..757aaec 100644
--- a/native/android/sharedmem.cpp
+++ b/native/android/sharedmem.cpp
@@ -14,10 +14,36 @@
* limitations under the License.
*/
+#include <jni.h>
+
#include <android/sharedmem.h>
+#include <android/sharedmem_jni.h>
#include <cutils/ashmem.h>
+#include <log/log.h>
#include <utils/Errors.h>
+#include <mutex>
+#include <unistd.h>
+
+static struct {
+ jclass clazz;
+ jmethodID getFd;
+} sSharedMemory;
+
+static void jniInit(JNIEnv* env) {
+ static std::once_flag sJniInitialized;
+ std::call_once(sJniInitialized, [](JNIEnv* env) {
+ jclass clazz = env->FindClass("android/os/SharedMemory");
+ LOG_ALWAYS_FATAL_IF(clazz == nullptr, "Failed to find android.os.SharedMemory");
+ sSharedMemory.clazz = (jclass) env->NewGlobalRef(clazz);
+ LOG_ALWAYS_FATAL_IF(sSharedMemory.clazz == nullptr,
+ "Failed to create global ref of android.os.SharedMemory");
+ sSharedMemory.getFd = env->GetMethodID(sSharedMemory.clazz, "getFd", "()I");
+ LOG_ALWAYS_FATAL_IF(sSharedMemory.getFd == nullptr,
+ "Failed to find method SharedMemory#getFd()");
+ }, env);
+}
+
int ASharedMemory_create(const char *name, size_t size) {
if (size == 0) {
return android::BAD_VALUE;
@@ -32,3 +58,20 @@
int ASharedMemory_setProt(int fd, int prot) {
return ashmem_set_prot_region(fd, prot);
}
+
+int ASharedMemory_dupFromJava(JNIEnv* env, jobject javaSharedMemory) {
+ if (env == nullptr || javaSharedMemory == nullptr) {
+ return -1;
+ }
+ jniInit(env);
+ if (!env->IsInstanceOf(javaSharedMemory, sSharedMemory.clazz)) {
+ ALOGW("ASharedMemory_dupFromJava called with object "
+ "that's not an instanceof android.os.SharedMemory");
+ return -1;
+ }
+ int fd = env->CallIntMethod(javaSharedMemory, sSharedMemory.getFd);
+ if (fd != -1) {
+ fd = dup(fd);
+ }
+ return fd;
+}
