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SharedMemory API changes

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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
This commit is contained in:
John Reck
2017-08-07 11:17:06 -07:00
parent cbf16572eb
commit e4f60cce85
7 changed files with 52 additions and 10 deletions
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43
native/android/sharedmem.cpp
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@@ -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 @@ size_t ASharedMemory_getSize(int fd) {
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;
}