libcutils: route to /dev/ashmem<boot_id> instead of ashmemd
Having libcutils ask ashmemd for ashmem fds results in unsatisfactory
performance/memory overhead. Introduce a duplicate of /dev/ashmem and
route to it instead.
Our goal remains as before, namely, use SELinux to phase out usage of
ashmem that doesn't go through libcutils.
Bug: 139855428
Test: boot aosp_crosshatch, browse internet, use camera
Change-Id: I02260a9042acb412571b11f1f4c1d8608483064a
diff --git a/libcutils/ashmem-dev.cpp b/libcutils/ashmem-dev.cpp
index e67b458..340572c 100644
--- a/libcutils/ashmem-dev.cpp
+++ b/libcutils/ashmem-dev.cpp
@@ -23,9 +23,6 @@
*/
#define LOG_TAG "ashmem"
-#ifndef __ANDROID_VNDK__
-#include <dlfcn.h>
-#endif
#include <errno.h>
#include <fcntl.h>
#include <linux/ashmem.h>
@@ -42,11 +39,11 @@
#include <sys/types.h>
#include <unistd.h>
+#include <android-base/file.h>
#include <android-base/properties.h>
+#include <android-base/strings.h>
#include <android-base/unique_fd.h>
-#define ASHMEM_DEVICE "/dev/ashmem"
-
/* Will be added to UAPI once upstream change is merged */
#define F_SEAL_FUTURE_WRITE 0x0010
@@ -66,32 +63,6 @@
static pthread_mutex_t __ashmem_lock = PTHREAD_MUTEX_INITIALIZER;
/*
- * We use ashmemd to enforce that apps don't open /dev/ashmem directly. Vendor
- * code can't access system aidl services per Treble requirements. So we limit
- * ashmemd access to the system variant of libcutils.
- */
-#ifndef __ANDROID_VNDK__
-using openFdType = int (*)();
-
-static openFdType openFd;
-
-openFdType initOpenAshmemFd() {
- openFdType openFd = nullptr;
- void* handle = dlopen("libashmemd_client.so", RTLD_NOW);
- if (!handle) {
- ALOGE("Failed to dlopen() libashmemd_client.so: %s", dlerror());
- return openFd;
- }
-
- openFd = reinterpret_cast<openFdType>(dlsym(handle, "openAshmemdFd"));
- if (!openFd) {
- ALOGE("Failed to dlsym() openAshmemdFd() function: %s", dlerror());
- }
- return openFd;
-}
-#endif
-
-/*
* has_memfd_support() determines if the device can use memfd. memfd support
* has been there for long time, but certain things in it may be missing. We
* check for needed support in it. Also we check if the VNDK version of
@@ -215,25 +186,31 @@
return memfd_supported;
}
+static std::string get_ashmem_device_path() {
+ static const std::string boot_id_path = "/proc/sys/kernel/random/boot_id";
+ std::string boot_id;
+ if (!android::base::ReadFileToString(boot_id_path, &boot_id)) {
+ ALOGE("Failed to read %s: %s.\n", boot_id_path.c_str(), strerror(errno));
+ return "";
+ };
+ boot_id = android::base::Trim(boot_id);
+
+ return "/dev/ashmem" + boot_id;
+}
+
/* logistics of getting file descriptor for ashmem */
static int __ashmem_open_locked()
{
+ static const std::string ashmem_device_path = get_ashmem_device_path();
+
int ret;
struct stat st;
- int fd = -1;
-#ifndef __ANDROID_VNDK__
- if (!openFd) {
- openFd = initOpenAshmemFd();
+ if (ashmem_device_path.empty()) {
+ return -1;
}
- if (openFd) {
- fd = openFd();
- }
-#endif
- if (fd < 0) {
- fd = TEMP_FAILURE_RETRY(open(ASHMEM_DEVICE, O_RDWR | O_CLOEXEC));
- }
+ int fd = TEMP_FAILURE_RETRY(open(ashmem_device_path.c_str(), O_RDWR | O_CLOEXEC));
if (fd < 0) {
return fd;
}
@@ -485,11 +462,3 @@
return __ashmem_check_failure(fd, TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_GET_SIZE, NULL)));
}
-
-void ashmem_init() {
-#ifndef __ANDROID_VNDK__
- pthread_mutex_lock(&__ashmem_lock);
- openFd = initOpenAshmemFd();
- pthread_mutex_unlock(&__ashmem_lock);
-#endif //__ANDROID_VNDK__
-}