libcutils/ashmem-dev.cpp - platform/system/core - Gitiles

 /*
  * Copyright (C) 2008 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 #include <cutils/ashmem.h>

 /*
  * Implementation of the user-space ashmem API for devices, which have our
  * ashmem-enabled kernel. See ashmem-sim.c for the "fake" tmp-based version,
  * used by the simulator.
  */
 #define LOG_TAG "ashmem"

 #ifndef __ANDROID_VNDK__
 #include <dlfcn.h>
 #endif
 #include <errno.h>
 #include <fcntl.h>
 #include <linux/ashmem.h>
 #include <linux/memfd.h>
 #include <log/log.h>
 #include <pthread.h>
 #include <stdio.h>
 #include <string.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
 #include <sys/sysmacros.h>
 #include <sys/types.h>
 #include <unistd.h>

 #include <android-base/properties.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

 /*
  * The minimum vendor API level at and after which it is safe to use memfd.
  * This is to facilitate deprecation of ashmem.
  */
 #define MIN_MEMFD_VENDOR_API_LEVEL 29
 #define MIN_MEMFD_VENDOR_API_LEVEL_CHAR 'Q'

 /* ashmem identity */
 static dev_t __ashmem_rdev;
 /*
  * If we trigger a signal handler in the middle of locked activity and the
  * signal handler calls ashmem, we could get into a deadlock state.
  */
 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
  * libcutils being used is new enough, if its not, then we cannot use memfd
  * since the older copies may be using ashmem so we just use ashmem. Once all
  * Android devices that are getting updates are new enough (ex, they were
  * originally shipped with Android release > P), then we can just use memfd and
  * delete all ashmem code from libcutils (while preserving the interface).
  *
  * NOTE:
  * The sys.use_memfd property is set by default to false in Android
  * to temporarily disable memfd, till vendor and apps are ready for it.
  * The main issue: either apps or vendor processes can directly make ashmem
  * IOCTLs on FDs they receive by assuming they are ashmem, without going
  * through libcutils. Such fds could have very well be originally created with
  * libcutils hence they could be memfd. Thus the IOCTLs will break.
  *
  * Set default value of sys.use_memfd property to true once the issue is
  * resolved, so that the code can then self-detect if kernel support is present
  * on the device. The property can also set to true from adb shell, for
  * debugging.
  */

 static bool debug_log = false;            /* set to true for verbose logging and other debug  */
 static bool pin_deprecation_warn = true; /* Log the pin deprecation warning only once */

 /* Determine if vendor processes would be ok with memfd in the system:
  *
  * If VNDK is using older libcutils, don't use memfd. This is so that the
  * same shared memory mechanism is used across binder transactions between
  * vendor partition processes and system partition processes.
  */
 static bool check_vendor_memfd_allowed() {
     std::string vndk_version = android::base::GetProperty("ro.vndk.version", "");

     if (vndk_version == "") {
         ALOGE("memfd: ro.vndk.version not defined or invalid (%s), this is mandated since P.\n",
               vndk_version.c_str());
         return false;
     }

     /* No issues if vendor is targetting current Dessert */
     if (vndk_version == "current") {
         return false;
     }

     /* Check if VNDK version is a number and act on it */
     char* p;
     long int vers = strtol(vndk_version.c_str(), &p, 10);
     if (*p == 0) {
         if (vers < MIN_MEMFD_VENDOR_API_LEVEL) {
             ALOGI("memfd: device VNDK version (%s) is < Q so using ashmem.\n",
                   vndk_version.c_str());
             return false;
         }

         return true;
     }

     /* If its not a number, assume string, but check if its a sane string */
     if (tolower(vndk_version[0]) < 'a' || tolower(vndk_version[0]) > 'z') {
         ALOGE("memfd: ro.vndk.version not defined or invalid (%s), this is mandated since P.\n",
               vndk_version.c_str());
         return false;
     }

     if (tolower(vndk_version[0]) < tolower(MIN_MEMFD_VENDOR_API_LEVEL_CHAR)) {
         ALOGI("memfd: device is using VNDK version (%s) which is less than Q. Use ashmem only.\n",
               vndk_version.c_str());
         return false;
     }

     return true;
 }


 /* Determine if memfd can be supported. This is just one-time hardwork
  * which will be cached by the caller.
  */
 static bool __has_memfd_support() {
     if (check_vendor_memfd_allowed() == false) {
         return false;
     }

     /* Used to turn on/off the detection at runtime, in the future this
      * property will be removed once we switch everything over to ashmem.
      * Currently it is used only for debugging to switch the system over.
      */
     if (!android::base::GetBoolProperty("sys.use_memfd", false)) {
         if (debug_log) {
             ALOGD("sys.use_memfd=false so memfd disabled\n");
         }
         return false;
     }

     /* Check if kernel support exists, otherwise fall back to ashmem */
     android::base::unique_fd fd(
             syscall(__NR_memfd_create, "test_android_memfd", MFD_ALLOW_SEALING));
     if (fd == -1) {
         ALOGE("memfd_create failed: %s, no memfd support.\n", strerror(errno));
         return false;
     }

     if (fcntl(fd, F_ADD_SEALS, F_SEAL_FUTURE_WRITE) == -1) {
         ALOGE("fcntl(F_ADD_SEALS) failed: %s, no memfd support.\n", strerror(errno));
         return false;
     }

     if (debug_log) {
         ALOGD("memfd: device has memfd support, using it\n");
     }
     return true;
 }

 static bool has_memfd_support() {
     /* memfd_supported is the initial global per-process state of what is known
      * about memfd.
      */
     static bool memfd_supported = __has_memfd_support();

     return memfd_supported;
 }

 /* logistics of getting file descriptor for ashmem */
 static int __ashmem_open_locked()
 {
     int ret;
     struct stat st;

     int fd = -1;
 #ifndef __ANDROID_VNDK__
     if (!openFd) {
         openFd = initOpenAshmemFd();
     }

     if (openFd) {
         fd = openFd();
     }
 #endif
     if (fd < 0) {
         fd = TEMP_FAILURE_RETRY(open(ASHMEM_DEVICE, O_RDWR | O_CLOEXEC));
     }
     if (fd < 0) {
         return fd;
     }

     ret = TEMP_FAILURE_RETRY(fstat(fd, &st));
     if (ret < 0) {
         int save_errno = errno;
         close(fd);
         errno = save_errno;
         return ret;
     }
     if (!S_ISCHR(st.st_mode) || !st.st_rdev) {
         close(fd);
         errno = ENOTTY;
         return -1;
     }

     __ashmem_rdev = st.st_rdev;
     return fd;
 }

 static int __ashmem_open()
 {
     int fd;

     pthread_mutex_lock(&__ashmem_lock);
     fd = __ashmem_open_locked();
     pthread_mutex_unlock(&__ashmem_lock);

     return fd;
 }

 /* Make sure file descriptor references ashmem, negative number means false */
 static int __ashmem_is_ashmem(int fd, int fatal)
 {
     dev_t rdev;
     struct stat st;

     if (fstat(fd, &st) < 0) {
         return -1;
     }

     rdev = 0; /* Too much complexity to sniff __ashmem_rdev */
     if (S_ISCHR(st.st_mode) && st.st_rdev) {
         pthread_mutex_lock(&__ashmem_lock);
         rdev = __ashmem_rdev;
         if (rdev) {
             pthread_mutex_unlock(&__ashmem_lock);
         } else {
             int fd = __ashmem_open_locked();
             if (fd < 0) {
                 pthread_mutex_unlock(&__ashmem_lock);
                 return -1;
             }
             rdev = __ashmem_rdev;
             pthread_mutex_unlock(&__ashmem_lock);

             close(fd);
         }

         if (st.st_rdev == rdev) {
             return 0;
         }
     }

     if (fatal) {
         if (rdev) {
             LOG_ALWAYS_FATAL("illegal fd=%d mode=0%o rdev=%d:%d expected 0%o %d:%d",
               fd, st.st_mode, major(st.st_rdev), minor(st.st_rdev),
               S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IRGRP,
               major(rdev), minor(rdev));
         } else {
             LOG_ALWAYS_FATAL("illegal fd=%d mode=0%o rdev=%d:%d expected 0%o",
               fd, st.st_mode, major(st.st_rdev), minor(st.st_rdev),
               S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IRGRP);
         }
         /* NOTREACHED */
     }

     errno = ENOTTY;
     return -1;
 }

 static int __ashmem_check_failure(int fd, int result)
 {
     if (result == -1 && errno == ENOTTY) __ashmem_is_ashmem(fd, 1);
     return result;
 }

 static bool memfd_is_ashmem(int fd) {
     static bool fd_check_error_once = false;

     if (__ashmem_is_ashmem(fd, 0) == 0) {
         if (!fd_check_error_once) {
             ALOGE("memfd: memfd expected but ashmem fd used - please use libcutils.\n");
             fd_check_error_once = true;
         }

         return true;
     }

     return false;
 }

 int ashmem_valid(int fd)
 {
     if (has_memfd_support() && !memfd_is_ashmem(fd)) {
         return 1;
     }

     return __ashmem_is_ashmem(fd, 0) >= 0;
 }

 static int memfd_create_region(const char* name, size_t size) {
     android::base::unique_fd fd(syscall(__NR_memfd_create, name, MFD_ALLOW_SEALING));

     if (fd == -1) {
         ALOGE("memfd_create(%s, %zd) failed: %s\n", name, size, strerror(errno));
         return -1;
     }

     if (ftruncate(fd, size) == -1) {
         ALOGE("ftruncate(%s, %zd) failed for memfd creation: %s\n", name, size, strerror(errno));
         return -1;
     }

     if (debug_log) {
         ALOGE("memfd_create(%s, %zd) success. fd=%d\n", name, size, fd.get());
     }
     return fd.release();
 }

 /*
  * ashmem_create_region - creates a new ashmem region and returns the file
  * descriptor, or <0 on error
  *
  * `name' is an optional label to give the region (visible in /proc/pid/maps)
  * `size' is the size of the region, in page-aligned bytes
  */
 int ashmem_create_region(const char *name, size_t size)
 {
     int ret, save_errno;

     if (has_memfd_support()) {
         return memfd_create_region(name ? name : "none", size);
     }

     int fd = __ashmem_open();
     if (fd < 0) {
         return fd;
     }

     if (name) {
         char buf[ASHMEM_NAME_LEN] = {0};

         strlcpy(buf, name, sizeof(buf));
         ret = TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_NAME, buf));
         if (ret < 0) {
             goto error;
         }
     }

     ret = TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_SIZE, size));
     if (ret < 0) {
         goto error;
     }

     return fd;

 error:
     save_errno = errno;
     close(fd);
     errno = save_errno;
     return ret;
 }

 static int memfd_set_prot_region(int fd, int prot) {
     /* Only proceed if an fd needs to be write-protected */
     if (prot & PROT_WRITE) {
         return 0;
     }

     if (fcntl(fd, F_ADD_SEALS, F_SEAL_FUTURE_WRITE) == -1) {
         ALOGE("memfd_set_prot_region(%d, %d): F_SEAL_FUTURE_WRITE seal failed: %s\n", fd, prot,
               strerror(errno));
         return -1;
     }

     return 0;
 }

 int ashmem_set_prot_region(int fd, int prot)
 {
     if (has_memfd_support() && !memfd_is_ashmem(fd)) {
         return memfd_set_prot_region(fd, prot);
     }

     return __ashmem_check_failure(fd, TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_PROT_MASK, prot)));
 }

 int ashmem_pin_region(int fd, size_t offset, size_t len)
 {
     if (!pin_deprecation_warn || debug_log) {
         ALOGE("Pinning is deprecated since Android Q. Please use trim or other methods.\n");
         pin_deprecation_warn = true;
     }

     if (has_memfd_support() && !memfd_is_ashmem(fd)) {
         return 0;
     }

     // TODO: should LP64 reject too-large offset/len?
     ashmem_pin pin = { static_cast<uint32_t>(offset), static_cast<uint32_t>(len) };
     return __ashmem_check_failure(fd, TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_PIN, &pin)));
 }

 int ashmem_unpin_region(int fd, size_t offset, size_t len)
 {
     if (!pin_deprecation_warn || debug_log) {
         ALOGE("Pinning is deprecated since Android Q. Please use trim or other methods.\n");
         pin_deprecation_warn = true;
     }

     if (has_memfd_support() && !memfd_is_ashmem(fd)) {
         return 0;
     }

     // TODO: should LP64 reject too-large offset/len?
     ashmem_pin pin = { static_cast<uint32_t>(offset), static_cast<uint32_t>(len) };
     return __ashmem_check_failure(fd, TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_UNPIN, &pin)));
 }

 int ashmem_get_size_region(int fd)
 {
     if (has_memfd_support() && !memfd_is_ashmem(fd)) {
         struct stat sb;

         if (fstat(fd, &sb) == -1) {
             ALOGE("ashmem_get_size_region(%d): fstat failed: %s\n", fd, strerror(errno));
             return -1;
         }

         if (debug_log) {
             ALOGD("ashmem_get_size_region(%d): %d\n", fd, static_cast<int>(sb.st_size));
         }

         return sb.st_size;
     }

     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__
 }
	/*
	* Copyright (C) 2008 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	#include <cutils/ashmem.h>

	/*
	* Implementation of the user-space ashmem API for devices, which have our
	* ashmem-enabled kernel. See ashmem-sim.c for the "fake" tmp-based version,
	* used by the simulator.
	*/
	#define LOG_TAG "ashmem"

	#ifndef __ANDROID_VNDK__
	#include <dlfcn.h>
	#endif
	#include <errno.h>
	#include <fcntl.h>
	#include <linux/ashmem.h>
	#include <linux/memfd.h>
	#include <log/log.h>
	#include <pthread.h>
	#include <stdio.h>
	#include <string.h>
	#include <sys/ioctl.h>
	#include <sys/mman.h>
	#include <sys/stat.h>
	#include <sys/syscall.h>
	#include <sys/sysmacros.h>
	#include <sys/types.h>
	#include <unistd.h>

	#include <android-base/properties.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

	/*
	* The minimum vendor API level at and after which it is safe to use memfd.
	* This is to facilitate deprecation of ashmem.
	*/
	#define MIN_MEMFD_VENDOR_API_LEVEL 29
	#define MIN_MEMFD_VENDOR_API_LEVEL_CHAR 'Q'

	/* ashmem identity */
	static dev_t __ashmem_rdev;
	/*
	* If we trigger a signal handler in the middle of locked activity and the
	* signal handler calls ashmem, we could get into a deadlock state.
	*/
	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
	* libcutils being used is new enough, if its not, then we cannot use memfd
	* since the older copies may be using ashmem so we just use ashmem. Once all
	* Android devices that are getting updates are new enough (ex, they were
	* originally shipped with Android release > P), then we can just use memfd and
	* delete all ashmem code from libcutils (while preserving the interface).
	*
	* NOTE:
	* The sys.use_memfd property is set by default to false in Android
	* to temporarily disable memfd, till vendor and apps are ready for it.
	* The main issue: either apps or vendor processes can directly make ashmem
	* IOCTLs on FDs they receive by assuming they are ashmem, without going
	* through libcutils. Such fds could have very well be originally created with
	* libcutils hence they could be memfd. Thus the IOCTLs will break.
	*
	* Set default value of sys.use_memfd property to true once the issue is
	* resolved, so that the code can then self-detect if kernel support is present
	* on the device. The property can also set to true from adb shell, for
	* debugging.
	*/

	static bool debug_log = false; /* set to true for verbose logging and other debug */
	static bool pin_deprecation_warn = true; /* Log the pin deprecation warning only once */

	/* Determine if vendor processes would be ok with memfd in the system:
	*
	* If VNDK is using older libcutils, don't use memfd. This is so that the
	* same shared memory mechanism is used across binder transactions between
	* vendor partition processes and system partition processes.
	*/
	static bool check_vendor_memfd_allowed() {
	std::string vndk_version = android::base::GetProperty("ro.vndk.version", "");

	if (vndk_version == "") {
	ALOGE("memfd: ro.vndk.version not defined or invalid (%s), this is mandated since P.\n",
	vndk_version.c_str());
	return false;
	}

	/* No issues if vendor is targetting current Dessert */
	if (vndk_version == "current") {
	return false;
	}

	/* Check if VNDK version is a number and act on it */
	char* p;
	long int vers = strtol(vndk_version.c_str(), &p, 10);
	if (*p == 0) {
	if (vers < MIN_MEMFD_VENDOR_API_LEVEL) {
	ALOGI("memfd: device VNDK version (%s) is < Q so using ashmem.\n",
	vndk_version.c_str());
	return false;
	}

	return true;
	}

	/* If its not a number, assume string, but check if its a sane string */
	if (tolower(vndk_version[0]) < 'a' \|\| tolower(vndk_version[0]) > 'z') {
	ALOGE("memfd: ro.vndk.version not defined or invalid (%s), this is mandated since P.\n",
	vndk_version.c_str());
	return false;
	}

	if (tolower(vndk_version[0]) < tolower(MIN_MEMFD_VENDOR_API_LEVEL_CHAR)) {
	ALOGI("memfd: device is using VNDK version (%s) which is less than Q. Use ashmem only.\n",
	vndk_version.c_str());
	return false;
	}

	return true;
	}


	/* Determine if memfd can be supported. This is just one-time hardwork
	* which will be cached by the caller.
	*/
	static bool __has_memfd_support() {
	if (check_vendor_memfd_allowed() == false) {
	return false;
	}

	/* Used to turn on/off the detection at runtime, in the future this
	* property will be removed once we switch everything over to ashmem.
	* Currently it is used only for debugging to switch the system over.
	*/
	if (!android::base::GetBoolProperty("sys.use_memfd", false)) {
	if (debug_log) {
	ALOGD("sys.use_memfd=false so memfd disabled\n");
	}
	return false;
	}

	/* Check if kernel support exists, otherwise fall back to ashmem */
	android::base::unique_fd fd(
	syscall(__NR_memfd_create, "test_android_memfd", MFD_ALLOW_SEALING));
	if (fd == -1) {
	ALOGE("memfd_create failed: %s, no memfd support.\n", strerror(errno));
	return false;
	}

	if (fcntl(fd, F_ADD_SEALS, F_SEAL_FUTURE_WRITE) == -1) {
	ALOGE("fcntl(F_ADD_SEALS) failed: %s, no memfd support.\n", strerror(errno));
	return false;
	}

	if (debug_log) {
	ALOGD("memfd: device has memfd support, using it\n");
	}
	return true;
	}

	static bool has_memfd_support() {
	/* memfd_supported is the initial global per-process state of what is known
	* about memfd.
	*/
	static bool memfd_supported = __has_memfd_support();

	return memfd_supported;
	}

	/* logistics of getting file descriptor for ashmem */
	static int __ashmem_open_locked()
	{
	int ret;
	struct stat st;

	int fd = -1;
	#ifndef __ANDROID_VNDK__
	if (!openFd) {
	openFd = initOpenAshmemFd();
	}

	if (openFd) {
	fd = openFd();
	}
	#endif
	if (fd < 0) {
	fd = TEMP_FAILURE_RETRY(open(ASHMEM_DEVICE, O_RDWR \| O_CLOEXEC));
	}
	if (fd < 0) {
	return fd;
	}

	ret = TEMP_FAILURE_RETRY(fstat(fd, &st));
	if (ret < 0) {
	int save_errno = errno;
	close(fd);
	errno = save_errno;
	return ret;
	}
	if (!S_ISCHR(st.st_mode) \|\| !st.st_rdev) {
	close(fd);
	errno = ENOTTY;
	return -1;
	}

	__ashmem_rdev = st.st_rdev;
	return fd;
	}

	static int __ashmem_open()
	{
	int fd;

	pthread_mutex_lock(&__ashmem_lock);
	fd = __ashmem_open_locked();
	pthread_mutex_unlock(&__ashmem_lock);

	return fd;
	}

	/* Make sure file descriptor references ashmem, negative number means false */
	static int __ashmem_is_ashmem(int fd, int fatal)
	{
	dev_t rdev;
	struct stat st;

	if (fstat(fd, &st) < 0) {
	return -1;
	}

	rdev = 0; /* Too much complexity to sniff __ashmem_rdev */
	if (S_ISCHR(st.st_mode) && st.st_rdev) {
	pthread_mutex_lock(&__ashmem_lock);
	rdev = __ashmem_rdev;
	if (rdev) {
	pthread_mutex_unlock(&__ashmem_lock);
	} else {
	int fd = __ashmem_open_locked();
	if (fd < 0) {
	pthread_mutex_unlock(&__ashmem_lock);
	return -1;
	}
	rdev = __ashmem_rdev;
	pthread_mutex_unlock(&__ashmem_lock);

	close(fd);
	}

	if (st.st_rdev == rdev) {
	return 0;
	}
	}

	if (fatal) {
	if (rdev) {
	LOG_ALWAYS_FATAL("illegal fd=%d mode=0%o rdev=%d:%d expected 0%o %d:%d",
	fd, st.st_mode, major(st.st_rdev), minor(st.st_rdev),
	S_IFCHR \| S_IRUSR \| S_IWUSR \| S_IRGRP \| S_IWGRP \| S_IROTH \| S_IRGRP,
	major(rdev), minor(rdev));
	} else {
	LOG_ALWAYS_FATAL("illegal fd=%d mode=0%o rdev=%d:%d expected 0%o",
	fd, st.st_mode, major(st.st_rdev), minor(st.st_rdev),
	S_IFCHR \| S_IRUSR \| S_IWUSR \| S_IRGRP \| S_IWGRP \| S_IROTH \| S_IRGRP);
	}
	/* NOTREACHED */
	}

	errno = ENOTTY;
	return -1;
	}

	static int __ashmem_check_failure(int fd, int result)
	{
	if (result == -1 && errno == ENOTTY) __ashmem_is_ashmem(fd, 1);
	return result;
	}

	static bool memfd_is_ashmem(int fd) {
	static bool fd_check_error_once = false;

	if (__ashmem_is_ashmem(fd, 0) == 0) {
	if (!fd_check_error_once) {
	ALOGE("memfd: memfd expected but ashmem fd used - please use libcutils.\n");
	fd_check_error_once = true;
	}

	return true;
	}

	return false;
	}

	int ashmem_valid(int fd)
	{
	if (has_memfd_support() && !memfd_is_ashmem(fd)) {
	return 1;
	}

	return __ashmem_is_ashmem(fd, 0) >= 0;
	}

	static int memfd_create_region(const char* name, size_t size) {
	android::base::unique_fd fd(syscall(__NR_memfd_create, name, MFD_ALLOW_SEALING));

	if (fd == -1) {
	ALOGE("memfd_create(%s, %zd) failed: %s\n", name, size, strerror(errno));
	return -1;
	}

	if (ftruncate(fd, size) == -1) {
	ALOGE("ftruncate(%s, %zd) failed for memfd creation: %s\n", name, size, strerror(errno));
	return -1;
	}

	if (debug_log) {
	ALOGE("memfd_create(%s, %zd) success. fd=%d\n", name, size, fd.get());
	}
	return fd.release();
	}

	/*
	* ashmem_create_region - creates a new ashmem region and returns the file
	* descriptor, or <0 on error
	*
	* `name' is an optional label to give the region (visible in /proc/pid/maps)
	* `size' is the size of the region, in page-aligned bytes
	*/
	int ashmem_create_region(const char *name, size_t size)
	{
	int ret, save_errno;

	if (has_memfd_support()) {
	return memfd_create_region(name ? name : "none", size);
	}

	int fd = __ashmem_open();
	if (fd < 0) {
	return fd;
	}

	if (name) {
	char buf[ASHMEM_NAME_LEN] = {0};

	strlcpy(buf, name, sizeof(buf));
	ret = TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_NAME, buf));
	if (ret < 0) {
	goto error;
	}
	}

	ret = TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_SIZE, size));
	if (ret < 0) {
	goto error;
	}

	return fd;

	error:
	save_errno = errno;
	close(fd);
	errno = save_errno;
	return ret;
	}

	static int memfd_set_prot_region(int fd, int prot) {
	/* Only proceed if an fd needs to be write-protected */
	if (prot & PROT_WRITE) {
	return 0;
	}

	if (fcntl(fd, F_ADD_SEALS, F_SEAL_FUTURE_WRITE) == -1) {
	ALOGE("memfd_set_prot_region(%d, %d): F_SEAL_FUTURE_WRITE seal failed: %s\n", fd, prot,
	strerror(errno));
	return -1;
	}

	return 0;
	}

	int ashmem_set_prot_region(int fd, int prot)
	{
	if (has_memfd_support() && !memfd_is_ashmem(fd)) {
	return memfd_set_prot_region(fd, prot);
	}

	return __ashmem_check_failure(fd, TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_PROT_MASK, prot)));
	}

	int ashmem_pin_region(int fd, size_t offset, size_t len)
	{
	if (!pin_deprecation_warn \|\| debug_log) {
	ALOGE("Pinning is deprecated since Android Q. Please use trim or other methods.\n");
	pin_deprecation_warn = true;
	}

	if (has_memfd_support() && !memfd_is_ashmem(fd)) {
	return 0;
	}

	// TODO: should LP64 reject too-large offset/len?
	ashmem_pin pin = { static_cast<uint32_t>(offset), static_cast<uint32_t>(len) };
	return __ashmem_check_failure(fd, TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_PIN, &pin)));
	}

	int ashmem_unpin_region(int fd, size_t offset, size_t len)
	{
	if (!pin_deprecation_warn \|\| debug_log) {
	ALOGE("Pinning is deprecated since Android Q. Please use trim or other methods.\n");
	pin_deprecation_warn = true;
	}

	if (has_memfd_support() && !memfd_is_ashmem(fd)) {
	return 0;
	}

	// TODO: should LP64 reject too-large offset/len?
	ashmem_pin pin = { static_cast<uint32_t>(offset), static_cast<uint32_t>(len) };
	return __ashmem_check_failure(fd, TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_UNPIN, &pin)));
	}

	int ashmem_get_size_region(int fd)
	{
	if (has_memfd_support() && !memfd_is_ashmem(fd)) {
	struct stat sb;

	if (fstat(fd, &sb) == -1) {
	ALOGE("ashmem_get_size_region(%d): fstat failed: %s\n", fd, strerror(errno));
	return -1;
	}

	if (debug_log) {
	ALOGD("ashmem_get_size_region(%d): %d\n", fd, static_cast<int>(sb.st_size));
	}

	return sb.st_size;
	}

	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__
	}