/* * Copyright (c) 2001, 2022, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 2012, 2021 SAP SE. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. *
*/
// put OS-includes here # include <sys/types.h> # include <sys/mman.h> # include <errno.h> # include <stdio.h> # include <unistd.h> # include <sys/stat.h> # include <signal.h> # include <pwd.h>
#ifdefined(LINUX) # include <sys/file.h> #endif
staticchar* backing_store_file_name = NULL; // name of the backing store // file, if successfully created.
// Standard Memory Implementation Details
// create the PerfData memory region in standard memory. // staticchar* create_standard_memory(size_t size) {
// allocate an aligned chuck of memory char* mapAddress = os::reserve_memory(size);
if (mapAddress == NULL) { return NULL;
}
// commit memory if (!os::commit_memory(mapAddress, size, !ExecMem)) { if (PrintMiscellaneous && Verbose) {
warning("Could not commit PerfData memory\n");
}
os::release_memory(mapAddress, size); return NULL;
}
return mapAddress;
}
// save the specified memory region to the given file // // Note: this function might be called from signal handler (by os::abort()), // don't allocate heap memory. // staticvoid save_memory_to_file(char* addr, size_t size) {
RESTARTABLE(os::open(destfile, O_CREAT|O_WRONLY|O_TRUNC, S_IRUSR|S_IWUSR), fd); if (fd == OS_ERR) { if (PrintMiscellaneous && Verbose) {
warning("Could not create Perfdata save file: %s: %s\n",
destfile, os::strerror(errno));
}
} else {
ssize_t result;
for (size_t remaining = size; remaining > 0;) {
result = os::write(fd, addr, remaining); if (result == OS_ERR) { if (PrintMiscellaneous && Verbose) {
warning("Could not write Perfdata save file: %s: %s\n",
destfile, os::strerror(errno));
} break;
}
remaining -= (size_t)result;
addr += result;
}
result = ::close(fd); if (PrintMiscellaneous && Verbose) { if (result == OS_ERR) {
warning("Could not close %s: %s\n", destfile, os::strerror(errno));
}
}
}
FREE_C_HEAP_ARRAY(char, destfile);
}
// Shared Memory Implementation Details
// Note: the Posix shared memory implementation uses the mmap // interface with a backing store file to implement named shared memory. // Using the file system as the name space for shared memory allows a // common name space to be supported across a variety of platforms. It // also provides a name space that Java applications can deal with through // simple file apis. //
// return the user specific temporary directory name. // the caller is expected to free the allocated memory. // #define TMP_BUFFER_LEN (4+22) staticchar* get_user_tmp_dir(constchar* user, int vmid, int nspid) { char* tmpdir = (char *)os::get_temp_directory(); #ifdefined(LINUX) // On linux, if containerized process, get dirname of // /proc/{vmid}/root/tmp/{PERFDATA_NAME_user} // otherwise /tmp/{PERFDATA_NAME_user} char buffer[TMP_BUFFER_LEN];
assert(strlen(tmpdir) == 4, "No longer using /tmp - update buffer size");
// construct the path name to user specific tmp directory
snprintf(dirname, nbytes, "%s/%s_%s", tmpdir, perfdir, user);
return dirname;
}
// convert the given file name into a process id. if the file // does not meet the file naming constraints, return 0. // static pid_t filename_to_pid(constchar* filename) {
// a filename that doesn't begin with a digit is not a // candidate for conversion. // if (!isdigit(*filename)) { return 0;
}
// check if file name can be converted to an integer without // any leftover characters. // char* remainder = NULL;
errno = 0;
pid_t pid = (pid_t)strtol(filename, &remainder, 10);
if (errno != 0) { return 0;
}
// check for left over characters. If any, then the filename is // not a candidate for conversion. // if (remainder != NULL && *remainder != '\0') { return 0;
}
// successful conversion, return the pid return pid;
}
// Check if the given statbuf is considered a secure directory for // the backing store files. Returns true if the directory is considered // a secure location. Returns false if the statbuf is a symbolic link or // if an error occurred. // staticbool is_statbuf_secure(struct stat *statp) { if (S_ISLNK(statp->st_mode) || !S_ISDIR(statp->st_mode)) { // The path represents a link or some non-directory file type, // which is not what we expected. Declare it insecure. // returnfalse;
} // We have an existing directory, check if the permissions are safe. // if ((statp->st_mode & (S_IWGRP|S_IWOTH)) != 0) { // The directory is open for writing and could be subjected // to a symlink or a hard link attack. Declare it insecure. // returnfalse;
} // If user is not root then see if the uid of the directory matches the effective uid of the process.
uid_t euid = geteuid(); if ((euid != 0) && (statp->st_uid != euid)) { // The directory was not created by this user, declare it insecure. // returnfalse;
} returntrue;
}
// Check if the given path is considered a secure directory for // the backing store files. Returns true if the directory exists // and is considered a secure location. Returns false if the path // is a symbolic link or if an error occurred. // staticbool is_directory_secure(constchar* path) { struct stat statbuf; int result = 0;
RESTARTABLE(::lstat(path, &statbuf), result); if (result == OS_ERR) { returnfalse;
}
// The path exists, see if it is secure. return is_statbuf_secure(&statbuf);
}
// Check if the given directory file descriptor is considered a secure // directory for the backing store files. Returns true if the directory // exists and is considered a secure location. Returns false if the path // is a symbolic link or if an error occurred. // staticbool is_dirfd_secure(int dir_fd) { struct stat statbuf; int result = 0;
RESTARTABLE(::fstat(dir_fd, &statbuf), result); if (result == OS_ERR) { returnfalse;
}
// The path exists, now check its mode. return is_statbuf_secure(&statbuf);
}
// Check to make sure fd1 and fd2 are referencing the same file system object. // staticbool is_same_fsobject(int fd1, int fd2) { struct stat statbuf1; struct stat statbuf2; int result = 0;
RESTARTABLE(::fstat(fd1, &statbuf1), result); if (result == OS_ERR) { returnfalse;
}
RESTARTABLE(::fstat(fd2, &statbuf2), result); if (result == OS_ERR) { returnfalse;
}
// Open the directory of the given path and validate it. // Return a DIR * of the open directory. // static DIR *open_directory_secure(constchar* dirname) { // Open the directory using open() so that it can be verified // to be secure by calling is_dirfd_secure(), opendir() and then check // to see if they are the same file system object. This method does not // introduce a window of opportunity for the directory to be attacked that // calling opendir() and is_directory_secure() does. int result;
DIR *dirp = NULL;
RESTARTABLE(::open(dirname, O_RDONLY|O_NOFOLLOW), result); if (result == OS_ERR) { // Directory doesn't exist or is a symlink, so there is nothing to cleanup. if (PrintMiscellaneous && Verbose) { if (errno == ELOOP) {
warning("directory %s is a symlink and is not secure\n", dirname);
} else {
warning("could not open directory %s: %s\n", dirname, os::strerror(errno));
}
} return dirp;
} int fd = result;
// Determine if the open directory is secure. if (!is_dirfd_secure(fd)) { // The directory is not a secure directory.
::close(fd); return dirp;
}
// Open the directory.
dirp = ::opendir(dirname); if (dirp == NULL) { // The directory doesn't exist, close fd and return.
::close(fd); return dirp;
}
// Check to make sure fd and dirp are referencing the same file system object. if (!is_same_fsobject(fd, AIX_ONLY(dirp->dd_fd) NOT_AIX(dirfd(dirp)))) { // The directory is not secure.
::close(fd);
os::closedir(dirp);
dirp = NULL; return dirp;
}
// Close initial open now that we know directory is secure
::close(fd);
return dirp;
}
// NOTE: The code below uses fchdir(), open() and unlink() because // fdopendir(), openat() and unlinkat() are not supported on all // versions. Once the support for fdopendir(), openat() and unlinkat() // is available on all supported versions the code can be changed // to use these functions.
// Open the directory of the given path, validate it and set the // current working directory to it. // Return a DIR * of the open directory and the saved cwd fd. // static DIR *open_directory_secure_cwd(constchar* dirname, int *saved_cwd_fd) {
// Open the directory.
DIR* dirp = open_directory_secure(dirname); if (dirp == NULL) { // Directory doesn't exist or is insecure, so there is nothing to cleanup. return dirp;
} int fd = AIX_ONLY(dirp->dd_fd) NOT_AIX(dirfd(dirp));
// Open a fd to the cwd and save it off. int result;
RESTARTABLE(::open(".", O_RDONLY), result); if (result == OS_ERR) {
*saved_cwd_fd = -1;
} else {
*saved_cwd_fd = result;
}
// Set the current directory to dirname by using the fd of the directory and // handle errors, otherwise shared memory files will be created in cwd.
result = fchdir(fd); if (result == OS_ERR) { if (PrintMiscellaneous && Verbose) {
warning("could not change to directory %s", dirname);
} if (*saved_cwd_fd != -1) {
::close(*saved_cwd_fd);
*saved_cwd_fd = -1;
} // Close the directory.
os::closedir(dirp); return NULL;
} else { return dirp;
}
}
// Close the directory and restore the current working directory. // staticvoid close_directory_secure_cwd(DIR* dirp, int saved_cwd_fd) {
int result; // If we have a saved cwd change back to it and close the fd. if (saved_cwd_fd != -1) {
result = fchdir(saved_cwd_fd);
::close(saved_cwd_fd);
}
// Close the directory.
os::closedir(dirp);
}
// Check if the given file descriptor is considered a secure. // staticbool is_file_secure(int fd, constchar *filename) {
int result; struct stat statbuf;
// Determine if the file is secure.
RESTARTABLE(::fstat(fd, &statbuf), result); if (result == OS_ERR) { if (PrintMiscellaneous && Verbose) {
warning("fstat failed on %s: %s\n", filename, os::strerror(errno));
} returnfalse;
} if (statbuf.st_nlink > 1) { // A file with multiple links is not expected. if (PrintMiscellaneous && Verbose) {
warning("file %s has multiple links\n", filename);
} returnfalse;
} returntrue;
}
// return the user name for the given user id // // the caller is expected to free the allocated memory. // staticchar* get_user_name(uid_t uid) {
struct passwd pwent;
// Determine the max pwbuf size from sysconf, and hardcode // a default if this not available through sysconf. long bufsize = sysconf(_SC_GETPW_R_SIZE_MAX); if (bufsize == -1)
bufsize = 1024;
struct passwd* p = NULL; int result = getpwuid_r(uid, &pwent, pwbuf, (size_t)bufsize, &p);
if (result != 0 || p == NULL || p->pw_name == NULL || *(p->pw_name) == '\0') { if (PrintMiscellaneous && Verbose) { if (result != 0) {
warning("Could not retrieve passwd entry: %s\n",
os::strerror(result));
} elseif (p == NULL) { // this check is added to protect against an observed problem // with getpwuid_r() on RedHat 9 where getpwuid_r returns 0, // indicating success, but has p == NULL. This was observed when // inserting a file descriptor exhaustion fault prior to the call // getpwuid_r() call. In this case, error is set to the appropriate // error condition, but this is undocumented behavior. This check // is safe under any condition, but the use of errno in the output // message may result in an erroneous message. // Bug Id 89052 was opened with RedHat. //
warning("Could not retrieve passwd entry: %s\n",
os::strerror(errno));
} else {
warning("Could not determine user name: %s\n",
p->pw_name == NULL ? "pw_name = NULL" : "pw_name zero length");
}
}
FREE_C_HEAP_ARRAY(char, pwbuf); return NULL;
}
// return the name of the user that owns the process identified by vmid. // // This method uses a slow directory search algorithm to find the backing // store file for the specified vmid and returns the user name, as determined // by the user name suffix of the hsperfdata_<username> directory name. // // the caller is expected to free the allocated memory. // // staticchar* get_user_name_slow(int vmid, int nspid, TRAPS) {
// short circuit the directory search if the process doesn't even exist. if (kill(vmid, 0) == OS_ERR) { if (errno == ESRCH) {
THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(), "Process not found");
} else/* EPERM */ {
THROW_MSG_0(vmSymbols::java_io_IOException(), os::strerror(errno));
}
}
// On Linux, if nspid != -1, look in /proc/{vmid}/root/tmp for directories // containing nspid, otherwise just look for vmid in /tmp. if (nspid == -1) {
searchpid = vmid;
} else {
jio_snprintf(buffer, MAXPATHLEN, "/proc/%d/root%s", vmid, tmpdirname);
tmpdirname = buffer;
searchpid = nspid;
} #else
searchpid = vmid; #endif
// open the temp directory
DIR* tmpdirp = os::opendir(tmpdirname);
if (tmpdirp == NULL) { // Cannot open the directory to get the user name, return. return NULL;
}
// for each entry in the directory that matches the pattern hsperfdata_*, // open the directory and check if the file for the given vmid (or nspid) exists. // The file with the expected name and the latest creation date is used // to determine the user name for the process id. // struct dirent* dentry;
errno = 0; while ((dentry = os::readdir(tmpdirp)) != NULL) {
// check if the directory entry is a hsperfdata file if (strncmp(dentry->d_name, PERFDATA_NAME, strlen(PERFDATA_NAME)) != 0) { continue;
}
// open the user directory
DIR* subdirp = open_directory_secure(usrdir_name);
if (subdirp == NULL) {
FREE_C_HEAP_ARRAY(char, usrdir_name); continue;
}
// Since we don't create the backing store files in directories // pointed to by symbolic links, we also don't follow them when // looking for the files. We check for a symbolic link after the // call to opendir in order to eliminate a small window where the // symlink can be exploited. // if (!is_directory_secure(usrdir_name)) {
FREE_C_HEAP_ARRAY(char, usrdir_name);
os::closedir(subdirp); continue;
}
// return the name of the user that owns the JVM indicated by the given vmid. // staticchar* get_user_name(int vmid, int *nspid, TRAPS) { char *result = get_user_name_slow(vmid, *nspid, CHECK_NULL);
#ifdefined(LINUX) // If we are examining a container process without PID namespaces enabled // we need to use /proc/{pid}/root/tmp to find hsperfdata files. if (result == NULL) {
result = get_user_name_slow(vmid, vmid, CHECK_NULL); // Enable nspid logic going forward if (result != NULL) *nspid = vmid;
} #endif return result;
}
// return the file name of the backing store file for the named // shared memory region for the given user name and vmid. // // the caller is expected to free the allocated memory. // staticchar* get_sharedmem_filename(constchar* dirname, int vmid, int nspid) {
// remove file // // this method removes the file specified by the given path // staticvoid remove_file(constchar* path) {
int result;
// if the file is a directory, the following unlink will fail. since // we don't expect to find directories in the user temp directory, we // won't try to handle this situation. even if accidentally or // maliciously planted, the directory's presence won't hurt anything. //
RESTARTABLE(::unlink(path), result); if (PrintMiscellaneous && Verbose && result == OS_ERR) { if (errno != ENOENT) {
warning("Could not unlink shared memory backing" " store file %s : %s\n", path, os::strerror(errno));
}
}
}
// cleanup stale shared memory files // // This method attempts to remove all stale shared memory files in // the named user temporary directory. It scans the named directory // for files matching the pattern ^$[0-9]*$. // // This directory should be used only by JVM processes owned by the // current user to store PerfMemory files. Any other files found // in this directory may be removed. // staticvoid cleanup_sharedmem_files(constchar* dirname) {
int saved_cwd_fd; // open the directory and set the current working directory to it
DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd); if (dirp == NULL) { // directory doesn't exist or is insecure, so there is nothing to cleanup return;
}
// For each entry in the directory that matches the expected file // name pattern, remove the file if it's determine to be stale // Note, instrumented HotSpot processes for this user may start and/or // terminate during this search and remove or create new files in this // directory. The behavior of this loop under these conditions is dependent // upon the implementation of opendir/readdir. // struct dirent* entry;
errno = 0; while ((entry = os::readdir(dirp)) != NULL) { constchar* filename = entry->d_name;
pid_t pid = filename_to_pid(filename);
if (pid == 0) { if (strcmp(filename, ".") != 0 && strcmp(filename, "..") != 0) { // attempt to remove all unexpected files, except "." and ".."
unlink(filename);
}
errno = 0; continue;
}
#ifdefined(LINUX) // Special case on Linux, if multiple containers share the // same /tmp directory: // // - All the JVMs must have the JDK-8286030 fix, or the behavior // is undefined. // - We cannot rely on the values of the pid, because it could // be a process in a different namespace. We must use the flock // protocol to determine if a live process is using this file. // See create_sharedmem_file(). int fd;
RESTARTABLE(os::open(filename, O_RDONLY, 0), fd); if (fd == OS_ERR) { // Something wrong happened. Ignore the error and don't try to remove the // file.
log_debug(perf, memops)("os::open() for stale file check failed for %s/%s", dirname, filename);
errno = 0; continue;
}
int n;
RESTARTABLE(::flock(fd, LOCK_EX|LOCK_NB), n); if (n != 0) { // Either another process holds the exclusive lock on this file, or // something wrong happened. Ignore the error and don't try to remove the // file.
log_debug(perf, memops)("flock for stale file check failed for %s/%s", dirname, filename);
::close(fd);
errno = 0; continue;
} // We are able to lock the file, but this file might have been created // by an older JVM that doesn't use the flock prototol, so we must do // the folowing checks (which are also done by older JVMs). #endif
// The following code assumes that pid must be in the same // namespace as the current process. bool stale = false;
if (pid == os::current_process_id()) { // The file was created by a terminated process that happened // to have the same pid as the current process.
stale = true;
} elseif (kill(pid, 0) == OS_ERR) { if (errno == ESRCH) { // The target process does not exist.
stale = true;
} elseif (errno == EPERM) { // The file was created by a terminated process that happened // to have the same pid as a process not owned by the current user.
stale = true;
}
}
if (stale) {
log_info(perf, memops)("Remove stale file %s/%s", dirname, filename);
unlink(filename);
}
#ifdefined(LINUX) // Hold the lock until here to prevent other JVMs from using this file // while we were in the middle of deleting it.
::close(fd); #endif
errno = 0;
}
// close the directory and reset the current working directory
close_directory_secure_cwd(dirp, saved_cwd_fd);
}
// make the user specific temporary directory. Returns true if // the directory exists and is secure upon return. Returns false // if the directory exists but is either a symlink, is otherwise // insecure, or if an error occurred. // staticbool make_user_tmp_dir(constchar* dirname) {
// create the directory with 0755 permissions. note that the directory // will be owned by euid::egid, which may not be the same as uid::gid. // if (mkdir(dirname, S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) == OS_ERR) { if (errno == EEXIST) { // The directory already exists and was probably created by another // JVM instance. However, this could also be the result of a // deliberate symlink. Verify that the existing directory is safe. // if (!is_directory_secure(dirname)) { // directory is not secure if (PrintMiscellaneous && Verbose) {
warning("%s directory is insecure\n", dirname);
} returnfalse;
}
} else { // we encountered some other failure while attempting // to create the directory // if (PrintMiscellaneous && Verbose) {
warning("could not create directory %s: %s\n",
dirname, os::strerror(errno));
} returnfalse;
}
} returntrue;
}
// create the shared memory file // // This method creates the shared memory file with the given size // This method also creates the user specific temporary directory, if // it does not yet exist. // staticint create_sharedmem_file(constchar* dirname, constchar* filename, size_t size) {
// make the user temporary directory if (!make_user_tmp_dir(dirname)) { // could not make/find the directory or the found directory // was not secure return -1;
}
int saved_cwd_fd; // open the directory and set the current working directory to it
DIR* dirp = open_directory_secure_cwd(dirname, &saved_cwd_fd); if (dirp == NULL) { // Directory doesn't exist or is insecure, so cannot create shared // memory file. return -1;
}
// Open the filename in the current directory. // Cannot use O_TRUNC here; truncation of an existing file has to happen // after the is_file_secure() check below. int fd;
RESTARTABLE(os::open(filename, O_RDWR|O_CREAT|O_NOFOLLOW, S_IRUSR|S_IWUSR), fd); if (fd == OS_ERR) { if (PrintMiscellaneous && Verbose) { if (errno == ELOOP) {
warning("file %s is a symlink and is not secure\n", filename);
} else {
warning("could not create file %s: %s\n", filename, os::strerror(errno));
}
} // close the directory and reset the current working directory
close_directory_secure_cwd(dirp, saved_cwd_fd);
return -1;
} // close the directory and reset the current working directory
close_directory_secure_cwd(dirp, saved_cwd_fd);
// check to see if the file is secure if (!is_file_secure(fd, filename)) {
::close(fd); return -1;
}
#ifdefined(LINUX) // On Linux, different containerized processes that share the same /tmp // directory (e.g., with "docker --volume ...") may have the same pid and // try to use the same file. To avoid conflicts among such // processes, we allow only one of them (the winner of the flock() call) // to write to the file. All the other processes will give up and will // have perfdata disabled. // // Note that the flock will be automatically given up when the winner // process exits. // // The locking protocol works only with other JVMs that have the JDK-8286030 // fix. If you are sharing the /tmp difrectory among different containers, // do not use older JVMs that don't have this fix, or the behavior is undefined. int n;
RESTARTABLE(::flock(fd, LOCK_EX|LOCK_NB), n); if (n != 0) {
log_warning(perf, memops)("Cannot use file %s/%s because %s (errno = %d)", dirname, filename,
(errno == EWOULDBLOCK) ? "it is locked by another process" : "flock() failed", errno);
::close(fd); return -1;
} #endif
ssize_t result;
// truncate the file to get rid of any existing data
RESTARTABLE(::ftruncate(fd, (off_t)0), result); if (result == OS_ERR) { if (PrintMiscellaneous && Verbose) {
warning("could not truncate shared memory file: %s\n", os::strerror(errno));
}
::close(fd); return -1;
} // set the file size
RESTARTABLE(::ftruncate(fd, (off_t)size), result); if (result == OS_ERR) { if (PrintMiscellaneous && Verbose) {
warning("could not set shared memory file size: %s\n", os::strerror(errno));
}
::close(fd); return -1;
}
// Verify that we have enough disk space for this file. // We'll get random SIGBUS crashes on memory accesses if // we don't. for (size_t seekpos = 0; seekpos < size; seekpos += os::vm_page_size()) { int zero_int = 0;
result = (int)os::seek_to_file_offset(fd, (jlong)(seekpos)); if (result == -1 ) break;
result = os::write(fd, &zero_int, 1); if (result != 1) { if (errno == ENOSPC) {
warning("Insufficient space for shared memory file:\n %s\nTry using the -Djava.io.tmpdir= option to select an alternate temp location.\n", filename);
} break;
}
}
// open the shared memory file for the given user and vmid. returns // the file descriptor for the open file or -1 if the file could not // be opened. // staticint open_sharedmem_file(constchar* filename, int oflags, TRAPS) {
// open the file int result;
RESTARTABLE(os::open(filename, oflags, 0), result); if (result == OS_ERR) { if (errno == ENOENT) {
THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(), "Process not found", OS_ERR);
} elseif (errno == EACCES) {
THROW_MSG_(vmSymbols::java_lang_IllegalArgumentException(), "Permission denied", OS_ERR);
} else {
THROW_MSG_(vmSymbols::java_io_IOException(),
os::strerror(errno), OS_ERR);
}
} int fd = result;
// check to see if the file is secure if (!is_file_secure(fd, filename)) {
::close(fd); return OS_ERR;
}
return fd;
}
// create a named shared memory region. returns the address of the // memory region on success or NULL on failure. A return value of // NULL will ultimately disable the shared memory feature. // // The name space for shared memory objects is the file system name space. // // A monitoring application attaching to a JVM does not need to know // the file system name of the shared memory object. However, it may // be convenient for applications to discover the existence of newly // created and terminating JVMs by watching the file system name space // for files being created or removed. // staticchar* mmap_create_shared(size_t size) {
// save the file name for use in delete_shared_memory()
backing_store_file_name = filename;
// clear the shared memory region
(void)::memset((void*) mapAddress, 0, size);
// it does not go through os api, the operation has to record from here
MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
log_info(perf, memops)("Successfully opened");
return mapAddress;
}
// release a named shared memory region that was mmap-ed. // staticvoid unmap_shared(char* addr, size_t bytes) { int res; if (MemTracker::enabled()) { // Note: Tracker contains a ThreadCritical.
Tracker tkr(Tracker::release);
res = ::munmap(addr, bytes); if (res == 0) {
tkr.record((address)addr, bytes);
}
} else {
res = ::munmap(addr, bytes);
} if (res != 0) {
log_info(os)("os::release_memory failed (" PTR_FORMAT ", " SIZE_FORMAT ")", p2i(addr), bytes);
}
}
// create the PerfData memory region in shared memory. // staticchar* create_shared_memory(size_t size) {
// create the shared memory region. return mmap_create_shared(size);
}
// delete the shared PerfData memory region // staticvoid delete_shared_memory(char* addr, size_t size) {
// Remove the shared memory file. Since DestroyJavaVM does // not support unloading of the JVM, unmapping of the memory region is // not performed. The memory will be reclaimed by the OS upon termination of // the process.
assert(!PerfDisableSharedMem, "shouldn't be here");
if (backing_store_file_name != NULL) {
remove_file(backing_store_file_name); // Don't.. Free heap memory could deadlock os::abort() if it is called // from signal handler. OS will reclaim the heap memory. // FREE_C_HEAP_ARRAY(char, backing_store_file_name);
backing_store_file_name = NULL;
}
}
// return the size of the file for the given file descriptor // or 0 if it is not a valid size for a shared memory file // static size_t sharedmem_filesize(int fd, TRAPS) {
struct stat statbuf; int result;
RESTARTABLE(::fstat(fd, &statbuf), result); if (result == OS_ERR) { if (PrintMiscellaneous && Verbose) {
warning("fstat failed: %s\n", os::strerror(errno));
}
THROW_MSG_0(vmSymbols::java_io_IOException(), "Could not determine PerfMemory size");
}
// attach to a named shared memory region. // staticvoid mmap_attach_shared(int vmid, char** addr, size_t* sizep, TRAPS) {
int mmap_prot = PROT_READ; int file_flags = O_RDONLY | O_NOFOLLOW;
// for linux, determine if vmid is for a containerized process int nspid = LINUX_ONLY(os::Linux::get_namespace_pid(vmid)) NOT_LINUX(-1); constchar* luser = get_user_name(vmid, &nspid, CHECK);
if (luser == NULL) {
THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "Could not map vmid to user Name");
}
// since we don't follow symbolic links when creating the backing // store file, we don't follow them when attaching either. // if (!is_directory_secure(dirname)) {
FREE_C_HEAP_ARRAY(char, dirname);
FREE_C_HEAP_ARRAY(char, luser);
THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "Process not found");
}
// open the shared memory file for the give vmid char* filename = get_sharedmem_filename(dirname, vmid, nspid);
// We don't use CHECK as we need to free the strings even if an exception occurred. int fd = open_sharedmem_file(filename, file_flags, THREAD);
// free the c heap resources that are no longer needed
FREE_C_HEAP_ARRAY(char, luser);
FREE_C_HEAP_ARRAY(char, dirname);
FREE_C_HEAP_ARRAY(char, filename);
if (fd == OS_ERR || HAS_PENDING_EXCEPTION) { return;
}
int result = ::close(fd);
assert(result != OS_ERR, "could not close file");
if (mapAddress == MAP_FAILED) { if (PrintMiscellaneous && Verbose) {
warning("mmap failed: %s\n", os::strerror(errno));
}
THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(), "Could not map PerfMemory");
}
// it does not go through os api, the operation has to record from here
MemTracker::record_virtual_memory_reserve_and_commit((address)mapAddress, size, CURRENT_PC, mtInternal);
*addr = mapAddress;
*sizep = size;
log_debug(perf, memops)("mapped " SIZE_FORMAT " bytes for vmid %d at "
INTPTR_FORMAT, size, vmid, p2i((void*)mapAddress));
}
// create the PerfData memory region // // This method creates the memory region used to store performance // data for the JVM. The memory may be created in standard or // shared memory. // void PerfMemory::create_memory_region(size_t size) {
if (PerfDisableSharedMem) { // do not share the memory for the performance data.
_start = create_standard_memory(size);
} else {
_start = create_shared_memory(size); if (_start == NULL) {
// creation of the shared memory region failed, attempt // to create a contiguous, non-shared memory region instead. // if (PrintMiscellaneous && Verbose) {
warning("Reverting to non-shared PerfMemory region.\n");
}
FLAG_SET_ERGO(PerfDisableSharedMem, true);
_start = create_standard_memory(size);
}
}
if (_start != NULL) _capacity = size;
}
// delete the PerfData memory region // // This method deletes the memory region used to store performance // data for the JVM. The memory region indicated by the <address, size> // tuple will be inaccessible after a call to this method. // void PerfMemory::delete_memory_region() {
// If user specifies PerfDataSaveFile, it will save the performance data // to the specified file name no matter whether PerfDataSaveToFile is specified // or not. In other word, -XX:PerfDataSaveFile=.. overrides flag // -XX:+PerfDataSaveToFile. if (PerfDataSaveToFile || PerfDataSaveFile != NULL) {
save_memory_to_file(start(), capacity());
}
if (!PerfDisableSharedMem) {
delete_shared_memory(start(), capacity());
}
}
// attach to the PerfData memory region for another JVM // // This method returns an <address, size> tuple that points to // a memory buffer that is kept reasonably synchronized with // the PerfData memory region for the indicated JVM. This // buffer may be kept in synchronization via shared memory // or some other mechanism that keeps the buffer updated. // // If the JVM chooses not to support the attachability feature, // this method should throw an UnsupportedOperation exception. // // This implementation utilizes named shared memory to map // the indicated process's PerfData memory region into this JVMs // address space. // void PerfMemory::attach(int vmid, char** addrp, size_t* sizep, TRAPS) {
// detach from the PerfData memory region of another JVM // // This method detaches the PerfData memory region of another // JVM, specified as an <address, size> tuple of a buffer // in this process's address space. This method may perform // arbitrary actions to accomplish the detachment. The memory // region specified by <address, size> will be inaccessible after // a call to this method. // // If the JVM chooses not to support the attachability feature, // this method should throw an UnsupportedOperation exception. // // This implementation utilizes named shared memory to detach // the indicated process's PerfData memory region from this // process's address space. // void PerfMemory::detach(char* addr, size_t bytes) {
if (PerfMemory::contains(addr) || PerfMemory::contains(addr + bytes - 1)) { // prevent accidental detachment of this process's PerfMemory region return;
}
unmap_shared(addr, bytes);
}
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