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/*
* 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.
*
*/
#include "precompiled.hpp"
#include "classfile/vmSymbols.hpp"
#include "jvm_io.h"
#include "logging/log.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/resourceArea.hpp"
#include "oops/oop.inline.hpp"
#include "os_posix.inline.hpp"
#include "runtime/globals_extension.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/os.hpp"
#include "runtime/perfMemory.hpp"
#include "services/memTracker.hpp"
#include "utilities/exceptions.hpp"
#if defined(LINUX)
#include "os_linux.hpp"
#endif
// 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>
#if defined(LINUX)
# include <sys/file.h>
#endif
static char* 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.
//
static char* 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.
//
static void save_memory_to_file(char* addr, size_t size) {
const char* destfile = PerfMemory::get_perfdata_file_path();
assert(destfile[0] != '\0', "invalid PerfData file path");
int fd;
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)
static char* get_user_tmp_dir(const char* user, int vmid, int nspid) {
char* tmpdir = (char *)os::get_temp_directory();
#if defined(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");
if (nspid != -1) {
jio_snprintf(buffer, TMP_BUFFER_LEN, "/proc/%d/root%s", vmid, tmpdir);
tmpdir = buffer;
}
#endif
const char* perfdir = PERFDATA_NAME;
size_t nbytes = strlen(tmpdir) + strlen(perfdir) + strlen(user) + 3;
char* dirname = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
// 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(const char* 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.
//
static bool 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.
//
return false;
}
// 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.
//
return false;
}
// 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.
//
return false;
}
return true;
}
// 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.
//
static bool is_directory_secure(const char* path) {
struct stat statbuf;
int result = 0;
RESTARTABLE(::lstat(path, &statbuf), result);
if (result == OS_ERR) {
return false;
}
// 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.
//
static bool is_dirfd_secure(int dir_fd) {
struct stat statbuf;
int result = 0;
RESTARTABLE(::fstat(dir_fd, &statbuf), result);
if (result == OS_ERR) {
return false;
}
// 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.
//
static bool 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) {
return false;
}
RESTARTABLE(::fstat(fd2, &statbuf2), result);
if (result == OS_ERR) {
return false;
}
if ((statbuf1.st_ino == statbuf2.st_ino) &&
(statbuf1.st_dev == statbuf2.st_dev)) {
return true;
} else {
return false;
}
}
// Open the directory of the given path and validate it.
// Return a DIR * of the open directory.
//
static DIR *open_directory_secure(const char* 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(const char* 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.
//
static void 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.
//
static bool is_file_secure(int fd, const char *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));
}
return false;
}
if (statbuf.st_nlink > 1) {
// A file with multiple links is not expected.
if (PrintMiscellaneous && Verbose) {
warning("file %s has multiple links\n", filename);
}
return false;
}
return true;
}
// return the user name for the given user id
//
// the caller is expected to free the allocated memory.
//
static char* 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;
char* pwbuf = NEW_C_HEAP_ARRAY(char, bufsize, mtInternal);
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));
}
else if (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;
}
char* user_name = NEW_C_HEAP_ARRAY(char, strlen(p->pw_name) + 1, mtInternal);
strcpy(user_name, p->pw_name);
FREE_C_HEAP_ARRAY(char, pwbuf);
return user_name;
}
// 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.
//
//
static char* 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));
}
}
// directory search
char* oldest_user = NULL;
time_t oldest_ctime = 0;
int searchpid;
char* tmpdirname = (char *)os::get_temp_directory();
#if defined(LINUX)
char buffer[MAXPATHLEN + 1];
assert(strlen(tmpdirname) == 4, "No longer using /tmp - update buffer size");
// 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;
}
char* usrdir_name = NEW_C_HEAP_ARRAY(char,
strlen(tmpdirname) + strlen(dentry->d_name) + 2,
mtInternal);
strcpy(usrdir_name, tmpdirname);
strcat(usrdir_name, "/");
strcat(usrdir_name, dentry->d_name);
// 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;
}
struct dirent* udentry;
errno = 0;
while ((udentry = os::readdir(subdirp)) != NULL) {
if (filename_to_pid(udentry->d_name) == searchpid) {
struct stat statbuf;
int result;
char* filename = NEW_C_HEAP_ARRAY(char,
strlen(usrdir_name) + strlen(udentry->d_name) + 2,
mtInternal);
strcpy(filename, usrdir_name);
strcat(filename, "/");
strcat(filename, udentry->d_name);
// don't follow symbolic links for the file
RESTARTABLE(::lstat(filename, &statbuf), result);
if (result == OS_ERR) {
FREE_C_HEAP_ARRAY(char, filename);
continue;
}
// skip over files that are not regular files.
if (!S_ISREG(statbuf.st_mode)) {
FREE_C_HEAP_ARRAY(char, filename);
continue;
}
// compare and save filename with latest creation time
if (statbuf.st_size > 0 && statbuf.st_ctime > oldest_ctime) {
if (statbuf.st_ctime > oldest_ctime) {
char* user = strchr(dentry->d_name, '_') + 1;
FREE_C_HEAP_ARRAY(char, oldest_user);
oldest_user = NEW_C_HEAP_ARRAY(char, strlen(user)+1, mtInternal);
strcpy(oldest_user, user);
oldest_ctime = statbuf.st_ctime;
}
}
FREE_C_HEAP_ARRAY(char, filename);
}
}
os::closedir(subdirp);
FREE_C_HEAP_ARRAY(char, usrdir_name);
}
os::closedir(tmpdirp);
return(oldest_user);
}
// return the name of the user that owns the JVM indicated by the given vmid.
//
static char* get_user_name(int vmid, int *nspid, TRAPS) {
char *result = get_user_name_slow(vmid, *nspid, CHECK_NULL);
#if defined(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.
//
static char* get_sharedmem_filename(const char* dirname, int vmid, int nspid) {
int pid = LINUX_ONLY((nspid == -1) ? vmid : nspid) NOT_LINUX(vmid);
// add 2 for the file separator and a null terminator.
size_t nbytes = strlen(dirname) + UINT_CHARS + 2;
char* name = NEW_C_HEAP_ARRAY(char, nbytes, mtInternal);
snprintf(name, nbytes, "%s/%d", dirname, pid);
return name;
}
// remove file
//
// this method removes the file specified by the given path
//
static void remove_file(const char* 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.
//
static void cleanup_sharedmem_files(const char* 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) {
const char* 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;
}
#if defined(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;
} else if (kill(pid, 0) == OS_ERR) {
if (errno == ESRCH) {
// The target process does not exist.
stale = true;
} else if (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);
}
#if defined(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.
//
static bool make_user_tmp_dir(const char* 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);
}
return false;
}
}
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));
}
return false;
}
}
return true;
}
// 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.
//
static int create_sharedmem_file(const char* dirname, const char* 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;
}
#if defined(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;
}
}
if (result != -1) {
return fd;
} else {
::close(fd);
return -1;
}
}
// 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.
//
static int open_sharedmem_file(const char* 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);
}
else if (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.
//
static char* mmap_create_shared(size_t size) {
int result;
int fd;
char* mapAddress;
int vmid = os::current_process_id();
char* user_name = get_user_name(geteuid());
if (user_name == NULL)
return NULL;
char* dirname = get_user_tmp_dir(user_name, vmid, -1);
char* filename = get_sharedmem_filename(dirname, vmid, -1);
// get the short filename
char* short_filename = strrchr(filename, '/');
if (short_filename == NULL) {
short_filename = filename;
} else {
short_filename++;
}
// cleanup any stale shared memory files
cleanup_sharedmem_files(dirname);
assert(((size > 0) && (size % os::vm_page_size() == 0)),
"unexpected PerfMemory region size");
log_info(perf, memops)("Trying to open %s/%s", dirname, short_filename);
fd = create_sharedmem_file(dirname, short_filename, size);
FREE_C_HEAP_ARRAY(char, user_name);
FREE_C_HEAP_ARRAY(char, dirname);
if (fd == -1) {
FREE_C_HEAP_ARRAY(char, filename);
return NULL;
}
mapAddress = (char*)::mmap((char*)0, size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
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));
}
remove_file(filename);
FREE_C_HEAP_ARRAY(char, filename);
return NULL;
}
// 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.
//
static void 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.
//
static char* create_shared_memory(size_t size) {
// create the shared memory region.
return mmap_create_shared(size);
}
// delete the shared PerfData memory region
//
static void 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");
}
if ((statbuf.st_size == 0) ||
((size_t)statbuf.st_size % os::vm_page_size() != 0)) {
THROW_MSG_0(vmSymbols::java_io_IOException(),
"Invalid PerfMemory size");
}
return (size_t)statbuf.st_size;
}
// attach to a named shared memory region.
//
static void 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);
const char* luser = get_user_name(vmid, &nspid, CHECK);
if (luser == NULL) {
THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(),
"Could not map vmid to user Name");
}
char* dirname = get_user_tmp_dir(luser, vmid, nspid);
// 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;
}
size_t size;
if (*sizep == 0) {
size = sharedmem_filesize(fd, CHECK);
} else {
size = *sizep;
}
assert(size > 0, "unexpected size <= 0");
char* mapAddress = (char*)::mmap((char*)0, size, mmap_prot, MAP_SHARED, fd, 0);
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() {
assert((start() != NULL && capacity() > 0), "verify proper state");
// 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) {
if (vmid == 0 || vmid == os::current_process_id()) {
*addrp = start();
*sizep = capacity();
return;
}
mmap_attach_shared(vmid, addrp, sizep, CHECK);
}
// 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) {
assert(addr != 0, "address sanity check");
assert(bytes > 0, "capacity sanity check");
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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