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SystemLookup.java
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SystemLookup.java
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/*
* Copyright (c) 2021, 2023, Oracle and/or its affiliates. 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. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* 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.
*/
package jdk.internal.foreign;
import java.lang.foreign.*;
import java.lang.invoke.MethodHandles;
import java.nio.file.Files;
import java.nio.file.Path;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Objects;
import java.util.Optional;
import java.util.function.Function;
import jdk.internal.loader.NativeLibrary;
import jdk.internal.loader.RawNativeLibraries;
import sun.security.action.GetPropertyAction;
import static java.lang.foreign.ValueLayout.ADDRESS;
public final class SystemLookup implements SymbolLookup {
private SystemLookup() { }
private static final SystemLookup INSTANCE = new SystemLookup();
/* A fallback lookup, used when creation of system lookup fails. */
private static final SymbolLookup FALLBACK_LOOKUP = name -> {
Objects.requireNonNull(name);
return Optional.empty();
};
/*
* On POSIX systems, dlsym will allow us to lookup symbol in library dependencies; the same trick doesn't work
* on Windows. For this reason, on Windows we do not generate any side-library, and load msvcrt.dll directly instead.
*/
private static final SymbolLookup SYSTEM_LOOKUP = makeSystemLookup();
private static SymbolLookup makeSystemLookup() {
try {
if (Utils.IS_WINDOWS) {
return makeWindowsLookup();
} else {
return libLookup(libs -> libs.load(jdkLibraryPath("syslookup")));
}
} catch (Throwable ex) {
// This can happen in the event of a library loading failure - e.g. if one of the libraries the
// system lookup depends on cannot be loaded for some reason. In such extreme cases, rather than
// fail, return a dummy lookup.
return FALLBACK_LOOKUP;
}
}
private static SymbolLookup makeWindowsLookup() {
@SuppressWarnings("removal")
String systemRoot = AccessController.doPrivileged(new PrivilegedAction<>() {
@Override
public String run() {
return System.getenv("SystemRoot");
}
});
Path system32 = Path.of(systemRoot, "System32");
Path ucrtbase = system32.resolve("ucrtbase.dll");
Path msvcrt = system32.resolve("msvcrt.dll");
@SuppressWarnings("removal")
boolean useUCRT = AccessController.doPrivileged(new PrivilegedAction<>() {
@Override
public Boolean run() {
return Files.exists(ucrtbase);
}
});
Path stdLib = useUCRT ? ucrtbase : msvcrt;
SymbolLookup lookup = libLookup(libs -> libs.load(stdLib));
if (useUCRT) {
// use a fallback lookup to look up inline functions from fallback lib
SymbolLookup fallbackLibLookup =
libLookup(libs -> libs.load(jdkLibraryPath("syslookup")));
MemorySegment funcs = fallbackLibLookup.find("funcs").orElseThrow()
.reinterpret(WindowsFallbackSymbols.LAYOUT.byteSize());
Function<String, Optional<MemorySegment>> fallbackLookup = name -> Optional.ofNullable(WindowsFallbackSymbols.valueOfOrNull(name))
.map(symbol -> funcs.getAtIndex(ADDRESS, symbol.ordinal()));
final SymbolLookup finalLookup = lookup;
lookup = name -> {
Objects.requireNonNull(name);
if (Utils.containsNullChars(name)) return Optional.empty();
return finalLookup.find(name).or(() -> fallbackLookup.apply(name));
};
}
return lookup;
}
private static SymbolLookup libLookup(Function<RawNativeLibraries, NativeLibrary> loader) {
NativeLibrary lib = loader.apply(RawNativeLibraries.newInstance(MethodHandles.lookup()));
return name -> {
Objects.requireNonNull(name);
if (Utils.containsNullChars(name)) return Optional.empty();
try {
long addr = lib.lookup(name);
return addr == 0 ?
Optional.empty() :
Optional.of(MemorySegment.ofAddress(addr));
} catch (NoSuchMethodException e) {
return Optional.empty();
}
};
}
/*
* Returns the path of the given library name from JDK
*/
private static Path jdkLibraryPath(String name) {
Path javahome = Path.of(GetPropertyAction.privilegedGetProperty("java.home"));
String lib = Utils.IS_WINDOWS ? "bin" : "lib";
String libname = System.mapLibraryName(name);
return javahome.resolve(lib).resolve(libname);
}
public static SystemLookup getInstance() {
return INSTANCE;
}
@Override
public Optional<MemorySegment> find(String name) {
return SYSTEM_LOOKUP.find(name);
}
// fallback symbols missing from ucrtbase.dll
// this list has to be kept in sync with the table in the companion native library
private enum WindowsFallbackSymbols {
// stdio
fprintf,
fprintf_s,
fscanf,
fscanf_s,
fwprintf,
fwprintf_s,
fwscanf,
fwscanf_s,
printf,
printf_s,
scanf,
scanf_s,
snprintf,
sprintf,
sprintf_s,
sscanf,
sscanf_s,
swprintf,
swprintf_s,
swscanf,
swscanf_s,
vfprintf,
vfprintf_s,
vfscanf,
vfscanf_s,
vfwprintf,
vfwprintf_s,
vfwscanf,
vfwscanf_s,
vprintf,
vprintf_s,
vscanf,
vscanf_s,
vsnprintf,
vsnprintf_s,
vsprintf,
vsprintf_s,
vsscanf,
vsscanf_s,
vswprintf,
vswprintf_s,
vswscanf,
vswscanf_s,
vwprintf,
vwprintf_s,
vwscanf,
vwscanf_s,
wprintf,
wprintf_s,
wscanf,
wscanf_s,
// time
gmtime;
static WindowsFallbackSymbols valueOfOrNull(String name) {
try {
return valueOf(name);
} catch (IllegalArgumentException e) {
return null;
}
}
static final SequenceLayout LAYOUT = MemoryLayout.sequenceLayout(
values().length, ADDRESS);
}
}