src/java.base/unix/native/libnio/MappedMemoryUtils.c

/*
 * Copyright (c) 2001, 2024, 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
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 */

#include "jni.h"
#include "jni_util.h"
#include "jvm.h"
#include "jlong.h"
#include "java_nio_MappedMemoryUtils.h"
#include <assert.h>
#include <sys/mman.h>
#include <stddef.h>
#include <stdlib.h>

/* Output type for mincore(2) */
#ifdef __linux__
typedef unsigned char mincore_vec_t;
#else
typedef char mincore_vec_t;
#endif

jboolean JNICALL MappedMemoryUtils_isLoaded0(JNIEnv *env, jobject obj, jlong address,
                                             jlong len, jlong numPages)
{
    jboolean loaded = JNI_TRUE;
    int result = 0;
    long i = 0;
    void *a = (void *) jlong_to_ptr(address);
    mincore_vec_t* vec = NULL;

    /* Include space for one sentinel byte at the end of the buffer
     * to catch overflows. */
    vec = (mincore_vec_t*) malloc(numPages + 1);

    if (vec == NULL) {
        JNU_ThrowOutOfMemoryError(env, NULL);
        return JNI_FALSE;
    }

    vec[numPages] = '\x7f'; /* Write sentinel. */
    result = mincore(a, (size_t)len, vec);
    assert(vec[numPages] == '\x7f'); /* Check sentinel. */

    if (result == -1) {
        JNU_ThrowIOExceptionWithLastError(env, "mincore failed");
        free(vec);
        return JNI_FALSE;
    }

    for (i=0; i<numPages; i++) {
        if (vec[i] == 0) {
            loaded = JNI_FALSE;
            break;
        }
    }
    free(vec);
    return loaded;
}


void JNICALL MappedMemoryUtils_load0(JNIEnv *env, jobject obj, jlong address,
                                     jlong len)
{
    char *a = (char *)jlong_to_ptr(address);
    int result = madvise((caddr_t)a, (size_t)len, MADV_WILLNEED);
    if (result == -1) {
        JNU_ThrowIOExceptionWithMessageAndLastError(env, "madvise with advise MADV_WILLNEED failed");
    }
}

void JNICALL MappedMemoryUtils_unload0(JNIEnv *env, jobject obj, jlong address,
                                       jlong len)
{
    char *a = (char *)jlong_to_ptr(address);
    int result = madvise((caddr_t)a, (size_t)len, MADV_DONTNEED);
    if (result == -1) {
        JNU_ThrowIOExceptionWithMessageAndLastError(env, "madvise with advise MADV_DONTNEED failed");
    }
}

void JNICALL MappedMemoryUtils_force0(JNIEnv *env, jobject obj, jobject fdo,
                                      jlong address, jlong len)
{
    void* a = (void *)jlong_to_ptr(address);
    int result = msync(a, (size_t)len, MS_SYNC);
    if (result == -1) {
        JNU_ThrowIOExceptionWithMessageAndLastError(env, "msync with parameter MS_SYNC failed");
    }
}

#define FD "Ljava/io/FileDescriptor;"

static JNINativeMethod methods[] = {
    {"isLoaded0", "(JJJ)Z",             (void *)&MappedMemoryUtils_isLoaded0},
    {"load0",     "(JJ)V",              (void *)&MappedMemoryUtils_load0},
    {"unload0",   "(JJ)V",              (void *)&MappedMemoryUtils_unload0},
    {"force0",    "(" FD "JJ)V",        (void *)&MappedMemoryUtils_force0},
};

JNIEXPORT void JNICALL
Java_java_nio_MappedMemoryUtils_registerNatives(JNIEnv *env, jclass cls)
{
    (*env)->RegisterNatives(env, cls,
                            methods, sizeof(methods)/sizeof(methods[0]));
}