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src/os/linux/vm/os_linux.cpp
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@@ -3464,10 +3464,76 @@
}
return start;
}
+// Helper function to create a temp file in the given directory
+int os::Linux::create_tmpfile(const char* dir, size_t size, bool exec) {
+
+ static char name_template[] = "/jvmheap.XXXXXX";
+
+ char fullname[strlen(dir) + sizeof(name_template)];
+ (void)strcpy(fullname, dir);
+ (void)strcat(fullname, name_template);
+
+ sigset_t set, oldset;
+ sigfillset(&set);
+
+ // block all signals while we do the file operation
+ (void)sigprocmask(SIG_BLOCK, &set, &oldset);
+
+ // set the file creation mask
+ mode_t new_mask = exec ? (S_IRUSR | S_IWUSR | S_IXUSR) : (S_IRUSR | S_IWUSR);
+ mode_t prev_umask = umask(new_mask);
+
+ // create a new file
+ int fd = mkstemp(fullname);
+
+ // reset the file creation mask
+ umask(prev_umask);
+
+ if (fd < 0) {
+ warning("Could not create file for heap");
+ return -1;
+ }
+
+ // delete the name from the filesystem. When 'fd' is closed, the file (and space) will be deleted
+ (void)unlink(fullname);
+
+ // reset the signal mask
+ (void)sigprocmask(SIG_SETMASK, &oldset, NULL);
+
+ // allocate space for the file
+ if ((errno = posix_fallocate(fd, 0, (off_t)size)) != 0) {
+ warning("Could not allocate sufficient disk space for heap");
+ return -1;
+ }
+
+ return fd;
+}
+
+// Map the given address range to a temporary file created at the specified directory.
+// The address range must already be reserved for guaranteed success. If it not reserved, their could be an error while mapping leading to JVM shutdown
+bool os::map_memory_to_file(char* base, size_t size, const char* backingFileDir) {
+
+ int fd = os::Linux::create_tmpfile(backingFileDir, size, false);
+ if (fd == -1) {
+ vm_exit_during_initialization(err_msg("Could not create temporary file in %s for object heap", backingFileDir));
+ return false;
+ }
+ int prot = PROT_READ | PROT_WRITE;
+ char* addr = (char*)mmap(base, size, prot, MAP_SHARED | MAP_FIXED, fd, 0);
+
+ if (addr == MAP_FAILED || addr != base) {
+ close(fd);
+ vm_exit_during_initialization(err_msg("Error in mapping object heap at the given filesystem dir %s", backingFileDir));
+ return false;
+ }
+
+ return true;
+}
+
// Reserve memory using mmap(MAP_HUGETLB).
// - bytes shall be a multiple of alignment.
// - req_addr can be NULL. If not NULL, it must be a multiple of alignment.
// - alignment sets the alignment at which memory shall be allocated.
// It must be a multiple of allocation granularity.
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