1 /*
   2  * Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 #include "precompiled.hpp"
  25 #include "gc/z/zArray.inline.hpp"
  26 #include "gc/z/zBackingPath_linux_x86.hpp"
  27 #include "gc/z/zErrno.hpp"
  28 #include "logging/log.hpp"
  29 
  30 #include <stdio.h>
  31 #include <unistd.h>
  32 
  33 // Mount information, see proc(5) for more details.
  34 #define PROC_SELF_MOUNTINFO        "/proc/self/mountinfo"
  35 
  36 ZBackingPath::ZBackingPath(const char* filesystem, const char** preferred_mountpoints) {
  37   if (ZPath != NULL) {
  38     // Use specified path
  39     _path = strdup(ZPath);
  40   } else {
  41     // Find suitable path
  42     _path = find_mountpoint(filesystem, preferred_mountpoints);
  43   }
  44 }
  45 
  46 ZBackingPath::~ZBackingPath() {
  47   free(_path);
  48   _path = NULL;
  49 }
  50 
  51 char* ZBackingPath::get_mountpoint(const char* line, const char* filesystem) const {
  52   char* line_mountpoint = NULL;
  53   char* line_filesystem = NULL;
  54 
  55   // Parse line and return a newly allocated string containing the mount point if
  56   // the line contains a matching filesystem and the mount point is accessible by
  57   // the current user.
  58   if (sscanf(line, "%*u %*u %*u:%*u %*s %ms %*[^-]- %ms", &line_mountpoint, &line_filesystem) != 2 ||
  59       strcmp(line_filesystem, filesystem) != 0 ||
  60       access(line_mountpoint, R_OK|W_OK|X_OK) != 0) {
  61     // Not a matching or accessible filesystem
  62     free(line_mountpoint);
  63     line_mountpoint = NULL;
  64   }
  65 
  66   free(line_filesystem);
  67 
  68   return line_mountpoint;
  69 }
  70 
  71 void ZBackingPath::get_mountpoints(const char* filesystem, ZArray<char*>* mountpoints) const {
  72   FILE* fd = fopen(PROC_SELF_MOUNTINFO, "r");
  73   if (fd == NULL) {
  74     ZErrno err;
  75     log_error(gc)("Failed to open %s: %s", PROC_SELF_MOUNTINFO, err.to_string());
  76     return;
  77   }
  78 
  79   char* line = NULL;
  80   size_t length = 0;
  81 
  82   while (getline(&line, &length, fd) != -1) {
  83     char* const mountpoint = get_mountpoint(line, filesystem);
  84     if (mountpoint != NULL) {
  85       mountpoints->add(mountpoint);
  86     }
  87   }
  88 
  89   free(line);
  90   fclose(fd);
  91 }
  92 
  93 void ZBackingPath::free_mountpoints(ZArray<char*>* mountpoints) const {
  94   ZArrayIterator<char*> iter(mountpoints);
  95   for (char* mountpoint; iter.next(&mountpoint);) {
  96     free(mountpoint);
  97   }
  98   mountpoints->clear();
  99 }
 100 
 101 char* ZBackingPath::find_preferred_mountpoint(const char* filesystem,
 102                                               ZArray<char*>* mountpoints,
 103                                               const char** preferred_mountpoints) const {
 104   // Find preferred mount point
 105   ZArrayIterator<char*> iter1(mountpoints);
 106   for (char* mountpoint; iter1.next(&mountpoint);) {
 107     for (const char** preferred = preferred_mountpoints; *preferred != NULL; preferred++) {
 108       if (!strcmp(mountpoint, *preferred)) {
 109         // Preferred mount point found
 110         return strdup(mountpoint);
 111       }
 112     }
 113   }
 114 
 115   // Preferred mount point not found
 116   log_error(gc)("More than one %s filesystem found:", filesystem);
 117   ZArrayIterator<char*> iter2(mountpoints);
 118   for (char* mountpoint; iter2.next(&mountpoint);) {
 119     log_error(gc)("  %s", mountpoint);
 120   }
 121 
 122   return NULL;
 123 }
 124 
 125 char* ZBackingPath::find_mountpoint(const char* filesystem, const char** preferred_mountpoints) const {
 126   char* path = NULL;
 127   ZArray<char*> mountpoints;
 128 
 129   get_mountpoints(filesystem, &mountpoints);
 130 
 131   if (mountpoints.size() == 0) {
 132     // No mount point found
 133     log_error(gc)("Failed to find an accessible %s filesystem", filesystem);
 134   } else if (mountpoints.size() == 1) {
 135     // One mount point found
 136     path = strdup(mountpoints.at(0));
 137   } else {
 138     // More than one mount point found
 139     path = find_preferred_mountpoint(filesystem, &mountpoints, preferred_mountpoints);
 140   }
 141 
 142   free_mountpoints(&mountpoints);
 143 
 144   return path;
 145 }
 146 
 147 const char* ZBackingPath::get() const {
 148   return _path;
 149 }