1 /*
   2  * Copyright (c) 2016, 2020, 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/zErrno.hpp"
  27 #include "gc/z/zMountPoint_linux.hpp"
  28 #include "runtime/globals.hpp"
  29 #include "logging/log.hpp"
  30 
  31 #include <stdio.h>
  32 #include <unistd.h>
  33 
  34 // Mount information, see proc(5) for more details.
  35 #define PROC_SELF_MOUNTINFO        "/proc/self/mountinfo"
  36 
  37 ZMountPoint::ZMountPoint(const char* filesystem, const char** preferred_mountpoints) {
  38   if (AllocateHeapAt != NULL) {
  39     // Use specified path
  40     _path = strdup(AllocateHeapAt);
  41   } else {
  42     // Find suitable path
  43     _path = find_mountpoint(filesystem, preferred_mountpoints);
  44   }
  45 }
  46 
  47 ZMountPoint::~ZMountPoint() {
  48   free(_path);
  49   _path = NULL;
  50 }
  51 
  52 char* ZMountPoint::get_mountpoint(const char* line, const char* filesystem) const {
  53   char* line_mountpoint = NULL;
  54   char* line_filesystem = NULL;
  55 
  56   // Parse line and return a newly allocated string containing the mount point if
  57   // the line contains a matching filesystem and the mount point is accessible by
  58   // the current user.
  59   if (sscanf(line, "%*u %*u %*u:%*u %*s %ms %*[^-]- %ms", &line_mountpoint, &line_filesystem) != 2 ||
  60       strcmp(line_filesystem, filesystem) != 0 ||
  61       access(line_mountpoint, R_OK|W_OK|X_OK) != 0) {
  62     // Not a matching or accessible filesystem
  63     free(line_mountpoint);
  64     line_mountpoint = NULL;
  65   }
  66 
  67   free(line_filesystem);
  68 
  69   return line_mountpoint;
  70 }
  71 
  72 void ZMountPoint::get_mountpoints(const char* filesystem, ZArray<char*>* mountpoints) const {
  73   FILE* fd = fopen(PROC_SELF_MOUNTINFO, "r");
  74   if (fd == NULL) {
  75     ZErrno err;
  76     log_error(gc)("Failed to open %s: %s", PROC_SELF_MOUNTINFO, err.to_string());
  77     return;
  78   }
  79 
  80   char* line = NULL;
  81   size_t length = 0;
  82 
  83   while (getline(&line, &length, fd) != -1) {
  84     char* const mountpoint = get_mountpoint(line, filesystem);
  85     if (mountpoint != NULL) {
  86       mountpoints->add(mountpoint);
  87     }
  88   }
  89 
  90   free(line);
  91   fclose(fd);
  92 }
  93 
  94 void ZMountPoint::free_mountpoints(ZArray<char*>* mountpoints) const {
  95   ZArrayIterator<char*> iter(mountpoints);
  96   for (char* mountpoint; iter.next(&mountpoint);) {
  97     free(mountpoint);
  98   }
  99   mountpoints->clear();
 100 }
 101 
 102 char* ZMountPoint::find_preferred_mountpoint(const char* filesystem,
 103                                               ZArray<char*>* mountpoints,
 104                                               const char** preferred_mountpoints) const {
 105   // Find preferred mount point
 106   ZArrayIterator<char*> iter1(mountpoints);
 107   for (char* mountpoint; iter1.next(&mountpoint);) {
 108     for (const char** preferred = preferred_mountpoints; *preferred != NULL; preferred++) {
 109       if (!strcmp(mountpoint, *preferred)) {
 110         // Preferred mount point found
 111         return strdup(mountpoint);
 112       }
 113     }
 114   }
 115 
 116   // Preferred mount point not found
 117   log_error(gc)("More than one %s filesystem found:", filesystem);
 118   ZArrayIterator<char*> iter2(mountpoints);
 119   for (char* mountpoint; iter2.next(&mountpoint);) {
 120     log_error(gc)("  %s", mountpoint);
 121   }
 122 
 123   return NULL;
 124 }
 125 
 126 char* ZMountPoint::find_mountpoint(const char* filesystem, const char** preferred_mountpoints) const {
 127   char* path = NULL;
 128   ZArray<char*> mountpoints;
 129 
 130   get_mountpoints(filesystem, &mountpoints);
 131 
 132   if (mountpoints.size() == 0) {
 133     // No mount point found
 134     log_error(gc)("Failed to find an accessible %s filesystem", filesystem);
 135   } else if (mountpoints.size() == 1) {
 136     // One mount point found
 137     path = strdup(mountpoints.at(0));
 138   } else {
 139     // More than one mount point found
 140     path = find_preferred_mountpoint(filesystem, &mountpoints, preferred_mountpoints);
 141   }
 142 
 143   free_mountpoints(&mountpoints);
 144 
 145   return path;
 146 }
 147 
 148 const char* ZMountPoint::get() const {
 149   return _path;
 150 }