common: add a class to safely wrap mlock/munlock

This class will allow mlocking small objects, of which there
may be several per page. It adds refcounting so pages are only
munlocked when the last object on that page munlocks.

2 files changed, 183 insertions, 1 deletions

diff --git a/contrib/epee/src/CMakeLists.txt b/contrib/epee/src/CMakeLists.txt
index c4750cea0..0b5e7ae6c 100644
--- a/contrib/epee/src/CMakeLists.txt
+++ b/contrib/epee/src/CMakeLists.txt
@@ -27,7 +27,7 @@
 # THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 add_library(epee STATIC hex.cpp http_auth.cpp mlog.cpp net_utils_base.cpp string_tools.cpp wipeable_string.cpp memwipe.c
-    connection_basic.cpp network_throttle.cpp network_throttle-detail.cpp)
+    connection_basic.cpp network_throttle.cpp network_throttle-detail.cpp mlocker.cpp)
 if (USE_READLINE AND GNU_READLINE_FOUND)
   add_library(epee_readline STATIC readline_buffer.cpp)
 endif()
diff --git a/contrib/epee/src/mlocker.cpp b/contrib/epee/src/mlocker.cpp
new file mode 100644
index 000000000..5573d591a
--- /dev/null
+++ b/contrib/epee/src/mlocker.cpp
@@ -0,0 +1,182 @@
+// Copyright (c) 2018, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#if defined __GNUC__ && !defined _WIN32
+#define HAVE_MLOCK 1
+#endif
+
+#include <unistd.h>
+#if defined HAVE_MLOCK
+#include <sys/mman.h>
+#endif
+#include "misc_log_ex.h"
+#include "syncobj.h"
+#include "mlocker.h"
+
+static size_t query_page_size()
+{
+#if defined HAVE_MLOCK
+  long ret = sysconf(_SC_PAGESIZE);
+  if (ret <= 0)
+  {
+    MERROR("Failed to determine page size");
+    return 0;
+  }
+  MINFO("Page size: " << ret);
+  return ret;
+#else
+#warning Missing query_page_size implementation
+#endif
+  return 0;
+}
+
+static void do_lock(void *ptr, size_t len)
+{
+#if defined HAVE_MLOCK
+  int ret = mlock(ptr, len);
+  if (ret < 0)
+    MERROR("Error locking page at " << ptr << ": " << strerror(errno));
+#else
+#warning Missing do_lock implementation
+#endif
+}
+
+static void do_unlock(void *ptr, size_t len)
+{
+#if defined HAVE_MLOCK
+  int ret = munlock(ptr, len);
+  if (ret < 0)
+    MERROR("Error unlocking page at " << ptr << ": " << strerror(errno));
+#else
+#warning Missing implementation of page size detection
+#endif
+}
+
+namespace epee
+{
+  size_t mlocker::page_size = 0;
+  size_t mlocker::num_locked_objects = 0;
+
+  boost::mutex &mlocker::mutex()
+  {
+    static boost::mutex vmutex;
+    return vmutex;
+  }
+  std::map<size_t, unsigned int> &mlocker::map()
+  {
+    static std::map<size_t, unsigned int> vmap;
+    return vmap;
+  }
+
+  size_t mlocker::get_page_size()
+  {
+    CRITICAL_REGION_LOCAL(mutex());
+    if (page_size == 0)
+      page_size = query_page_size();
+    return page_size;
+  }
+
+  mlocker::mlocker(void *ptr, size_t len): ptr(ptr), len(len)
+  {
+    lock(ptr, len);
+  }
+
+  mlocker::~mlocker()
+  {
+    unlock(ptr, len);
+  }
+
+  void mlocker::lock(void *ptr, size_t len)
+  {
+    size_t page_size = get_page_size();
+    if (page_size == 0)
+      return;
+
+    CRITICAL_REGION_LOCAL(mutex());
+    const size_t first = ((uintptr_t)ptr) / page_size;
+    const size_t last = (((uintptr_t)ptr) + len - 1) / page_size;
+    for (size_t page = first; page <= last; ++page)
+      lock_page(page);
+    ++num_locked_objects;
+  }
+
+  void mlocker::unlock(void *ptr, size_t len)
+  {
+    size_t page_size = get_page_size();
+    if (page_size == 0)
+      return;
+    CRITICAL_REGION_LOCAL(mutex());
+    const size_t first = ((uintptr_t)ptr) / page_size;
+    const size_t last = (((uintptr_t)ptr) + len - 1) / page_size;
+    for (size_t page = first; page <= last; ++page)
+      unlock_page(page);
+    --num_locked_objects;
+  }
+
+  size_t mlocker::get_num_locked_pages()
+  {
+    CRITICAL_REGION_LOCAL(mutex());
+    return map().size();
+  }
+
+  size_t mlocker::get_num_locked_objects()
+  {
+    CRITICAL_REGION_LOCAL(mutex());
+    return num_locked_objects;
+  }
+
+  void mlocker::lock_page(size_t page)
+  {
+    std::pair<std::map<size_t, unsigned int>::iterator, bool> p = map().insert(std::make_pair(page, 1));
+    if (p.second)
+    {
+      do_lock((void*)(page * page_size), page_size);
+    }
+    else
+    {
+      ++p.first->second;
+    }
+  }
+
+  void mlocker::unlock_page(size_t page)
+  {
+    std::map<size_t, unsigned int>::iterator i = map().find(page);
+    if (i == map().end())
+    {
+      MERROR("Attempt to unlock unlocked page at " << (void*)(page * page_size));
+    }
+    else
+    {
+      if (!--i->second)
+      {
+        map().erase(i);
+        do_unlock((void*)(page * page_size), page_size);
+      }
+    }
+  }
+}