Handle locked pages more robustly (Fixes issue #1462)

Memory locks do not stack, that is, pages which have been locked several times by calls to mlock()
will be unlocked by a single call to munlock(). This can result in keying material ending up in swap when
those functions are used naively. In this commit a class "LockedPageManager" is added
that simulates stacking memory locks by keeping a counter per page.

1 files changed, 115 insertions, 0 deletions

diff --git a/src/test/allocator_tests.cpp b/src/test/allocator_tests.cpp
new file mode 100644
index 0000000000..d5cb8e8101
--- /dev/null
+++ b/src/test/allocator_tests.cpp
@@ -0,0 +1,115 @@
+#include <boost/test/unit_test.hpp>
+
+#include "init.h"
+#include "main.h"
+#include "util.h"
+
+BOOST_AUTO_TEST_SUITE(allocator_tests)
+
+// Dummy memory page locker for platform independent tests
+static const void *last_lock_addr, *last_unlock_addr;
+static size_t last_lock_len, last_unlock_len;
+class TestLocker
+{
+public:
+    bool Lock(const void *addr, size_t len)
+    {
+        last_lock_addr = addr;
+        last_lock_len = len;
+        return true;
+    }
+    bool Unlock(const void *addr, size_t len)
+    {
+        last_unlock_addr = addr;
+        last_unlock_len = len;
+        return true;
+    }
+};
+
+BOOST_AUTO_TEST_CASE(test_LockedPageManagerBase)
+{
+    const size_t test_page_size = 4096;
+    LockedPageManagerBase<TestLocker> lpm(test_page_size);
+    size_t addr;
+    last_lock_addr = last_unlock_addr = 0;
+    last_lock_len = last_unlock_len = 0;
+
+    /* Try large number of small objects */
+    addr = 0;
+    for(int i=0; i<1000; ++i)
+    {
+        lpm.LockRange(reinterpret_cast<void*>(addr), 33);
+        addr += 33;
+    }
+    /* Try small number of page-sized objects, straddling two pages */
+    addr = test_page_size*100 + 53;
+    for(int i=0; i<100; ++i)
+    {
+        lpm.LockRange(reinterpret_cast<void*>(addr), test_page_size);
+        addr += test_page_size;
+    }
+    /* Try small number of page-sized objects aligned to exactly one page */
+    addr = test_page_size*300;
+    for(int i=0; i<100; ++i)
+    {
+        lpm.LockRange(reinterpret_cast<void*>(addr), test_page_size);
+        addr += test_page_size;
+    }
+    /* one very large object, straddling pages */
+    lpm.LockRange(reinterpret_cast<void*>(test_page_size*600+1), test_page_size*500);
+    BOOST_CHECK(last_lock_addr == reinterpret_cast<void*>(test_page_size*(600+500)));
+    /* one very large object, page aligned */
+    lpm.LockRange(reinterpret_cast<void*>(test_page_size*1200), test_page_size*500-1);
+    BOOST_CHECK(last_lock_addr == reinterpret_cast<void*>(test_page_size*(1200+500-1)));
+
+    BOOST_CHECK(lpm.GetLockedPageCount() == (
+        (1000*33+test_page_size-1)/test_page_size + // small objects
+        101 + 100 +  // page-sized objects
+        501 + 500)); // large objects
+    BOOST_CHECK((last_lock_len & (test_page_size-1)) == 0); // always lock entire pages
+    BOOST_CHECK(last_unlock_len == 0); // nothing unlocked yet
+
+    /* And unlock again */
+    addr = 0;
+    for(int i=0; i<1000; ++i)
+    {
+        lpm.UnlockRange(reinterpret_cast<void*>(addr), 33);
+        addr += 33;
+    }
+    addr = test_page_size*100 + 53;
+    for(int i=0; i<100; ++i)
+    {
+        lpm.UnlockRange(reinterpret_cast<void*>(addr), test_page_size);
+        addr += test_page_size;
+    }
+    addr = test_page_size*300;
+    for(int i=0; i<100; ++i)
+    {
+        lpm.UnlockRange(reinterpret_cast<void*>(addr), test_page_size);
+        addr += test_page_size;
+    }
+    lpm.UnlockRange(reinterpret_cast<void*>(test_page_size*600+1), test_page_size*500);
+    lpm.UnlockRange(reinterpret_cast<void*>(test_page_size*1200), test_page_size*500-1);
+
+    /* Check that everything is released */
+    BOOST_CHECK(lpm.GetLockedPageCount() == 0);
+
+    /* A few and unlocks of size zero (should have no effect) */
+    addr = 0;
+    for(int i=0; i<1000; ++i)
+    {
+        lpm.LockRange(reinterpret_cast<void*>(addr), 0);
+        addr += 1;
+    }
+    BOOST_CHECK(lpm.GetLockedPageCount() == 0);
+    addr = 0;
+    for(int i=0; i<1000; ++i)
+    {
+        lpm.UnlockRange(reinterpret_cast<void*>(addr), 0);
+        addr += 1;
+    }
+    BOOST_CHECK(lpm.GetLockedPageCount() == 0);
+    BOOST_CHECK((last_unlock_len & (test_page_size-1)) == 0); // always unlock entire pages
+}
+
+BOOST_AUTO_TEST_SUITE_END()