intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 38 insertions, 0 deletions

diff --git a/util/system/mincore.h b/util/system/mincore.h
new file mode 100644
index 0000000000..0f5d8b78c7
--- /dev/null
+++ b/util/system/mincore.h
@@ -0,0 +1,38 @@
+#pragma once
+
+#include "defaults.h"
+/**
+ * Fills a vector that indicates whether pages of the calling process's virtual memory are resident in RAM. Each byte
+ * in the vector contains the status of a single page. The page size can be obtained via the NSystemInfo::GetPageSize()
+ * function. Use the IsPageInCore function to interpret the page status byte.
+ *
+ * Can be overly pessimistic:
+ * - Assumes nothing is in RAM on platforms other than Linux
+ * - Recent Linux kernels (4.21 and some backports) may return zeroes if the process doesn't have writing permissions
+ *   for the given file. See CVE-2019-5489.
+ *
+ * @param[in] addr      starting address of the memory range to be examined
+ * @param[in] len       length (bytes) of the memory range to be examined
+ * @param[out] vec      vector of bytes to store statuses of memory pages
+ * @param[in] vecLen    length (bytes) of the vec, should be large enough to hold the requested pages count
+ * @throws yexception   if there was a system error or if the vecLen is too small
+ *
+ * @note                this is only a snapshot, results may be stale by the time they're used
+ * @see                 man 2 mincore
+ */
+void InCoreMemory(const void* addr, size_t len, unsigned char* vec, size_t vecLen);
+
+/**
+ * Takes as an argument an element of the vector previously filled by InCoreMemory.
+ *
+ * @param[in]           byte corresponding to the status of a single page
+ *
+ * @returns             true if this page was resident in memory at the time out the InCoreMemory execution
+ */
+inline bool IsPageInCore(unsigned char s) {
+    /* From mincore(2): On return, the least significant bit of each byte will be set if the corresponding page is
+     * currently resident in memory, and be clear otherwise.  (The settings of the other bits in each byte are
+     * undefined; these bits are reserved for possible later use.)
+     */
+    return s & 1;
+}