introduce pointer dereference validation method

src/common.c

@@ -114,3 +114,15 @@ unsigned getSLEB128Size(int64_t Value)
 
 	return Size;
 }
+
+#include <sys/mman.h>
+#include <unistd.h>
+bool is_pointer_valid(void *p)
+{
+    /* get the page size */
+    size_t page_size = sysconf(_SC_PAGESIZE);
+    /* find the address of the page that contains p */
+    void *base = (void *)((((size_t)p) / page_size) * page_size);
+    /* call msync, if it returns non-zero, return false */
+    return msync(base, page_size, MS_ASYNC) == 0;
+}

src/common.h

@@ -9,6 +9,7 @@
 
 
 #include <stdint.h>
+#include <stdbool.h>
 
 #define USE_LIBUNWIND
 
@@ -20,5 +21,6 @@
 
 int32_t decode_sleb128(uint8_t *sleb128);
 uint32_t decode_uleb128(uint8_t *uleb128);
+bool is_pointer_valid(void *p);
 
 #endif // __PST_COMMON_H__