add winkernel specific files

windows/README

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+This directory contains code specific to Windows platforms. 

windows/winkernel_mm.c

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+/* Capstone Disassembly Engine */
+/* By Nguyen Anh Quynh <aquynh@gmail.com>, 2013-2016 */
+#include "winkernel_mm.h"
+#include <ntddk.h>
+
+// A pool tag for memory allocation
+static const ULONG CS_WINKERNEL_POOL_TAG = 'kwsC';
+
+
+// A structure to implement realloc()
+typedef struct _CS_WINKERNEL_MEMBLOCK
+{
+  size_t size;   // A number of bytes allocated
+  char data[1];  // An address returned to a caller
+} CS_WINKERNEL_MEMBLOCK;
+C_ASSERT(sizeof(CS_WINKERNEL_MEMBLOCK) == sizeof(void *) * 2);
+
+
+// free()
+void CAPSTONE_API cs_winkernel_free(void *ptr)
+{
+  if (ptr)
+  {
+    ExFreePoolWithTag(CONTAINING_RECORD(ptr, CS_WINKERNEL_MEMBLOCK, data), CS_WINKERNEL_POOL_TAG);
+  }
+}
+
+// malloc()
+void * CAPSTONE_API cs_winkernel_malloc(size_t size)
+{
+  // Disallow zero length allocation because they waste pool header space and,
+  // in many cases, indicate a potential validation issue in the calling code.
+  NT_ASSERT(size);
+
+  CS_WINKERNEL_MEMBLOCK *block = (CS_WINKERNEL_MEMBLOCK *)ExAllocatePoolWithTag(
+    NonPagedPoolNx, size + sizeof(CS_WINKERNEL_MEMBLOCK), CS_WINKERNEL_POOL_TAG);
+  if (!block)
+  {
+    return NULL;
+  }
+  block->size = size;
+  return block->data;
+}
+
+// calloc()
+void * CAPSTONE_API cs_winkernel_calloc(size_t n, size_t size)
+{
+  size_t total = n * size;
+
+  void *new_ptr = cs_winkernel_malloc(total);
+  if (!new_ptr)
+  {
+    return NULL;
+  }
+
+  return RtlFillMemory(new_ptr, total, 0);
+}
+
+// realloc()
+void * CAPSTONE_API cs_winkernel_realloc(void *ptr, size_t size)
+{
+  void *new_ptr = NULL;
+  size_t current_size = 0;
+  size_t smaller_size = 0;
+
+  if (!ptr)
+  {
+    return cs_winkernel_malloc(size);
+  }
+
+  new_ptr = cs_winkernel_malloc(size);
+  if (!new_ptr)
+  {
+    return NULL;
+  }
+
+  current_size = CONTAINING_RECORD(ptr, CS_WINKERNEL_MEMBLOCK, data)->size;
+  smaller_size = (current_size < size) ? current_size : size;
+  RtlCopyMemory(new_ptr, ptr, smaller_size);
+  cs_winkernel_free(ptr);
+  return new_ptr;
+}
+
+// vsnprintf(). _vsnprintf() is avaialable for drivers, but it differs from
+// vsnprintf() in a return value and when a null-terminater is set.
+// cs_winkernel_vsnprintf() takes care of those differences.
+#pragma warning(push)
+#pragma warning(disable : 28719)  // Banned API Usage : _vsnprintf is a Banned
+                                  // API as listed in dontuse.h for security
+                                  // purposes.
+int CAPSTONE_API cs_winkernel_vsnprintf(char *buffer, size_t count, const char *format, va_list argptr)
+{
+  int result = _vsnprintf(buffer, count, format, argptr);
+
+  // _vsnprintf() returns -1 when a string is truncated, and returns "count"
+  // when an entire string is stored but without '\0' at the end of "buffer".
+  // In both cases, null-terminater needs to be added manually.
+  if (result == -1 || (size_t)result == count)
+  {
+    buffer[count - 1] = '\0';
+  }
+  if (result == -1)
+  {
+    // In case when -1 is returned, the function has to get and return a number
+    // of characters that would have been written. This attempts so by re-tring
+    // the same conversion with temp buffer that is most likely big enough to
+    // complete formatting and get a number of characters that would have been
+    // written.
+    char* tmp = cs_winkernel_malloc(0x1000);
+    if (!tmp) {
+      return result;
+    }
+    result = _vsnprintf(tmp, 0x1000, format, argptr);
+    NT_ASSERT(result != -1);
+    cs_winkernel_free(tmp);
+  }
+
+  return result;
+}
+#pragma warning(pop)

windows/winkernel_mm.h

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+/* Capstone Disassembly Engine */
+/* By Nguyen Anh Quynh <aquynh@gmail.com>, 2013-2016 */
+#ifndef CS_WINDOWS_WINKERNEL_MM_H_
+#define CS_WINDOWS_WINKERNEL_MM_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <capstone.h>
+
+void CAPSTONE_API cs_winkernel_free(void *ptr);
+void * CAPSTONE_API cs_winkernel_malloc(size_t size);
+void * CAPSTONE_API cs_winkernel_calloc(size_t n, size_t size);
+void * CAPSTONE_API cs_winkernel_realloc(void *ptr, size_t size);
+int CAPSTONE_API cs_winkernel_vsnprintf(char *buffer, size_t count, const char *format, va_list argptr);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // CS_WINDOWS_WINKERNEL_MM_H_