MinSFI: Passing arguments to the entry function

src/include/minsfi_ptr.h

+/*
+ * Copyright (c) 2014 The Native Client Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef NATIVE_CLIENT_SRC_INCLUDE_MINSFI_PTR_H_
+#define NATIVE_CLIENT_SRC_INCLUDE_MINSFI_PTR_H_
+
+#include <assert.h>
+
+#include "native_client/src/include/minsfi_priv.h"
+
+/*
+ * This defines what ToMinsfiPtr should do if the given native pointer
+ * is not within the bounds of the allocated memory region. We abort in
+ * production code and return a magic constant when invoked inside tests.
+ */
+#ifndef MINSFI_PTR_CONVERSION_TEST
+#define ToMinsfiPtr_AbortAction    abort();
+#else  // MINSFI_PTR_CONVERSION_TEST
+#define ToMinsfiPtr_AbortAction    return 0xCAFEBABE;
+#endif  // MINSFI_PTR_CONVERSION_TEST
+
+/*
+ * Convert an untrusted pointer into a native pointer. Because this is just
+ * some integer provided by the untrusted code, we must sandbox it the same
+ * way the SandboxMemoryAccesses compiler pass does.
+ */
+static inline char *FromMinsfiPtr(sfiptr_t sfiptr, const MinsfiSandbox *sb) {
+  uint32_t masked_sfiptr = sfiptr & sb->ptr_mask;
+  return sb->mem_base + masked_sfiptr;
+}
+
+/*
+ * Convert a native pointer into an untrusted pointer. This means simply
+ * subtracting the memory base from the address.
+ */
+static inline sfiptr_t ToMinsfiPtr(char *ptr, const MinsfiSandbox *sb) {

[jvoung (off chromium), 2014/09/10 17:04:29]

you could probably make this a const char *ptr

[dbrazdil, 2014/09/10 18:49:47]

Done.

+  uintptr_t ptr_int = (uintptr_t) ptr;
+  uintptr_t base_int = (uintptr_t) sb->mem_base;
+  sfiptr_t sb_ptr = ptr_int - base_int;
+
+  /* Check that the pointer is in the bounds of the allocated memory region. */
+  if ((base_int > ptr_int) || ((sb_ptr & (~sb->ptr_mask)) != 0)) {
+    ToMinsfiPtr_AbortAction
+  }
+
+  return sb_ptr;
+}
+
+#endif  // NATIVE_CLIENT_SRC_INCLUDE_MINSFI_PTR_H_