Change startup ABI for untrusted code to be C-compatible

src/untrusted/nacl/nacl_startup.h

+/*
+ * Copyright (c) 2011 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_UNTRUSTED_NACL_NACL_STARTUP_H_
+#define NATIVE_CLIENT_SRC_UNTRUSTED_NACL_NACL_STARTUP_H_ 1
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * The true entry point for untrusted code is called with the normal C ABI,
+ * taking one argument.  This is a pointer to stack space containing these
+ * words:
+ *      [0]             cleanup function pointer (always NULL in actual startup)
+ *      [1]             envc, count of envp[] pointers
+ *      [2]             argc, count of argv[] pointers
+ *      [3]             argv[0..argc] pointers, argv[argc] being NULL
+ *      [3+argc]        envp[0..envc] pointers, envp[envc] being NULL
+ *      [3+argc+envc]   auxv[] pairs
+ */
+
+enum NaClStartupInfoIndex {
+  NACL_STARTUP_FINI,  /* Cleanup function pointer for dynamic linking.  */
+  NACL_STARTUP_ENVC,  /* Count of envp[] pointers.  */
+  NACL_STARTUP_ARGC,  /* Count of argv[] pointers.  */
+  NACL_STARTUP_ARGV   /* argv[0] pointer.  */
+};
+
+/*
+ * Return the dynamic linker finalizer function.
+ */
+static inline __attribute__((unused))
+void (*nacl_startup_fini(const uint32_t info[]))(void) {
+  return (void (*)(void)) info[NACL_STARTUP_FINI];
+}
+
+/*
+ * Return the count of argument strings.
+ */
+static inline __attribute__((unused))
+int nacl_startup_argc(const uint32_t info[]) {
+  return info[NACL_STARTUP_ARGC];
+}
+
+/*
+ * Return the vector of argument strings.
+ */
+static inline __attribute__((unused))
+char **nacl_startup_argv(const uint32_t info[]) {
+  return (char **) &info[NACL_STARTUP_ARGV];
+}
+
+/*
+ * Return the count of environment strings.
+ */
+static inline __attribute__((unused))
+int nacl_startup_envc(const uint32_t info[]) {
+  return info[NACL_STARTUP_ENVC];
+}
+
+/*
+ * Return the vector of environment strings.
+ */
+static inline __attribute__((unused))
+char **nacl_startup_envp(const uint32_t info[]) {
+  return &nacl_startup_argv(info)[nacl_startup_argc(info) + 1];
+}
+
+/*
+ * Return the vector of auxiliary data items.
+ */
+static inline __attribute__((unused))
+Elf32_auxv_t *nacl_startup_auxv(const uint32_t info[]) {
+  char **envend = &nacl_startup_envp(info)[nacl_startup_envc(info) + 1];
+  return (Elf32_auxv_t *) envend;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  /* NATIVE_CLIENT_SRC_UNTRUSTED_NACL_NACL_STARTUP_H_ */