Fix x86 system calls made from ELF preinit.

Used by CFI, so broke cfi_test#early_init@x86, but I've added a specific
test for this (and a similar test for getauxval from preinit, which this
patch does not fix).

Bug: http://b/35885875
Test: ran tests
Change-Id: I43885bedfb88c0a26b4474bd3c27a87dec7bbc97
diff --git a/tests/libs/Android.bp b/tests/libs/Android.bp
index 5eb16c5..a031fe9 100644
--- a/tests/libs/Android.bp
+++ b/tests/libs/Android.bp
@@ -547,3 +547,17 @@
     shared_libs: ["libcfi-test"],
     ldflags: ["-Wl,--rpath,${ORIGIN}/.."],
 }
+
+cc_test {
+    name: "preinit_getauxval_test_helper",
+    host_supported: false,
+    defaults: ["bionic_testlib_defaults"],
+    srcs: ["preinit_getauxval_test_helper.cpp"],
+}
+
+cc_test {
+    name: "preinit_syscall_test_helper",
+    host_supported: false,
+    defaults: ["bionic_testlib_defaults"],
+    srcs: ["preinit_syscall_test_helper.cpp"],
+}
diff --git a/tests/libs/libs_utils.h b/tests/libs/libs_utils.h
index f11cbe7..7dae241 100644
--- a/tests/libs/libs_utils.h
+++ b/tests/libs/libs_utils.h
@@ -17,13 +17,11 @@
 #ifndef LIBS_UTILS_H
 #define LIBS_UTILS_H
 
+#include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
 
-#define CHECK(x)                                                            \
-  do {                                                                      \
-    fprintf(stderr, "CHECK(" #x ") failed at %s:%d\n", __FILE__, __LINE__); \
-    if (!(x)) abort();                                                      \
-  } while (0)
+#define CHECK(e) \
+    ((e) ? static_cast<void>(0) : __assert2(__FILE__, __LINE__, __PRETTY_FUNCTION__, #e))
 
 #endif  // LIBS_UTILS_H
diff --git a/tests/libs/preinit_getauxval_test_helper.cpp b/tests/libs/preinit_getauxval_test_helper.cpp
new file mode 100644
index 0000000..2a79b97
--- /dev/null
+++ b/tests/libs/preinit_getauxval_test_helper.cpp
@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/auxv.h>
+
+#include "libs_utils.h"
+
+static unsigned long g_AT_RANDOM;
+static unsigned long g_AT_PAGESZ;
+
+static void preinit_ctor() {
+  g_AT_RANDOM = getauxval(AT_RANDOM);
+  g_AT_PAGESZ = getauxval(AT_PAGESZ);
+}
+
+__attribute__((section(".preinit_array"), used)) void (*preinit_ctor_p)(void) = preinit_ctor;
+
+int main() {
+  // Did getauxval during preinit get the same results as getauxval now?
+  CHECK(getauxval(AT_RANDOM) == g_AT_RANDOM);
+  CHECK(getauxval(AT_PAGESZ) == g_AT_PAGESZ);
+  return 0;
+}
diff --git a/tests/libs/preinit_syscall_test_helper.cpp b/tests/libs/preinit_syscall_test_helper.cpp
new file mode 100644
index 0000000..9b6b6df
--- /dev/null
+++ b/tests/libs/preinit_syscall_test_helper.cpp
@@ -0,0 +1,40 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/auxv.h>
+
+#include "libs_utils.h"
+
+static ssize_t g_result;
+static int g_errno;
+
+static void preinit_ctor() {
+  // Can we make a system call?
+  g_result = write(-1, "", 1);
+  g_errno = errno;
+}
+
+__attribute__((section(".preinit_array"), used)) void (*preinit_ctor_p)(void) = preinit_ctor;
+
+int main() {
+  // Did we get the expected failure?
+  CHECK(g_result == -1);
+  CHECK(g_errno == EBADF);
+  return 0;
+}