yama test workaround: Do feature detection, not OS version sniffing.

sandbox/linux/services/yama_unittests.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <errno.h>
 #include <fcntl.h>
 #include <sys/ptrace.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/strings/string_util.h"
 #include "base/sys_info.h"
 #include "sandbox/linux/services/scoped_process.h"
 #include "sandbox/linux/services/yama.h"
 #include "sandbox/linux/tests/unit_tests.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace sandbox {
 
 namespace {
 
 bool HasLinux32Bug() {
-#if defined(__i386__)
   // On 3.2 kernels, yama doesn't work for 32-bit binaries on 64-bit kernels.
   // This is fixed in 3.4.
-  bool is_kernel_64bit =
-      base::SysInfo::OperatingSystemArchitecture() == "x86_64";
-  bool is_linux = base::SysInfo::OperatingSystemName() == "Linux";
-  bool is_3_dot_2 = StartsWithASCII(
-      base::SysInfo::OperatingSystemVersion(), "3.2", /*case_sensitive=*/false);
-  if (is_kernel_64bit && is_linux && is_3_dot_2)
-    return true;
-#endif  // defined(__i386__)
-  return false;
+  return prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, 0, 0, 0) < 0 &&
+         errno == EINVAL;
 }
 
 bool CanPtrace(pid_t pid) {
   int ret;
   ret = ptrace(PTRACE_ATTACH, pid, NULL, NULL);
   if (ret == -1) {
     CHECK_EQ(EPERM, errno);
     return false;
   }
   // Wait for the process to be stopped so that it can be detached.
@@ skipping 114 matching lines @@
   if (Yama::IsEnforcing()) {
     // Check that process1 is protected by Yama, even though it has
     // been created from a process that disabled Yama.
     CHECK(!CanSubProcessPtrace(process1.GetPid()));
   }
 }
 
 }  // namespace
 
 }  // namespace sandbox