Intercept file Open/Close

base/files/file_posix.cc

 // Copyright (c) 2012 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 "base/files/file.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <unistd.h>
@@ skipping 148 matching lines @@
       Time::FromTimeT(last_accessed_sec) +
       TimeDelta::FromMicroseconds(last_accessed_nsec /
                                   Time::kNanosecondsPerMicrosecond);
 
   creation_time =
       Time::FromTimeT(creation_time_sec) +
       TimeDelta::FromMicroseconds(creation_time_nsec /
                                   Time::kNanosecondsPerMicrosecond);
 }
 
+// Define empty hooks for blacklisting file descriptors used in base::File.
+// These functions should be declared 'weak', i.e. the functions declared in
+// a default way would have precedence over the weak ones at link time. This
+// works for both static and dynamic linking.
+//
+// With compilers other than GCC define strong no-op symbols for simplicity.

[Fabrice (no longer in Chrome), 2014/11/04 15:37:21]

Nit: other than GCC and Clang (so msvc, essentially)
COMPILER_GCC is defined for GCC and Clang.

[pasko, 2014/11/04 17:48:05]

Thanks, I did not realize COMPILER_GCC is defined for Clang. That's actually
logical. OK, since !defined(__clang__) is ugly, I'll hope for the best on both
compilers. And of course clang supports this attribute, wow!

Done.

+#if defined(COMPILER_GCC)
+#define ATTRIBUTE_WEAK __attribute__ ((weak))
+#else
+#define ATTRIBUTE_WEAK
+#endif
+BASE_EXPORT void ProtectFileDescriptor(int fd) ATTRIBUTE_WEAK;
+BASE_EXPORT void UnprotectFileDescriptor(int fd) ATTRIBUTE_WEAK;
+#undef ATTRIBUTE_WEAK
+
+void ProtectFileDescriptor(int fd) {
+}
+
+void UnprotectFileDescriptor(int fd) {
+}
+
 // NaCl doesn't implement system calls to open files directly.
 #if !defined(OS_NACL)
 // TODO(erikkay): does it make sense to support FLAG_EXCLUSIVE_* here?
 void File::InitializeUnsafe(const FilePath& name, uint32 flags) {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(!IsValid());
 
   int open_flags = 0;
   if (flags & FLAG_CREATE)
     open_flags = O_CREAT | O_EXCL;
@@ skipping 66 matching lines @@
 
   if (flags & (FLAG_CREATE_ALWAYS | FLAG_CREATE))
     created_ = true;
 
   if (flags & FLAG_DELETE_ON_CLOSE)
     unlink(name.value().c_str());
 
   async_ = ((flags & FLAG_ASYNC) == FLAG_ASYNC);
   error_details_ = FILE_OK;
   file_.reset(descriptor);
+  ProtectFileDescriptor(descriptor);
 }
 #endif  // !defined(OS_NACL)
 
 bool File::IsValid() const {
   return file_.is_valid();
 }
 
 PlatformFile File::GetPlatformFile() const {
   return file_.get();
 }
 
 PlatformFile File::TakePlatformFile() {
+  UnprotectFileDescriptor(GetPlatformFile());
   return file_.release();
 }
 
 void File::Close() {
   if (!IsValid())
     return;
 
   base::ThreadRestrictions::AssertIOAllowed();
+  UnprotectFileDescriptor(GetPlatformFile());
   file_.reset();
 }
 
 int64 File::Seek(Whence whence, int64 offset) {
   base::ThreadRestrictions::AssertIOAllowed();
   DCHECK(IsValid());
 
 #if defined(OS_ANDROID)
   COMPILE_ASSERT(sizeof(int64) == sizeof(off64_t), off64_t_64_bit);
   return lseek64(file_.get(), static_cast<off64_t>(offset),
@@ skipping 192 matching lines @@
     default:
 #if !defined(OS_NACL)  // NaCl build has no metrics code.
       UMA_HISTOGRAM_SPARSE_SLOWLY("PlatformFile.UnknownErrors.Posix",
                                   saved_errno);
 #endif
       return FILE_ERROR_FAILED;
   }
 }
 
 void File::SetPlatformFile(PlatformFile file) {
-  DCHECK(!file_.is_valid());
+  CHECK(!file_.is_valid());
   file_.reset(file);
+  if (file_.is_valid())
+    ProtectFileDescriptor(GetPlatformFile());
 }
 
 }  // namespace base