base: add support for tagged fd closure to unique_fd.

Test: libbase_test
Change-Id: Ibba5e60d7007265a566eb8f76021d5dbeb734532

1 files changed, 68 insertions, 14 deletions

diff --git a/base/include/android-base/unique_fd.h b/base/include/android-base/unique_fd.h
index 6cfcd3fb0..057f462e5 100644
--- a/base/include/android-base/unique_fd.h
+++ b/base/include/android-base/unique_fd.h
@@ -42,10 +42,29 @@
 //
 // unique_fd is also known as ScopedFd/ScopedFD/scoped_fd; mentioned here to help
 // you find this class if you're searching for one of those names.
+
+#if defined(__BIONIC__)
+#include <android/fdsan.h>
+#endif
+
 namespace android {
 namespace base {
 
 struct DefaultCloser {
+#if defined(__BIONIC__)
+  static void Tag(int fd, void* old_addr, void* new_addr) {
+    uint64_t old_tag = android_fdsan_create_owner_tag(ANDROID_FDSAN_OWNER_TYPE_UNIQUE_FD,
+                                                      reinterpret_cast<uint64_t>(old_addr));
+    uint64_t new_tag = android_fdsan_create_owner_tag(ANDROID_FDSAN_OWNER_TYPE_UNIQUE_FD,
+                                                      reinterpret_cast<uint64_t>(new_addr));
+    android_fdsan_exchange_owner_tag(fd, old_tag, new_tag);
+  }
+  static void Close(int fd, void* addr) {
+    uint64_t tag = android_fdsan_create_owner_tag(ANDROID_FDSAN_OWNER_TYPE_UNIQUE_FD,
+                                                  reinterpret_cast<uint64_t>(addr));
+    android_fdsan_close_with_tag(fd, tag);
+  }
+#else
   static void Close(int fd) {
     // Even if close(2) fails with EINTR, the fd will have been closed.
     // Using TEMP_FAILURE_RETRY will either lead to EBADF or closing someone
@@ -53,40 +72,75 @@ struct DefaultCloser {
     // http://lkml.indiana.edu/hypermail/linux/kernel/0509.1/0877.html
     ::close(fd);
   }
+#endif
 };
 
 template <typename Closer>
 class unique_fd_impl final {
  public:
-  unique_fd_impl() : value_(-1) {}
+  unique_fd_impl() {}
 
-  explicit unique_fd_impl(int value) : value_(value) {}
+  explicit unique_fd_impl(int fd) { reset(fd); }
   ~unique_fd_impl() { reset(); }
 
-  unique_fd_impl(unique_fd_impl&& other) : value_(other.release()) {}
+  unique_fd_impl(unique_fd_impl&& other) { reset(other.release()); }
   unique_fd_impl& operator=(unique_fd_impl&& s) {
-    reset(s.release());
+    int fd = s.fd_;
+    s.fd_ = -1;
+    reset(fd, &s);
     return *this;
   }
 
-  void reset(int new_value = -1) {
-    if (value_ != -1) {
-      Closer::Close(value_);
-    }
-    value_ = new_value;
-  }
+  void reset(int new_value = -1) { reset(new_value, nullptr); }
 
-  int get() const { return value_; }
+  int get() const { return fd_; }
   operator int() const { return get(); }
 
   int release() __attribute__((warn_unused_result)) {
-    int ret = value_;
-    value_ = -1;
+    tag(fd_, this, nullptr);
+    int ret = fd_;
+    fd_ = -1;
     return ret;
   }
 
  private:
-  int value_;
+  void reset(int new_value, void* previous_tag) {
+    if (fd_ != -1) {
+      close(fd_, this);
+    }
+
+    fd_ = new_value;
+    if (new_value != -1) {
+      tag(new_value, previous_tag, this);
+    }
+  }
+
+  int fd_ = -1;
+
+  // Template magic to use Closer::Tag if available, and do nothing if not.
+  // If Closer::Tag exists, this implementation is preferred, because int is a better match.
+  // If not, this implementation is SFINAEd away, and the no-op below is the only one that exists.
+  template <typename T = Closer>
+  static auto tag(int fd, void* old_tag, void* new_tag)
+      -> decltype(T::Tag(fd, old_tag, new_tag), void()) {
+    T::Tag(fd, old_tag, new_tag);
+  }
+
+  template <typename T = Closer>
+  static void tag(long, void*, void*) {
+    // No-op.
+  }
+
+  // Same as above, to select between Closer::Close(int) and Closer::Close(int, void*).
+  template <typename T = Closer>
+  static auto close(int fd, void* tag_value) -> decltype(T::Close(fd, tag_value), void()) {
+    T::Close(fd, tag_value);
+  }
+
+  template <typename T = Closer>
+  static auto close(int fd, void*) -> decltype(T::Close(fd), void()) {
+    T::Close(fd);
+  }
 
   unique_fd_impl(const unique_fd_impl&);
   void operator=(const unique_fd_impl&);