Load library using file handle.

 * This patch enables dlopen by file descriptor
   instead of path/name.

Bug: 15984217
Change-Id: Ib39051e00567fb97070bf96d8ce63993877c0a01

7 files changed, 122 insertions, 9 deletions

diff --git a/libc/include/android/dlext.h b/libc/include/android/dlext.h
index 90962fa..616e08e 100644
--- a/libc/include/android/dlext.h
+++ b/libc/include/android/dlext.h
@@ -49,11 +49,17 @@ enum {
    */
   ANDROID_DLEXT_USE_RELRO             = 0x8,
 
+  /* Instruct dlopen to use library_fd instead of opening file by name.
+   * The filename parameter is still used to identify the library.
+   */
+  ANDROID_DLEXT_USE_LIBRARY_FD        = 0x10,
+
   /* Mask of valid bits */
   ANDROID_DLEXT_VALID_FLAG_BITS       = ANDROID_DLEXT_RESERVED_ADDRESS |
                                         ANDROID_DLEXT_RESERVED_ADDRESS_HINT |
                                         ANDROID_DLEXT_WRITE_RELRO |
-                                        ANDROID_DLEXT_USE_RELRO,
+                                        ANDROID_DLEXT_USE_RELRO |
+                                        ANDROID_DLEXT_USE_LIBRARY_FD,
 };
 
 typedef struct {
@@ -61,6 +67,7 @@ typedef struct {
   void*   reserved_addr;
   size_t  reserved_size;
   int     relro_fd;
+  int     library_fd;
 } android_dlextinfo;
 
 extern void* android_dlopen_ext(const char* filename, int flag, const android_dlextinfo* extinfo);
diff --git a/libc/private/ScopedFd.h b/libc/private/ScopedFd.h
new file mode 100644
index 0000000..e56c139
--- /dev/null
+++ b/libc/private/ScopedFd.h
@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2009 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.
+ */
+
+#ifndef SCOPED_FD_H
+#define SCOPED_FD_H
+
+#include <unistd.h>
+#include "bionic_macros.h"
+
+// A smart pointer that closes the given fd on going out of scope.
+// Use this when the fd is incidental to the purpose of your function,
+// but needs to be cleaned up on exit.
+class ScopedFd {
+public:
+    explicit ScopedFd(int fd) : fd(fd) {
+    }
+
+    ~ScopedFd() {
+      reset();
+    }
+
+    int get() const {
+        return fd;
+    }
+
+    int release() __attribute__((warn_unused_result)) {
+        int localFd = fd;
+        fd = -1;
+        return localFd;
+    }
+
+    void reset(int new_fd = -1) {
+      if (fd != -1) {
+          TEMP_FAILURE_RETRY(close(fd));
+      }
+      fd = new_fd;
+    }
+
+private:
+    int fd;
+
+    // Disallow copy and assignment.
+    DISALLOW_COPY_AND_ASSIGN(ScopedFd);
+};
+
+#endif  // SCOPED_FD_H
diff --git a/linker/linker.cpp b/linker/linker.cpp
index bf923c1..2065231 100644
--- a/linker/linker.cpp
+++ b/linker/linker.cpp
@@ -42,6 +42,7 @@
 #include "private/bionic_tls.h"
 #include "private/KernelArgumentBlock.h"
 #include "private/ScopedPthreadMutexLocker.h"
+#include "private/ScopedFd.h"
 
 #include "linker.h"
 #include "linker_debug.h"
@@ -696,11 +697,20 @@ static int open_library(const char* name) {
 }
 
 static soinfo* load_library(const char* name, int dlflags, const android_dlextinfo* extinfo) {
-    // Open the file.
-    int fd = open_library(name);
-    if (fd == -1) {
+    int fd = -1;
+    ScopedFd file_guard(-1);
+
+    if (extinfo != NULL && (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) != 0) {
+      fd = extinfo->library_fd;
+    } else {
+      // Open the file.
+      fd = open_library(name);
+      if (fd == -1) {
         DL_ERR("library \"%s\" not found", name);
         return NULL;
+      }
+
+      file_guard.reset(fd);
     }
 
     ElfReader elf_reader(name, fd);
@@ -744,7 +754,7 @@ static soinfo* load_library(const char* name, int dlflags, const android_dlextin
 
     // At this point we know that whatever is loaded @ base is a valid ELF
     // shared library whose segments are properly mapped in.
-    TRACE("[ find_library_internal base=%p size=%zu name='%s' ]",
+    TRACE("[ load_library base=%p size=%zu name='%s' ]",
           reinterpret_cast<void*>(si->base), si->size, si->name);
 
     if (!soinfo_link_image(si, extinfo)) {
@@ -847,7 +857,7 @@ soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo)
     return NULL;
   }
   if (extinfo != NULL && ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0)) {
-    DL_ERR("invalid extended flags to android_dlopen_ext: %x", extinfo->flags);
+    DL_ERR("invalid extended flags to android_dlopen_ext: %llx", extinfo->flags);
     return NULL;
   }
   protect_data(PROT_READ | PROT_WRITE);
diff --git a/linker/linker_phdr.cpp b/linker/linker_phdr.cpp
index 12e9779..11585af 100644
--- a/linker/linker_phdr.cpp
+++ b/linker/linker_phdr.cpp
@@ -127,9 +127,6 @@ ElfReader::ElfReader(const char* name, int fd)
 }
 
 ElfReader::~ElfReader() {
-  if (fd_ != -1) {
-    close(fd_);
-  }
   if (phdr_mmap_ != NULL) {
     munmap(phdr_mmap_, phdr_size_);
   }
diff --git a/tests/Android.build.mk b/tests/Android.build.mk
index 62e9718..bb00648 100644
--- a/tests/Android.build.mk
+++ b/tests/Android.build.mk
@@ -26,6 +26,11 @@ endif
 ifneq ($(findstring LIBRARY, $(build_target)),LIBRARY)
     LOCAL_MODULE_STEM_32 := $(module)32
     LOCAL_MODULE_STEM_64 := $(module)64
+else
+ifeq ($($(module)_install_to_out_data),true)
+    LOCAL_MODULE_PATH_32 := $(TARGET_OUT_DATA_NATIVE_TESTS)/$(module)
+    LOCAL_MODULE_PATH_64 := $(TARGET_OUT_DATA_NATIVE_TESTS)64/$(module)
+endif
 endif
 
 LOCAL_CLANG := $($(module)_clang_$(build_type))
diff --git a/tests/dlext_test.cpp b/tests/dlext_test.cpp
index b56fc41..da63046 100644
--- a/tests/dlext_test.cpp
+++ b/tests/dlext_test.cpp
@@ -45,6 +45,11 @@ typedef int (*fn)(void);
 #define LIBNAME_NORELRO "libdlext_test_norelro.so"
 #define LIBSIZE 1024*1024 // how much address space to reserve for it
 
+#if defined(__LP64__)
+#define LIBPATH "%s/nativetest64/libdlext_test_fd/libdlext_test_fd.so"
+#else
+#define LIBPATH "%s/nativetest/libdlext_test_fd/libdlext_test_fd.so"
+#endif
 
 class DlExtTest : public ::testing::Test {
 protected:
@@ -83,6 +88,23 @@ TEST_F(DlExtTest, ExtInfoNoFlags) {
   EXPECT_EQ(4, f());
 }
 
+TEST_F(DlExtTest, ExtInfoUseFd) {
+  const char* android_data = getenv("ANDROID_DATA");
+  ASSERT_TRUE(android_data != NULL);
+  char lib_path[PATH_MAX];
+  snprintf(lib_path, sizeof(lib_path), LIBPATH, android_data);
+
+  android_dlextinfo extinfo;
+  extinfo.flags = ANDROID_DLEXT_USE_LIBRARY_FD;
+  extinfo.library_fd = TEMP_FAILURE_RETRY(open(lib_path, O_RDONLY | O_CLOEXEC));
+  ASSERT_TRUE(extinfo.library_fd != -1);
+  handle_ = android_dlopen_ext(lib_path, RTLD_NOW, &extinfo);
+  ASSERT_DL_NOTNULL(handle_);
+  fn f = reinterpret_cast<fn>(dlsym(handle_, "getRandomNumber"));
+  ASSERT_DL_NOTNULL(f);
+  EXPECT_EQ(4, f());
+}
+
 TEST_F(DlExtTest, Reserved) {
   void* start = mmap(NULL, LIBSIZE, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS,
                      -1, 0);
diff --git a/tests/libs/Android.mk b/tests/libs/Android.mk
index efce5b5..a374e48 100644
--- a/tests/libs/Android.mk
+++ b/tests/libs/Android.mk
@@ -78,6 +78,19 @@ build_target := SHARED_LIBRARY
 include $(TEST_PATH)/Android.build.mk
 
 # -----------------------------------------------------------------------------
+# Library used by dlext tests - different name non-default location
+# -----------------------------------------------------------------------------
+libdlext_test_fd_src_files := \
+    dlext_test_library.cpp \
+
+libdlext_test_fd_install_to_out_data := true
+module := libdlext_test_fd
+module_tag := optional
+build_type := target
+build_target := SHARED_LIBRARY
+include $(TEST_PATH)/Android.build.mk
+
+# -----------------------------------------------------------------------------
 # Library used by dlfcn tests
 # -----------------------------------------------------------------------------
 libtest_simple_src_files := \