Merge "Add support for ashmem-host for host Windows" into android12-hostruntime-devandroid12-hostruntime-dev

3 files changed, 42 insertions, 26 deletions

diff --git a/libcutils/Android.bp b/libcutils/Android.bp
index 68b21c6a0..94f80bb9f 100644
--- a/libcutils/Android.bp
+++ b/libcutils/Android.bp
@@ -170,20 +170,20 @@ cc_library {
         linux_bionic: {
             enabled: true,
         },
+        host: {
+            srcs: [
+                "ashmem-host.cpp",
+                "trace-host.cpp",
+            ],
+        },
         not_windows: {
             srcs: libcutils_nonwindows_sources + [
-                "ashmem-host.cpp",
                 "fs_config.cpp",
-                "trace-host.cpp",
             ],
         },
         windows: {
             host_ldlibs: ["-lws2_32"],
 
-            srcs: [
-                "trace-host.cpp",
-            ],
-
             enabled: true,
             cflags: [
                 "-D_GNU_SOURCE",
diff --git a/libcutils/OWNERS b/libcutils/OWNERS
index 7529cb920..e1cbe4aaf 100644
--- a/libcutils/OWNERS
+++ b/libcutils/OWNERS
@@ -1 +1,2 @@
+# Bug component: 128577
 include platform/system/core:/janitors/OWNERS
diff --git a/libcutils/ashmem-host.cpp b/libcutils/ashmem-host.cpp
index 2ba1eb0c3..9003b76c9 100644
--- a/libcutils/ashmem-host.cpp
+++ b/libcutils/ashmem-host.cpp
@@ -17,10 +17,13 @@
 #include <cutils/ashmem.h>
 
 /*
- * Implementation of the user-space ashmem API for the simulator, which lacks
- * an ashmem-enabled kernel. See ashmem-dev.c for the real ashmem-based version.
+ * Implementation of the user-space ashmem API for the simulator, which lacks an
+ * ashmem-enabled kernel. See ashmem-dev.c for the real ashmem-based version.  A
+ * disk-backed temp file is the best option that is consistently supported
+ * across all host platforms.
  */
 
+#include <android-base/unique_fd.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
@@ -31,8 +34,10 @@
 #include <sys/types.h>
 #include <time.h>
 #include <unistd.h>
-
 #include <utils/Compat.h>
+#include <memory>
+
+using android::base::unique_fd;
 
 static bool ashmem_validate_stat(int fd, struct stat* buf) {
     int result = fstat(fd, buf);
@@ -40,15 +45,20 @@ static bool ashmem_validate_stat(int fd, struct stat* buf) {
         return false;
     }
 
-    /*
-     * Check if this is an "ashmem" region.
-     * TODO: This is very hacky, and can easily break.
-     * We need some reliable indicator.
-     */
-    if (!(buf->st_nlink == 0 && S_ISREG(buf->st_mode))) {
+    // Check if this is an ashmem region. Since there's no such thing on the host,
+    // we can't actually implement that. Check that it's at least a regular file.
+    if (!S_ISREG(buf->st_mode)) {
         errno = ENOTTY;
         return false;
     }
+    // In Win32, unlike Unix, the temp file is not unlinked immediately after
+    // creation.
+#if !defined(_WIN32)
+    if (buf->st_nlink != 0) {
+        errno = ENOTTY;
+        return false;
+    }
+#endif
     return true;
 }
 
@@ -58,19 +68,24 @@ int ashmem_valid(int fd) {
 }
 
 int ashmem_create_region(const char* /*ignored*/, size_t size) {
-    char pattern[PATH_MAX];
-    snprintf(pattern, sizeof(pattern), "/tmp/android-ashmem-%d-XXXXXXXXX", getpid());
-    int fd = mkstemp(pattern);
-    if (fd == -1) return -1;
-
-    unlink(pattern);
+    // Files returned by tmpfile are automatically removed.
+    std::unique_ptr<FILE, decltype(&fclose)> tmp(tmpfile(), &fclose);
 
-    if (TEMP_FAILURE_RETRY(ftruncate(fd, size)) == -1) {
-      close(fd);
-      return -1;
+    if (!tmp) {
+        return -1;
     }
-
-    return fd;
+    int fd = fileno(tmp.get());
+    if (fd == -1) {
+        return -1;
+    }
+    unique_fd dupfd = unique_fd(dup(fd));
+    if (dupfd == -1) {
+        return -1;
+    }
+    if (TEMP_FAILURE_RETRY(ftruncate(dupfd, size)) == -1) {
+        return -1;
+    }
+    return dupfd.release();
 }
 
 int ashmem_set_prot_region(int /*fd*/, int /*prot*/) {