[res] Don't stat asset providers on RO filesystems

IsUpToDate() is one of the most often called functions, let's
make sure it only performs a syscall if it makes any sense and
the underlying file can really change.

Bug: 237583012
Test: build + boot + UTs
Change-Id: Ie5999ddadf10b56f35354d00ad3402b229ffa2c3

1 files changed, 38 insertions, 6 deletions

diff --git a/libs/androidfw/misc.cpp b/libs/androidfw/misc.cpp
index 52854205207c..7af506638ebc 100644
--- a/libs/androidfw/misc.cpp
+++ b/libs/androidfw/misc.cpp
@@ -21,12 +21,17 @@
 //
 #include <androidfw/misc.h>
 
-#include <sys/stat.h>
+#include "android-base/logging.h"
+
+#ifndef _WIN32
+#include <sys/statvfs.h>
+#include <sys/vfs.h>
+#endif  // _WIN32
+
 #include <cstring>
-#include <errno.h>
 #include <cstdio>
-
-using namespace android;
+#include <errno.h>
+#include <sys/stat.h>
 
 namespace android {
 
@@ -41,8 +46,7 @@ FileType getFileType(const char* fileName)
         if (errno == ENOENT || errno == ENOTDIR)
             return kFileTypeNonexistent;
         else {
-            fprintf(stderr, "getFileType got errno=%d on '%s'\n",
-                errno, fileName);
+            PLOG(ERROR) << "getFileType(): stat(" << fileName << ") failed";
             return kFileTypeUnknown;
         }
     } else {
@@ -82,4 +86,32 @@ time_t getFileModDate(const char* fileName)
     return sb.st_mtime;
 }
 
+#ifdef _WIN32
+// No need to implement these for Windows, the functions only matter on a device.
+bool isReadonlyFilesystem(const char*) {
+    return false;
+}
+bool isReadonlyFilesystem(int) {
+    return false;
+}
+#else   // _WIN32
+bool isReadonlyFilesystem(const char* path) {
+    struct statfs sfs;
+    if (::statfs(path, &sfs)) {
+        PLOG(ERROR) << "isReadonlyFilesystem(): statfs(" << path << ") failed";
+        return false;
+    }
+    return (sfs.f_flags & ST_RDONLY) != 0;
+}
+
+bool isReadonlyFilesystem(int fd) {
+    struct statfs sfs;
+    if (::fstatfs(fd, &sfs)) {
+        PLOG(ERROR) << "isReadonlyFilesystem(): fstatfs(" << fd << ") failed";
+        return false;
+    }
+    return (sfs.f_flags & ST_RDONLY) != 0;
+}
+#endif  // _WIN32
+
 }; // namespace android