hw/9pfs: Fix build error on platform that don't support futimens

Also don't do glibc version check to find handle support. Instead
do handle syscall support in configure.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

configure

@@ -2556,6 +2556,18 @@ EOF
   fi
 fi
 
+##########################################
+# check if we have open_by_handle_at
+
+open_by_hande_at=no
+cat > $TMPC << EOF
+#include <fcntl.h>
+int main(void) { struct file_handle *fh; open_by_handle_at(0, fh, 0); }
+EOF
+if compile_prog "" "" ; then
+    open_by_handle_at=yes
+fi
+
 ##########################################
 # End of CC checks
 # After here, no more $cc or $ld runs
@@ -3035,6 +3047,10 @@ if test "$ucontext_coroutine" = "yes" ; then
   echo "CONFIG_UCONTEXT_COROUTINE=y" >> $config_host_mak
 fi
 
+if test "$open_by_handle_at" = "yes" ; then
+  echo "CONFIG_OPEN_BY_HANDLE=y" >> $config_host_mak
+fi
+
 # USB host support
 case "$usb" in
 linux)

hw/9pfs/virtio-9p-handle.c

@@ -27,13 +27,24 @@ struct handle_data {
     int handle_bytes;
 };
 
-#if __GLIBC__ <= 2 && __GLIBC_MINOR__ < 14
+#ifdef CONFIG_OPEN_BY_HANDLE
+static inline int name_to_handle(int dirfd, const char *name,
+                                 struct file_handle *fh, int *mnt_id, int flags)
+{
+    return name_to_handle_at(dirfd, name, fh, mnt_id, flags);
+}
+
+static inline int open_by_handle(int mountfd, const char *fh, int flags)
+{
+    return open_by_handle_at(mountfd, (struct file_handle *)fh, flags);
+}
+#else
+
 struct file_handle {
-        unsigned int handle_bytes;
+    unsigned int handle_bytes;
-        int handle_type;
+    int handle_type;
-        unsigned char handle[0];
+    unsigned char handle[0];
 };
-#endif
 
 #ifndef AT_EMPTY_PATH
 #define AT_EMPTY_PATH   0x1000  /* Allow empty relative pathname */
@@ -42,28 +53,6 @@ struct file_handle {
 #define O_PATH    010000000
 #endif
 
-#ifndef __NR_name_to_handle_at
-#if defined(__i386__)
-#define __NR_name_to_handle_at  341
-#define __NR_open_by_handle_at  342
-#elif defined(__x86_64__)
-#define __NR_name_to_handle_at  303
-#define __NR_open_by_handle_at  304
-#endif
-#endif
-
-#ifdef __NR_name_to_handle_at
-static inline int name_to_handle(int dirfd, const char *name,
-                                 struct file_handle *fh, int *mnt_id, int flags)
-{
-    return syscall(__NR_name_to_handle_at, dirfd, name, fh, mnt_id, flags);
-}
-
-static inline int open_by_handle(int mountfd, const char *fh, int flags)
-{
-    return syscall(__NR_open_by_handle_at, mountfd, fh, flags);
-}
-#else
 static inline int name_to_handle(int dirfd, const char *name,
                                  struct file_handle *fh, int *mnt_id, int flags)
 {
@@ -380,7 +369,9 @@ static int handle_chown(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp)
 static int handle_utimensat(FsContext *ctx, V9fsPath *fs_path,
                             const struct timespec *buf)
 {
-    int fd, ret;
+    int ret;
+#ifdef CONFIG_UTIMENSAT
+    int fd;
     struct handle_data *data = (struct handle_data *)ctx->private;
 
     fd = open_by_handle(data->mountfd, fs_path->data, O_NONBLOCK);
@@ -389,6 +380,10 @@ static int handle_utimensat(FsContext *ctx, V9fsPath *fs_path,
     }
     ret = futimens(fd, buf);
     close(fd);
+#else
+    ret = -1;
+    errno = ENOSYS;
+#endif
     return ret;
 }
 
@@ -564,6 +559,7 @@ static int handle_init(FsContext *ctx)
     int ret, mnt_id;
     struct file_handle fh;
     struct handle_data *data = g_malloc(sizeof(struct handle_data));
+
     data->mountfd = open(ctx->fs_root, O_DIRECTORY);
     if (data->mountfd < 0) {
         ret = data->mountfd;