[3/3,v3] Implement remote_bfd_iovec_stat using vFile:fstat

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 8d4af3c..552da31 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -19748,6 +19748,10 @@  are:
 @tab @code{vFile:readlink}
 @tab Host I/O
 
+@item @code{hostio-fstat-packet}
+@tab @code{vFile:fstat}
+@tab Host I/O
+
 @item @code{noack-packet}
 @tab @code{QStartNoAckMode}
 @tab Packet acknowledgment
diff --git a/gdb/remote-fileio.c b/gdb/remote-fileio.c
index 0ce0714..aaf839d 100644
--- a/gdb/remote-fileio.c
+++ b/gdb/remote-fileio.c
@@ -1321,6 +1321,86 @@  remote_fileio_request (char *buf, int ctrlc_pending_p)
 
   remote_fileio_sig_exit ();
 }
+
+
+/* Unpack an fio_uint_t.  */
+
+static unsigned int
+remote_fileio_to_host_uint (fio_uint_t fnum)
+{
+  gdb_byte *buf, *lim;
+  unsigned int num = 0;
+
+  for (buf = (gdb_byte *) fnum, lim = buf + 4; buf < lim; buf++)
+    {
+      num <<= 8;
+      num |= *buf;
+    }
+
+  return num;
+}
+
+/* Unpack an fio_ulong_t.  */
+
+static ULONGEST
+remote_fileio_to_host_ulong (fio_ulong_t fnum)
+{
+  gdb_byte *buf, *lim;
+  ULONGEST num = 0;
+
+  for (buf = (gdb_byte *) fnum, lim = buf + 8; buf < lim; buf++)
+    {
+      num <<= 8;
+      num |= *buf;
+    }
+
+  return num;
+}
+
+/* Unpack an fio_mode_t.  */
+
+static mode_t
+remote_fileio_to_host_mode (fio_mode_t fnum)
+{
+  return remote_fileio_mode_to_host (remote_fileio_to_host_uint (fnum),
+				     0);
+}
+
+/* Unpack an fio_time_t.  */
+
+static time_t
+remote_fileio_to_host_time (fio_time_t fnum)
+{
+  return remote_fileio_to_host_uint (fnum);
+}
+
+
+/* See remote-fileio.h.  */
+
+void
+remote_fileio_to_host_stat (struct fio_stat *fst, struct stat *st)
+{
+  memset (st, 0, sizeof (struct stat));
+
+  st->st_dev = remote_fileio_to_host_uint (fst->fst_dev);
+  st->st_ino = remote_fileio_to_host_uint (fst->fst_ino);
+  st->st_mode = remote_fileio_to_host_mode (fst->fst_mode);
+  st->st_nlink = remote_fileio_to_host_uint (fst->fst_nlink);
+  st->st_uid = remote_fileio_to_host_uint (fst->fst_uid);
+  st->st_gid = remote_fileio_to_host_uint (fst->fst_gid);
+  st->st_rdev = remote_fileio_to_host_uint (fst->fst_rdev);
+  st->st_size = remote_fileio_to_host_ulong (fst->fst_size);
+#ifdef HAVE_STRUCT_STAT_ST_BLKSIZE
+  st->st_blksize = remote_fileio_to_host_ulong (fst->fst_blksize);
+#endif
+#if HAVE_STRUCT_STAT_ST_BLOCKS
+  st->st_blocks = remote_fileio_to_host_ulong (fst->fst_blocks);
+#endif
+  st->st_atime = remote_fileio_to_host_time (fst->fst_atime);
+  st->st_mtime = remote_fileio_to_host_time (fst->fst_mtime);
+  st->st_ctime = remote_fileio_to_host_time (fst->fst_ctime);
+}
+
 
 static void
 set_system_call_allowed (char *args, int from_tty)
diff --git a/gdb/remote-fileio.h b/gdb/remote-fileio.h
index 8b32868..d30ae6a 100644
--- a/gdb/remote-fileio.h
+++ b/gdb/remote-fileio.h
@@ -38,4 +38,8 @@  extern void initialize_remote_fileio (
   struct cmd_list_element *remote_set_cmdlist,
   struct cmd_list_element *remote_show_cmdlist);
 
+/* Unpack a struct fio_stat.  */
+extern void remote_fileio_to_host_stat (struct fio_stat *fst,
+					struct stat *st);
+
 #endif
diff --git a/gdb/remote.c b/gdb/remote.c
index 495dfdc..52adbbb 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -1253,6 +1253,7 @@  enum {
   PACKET_vFile_close,
   PACKET_vFile_unlink,
   PACKET_vFile_readlink,
+  PACKET_vFile_fstat,
   PACKET_qXfer_auxv,
   PACKET_qXfer_features,
   PACKET_qXfer_libraries,
@@ -4042,7 +4043,9 @@  static const struct protocol_feature remote_protocol_features[] = {
   { "Qbtrace-conf:bts:size", PACKET_DISABLE, remote_supported_packet,
     PACKET_Qbtrace_conf_bts_size },
   { "swbreak", PACKET_DISABLE, remote_supported_packet, PACKET_swbreak_feature },
-  { "hwbreak", PACKET_DISABLE, remote_supported_packet, PACKET_hwbreak_feature }
+  { "hwbreak", PACKET_DISABLE, remote_supported_packet, PACKET_hwbreak_feature },
+  { "vFile:fstat", PACKET_DISABLE, remote_supported_packet,
+    PACKET_vFile_fstat },
 };
 
 static char *remote_support_xml;
@@ -10059,6 +10062,55 @@  remote_hostio_readlink (struct target_ops *self,
   return ret;
 }
 
+/* Read information about the open file FD on the remote target
+   into ST.  Return 0 on success, or -1 if an error occurs (and
+   set *REMOTE_ERRNO).  */
+
+static int
+remote_hostio_fstat (struct target_ops *self,
+		     int fd, struct stat *st,
+		     int *remote_errno)
+{
+  struct remote_state *rs = get_remote_state ();
+  char *p = rs->buf;
+  int left = get_remote_packet_size ();
+  int attachment_len, ret;
+  char *attachment;
+  struct fio_stat fst;
+  int read_len;
+
+  if (packet_support (PACKET_vFile_fstat) != PACKET_ENABLE)
+    {
+      memset (st, 0, sizeof (struct stat));
+      st->st_size = INT_MAX;
+      return 0;
+    }
+
+  remote_buffer_add_string (&p, &left, "vFile:fstat:");
+
+  remote_buffer_add_int (&p, &left, fd);
+
+  ret = remote_hostio_send_command (p - rs->buf, PACKET_vFile_fstat,
+				    remote_errno, &attachment,
+				    &attachment_len);
+  if (ret < 0)
+    return ret;
+
+  read_len = remote_unescape_input ((gdb_byte *) attachment, attachment_len,
+				    (gdb_byte *) &fst, sizeof (fst));
+
+  if (read_len != ret)
+    error (_("vFile:fstat returned %d, but %d bytes."), ret, read_len);
+
+  if (read_len != sizeof (fst))
+    error (_("vFile:fstat returned %d bytes, but expecting %d."),
+	   read_len, (int) sizeof (fst));
+
+  remote_fileio_to_host_stat (&fst, st);
+
+  return 0;
+}
+
 static int
 remote_fileio_errno_to_host (int errnum)
 {
@@ -10203,9 +10255,20 @@  remote_bfd_iovec_pread (struct bfd *abfd, void *stream, void *buf,
 static int
 remote_bfd_iovec_stat (struct bfd *abfd, void *stream, struct stat *sb)
 {
-  /* FIXME: We should probably implement remote_hostio_stat.  */
-  sb->st_size = INT_MAX;
-  return 0;
+  int fd = *(int *) stream;
+  int remote_errno;
+  int result;
+
+  result = remote_hostio_fstat (find_target_at (process_stratum),
+				fd, sb, &remote_errno);
+
+  if (result == -1)
+    {
+      errno = remote_fileio_errno_to_host (remote_errno);
+      bfd_set_error (bfd_error_system_call);
+    }
+
+  return result;
 }
 
 int
@@ -12342,6 +12405,9 @@  Show the maximum size of the address (in bits) in a memory packet."), NULL,
   add_packet_config_cmd (&remote_protocol_packets[PACKET_vFile_readlink],
 			 "vFile:readlink", "hostio-readlink", 0);
 
+  add_packet_config_cmd (&remote_protocol_packets[PACKET_vFile_fstat],
+			 "vFile:fstat", "hostio-fstat", 0);
+
   add_packet_config_cmd (&remote_protocol_packets[PACKET_vAttach],
 			 "vAttach", "attach", 0);
 
diff --git a/gdb/symfile.c b/gdb/symfile.c
index c2a71ec..ba099d3 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -1377,11 +1377,12 @@  separate_debug_file_exists (const char *name, unsigned long crc,
 
      Some operating systems, e.g. Windows, do not provide a meaningful
      st_ino; they always set it to zero.  (Windows does provide a
-     meaningful st_dev.)  Do not indicate a duplicate library in that
-     case.  While there is no guarantee that a system that provides
-     meaningful inode numbers will never set st_ino to zero, this is
-     merely an optimization, so we do not need to worry about false
-     negatives.  */
+     meaningful st_dev.)  Files accessed from gdbservers that do not
+     support the vFile:fstat packet will also have st_ino set to zero.
+     Do not indicate a duplicate library in either case.  While there
+     is no guarantee that a system that provides meaningful inode
+     numbers will never set st_ino to zero, this is merely an
+     optimization, so we do not need to worry about false negatives.  */
 
   if (bfd_stat (abfd, &abfd_stat) == 0
       && abfd_stat.st_ino != 0
@@ -1409,9 +1410,9 @@  separate_debug_file_exists (const char *name, unsigned long crc,
     {
       unsigned long parent_crc;
 
-      /* If one (or both) the files are accessed for example the via "remote:"
-	 gdbserver way it does not support the bfd_stat operation.  Verify
-	 whether those two files are not the same manually.  */
+      /* If the files could not be verified as different with
+	 bfd_stat then we need to calculate the parent's CRC
+	 to verify whether the files are different or not.  */
 
       if (!verified_as_different)
 	{