[PATCH 3/3 v4] Implement remote_bfd_iovec_stat

[Gary Benson <gbenson at redhat dot com>]

Pedro Alves wrote:
> On 03/11/2015 10:23 AM, Gary Benson wrote:
> > Are you ok for me to commit this patch, reordered before the
> > gdbserver changes, with extract_unsigned_integer used in
> > remote_fileio_to_host_{uint,ulong}, and that comment added?
> 
> It be easier for me to just see the patch before answering, but I
> think I am, though I'd like to take another look at the docs patch
> with everything combined, to cross check whether more bits would be
> missing.

Ok, here goes:

---
This patch implements the function remote_bfd_iovec_stat using a
vFile:fstat hostio call to the remote target.  If vFile:fstat is
not supported GDB creates a dummy result by zeroing the supplied
stat structure and then setting it's st_size field to INT_MAX.
This mimic's GDB's previous behaviour, with the exception that
GDB did not previously zero the structure so all other fields
would have been returned unchanged, which is to say very likely
populated with random values from the stack.

gdb/ChangeLog:

	* remote-fileio.h (remote_fileio_to_host_stat): New declaration.
	* remote-fileio.c (remote_fileio_to_host_uint): New function.
	(remote_fileio_to_host_ulong): Likewise.
	(remote_fileio_to_host_mode): Likewise.
	(remote_fileio_to_host_time): Likewise.
	(remote_fileio_to_host_stat): Likewise.
	* remote.c (PACKET_vFile_fstat): New enum value.
	(remote_protocol_features): Register the "vFile:fstat" feature.
	(remote_hostio_fstat): New function.
	(remote_bfd_iovec_stat): Use the above.
	(_initialize_remote): Register new "set/show remote
	hostio-fstat-packet" command.
	* symfile.c (separate_debug_file_exists): Update comment.

gdb/doc/ChangeLog:

	* gdb.texinfo (Remote Configuration): Document the
	"set/show remote hostio-fstat-packet" command.
---
 gdb/ChangeLog       |   16 +++++++++
 gdb/doc/ChangeLog   |    5 +++
 gdb/doc/gdb.texinfo |    4 ++
 gdb/remote-fileio.c |   64 +++++++++++++++++++++++++++++++++++++
 gdb/remote-fileio.h |    4 ++
 gdb/remote.c        |   87 ++++++++++++++++++++++++++++++++++++++++++++++++--
 gdb/symfile.c       |   17 +++++-----
 7 files changed, 185 insertions(+), 12 deletions(-)

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 4b76ce9..1ee1346 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..3882321 100644
--- a/gdb/remote-fileio.c
+++ b/gdb/remote-fileio.c
@@ -1321,6 +1321,70 @@ 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)
+{
+  return extract_unsigned_integer ((gdb_byte *) fnum, 4,
+				   BFD_ENDIAN_BIG);
+}
+
+/* Unpack an fio_ulong_t.  */
+
+static ULONGEST
+remote_fileio_to_host_ulong (fio_ulong_t fnum)
+{
+  return extract_unsigned_integer ((gdb_byte *) fnum, 8,
+				   BFD_ENDIAN_BIG);
+}
+
+/* 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..14ad127 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 +10062,68 @@ 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)
+    {
+      /* Strictly we should return -1, ENOSYS here, but when
+	 "set sysroot remote:" was implemented in August 2008
+	 BFD's need for a stat function was sidestepped with
+	 this hack.  This was not remedied until March 2015
+	 so we retain the previous behavior to avoid breaking
+	 compatibility.
+
+	 Note that the memset is a March 2015 addition; older
+	 GDBs set st_size *and nothing else* so the structure
+	 would have garbage in all other fields.  This might
+	 break something but retaining the previous behavior
+	 here would be just too wrong.  */
+
+      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 +10268,20 @@ 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 +12418,9 @@ 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)
 	{
-- 
1.7.1