gdb: add GDB side target_ops::fileio_stat implementation

This commit adds the GDB side of target_ops::fileio_stat.  There's an
implementation for inf_child_target, which just calls 'lstat', and
there's an implementation for remote_target, which sends a new
vFile:stat packet.

The new packet is documented.

There's still no users of target_fileio_stat as I have not yet added
support for vFile::stat to gdbserver.  If these packets are currently
sent to gdbserver then they will be reported as not supported and the
ENOSYS error code will be returned.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>

gdb/NEWS

@@ -224,6 +224,11 @@ qIsAddressTagged
   file is about, this new packet provides a more generic way to perform such
   a check.
 
+vFile:stat
+  Return information about files on the remote system.  Like
+  vFile:fstat but takes a filename rather than an open file
+  descriptor.
+
 *** Changes in GDB 14
 
 * GDB now supports the AArch64 Scalable Matrix Extension 2 (SME2), which

gdb/doc/gdb.texinfo

@@ -24534,6 +24534,10 @@ future connections is shown.  The available settings are:
 @tab @code{vFile:fstat}
 @tab Host I/O
 
+@item @code{hostio-stat-packet}
+@tab @code{vFile:stat}
+@tab Host I/O
+
 @item @code{hostio-setfs-packet}
 @tab @code{vFile:setfs}
 @tab Host I/O
@@ -46326,6 +46330,13 @@ and the return value is the size of this attachment in bytes.
 If an error occurs the return value is -1.  The format of the
 returned binary attachment is as described in @ref{struct stat}.
 
+@item vFile:stat: @var{filename}
+Get information about the file @var{filename} on the target.
+On success the information is returned as a binary attachment
+and the return value is the size of this attachment in bytes.
+If an error occurs the return value is -1.  The format of the
+returned binary attachment is as described in @ref{struct stat}.
+
 @item vFile:unlink: @var{filename}
 Delete the file at @var{filename} on the target.  Return 0,
 or -1 if an error occurs.  The @var{filename} is a string.

gdb/inf-child.c

@@ -320,6 +320,21 @@ inf_child_target::fileio_fstat (int fd, struct stat *sb, fileio_error *target_er
   return ret;
 }
 
+/* Implementation of to_fileio_stat.  */
+
+int
+inf_child_target::fileio_stat (struct inferior *inf, const char *filename,
+			       struct stat *sb, fileio_error *target_errno)
+{
+  int ret;
+
+  ret = lstat (filename, sb);
+  if (ret == -1)
+    *target_errno = host_to_fileio_error (errno);
+
+  return ret;
+}
+
 /* Implementation of to_fileio_close.  */
 
 int

gdb/inf-child.h

@@ -81,6 +81,8 @@ class inf_child_target
   int fileio_pread (int fd, gdb_byte *read_buf, int len,
 		    ULONGEST offset, fileio_error *target_errno) override;
   int fileio_fstat (int fd, struct stat *sb, fileio_error *target_errno) override;
+  int fileio_stat (struct inferior *inf, const char *filename,
+		   struct stat *sb, fileio_error *target_errno) override;
   int fileio_close (int fd, fileio_error *target_errno) override;
   int fileio_unlink (struct inferior *inf,
 		     const char *filename,

gdb/remote.c

@@ -248,6 +248,7 @@ enum {
   PACKET_vFile_unlink,
   PACKET_vFile_readlink,
   PACKET_vFile_fstat,
+  PACKET_vFile_stat,
   PACKET_qXfer_auxv,
   PACKET_qXfer_features,
   PACKET_qXfer_exec_file,
@@ -1010,6 +1011,9 @@ class remote_target : public process_stratum_target
 
   int fileio_fstat (int fd, struct stat *sb, fileio_error *target_errno) override;
 
+  int fileio_stat (struct inferior *inf, const char *filename,
+		   struct stat *sb, fileio_error *target_errno) override;
+
   int fileio_close (int fd, fileio_error *target_errno) override;
 
   int fileio_unlink (struct inferior *inf,
@@ -13048,6 +13052,41 @@ remote_target::fileio_readlink (struct inferior *inf, const char *filename,
   return ret;
 }
 
+/* Helper function to handle ::fileio_fstat and ::fileio_stat result
+   processing.  When this function is called the remote syscall has been
+   performed and we know we didn't get an error back.
+
+   ATTACHMENT and ATTACHMENT_LEN are the attachment data extracted from the
+   remote syscall reply.  EXPECTED_LEN is the length returned from the
+   fstat or stat call, this the length of the returned data (in ATTACHMENT)
+   once it has been decoded.  The fstat/stat result (from the ATTACHMENT
+   data) is to be placed in ST.  */
+
+static int
+fileio_process_fstat_and_stat_reply (const char *attachment,
+				     int attachment_len,
+				     int expected_len,
+				     struct stat *st)
+{
+  struct fio_stat fst;
+
+  int read_len
+    = remote_unescape_input ((gdb_byte *) attachment, attachment_len,
+			     (gdb_byte *) &fst, sizeof (fst));
+
+  if (read_len != expected_len)
+    error (_("vFile:fstat returned %d, but %d bytes."),
+	   expected_len, 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;
+}
+
 /* Implementation of to_fileio_fstat.  */
 
 int
@@ -13058,8 +13097,6 @@ remote_target::fileio_fstat (int fd, struct stat *st, fileio_error *remote_errno
   int left = get_remote_packet_size ();
   int attachment_len, ret;
   const char *attachment;
-  struct fio_stat fst;
-  int read_len;
 
   remote_buffer_add_string (&p, &left, "vFile:fstat:");
 
@@ -13091,19 +13128,41 @@ remote_target::fileio_fstat (int fd, struct stat *st, fileio_error *remote_errno
       return 0;
     }
 
-  read_len = remote_unescape_input ((gdb_byte *) attachment, attachment_len,
-				    (gdb_byte *) &fst, sizeof (fst));
+  return fileio_process_fstat_and_stat_reply (attachment, attachment_len,
+					      ret, st);
+}
 
-  if (read_len != ret)
-    error (_("vFile:fstat returned %d, but %d bytes."), ret, read_len);
+/* Implementation of to_fileio_stat.  */
 
-  if (read_len != sizeof (fst))
-    error (_("vFile:fstat returned %d bytes, but expecting %d."),
-	   read_len, (int) sizeof (fst));
+int
+remote_target::fileio_stat (struct inferior *inf, const char *filename,
+			    struct stat *st, fileio_error *remote_errno)
+{
+  struct remote_state *rs = get_remote_state ();
+  char *p = rs->buf.data ();
+  int left = get_remote_packet_size () - 1;
 
-  remote_fileio_to_host_stat (&fst, st);
+  if (remote_hostio_set_filesystem (inf, remote_errno) != 0)
+    return {};
 
-  return 0;
+  remote_buffer_add_string (&p, &left, "vFile:stat:");
+
+  remote_buffer_add_bytes (&p, &left, (const gdb_byte *) filename,
+			   strlen (filename));
+
+  int attachment_len;
+  const char *attachment;
+  int ret = remote_hostio_send_command (p - rs->buf.data (), PACKET_vFile_stat,
+					remote_errno, &attachment,
+					&attachment_len);
+
+  /* Unlike ::fileio_fstat, the stat fileio call was added later on, and
+     has none of the legacy bfd issues, so we can just return the error.  */
+  if (ret < 0)
+    return ret;
+
+  return fileio_process_fstat_and_stat_reply (attachment, attachment_len,
+					      ret, st);
 }
 
 /* Implementation of to_filesystem_is_local.  */
@@ -16178,6 +16237,8 @@ Show the maximum size of the address (in bits) in a memory packet."), NULL,
 
   add_packet_config_cmd (PACKET_vFile_fstat, "vFile:fstat", "hostio-fstat", 0);
 
+  add_packet_config_cmd (PACKET_vFile_stat, "vFile:stat", "hostio-stat", 0);
+
   add_packet_config_cmd (PACKET_vAttach, "vAttach", "attach", 0);
 
   add_packet_config_cmd (PACKET_vRun, "vRun", "run", 0);