[5/5] gdb: fix reread_symbols when an objfile has target: prefix

diff --git a/gdb/symfile.c b/gdb/symfile.c
index 10074e281bd..b21c8ead225 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -2480,7 +2480,24 @@  reread_symbols (int from_tty)
       else
 	filename = objfile_name (objfile);
 
-      int res = stat (filename, &new_statbuf);
+      int res;
+      if (is_target_filename (filename))
+	{
+	  fileio_error target_errno;
+
+	  scoped_target_fileio_open fd (nullptr,
+					(filename
+					 + strlen (TARGET_SYSROOT_PREFIX)),
+					FILEIO_O_RDONLY, 0, false,
+					&target_errno);
+	  if (fd.get () == -1)
+	    res = -1;
+	  else
+	    res = target_fileio_fstat (fd.get (), &new_statbuf,
+				       &target_errno);
+	}
+      else
+	res = stat (filename, &new_statbuf);
       if (res != 0)
 	{
 	  warning (_("`%ps' has disappeared; keeping its symbols."),
diff --git a/gdb/target.c b/gdb/target.c
index 8cb4fa1736d..0d1608bb5fe 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -54,6 +54,7 @@ 
 #include "target-connection.h"
 #include "valprint.h"
 #include "cli/cli-decode.h"
+#include "cli/cli-style.h"
 
 static void generic_tls_error (void) ATTRIBUTE_NORETURN;
 
@@ -3577,6 +3578,20 @@  target_fileio_read_stralloc (struct inferior *inf, const char *filename)
   return gdb::unique_xmalloc_ptr<char> (bufstr);
 }
 
+/* See target.h.  */
+
+scoped_target_fileio_open::~scoped_target_fileio_open ()
+{
+  if (m_fd != -1)
+    {
+      fileio_error target_errno;
+      if (target_fileio_close (m_fd, &target_errno) != 0)
+	warning (_("failed to close %ps: %s"),
+		 styled_string (file_name_style.style (),
+				m_filename.c_str ()),
+		 safe_strerror (fileio_error_to_host (target_errno)));
+    }
+}
 
 static int
 default_region_ok_for_hw_watchpoint (struct target_ops *self,
diff --git a/gdb/target.h b/gdb/target.h
index 936ae79219c..5712adc367d 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -2235,6 +2235,45 @@  extern gdb::unique_xmalloc_ptr<char> target_fileio_read_stralloc
    with EIO.  */
 extern void fileio_handles_invalidate_target (target_ops *targ);
 
+/* A class that performs a target_fileio_open within a scope.  On leaving
+   the scope target_fileio_close is called.
+
+   If the close fails then a warning is issued.  */
+struct scoped_target_fileio_open
+{
+  /* Call target_fileio_open passing all the arguments through.  See
+     target_fileio_open for the meaning of all arguments.  */
+  scoped_target_fileio_open (struct inferior *inf,
+			     const char *filename, int flags,
+			     int mode, bool warn_if_slow,
+			     fileio_error *target_errno)
+    : m_filename (filename)
+  {
+    m_fd = target_fileio_open (inf, filename, flags, mode, warn_if_slow,
+			       target_errno);
+  }
+
+  /* Close the file that was opened in the constructor, issue a warning if
+     the close fails.  */
+  ~scoped_target_fileio_open ();
+
+  /* Return the file descriptor for the opened file.  This can only be used
+     with target_fileio_* calls.  This will return -1 if the open failed.  */
+  int get () const
+  {
+    return m_fd;
+  }
+
+private:
+  /* The filename that we opened.  Stored so we can give a warning if the
+     close fails for any reason.  */
+  std::string m_filename;
+
+  /* The target file descriptor for the opened file, or -1 if the open
+     failed for any reason.  */
+  int m_fd = -1;
+};
+
 /* Tracepoint-related operations.  */
 
 extern void target_trace_init ();
diff --git a/gdb/testsuite/gdb.server/target-exec-file.c b/gdb/testsuite/gdb.server/target-exec-file.c
new file mode 100644
index 00000000000..3a264f239ed
--- /dev/null
+++ b/gdb/testsuite/gdb.server/target-exec-file.c
@@ -0,0 +1,22 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2023 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+int
+main ()
+{
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.server/target-exec-file.exp b/gdb/testsuite/gdb.server/target-exec-file.exp
new file mode 100644
index 00000000000..9260df8b88d
--- /dev/null
+++ b/gdb/testsuite/gdb.server/target-exec-file.exp
@@ -0,0 +1,174 @@ 
+# This testcase is part of GDB, the GNU debugger.
+
+# Copyright 2023 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test GDB's handling of using a file with a 'target:' prefix as the
+# executable file.  This test includes checking what happens when the
+# file on the target system changes and GDB needs to reload it.
+
+load_lib gdbserver-support.exp
+
+require allow_gdbserver_tests !use_gdb_stub
+
+standard_testfile
+
+if { [build_executable "failed to prepare" $testfile $srcfile debug] } {
+    return -1
+}
+
+clean_restart
+
+# Some boards specifically set the sysroot to the empty string to
+# avoid copying files from the target.  But for this test we do want
+# to copy files from the target, so set the sysroot back to 'target:'.
+#
+# This is fine so long as we're not using a board file that sets the
+# sysroot to something else -- but none of the standard boards do
+# this, and plenty of other tests mess with the sysroot, so I guess we
+# don't worry about that too much.
+gdb_test "set sysroot target:" ".*"
+
+# Make sure we're disconnected, in case we're testing with an
+# extended-remote board, therefore already connected.
+gdb_test "disconnect" ".*"
+
+# Ensure the executable is on the target.
+set target_exec [gdb_remote_download target $binfile]
+
+# We're going to be restarting the inferior.  Lets ask GDB not to
+# prompt us if this is the right thing to do.
+gdb_test_no_output "set confirm off"
+
+# Start gdbserver, but always in extended-remote mode, and then
+# connect to it from GDB.
+set res [gdbserver_start "--multi" $target_exec]
+set gdbserver_protocol "extended-remote"
+set gdbserver_gdbport [lindex $res 1]
+gdb_target_cmd $gdbserver_protocol $gdbserver_gdbport
+
+# Issue a 'file' command and parse the output.  We look for a couple
+# of specific things to ensure that we are correctly reading the exec
+# from the remote target.
+set saw_read_of_remote_exec false
+set saw_read_of_syms_from_exec false
+gdb_test_multiple "file target:$target_exec" "run file command" {
+    -re "^file target:\[^\r\n\]+\r\n" {
+	exp_continue
+    }
+
+    -re "^Reading (\[^\r\n\]+) from remote target\\.\\.\\.\r\n" {
+	set filename $expect_out(1,string)
+	if { $filename eq $target_exec } {
+	    set saw_read_of_remote_exec true
+	}
+	exp_continue
+    }
+
+    -re "^warning: File transfers from remote targets can be slow\[^\r\n\]+\r\n" {
+	exp_continue
+    }
+
+    -re "^Reading symbols from target:(\[^\r\n\]+)\\.\\.\\.\r\n" {
+	set filename $expect_out(1,string)
+	if { $filename eq $target_exec } {
+	    set saw_read_of_syms_from_exec true
+	}
+	exp_continue
+    }
+
+    -re "^Expanding full symbols from \[^\r\n\]+\r\n" {
+	exp_continue
+    }
+
+    -re "^$gdb_prompt $" {
+	pass $gdb_test_name
+    }
+}
+
+gdb_assert { $saw_read_of_remote_exec } \
+    "exec was read from the remote target"
+
+gdb_assert { $saw_read_of_syms_from_exec } \
+    "symbols were read from remote exec file"
+
+# Start the inferior (with the 'start' command), use TESTNAME for any
+# pass/fail calls.  EXPECT_REREAD should be true or false and
+# indicates if we expect to too a line like:
+#
+#  `FILE' has changed; re-reading symbols.
+proc start_inferior { testname expect_reread } {
+    with_test_prefix $testname {
+	if { [gdb_start_cmd] < 0 } {
+	    fail "start command"
+	    return -1
+	}
+
+	set saw_reread false
+	gdb_test_multiple "" "stopped at main" {
+	    -re "^start\\s*\r\n" {
+		exp_continue
+	    }
+	    -re "^`\[^\r\n\]+' has changed; re-reading symbols\\.\r\n" {
+		set saw_reread true
+		exp_continue
+	    }
+	    -re "^Reading \[^\r\n\]+ from remote target\\.\\.\\.\r\n" {
+		exp_continue
+	    }
+	    -re "^Expanding full symbols from \[^\r\n\]+\\.\\.\\.\r\n" {
+		exp_continue
+	    }
+	    -re "^Temporary breakpoint $::decimal at $::hex: \[^\r\n\]+\r\n" {
+		exp_continue
+	    }
+	    -re "^Starting program: \[^\r\n\]+\r\n" {
+		exp_continue
+	    }
+	    -re "^\\s*\r\n" {
+		exp_continue
+	    }
+	    -re "^Temporary breakpoint $::decimal, main \\(\\) at .*$::gdb_prompt $" {
+		pass $testname
+	    }
+	}
+
+	gdb_assert { $expect_reread == $saw_reread } \
+	    "check symbol re-read behaviour"
+    }
+}
+
+# Start the inferior for the first time.  The symbols were already
+# read from the file when the 'file' command was used, we should not
+# see the symbols re-read now.
+start_inferior "start inferior the first time" false
+
+# Re-start the inferior.  The executable is unchanged so we should not
+# see the symbol file being re-read.
+start_inferior "start inferior a second time" false
+
+# Delay for a short while so, when we touch the exec, we know the
+# timestamp will change.
+sleep 1
+set res [remote_exec target "touch $target_exec"]
+set status [lindex $res 0]
+if { $status != 0 } {
+    fail "touching executable on target"
+    return -1
+}
+
+# Start the inferior again, we expect to see the symbols being re-read
+# from the remote file.
+start_inferior "start inferior a third time" true