Warn when accessing binaries from remote targets

GDB provides no indicator of progress during file operations, and can
appear to have locked up during slow remote transfers.  This commit
updates GDB to print a warning each time a file is accessed over RSP.
An additional message detailing how to avoid remote transfers is
printed for the first transfer only.

gdb/ChangeLog:

	* target.h (struct target_ops) <to_fileio_open>: New argument
	warn_if_slow.  Update comment.  All implementations updated.
	(target_fileio_open_warn_if_slow): New declaration.
	* target.c (target_fileio_open): Renamed as...
	(target_fileio_open_1): ...this.  New argument warn_if_slow.
	Pass warn_if_slow to implementation.  Update debug printing.
	(target_fileio_open): New function.
	(target_fileio_open_warn_if_slow): Likewise.
	* gdb_bfd.c (gdb_bfd_iovec_fileio_open): Use new function
	target_fileio_open_warn_if_slow.

gdb/testsuite/ChangeLog:

	* gdb.trace/pending.exp: Cope with remote transfer warnings.

9 files changed, 97 insertions, 24 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0cb0c7b..d8b23e0 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,18 @@
 2015-08-21  Gary Benson  <gbenson@redhat.com>
 
+	* target.h (struct target_ops) <to_fileio_open>: New argument
+	warn_if_slow.  Update comment.  All implementations updated.
+	(target_fileio_open_warn_if_slow): New declaration.
+	* target.c (target_fileio_open): Renamed as...
+	(target_fileio_open_1): ...this.  New argument warn_if_slow.
+	Pass warn_if_slow to implementation.  Update debug printing.
+	(target_fileio_open): New function.
+	(target_fileio_open_warn_if_slow): Likewise.
+	* gdb_bfd.c (gdb_bfd_iovec_fileio_open): Use new function
+	target_fileio_open_warn_if_slow.
+
+2015-08-21  Gary Benson  <gbenson@redhat.com>
+
 	* nat/linux-namespaces.c (linux_mntns_access_fs):
 	Do not overwrite old_chain.
 
diff --git a/gdb/gdb_bfd.c b/gdb/gdb_bfd.c
index eb53766..bffe589 100644
--- a/gdb/gdb_bfd.c
+++ b/gdb/gdb_bfd.c
@@ -261,10 +261,11 @@ gdb_bfd_iovec_fileio_open (struct bfd *abfd, void *inferior)
 
   gdb_assert (is_target_filename (filename));
 
-  fd = target_fileio_open ((struct inferior *) inferior,
-			   filename + strlen (TARGET_SYSROOT_PREFIX),
-			   FILEIO_O_RDONLY, 0,
-			   &target_errno);
+  fd = target_fileio_open_warn_if_slow ((struct inferior *) inferior,
+					filename
+					+ strlen (TARGET_SYSROOT_PREFIX),
+					FILEIO_O_RDONLY, 0,
+					&target_errno);
   if (fd == -1)
     {
       errno = fileio_errno_to_host (target_errno);
diff --git a/gdb/inf-child.c b/gdb/inf-child.c
index 0326a93..ada570d 100644
--- a/gdb/inf-child.c
+++ b/gdb/inf-child.c
@@ -209,7 +209,8 @@ inf_child_pid_to_exec_file (struct target_ops *self, int pid)
 static int
 inf_child_fileio_open (struct target_ops *self,
 		       struct inferior *inf, const char *filename,
-		       int flags, int mode, int *target_errno)
+		       int flags, int mode, int warn_if_slow,
+		       int *target_errno)
 {
   int nat_flags;
   mode_t nat_mode;
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index a13fb9e..19e242a 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -4922,7 +4922,8 @@ linux_nat_fileio_pid_of (struct inferior *inf)
 static int
 linux_nat_fileio_open (struct target_ops *self,
 		       struct inferior *inf, const char *filename,
-		       int flags, int mode, int *target_errno)
+		       int flags, int mode, int warn_if_slow,
+		       int *target_errno)
 {
   int nat_flags;
   mode_t nat_mode;
diff --git a/gdb/remote.c b/gdb/remote.c
index 068d079..12294bc 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -10498,12 +10498,29 @@ remote_hostio_set_filesystem (struct inferior *inf, int *remote_errno)
 static int
 remote_hostio_open (struct target_ops *self,
 		    struct inferior *inf, const char *filename,
-		    int flags, int mode, int *remote_errno)
+		    int flags, int mode, int warn_if_slow,
+		    int *remote_errno)
 {
   struct remote_state *rs = get_remote_state ();
   char *p = rs->buf;
   int left = get_remote_packet_size () - 1;
 
+  if (warn_if_slow)
+    {
+      static int warning_issued = 0;
+
+      printf_unfiltered (_("Reading %s from remote target...\n"),
+			 filename);
+
+      if (!warning_issued)
+	{
+	  warning (_("File transfers from remote targets can be slow."
+		     " Use \"set sysroot\" to access files locally"
+		     " instead."));
+	  warning_issued = 1;
+	}
+    }
+
   if (remote_hostio_set_filesystem (inf, remote_errno) != 0)
     return -1;
 
@@ -10827,7 +10844,7 @@ remote_filesystem_is_local (struct target_ops *self)
 	     filename is irrelevant, we only care about whether
 	     the stub recognizes the packet or not.  */
 	  fd = remote_hostio_open (self, NULL, "just probing",
-				   FILEIO_O_RDONLY, 0700,
+				   FILEIO_O_RDONLY, 0700, 0,
 				   &remote_errno);
 
 	  if (fd >= 0)
@@ -10949,7 +10966,7 @@ remote_file_put (const char *local_file, const char *remote_file, int from_tty)
   fd = remote_hostio_open (find_target_at (process_stratum), NULL,
 			   remote_file, (FILEIO_O_WRONLY | FILEIO_O_CREAT
 					 | FILEIO_O_TRUNC),
-			   0700, &remote_errno);
+			   0700, 0, &remote_errno);
   if (fd == -1)
     remote_hostio_error (remote_errno);
 
@@ -11033,7 +11050,8 @@ remote_file_get (const char *remote_file, const char *local_file, int from_tty)
     error (_("command can only be used with remote target"));
 
   fd = remote_hostio_open (find_target_at (process_stratum), NULL,
-			   remote_file, FILEIO_O_RDONLY, 0, &remote_errno);
+			   remote_file, FILEIO_O_RDONLY, 0, 0,
+			   &remote_errno);
   if (fd == -1)
     remote_hostio_error (remote_errno);
 
diff --git a/gdb/target.c b/gdb/target.c
index e41a338..a0a55d9 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -2779,11 +2779,13 @@ release_fileio_fd (int fd, fileio_fh_t *fh)
 #define fileio_fd_to_fh(fd) \
   VEC_index (fileio_fh_t, fileio_fhandles, (fd))
 
-/* See target.h.  */
+/* Helper for target_fileio_open and
+   target_fileio_open_warn_if_slow.  */
 
-int
-target_fileio_open (struct inferior *inf, const char *filename,
-		    int flags, int mode, int *target_errno)
+static int
+target_fileio_open_1 (struct inferior *inf, const char *filename,
+		      int flags, int mode, int warn_if_slow,
+		      int *target_errno)
 {
   struct target_ops *t;
 
@@ -2792,7 +2794,7 @@ target_fileio_open (struct inferior *inf, const char *filename,
       if (t->to_fileio_open != NULL)
 	{
 	  int fd = t->to_fileio_open (t, inf, filename, flags, mode,
-				      target_errno);
+				      warn_if_slow, target_errno);
 
 	  if (fd < 0)
 	    fd = -1;
@@ -2801,11 +2803,12 @@ target_fileio_open (struct inferior *inf, const char *filename,
 
 	  if (targetdebug)
 	    fprintf_unfiltered (gdb_stdlog,
-				"target_fileio_open (%d,%s,0x%x,0%o)"
+				"target_fileio_open (%d,%s,0x%x,0%o,%d)"
 				" = %d (%d)\n",
 				inf == NULL ? 0 : inf->num,
 				filename, flags, mode,
-				fd, fd != -1 ? 0 : *target_errno);
+				warn_if_slow, fd,
+				fd != -1 ? 0 : *target_errno);
 	  return fd;
 	}
     }
@@ -2817,6 +2820,27 @@ target_fileio_open (struct inferior *inf, const char *filename,
 /* See target.h.  */
 
 int
+target_fileio_open (struct inferior *inf, const char *filename,
+		    int flags, int mode, int *target_errno)
+{
+  return target_fileio_open_1 (inf, filename, flags, mode, 0,
+			       target_errno);
+}
+
+/* See target.h.  */
+
+int
+target_fileio_open_warn_if_slow (struct inferior *inf,
+				 const char *filename,
+				 int flags, int mode, int *target_errno)
+{
+  return target_fileio_open_1 (inf, filename, flags, mode, 1,
+			       target_errno);
+}
+
+/* See target.h.  */
+
+int
 target_fileio_pwrite (int fd, const gdb_byte *write_buf, int len,
 		      ULONGEST offset, int *target_errno)
 {
diff --git a/gdb/target.h b/gdb/target.h
index e283c86..1fdaf00 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -873,11 +873,14 @@ struct target_ops
     /* Open FILENAME on the target, in the filesystem as seen by INF,
        using FLAGS and MODE.  If INF is NULL, use the filesystem seen
        by the debugger (GDB or, for remote targets, the remote stub).
-       Return a target file descriptor, or -1 if an error occurs (and
-       set *TARGET_ERRNO).  */
+       If WARN_IF_SLOW is nonzero, print a warning message if the file
+       is being accessed over a link that may be slow.  Return a
+       target file descriptor, or -1 if an error occurs (and set
+       *TARGET_ERRNO).  */
     int (*to_fileio_open) (struct target_ops *,
 			   struct inferior *inf, const char *filename,
-			   int flags, int mode, int *target_errno);
+			   int flags, int mode, int warn_if_slow,
+			   int *target_errno);
 
     /* Write up to LEN bytes from WRITE_BUF to FD on the target.
        Return the number of bytes written, or -1 if an error occurs
@@ -2007,6 +2010,14 @@ extern int target_fileio_open (struct inferior *inf,
 			       const char *filename, int flags,
 			       int mode, int *target_errno);
 
+/* Like target_fileio_open, but print a warning message if the
+   file is being accessed over a link that may be slow.  */
+extern int target_fileio_open_warn_if_slow (struct inferior *inf,
+					    const char *filename,
+					    int flags,
+					    int mode,
+					    int *target_errno);
+
 /* Write up to LEN bytes from WRITE_BUF to FD on the target.
    Return the number of bytes written, or -1 if an error occurs
    (and set *TARGET_ERRNO).  */
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 3ab4d74..515a669 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2015-08-21  Gary Benson <gbenson@redhat.com>
+
+	* gdb.trace/pending.exp: Cope with remote transfer warnings.
+
 2015-08-20  Pedro Alves  <palves@redhat.com>
 
 	* gdb.server/solib-list.exp: No longer expect an interior stop in
diff --git a/gdb/testsuite/gdb.trace/pending.exp b/gdb/testsuite/gdb.trace/pending.exp
index 0399807..9938c5a 100644
--- a/gdb/testsuite/gdb.trace/pending.exp
+++ b/gdb/testsuite/gdb.trace/pending.exp
@@ -221,7 +221,7 @@ proc pending_tracepoint_resolved_during_trace { trace_type } \
 		fail $test
 	    }
 	}
-	-re "Continuing.\r\n\r\nBreakpoint.*marker.*at.*$srcfile.*$gdb_prompt $" {
+	-re "Continuing.\r\n(Reading .* from remote target...\r\n)?\r\nBreakpoint.*marker.*at.*$srcfile.*$gdb_prompt $" {
 	    pass $test
 	}
     }
@@ -294,7 +294,7 @@ proc pending_tracepoint_installed_during_trace { trace_type } \
 		fail $test
 	    }
 	}
-	-re "Continuing.\r\n\r\nBreakpoint.*marker.*at.*$srcfile.*$gdb_prompt $" {
+	-re "Continuing.\r\n(Reading .* from remote target...\r\n)?\r\nBreakpoint.*marker.*at.*$srcfile.*$gdb_prompt $" {
            pass $test
        }
     }
@@ -391,7 +391,7 @@ proc pending_tracepoint_disconnect_after_resolved { trace_type } \
 
     gdb_test "continue" "Continuing.\r\n\r\nBreakpoint.*marker.*at.*pending.c.*" \
 	"continue to marker 1"
-    gdb_test "continue" "Continuing.\r\n\r\nBreakpoint.*marker.*at.*pending.c.*" \
+    gdb_test "continue" "Continuing.\r\n(Reading .* from remote target...\r\n)?\r\nBreakpoint.*marker.*at.*pending.c.*" \
 	"continue to marker 2"
 
     # There should be no pending tracepoint, so no warning should be emitted.
@@ -473,7 +473,7 @@ proc pending_tracepoint_with_action_resolved { trace_type } \
 		fail $test
             }
 	}
-	-re "Continuing.\r\n\r\nBreakpoint.*marker.*at.*$srcfile.*$gdb_prompt $" {
+	-re "Continuing.\r\n(Reading .* from remote target...\r\n)?\r\nBreakpoint.*marker.*at.*$srcfile.*$gdb_prompt $" {
 	    pass "continue to marker 2"
 	}