[PATCH 4/5] Use TARGET_FILENAME_PREFIX as the system root in some cases

[Gary Benson <gbenson@redhat.com>]

This commit updates solib_find_1 to use TARGET_FILENAME_PREFIX as the
system root if auto-target-prefix is enabled and gdb_sysroot is empty
and the target filesystem is not the local filesystem.

gdb/ChangeLog:

	* solib.c (auto_target_prefix): New static variable.
	(solib_find_1): Use TARGET_FILENAME_PREFIX as sysroot
	in some cases.
	(show_auto_target_prefix): New function.
	(_initialize_solib): New "set/show auto-target-prefix"
	commands.
	* NEWS: Mention that GDB will use "target:" as the system
	root in some cases.  Mention new "set/show auto-target-prefix"
	commands.

gdb/doc/ChangeLog:

	* gdb.texinfo (Commands to Specify Files): Document the
	"set/show auto-target-prefix" commands.
---
 gdb/ChangeLog       |   12 ++++++++++
 gdb/NEWS            |    8 +++++-
 gdb/doc/ChangeLog   |    5 ++++
 gdb/doc/gdb.texinfo |   11 +++++++++
 gdb/solib.c         |   62 +++++++++++++++++++++++++++++++++++++++++++-------
 5 files changed, 88 insertions(+), 10 deletions(-)

diff --git a/gdb/NEWS b/gdb/NEWS
index 7ecdf93..3e22b82 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -40,7 +40,9 @@
   prefixed with "target:" to tell GDB to access shared libraries from
   the target system, be it local or remote.  This replaces the prefix
   "remote:", which is automatically converted to "target:" for
-  backward compatibility.
+  backward compatibility.  If the system root is unset, GDB will use
+  "target:" as the system root where necessary if auto-target-prefix
+  is enabled.  See "New commands" below.
 
 * The system root specified by "set sysroot" will be prepended to the
   filename of the main executable (if reported to GDB as absolute by
@@ -193,6 +195,10 @@ maint set|show btrace pt skip-pad
   Set and show whether PAD packets are skipped when computing the
   packet history.
 
+set auto-target-prefix
+show auto-target-prefix
+  Control automatic prefixing of binary filenames with "target:".
+
 * The command 'thread apply all' can now support new option '-ascending'
   to call its specified command for all threads in ascending order.
 
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 9e2ecd1..9ac6e2f 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -18091,6 +18091,17 @@ location.
 @item show sysroot
 Display the current executable and shared library prefix.
 
+@kindex set auto-target-prefix
+@item set solib-search-path @var{mode}
+If @var{mode} is @code{on}, and the system root is empty, @value{GDBN}
+will use @file{target:} as the system root if that is necessary for
+@value{GDBN} to be able to access the target binaries.
+
+@kindex show auto-target-prefix
+@item show auto-solib-add
+Display the current target-prefixing mode.
+@end table
+
 @kindex set solib-search-path
 @item set solib-search-path @var{path}
 If this variable is set, @var{path} is a colon-separated list of
diff --git a/gdb/solib.c b/gdb/solib.c
index 32931da..4fdfba0 100644
--- a/gdb/solib.c
+++ b/gdb/solib.c
@@ -105,6 +105,11 @@ show_solib_search_path (struct ui_file *file, int from_tty,
 		    value);
 }
 
+/* If nonzero, prefix executable and shared library filenames with
+   TARGET_FILENAME_PREFIX when attaching to processes whose filesystem
+   is not the local filesystem.  */
+static int auto_target_prefix = 1;
+
 /* Same as HAVE_DOS_BASED_FILE_SYSTEM, but useable as an rvalue.  */
 #if (HAVE_DOS_BASED_FILE_SYSTEM)
 #  define DOS_BASED_FILE_SYSTEM 1
@@ -124,7 +129,10 @@ show_solib_search_path (struct ui_file *file, int from_tty,
    is the local filesystem then the "target:" prefix will be
    stripped before the search starts.  This ensures that the
    same search algorithm is used for local files regardless of
-   whether a "target:" prefix was used.
+   whether a "target:" prefix was used.  If the target filesystem
+   is not the local filesystem then "target:" will be used as the
+   prefix directory for binary files if GDB_SYSROOT is empty and
+   AUTO_TARGET_PREFIX is nonzero.
 
    Global variable SOLIB_SEARCH_PATH is used as a prefix directory
    (or set of directories, as in LD_LIBRARY_PATH) to search for all
@@ -160,14 +168,30 @@ solib_find_1 (char *in_pathname, int *fd, int is_solib)
   char *sysroot = gdb_sysroot;
   int prefix_len, orig_prefix_len;
 
-  /* If the absolute prefix starts with "target:" but the filesystem
-     accessed by the target_fileio_* methods is the local filesystem
-     then we strip the "target:" prefix now and work with the local
-     filesystem.  This ensures that the same search algorithm is used
-     for all local files regardless of whether a "target:" prefix was
-     used.  */
-  if (is_target_filename (sysroot) && target_filesystem_is_local ())
-    sysroot += strlen (TARGET_FILENAME_PREFIX);
+  if (target_filesystem_is_local ())
+    {
+      /* If the absolute prefix starts with "target:" but the
+	 filesystem accessed by the target_fileio_* methods is the
+	 local filesystem then we strip the "target:" prefix now and
+	 work with the local filesystem.  This ensures that the same
+	 search algorithm is used for all local files regardless of
+	 whether a "target:" prefix was used.  */
+      if (is_target_filename (sysroot))
+	sysroot += strlen (TARGET_FILENAME_PREFIX);
+    }
+  else if (auto_target_prefix && *gdb_sysroot == '\0')
+    {
+      /* Set the absolute prefix to "target:" for executable files
+	 and for shared libraries whose executable filename has a
+	 "target:"-prefix.  */
+      if (!is_solib
+	  || (exec_filename != NULL
+	      && is_target_filename (exec_filename)))
+	{
+	  sysroot = xstrdup (TARGET_FILENAME_PREFIX);
+	  make_cleanup (xfree, sysroot);
+	}
+    }
 
   /* Strip any trailing slashes from the absolute prefix.  */
   prefix_len = orig_prefix_len = strlen (sysroot);
@@ -1507,6 +1531,15 @@ show_auto_solib_add (struct ui_file *file, int from_tty,
 		    value);
 }
 
+static void
+show_auto_target_prefix (struct ui_file *file, int from_tty,
+			 struct cmd_list_element *c, const char *value)
+{
+  fprintf_filtered (file,
+		    _("Automatic prefixing of binary filenames is %s.\n"),
+		    value);
+}
+
 
 /* Handler for library-specific lookup of global symbol NAME in OBJFILE.  Call
    the library-specific handler if it is installed for the current target.  */
@@ -1714,4 +1747,15 @@ PATH and LD_LIBRARY_PATH."),
 				     reload_shared_libraries,
 				     show_solib_search_path,
 				     &setlist, &showlist);
+
+  add_setshow_boolean_cmd ("auto-target-prefix", class_support,
+			   &auto_target_prefix, _("\
+Set automatic prefixing of binary filenames."), _("\
+Show automatic prefixing of binary filenames."), _("\
+If \"on\", filenames of binaries will be prefixed with \"target:\"\n\
+when attaching to processes whose filesystems GDB cannot access\n\
+directly."),
+			   NULL,
+			   show_auto_target_prefix,
+			   &setlist, &showlist);
 }
-- 
1.7.1