[PATCH 4/7] New commands for loading and unloading a reader.

[Sanjoy Das <sanjoy@playingwithpointers.com>]

Introduces two new GDB commands - `load-jit-reader' and
`unload-jit-reader'.
---
 gdb/jit.c |  103 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 102 insertions(+), 1 deletions(-)

diff --git a/gdb/jit.c b/gdb/jit.c
index cab27a9..f813625 100644
--- a/gdb/jit.c
+++ b/gdb/jit.c
@@ -31,6 +31,7 @@
 #include "symfile.h"
 #include "symtab.h"
 #include "target.h"
+#include "gdb-dlfcn.h"
 #include "gdb_stat.h"
 
 static const char *jit_reader_dir = NULL;
@@ -115,6 +116,96 @@ mem_bfd_iovec_stat (struct bfd *abfd, void *stream, struct stat *sb)
   return 0;
 }
 
+/* One reader that has been loaded successfully, and can potentially be used to
+   parse debug info. */
+static struct jit_reader
+{
+  struct gdb_reader_funcs *functions;
+} *loaded_jit_reader = NULL;
+
+typedef struct gdb_reader_funcs * (reader_init_fn_type) (void);
+static const char *reader_init_fn_sym = "gdb_init_reader";
+
+/* Try to load FILE_NAME as a JIT debug info reader. */
+
+static struct jit_reader *
+jit_reader_load (const char *file_name)
+{
+  void *so;
+  reader_init_fn_type *init_fn;
+  struct jit_reader *new_reader = NULL;
+  struct gdb_reader_funcs *funcs = NULL;
+  struct cleanup *old_cleanups;
+
+  if (jit_debug)
+    fprintf_unfiltered (gdb_stdlog, _("Opening shared object %s.\n"),
+                        file_name);
+  so = gdb_dlopen (file_name);
+  old_cleanups = make_cleanup_dlclose (so);
+
+  init_fn = gdb_dlsym (so, reader_init_fn_sym);
+  if (!init_fn)
+    error(_("Could not locate initialization function: %s."),
+          reader_init_fn_sym);
+
+  if (gdb_dlsym (so, "plugin_is_GPL_compatible") == NULL)
+    error(_("Reader not GPL compatible."));
+
+  funcs = init_fn ();
+  if (funcs->reader_version != GDB_READER_INTERFACE_VERSION)
+    error(_("Reader version does not match GDB version."));
+
+  new_reader = XZALLOC (struct jit_reader);
+  new_reader->functions = funcs;
+
+  discard_cleanups (old_cleanups);
+  return new_reader;
+}
+
+/* Provides the jit-reader-load command. */
+
+static void
+jit_reader_load_command (char *args, int from_tty)
+{
+  char so_name[PATH_MAX];
+  int len;
+
+  if (args == NULL)
+    {
+      error (_("No reader name provided."));
+      return;
+    }
+
+  if (loaded_jit_reader != NULL)
+    {
+      error (_("JIT reader already loaded.  Run jit-reader-unload first."));
+      return;
+    }
+
+  len = strlen (jit_reader_dir);
+  strcpy(so_name, jit_reader_dir);
+  so_name[len] = '/';
+  so_name[len + 1] = 0;
+
+  strncat (so_name, args, PATH_MAX - (len + 1));
+  loaded_jit_reader = jit_reader_load (so_name);
+}
+
+/* Provides the jit-reader-unload command. */
+
+static void
+jit_reader_unload_command (char *args, int from_tty)
+{
+  if (!loaded_jit_reader)
+    {
+      error(_("No JIT reader loaded."));
+      return;
+    }
+  loaded_jit_reader->functions->destroy (loaded_jit_reader->functions);
+  free (loaded_jit_reader);
+  loaded_jit_reader = NULL;
+}
+
 /* Open a BFD from the target's memory.  */
 
 static struct bfd *
@@ -535,7 +626,6 @@ jit_event_handler (struct gdbarch *gdbarch)
 			   paddress (gdbarch, entry_addr));
       else
         jit_unregister_code (objf);
-
       break;
     default:
       error (_("Unknown action_flag value in JIT descriptor!"));
@@ -566,4 +656,15 @@ _initialize_jit (void)
   jit_objfile_data = register_objfile_data ();
   jit_inferior_data =
     register_inferior_data_with_cleanup (jit_inferior_data_cleanup);
+  add_com ("jit-reader-load", no_class, jit_reader_load_command, _("\
+Load FILE as debug info reader and unwinder for JIT compiled code.\n\
+Try to load file FILE as a debug info reader (and unwinder) for\n\
+JIT compiled code. The file is loaded from\n\
+" JIT_READER_DIR ", relocated \n\
+relative to the GDB executable if required.\n\
+Usage is `jit-reader-load FILE`."));
+  add_com ("jit-reader-unload", no_class, jit_reader_unload_command, _("\
+Unload the currently loaded JIT debug info reader.\n\
+See jit-reader-load for how to load JIT debug readers.\n\
+"));
 }
-- 
1.7.5.4