[PATCH 3/7] New commands for loading and unloading a reader.

[Sanjoy Das <sanjoy at playingwithpointers dot com>]

Introduces two new GDB commands - `load-jit-reader' and
`unload-jit-reader'.
---
 gdb/ChangeLog |    6 +++
 gdb/jit.c     |  130 ++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 125 insertions(+), 11 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 639f1f7..884b51a 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,11 @@
 2011-08-09  Sanjoy Das  <sdas@igalia.com>
 
+	* jit.c (_initialize_jit): Add commands load-jit-reader and
+	unload-jit-reader.
+	(jit_reader_load): New function.
+
+2011-08-09  Sanjoy Das  <sdas@igalia.com>
+
 	* gdb-dlfcn.h, gdb-dlfcn.c: New.
     	* Makefile.in: Add gdb_dlcfn.c and gdb_dlcfn.h to the build
 	system.
diff --git a/gdb/jit.c b/gdb/jit.c
index e3bb81a..3f83065 100644
--- a/gdb/jit.c
+++ b/gdb/jit.c
@@ -31,8 +31,11 @@
 #include "symfile.h"
 #include "symtab.h"
 #include "target.h"
+#include "gdb-dlfcn.h"
 #include "gdb_stat.h"
 
+#define GDB_READER_DIR (LIBDIR "/gdb/")
+
 static const struct objfile_data *jit_objfile_data;
 
 static const char *const jit_break_name = "__jit_debug_register_code";
@@ -113,6 +116,102 @@ 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. */
+struct jit_reader
+{
+  struct gdb_reader_funcs *functions;
+} *loaded_jit_reader = NULL;
+
+typedef struct gdb_reader_funcs * (reader_init_fn_type) (void);
+const char *reader_init_fn_sym = "gdb_init_reader";
+
+/* Try to load FILE_NAME as a JIT debug info reader. Set ERROR_STRING
+   in case of an error (and return NULL), else return a correcly
+   formed struct jit_reader. */
+static struct jit_reader *
+jit_reader_load (const char *file_name, char **error_string)
+{
+  void *so;
+  reader_init_fn_type *init_fn;
+  struct jit_reader *new_reader = NULL;
+  struct gdb_reader_funcs *funcs = NULL;
+
+  if (jit_debug)
+    fprintf_unfiltered (gdb_stdlog, "Opening shared object %s.\n", file_name);
+  so = gdb_dlopen (file_name);
+
+  if (!so)
+    {
+      *error_string = _("could not open reader file");
+      return NULL;
+    }
+
+  init_fn = gdb_dlsym (so, reader_init_fn_sym);
+  if (!init_fn)
+    {
+      *error_string = _("could not locate initialization routine");
+      goto error;
+    }
+
+  if (gdb_dlsym (so, "plugin_is_GPL_compatible") == NULL)
+    {
+      *error_string = _("reader not GPL compatible");
+      goto error;
+    }
+
+  funcs = init_fn ();
+  if (funcs->reader_version != GDB_READER_INTERFACE_VERSION)
+    {
+      *error_string = _("incorrect module version");
+      goto error;
+    }
+
+  new_reader = XZALLOC (struct jit_reader);
+  new_reader->functions = funcs;
+  return new_reader;
+
+ error:
+  if (so)
+    gdb_dlclose(so);
+  return NULL;
+}
+
+/* Provides the load-jit-reader command. */
+static void
+load_jit_reader_command (char *args, int from_tty)
+{
+  char so_name[PATH_MAX] = GDB_READER_DIR;
+  char *error_string;
+
+  if (args == NULL)
+    {
+      error (_("No reader name provided."));
+      return;
+    }
+
+  strncat (so_name, args, PATH_MAX - sizeof(GDB_READER_DIR) - 4);
+  strcat (so_name, ".so");
+
+  loaded_jit_reader = jit_reader_load (so_name, &error_string);
+  if (loaded_jit_reader == NULL)
+    error(_("Unable to load reader: %s."), error_string);
+}
+
+/* Provides the unload-jit-reader command. */
+static void
+unload_jit_reader_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 *
@@ -137,6 +236,7 @@ struct jit_inferior_data
 {
   CORE_ADDR breakpoint_addr;  /* &__jit_debug_register_code()  */
   CORE_ADDR descriptor_addr;  /* &__jit_debug_descriptor  */
+  struct objfile *jit_objfile; /* All the JIT symbols will be added to this. */
 };
 
 /* Return jit_inferior_data for current inferior.  Allocate if not already
@@ -510,10 +610,10 @@ jit_event_handler (struct gdbarch *gdbarch)
   struct jit_code_entry code_entry;
   CORE_ADDR entry_addr;
   struct objfile *objf;
+  struct jit_inferior_data *inf_data = get_jit_inferior_data ();
 
   /* Read the descriptor from remote memory.  */
-  jit_read_descriptor (gdbarch, &descriptor,
-		       get_jit_inferior_data ()->descriptor_addr);
+  jit_read_descriptor (gdbarch, &descriptor, inf_data->descriptor_addr);
   entry_addr = descriptor.relevant_entry;
 
   /* Do the corresponding action.  */
@@ -526,15 +626,16 @@ jit_event_handler (struct gdbarch *gdbarch)
       jit_register_code (gdbarch, entry_addr, &code_entry);
       break;
     case JIT_UNREGISTER:
-      objf = jit_find_objf_with_entry_addr (entry_addr);
-      if (objf == NULL)
-	printf_unfiltered (_("Unable to find JITed code "
-			     "entry at address: %s\n"),
-			   paddress (gdbarch, entry_addr));
-      else
-        jit_unregister_code (objf);
-
-      break;
+      {
+        objf = jit_find_objf_with_entry_addr (entry_addr);
+        if (objf == NULL)
+          printf_unfiltered (_("Unable to find JITed code "
+                               "entry at address: %s\n"),
+                             paddress (gdbarch, entry_addr));
+        else
+          jit_unregister_code (objf);
+        break;
+      }
     default:
       error (_("Unknown action_flag value in JIT descriptor!"));
       break;
@@ -562,4 +663,11 @@ _initialize_jit (void)
   jit_objfile_data = register_objfile_data ();
   jit_inferior_data =
     register_inferior_data_with_cleanup (jit_inferior_data_cleanup);
+  add_com ("load-jit-reader", no_class, load_jit_reader_command, _("\
+Try to load file FILE as a debug info reader (and unwinder) for\n\
+JIT compiled code from " LIBDIR "/gdb\n\
+Usage is `load-jit-reader FILE`."));
+  add_com ("unload-jit-reader", no_class, unload_jit_reader_command, _("\
+Unload the currently loaded JIT reader (loaded using load-jit-reader)\n\
+Usage is simply `unload-jit-reader`."));
 }
-- 
1.7.5.4