Add interface for JIT code generation.

* NEWS: Announce JIT interface.
	* Makefile.in (SFILES): Add jit.c.
	(HFILES_NO_SRCDIR): Add jit.h.
	(COMMON_OBS): Add jit.o.
	* jit.c: New file.
	* jit.h: New file.
	* breakpoint.h (enum bptype): Add bp_jit_event to enum.
	* breakpoint.c:
	(update_breakpoints_after_exec): Delete jit breakpoints after exec.
	(bpstat_what): Update event table for bp_jit_event.
	(print_it_typical): Added case for bp_jit_event.
	(print_one_breakpoint_location): Added case for bp_jit_event.
	(allocate_bp_location): Added case for bp_jit_event.
	(mention): Added case for bp_jit_event.
	(delete_command): Added case for bp_jit_event.
	(breakpoint_re_set_one): Added case for bp_jit_event.
	(breakpoint_re_set): Added call to jit_inferior_created_hook.
	(create_jit_event_breakpoint): New.
	* infrun.c (handle_inferior_event): Add handler for jit event.
	(follow_exec): Add call to jit_inferior_created_hook.
	* doc/gdb.texinfo: Add chapter on JIT interface.

gdb/jit.h

@@ -0,0 +1,77 @@
+/* JIT declarations for GDB, the GNU Debugger.
+
+   Copyright (C) 2009
+   Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   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/>.  */
+
+#ifndef JIT_H
+#define JIT_H
+
+/* When the JIT breakpoint fires, the inferior wants us to take one of these
+   actions.  These values are used by the inferior, so the values of these enums
+   cannot be changed.  */
+
+typedef enum
+{
+  JIT_NOACTION = 0,
+  JIT_REGISTER,
+  JIT_UNREGISTER
+} jit_actions_t;
+
+/* This struct describes a single symbol file in a linked list of symbol files
+   describing generated code.  As the inferior generates code, it adds these
+   entries to the list, and when we attach to the inferior, we read them all.
+   For the first element prev_entry should be NULL, and for the last element
+   next_entry should be NULL.  */
+
+struct jit_code_entry
+{
+  CORE_ADDR next_entry;
+  CORE_ADDR prev_entry;
+  CORE_ADDR symfile_addr;
+  uint64_t symfile_size;
+};
+
+/* This is the global descriptor that the inferior uses to communicate
+   information to the debugger.  To alert the debugger to take an action, the
+   inferior sets the action_flag to the appropriate enum value, updates
+   relevant_entry to point to the relevant code entry, and calls the function at
+   the well-known symbol with our breakpoint.  We then read this descriptor from
+   another global well-known symbol.  */
+
+struct jit_descriptor
+{
+  uint32_t version;
+  /* This should be jit_actions_t, but we want to be specific about the
+     bit-width.  */
+  uint32_t action_flag;
+  CORE_ADDR relevant_entry;
+  CORE_ADDR first_entry;
+};
+
+/* Looks for the descriptor and registration symbols and breakpoints the
+   registration function.  If it finds both, it registers all the already JITed
+   code.  If it has already found the symbols, then it doesn't try again.  */
+
+extern void jit_inferior_created_hook (void);
+
+/* This function is called by handle_inferior_event when it decides that the JIT
+   event breakpoint has fired.  */
+
+extern void jit_event_handler (void);
+
+#endif /* JIT_H */