Implement displaced stepping.

gdb/
	* gdbarch.sh (max_insn_length): New 'variable'.
	(displaced_step_copy, displaced_step_fixup)
	(displaced_step_free_closure, displaced_step_location): New
	functions.
	(struct displaced_step_closure): Add forward declaration.
	* gdbarch.c, gdbarch.h: Regenerated.

	* arch-utils.c: #include "objfiles.h".
	(simple_displaced_step_copy_insn)
	(simple_displaced_step_free_closure)
	(displaced_step_at_entry_point): New functions.
	* arch-utils.h (simple_displaced_step_copy_insn)
	(simple_displaced_step_free_closure)
	(displaced_step_at_entry_point): New prototypes.

	* i386-tdep.c (I386_MAX_INSN_LEN): Rename to...
	(I386_MAX_MATCHED_INSN_LEN): ... this.
	(i386_absolute_jmp_p, i386_absolute_call_p)
	(i386_ret_p, i386_call_p, i386_breakpoint_p, i386_syscall_p)
	(i386_displaced_step_fixup): New functions.
	(struct i386_insn, i386_match_insn): Update.
	(i386_gdbarch_init): Set gdbarch_max_insn_length.
	* i386-tdep.h (I386_MAX_INSN_LEN): New.
	(i386_displaced_step_fixup): New prototype.
	* i386-linux-tdep.c (i386_linux_init_abi): Include "arch-utils.h".
	Register gdbarch_displaced_step_copy,
	gdbarch_displaced_step_fixup, gdbarch_displaced_step_free_closure,
	and gdbarch_displaced_step_location functions.

	* infrun.c (debug_displaced): New variable.
	(show_debug_displaced): New function.
	(struct displaced_step_request): New struct.
	(displaced_step_request_queue, displaced_step_ptid)
	(displaced_step_gdbarch, displaced_step_closure)
	(displaced_step_original, displaced_step_copy)
	(displaced_step_saved_copy, can_use_displaced_stepping): New
	variables.
	(show_can_use_displaced_stepping, use_displaced_stepping)
	(displaced_step_clear, cleanup_displaced_step_closure)
	(displaced_step_dump_bytes, displaced_step_prepare)
	(displaced_step_clear_cleanup, write_memory_ptid)
	(displaced_step_fixup): New functions.
	(resume): Call displaced_step_prepare.
	(proceed): Call read_pc once, and remember the value.  If using
	displaced stepping, don't remove breakpoints.
	(handle_inferior_event): Call displaced_step_fixup.  Add some
	debugging output.  When we try to step over a breakpoint, but get
	a signal to deliver to the thread instead, ensure the step-resume
	breakpoint is actually inserted.  If a thread hop is needed, and
	displaced stepping is enabled, don't remove breakpoints.
	(init_wait_for_inferior): Call displaced_step_clear.
	(_initialize_infrun): Add "set debug displaced" command.  Add
	"maint set can-use-displaced-stepping" command.  Clear
	displaced_step_ptid.
	* inferior.h (debug_displaced): Declare variable.
	(displaced_step_dump_bytes): Declare function.

	* Makefile.in (arch-utils.o, i386-linux-tdep.o): Update
	dependencies.

	gdb/testsuite/
	* gdb.asm/asmsrc1.s: Add scratch space.

	gdb/doc/
	* gdb.texinfo (Debugging Output): Document "set/show debug
	displaced".
	(Maintenance Commands): Document "maint set/show
	can-use-displaced-stepping".

gdb/arch-utils.h

@@ -30,6 +30,30 @@ struct gdbarch_info;
 /* gdbarch trace variable */
 extern int gdbarch_debug;
 
+/* An implementation of gdbarch_displaced_step_copy_insn for
+   processors that don't need to modify the instruction before
+   single-stepping the displaced copy.
+
+   Simply copy gdbarch_max_insn_length (ARCH) bytes from FROM to TO.
+   The closure is an array of that many bytes containing the
+   instruction's bytes, allocated with xmalloc.  */
+extern struct displaced_step_closure *
+  simple_displaced_step_copy_insn (struct gdbarch *gdbarch,
+                                   CORE_ADDR from, CORE_ADDR to,
+                                   struct regcache *regs);
+
+/* Simple implementation of gdbarch_displaced_step_free_closure: Call
+   xfree.
+   This is appropriate for use with simple_displaced_step_copy_insn.  */
+extern void
+  simple_displaced_step_free_closure (struct gdbarch *gdbarch,
+                                      struct displaced_step_closure *closure);
+
+/* Possible value for gdbarch_displaced_step_location:
+   Place displaced instructions at the program's entry point,
+   leaving space for inferior function call return breakpoints.  */
+extern CORE_ADDR displaced_step_at_entry_point (struct gdbarch *gdbarch);
+
 /* The only possible cases for inner_than. */
 extern int core_addr_lessthan (CORE_ADDR lhs, CORE_ADDR rhs);
 extern int core_addr_greaterthan (CORE_ADDR lhs, CORE_ADDR rhs);