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".

1 files changed, 90 insertions, 0 deletions

diff --git a/gdb/gdbarch.h b/gdb/gdbarch.h
index baba7c7..e89bd46 100644
--- a/gdb/gdbarch.h
+++ b/gdb/gdbarch.h
@@ -50,6 +50,7 @@ struct target_ops;
 struct obstack;
 struct bp_target_info;
 struct target_desc;
+struct displaced_step_closure;
 
 extern struct gdbarch *current_gdbarch;
 
@@ -663,6 +664,95 @@ typedef void (gdbarch_skip_permanent_breakpoint_ftype) (struct regcache *regcach
 extern void gdbarch_skip_permanent_breakpoint (struct gdbarch *gdbarch, struct regcache *regcache);
 extern void set_gdbarch_skip_permanent_breakpoint (struct gdbarch *gdbarch, gdbarch_skip_permanent_breakpoint_ftype *skip_permanent_breakpoint);
 
+/* The maximum length of an instruction on this architecture. */
+
+extern int gdbarch_max_insn_length_p (struct gdbarch *gdbarch);
+
+extern ULONGEST gdbarch_max_insn_length (struct gdbarch *gdbarch);
+extern void set_gdbarch_max_insn_length (struct gdbarch *gdbarch, ULONGEST max_insn_length);
+
+/* Copy the instruction at FROM to TO, and make any adjustments
+   necessary to single-step it at that address.
+  
+   REGS holds the state the thread's registers will have before
+   executing the copied instruction; the PC in REGS will refer to FROM,
+   not the copy at TO.  The caller should update it to point at TO later.
+  
+   Return a pointer to data of the architecture's choice to be passed
+   to gdbarch_displaced_step_fixup.  Or, return NULL to indicate that
+   the instruction's effects have been completely simulated, with the
+   resulting state written back to REGS.
+  
+   For a general explanation of displaced stepping and how GDB uses it,
+   see the comments in infrun.c.
+  
+   The TO area is only guaranteed to have space for
+   gdbarch_max_insn_length (arch) bytes, so this function must not
+   write more bytes than that to that area.
+  
+   If you do not provide this function, GDB assumes that the
+   architecture does not support displaced stepping.
+  
+   If your architecture doesn't need to adjust instructions before
+   single-stepping them, consider using simple_displaced_step_copy_insn
+   here. */
+
+extern int gdbarch_displaced_step_copy_insn_p (struct gdbarch *gdbarch);
+
+typedef struct displaced_step_closure * (gdbarch_displaced_step_copy_insn_ftype) (struct gdbarch *gdbarch, CORE_ADDR from, CORE_ADDR to, struct regcache *regs);
+extern struct displaced_step_closure * gdbarch_displaced_step_copy_insn (struct gdbarch *gdbarch, CORE_ADDR from, CORE_ADDR to, struct regcache *regs);
+extern void set_gdbarch_displaced_step_copy_insn (struct gdbarch *gdbarch, gdbarch_displaced_step_copy_insn_ftype *displaced_step_copy_insn);
+
+/* Fix up the state resulting from successfully single-stepping a
+   displaced instruction, to give the result we would have gotten from
+   stepping the instruction in its original location.
+  
+   REGS is the register state resulting from single-stepping the
+   displaced instruction.
+  
+   CLOSURE is the result from the matching call to
+   gdbarch_displaced_step_copy_insn.
+  
+   If you provide gdbarch_displaced_step_copy_insn.but not this
+   function, then GDB assumes that no fixup is needed after
+   single-stepping the instruction.
+  
+   For a general explanation of displaced stepping and how GDB uses it,
+   see the comments in infrun.c. */
+
+extern int gdbarch_displaced_step_fixup_p (struct gdbarch *gdbarch);
+
+typedef void (gdbarch_displaced_step_fixup_ftype) (struct gdbarch *gdbarch, struct displaced_step_closure *closure, CORE_ADDR from, CORE_ADDR to, struct regcache *regs);
+extern void gdbarch_displaced_step_fixup (struct gdbarch *gdbarch, struct displaced_step_closure *closure, CORE_ADDR from, CORE_ADDR to, struct regcache *regs);
+extern void set_gdbarch_displaced_step_fixup (struct gdbarch *gdbarch, gdbarch_displaced_step_fixup_ftype *displaced_step_fixup);
+
+/* Free a closure returned by gdbarch_displaced_step_copy_insn.
+  
+   If you provide gdbarch_displaced_step_copy_insn, you must provide
+   this function as well.
+  
+   If your architecture uses closures that don't need to be freed, then
+   you can use simple_displaced_step_free_closure here.
+  
+   For a general explanation of displaced stepping and how GDB uses it,
+   see the comments in infrun.c. */
+
+typedef void (gdbarch_displaced_step_free_closure_ftype) (struct gdbarch *gdbarch, struct displaced_step_closure *closure);
+extern void gdbarch_displaced_step_free_closure (struct gdbarch *gdbarch, struct displaced_step_closure *closure);
+extern void set_gdbarch_displaced_step_free_closure (struct gdbarch *gdbarch, gdbarch_displaced_step_free_closure_ftype *displaced_step_free_closure);
+
+/* Return the address of an appropriate place to put displaced
+   instructions while we step over them.  There need only be one such
+   place, since we're only stepping one thread over a breakpoint at a
+   time.
+  
+   For a general explanation of displaced stepping and how GDB uses it,
+   see the comments in infrun.c. */
+
+typedef CORE_ADDR (gdbarch_displaced_step_location_ftype) (struct gdbarch *gdbarch);
+extern CORE_ADDR gdbarch_displaced_step_location (struct gdbarch *gdbarch);
+extern void set_gdbarch_displaced_step_location (struct gdbarch *gdbarch, gdbarch_displaced_step_location_ftype *displaced_step_location);
+
 /* Refresh overlay mapped state for section OSECT. */
 
 extern int gdbarch_overlay_update_p (struct gdbarch *gdbarch);