Index: amd64-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/amd64-tdep.c,v
retrieving revision 1.94
diff -p -r1.94 amd64-tdep.c
*** amd64-tdep.c	13 Sep 2011 08:26:11 -0000	1.94
--- amd64-tdep.c	21 Sep 2011 21:27:00 -0000
***************
*** 45,50 ****
--- 45,53 ----
  #include "features/i386/amd64.c"
  #include "features/i386/amd64-avx.c"
  
+ #include "ax.h"
+ #include "ax-gdb.h"
+ 
  /* Note that the AMD64 architecture was previously known as x86-64.
     The latter is (forever) engraved into the canonical system name as
     returned by config.guess, and used as the name for the AMD64 port
*************** static const struct frame_unwind amd64_f
*** 2165,2170 ****
--- 2168,2191 ----
    default_frame_sniffer
  };
  
+ /* Generate a bytecode expression to get the value of the saved PC.
+    Since this is supposed to run on the target independently of GDB,
+    we don't have the full power of the unwinding machinery.  Instead,
+    make a guess as to the most likely location of the return address,
+    and issue byte codes for that.  */
+ 
+ void
+ amd64_gen_return_address (struct gdbarch *gdbarch,
+ 			  struct agent_expr *ax, struct axs_value *value,
+ 			  CORE_ADDR scope)
+ {
+   ax_reg (ax, AMD64_RBP_REGNUM);
+   ax_const_l (ax, 8);
+   ax_simple (ax, aop_add);
+   value->type = register_type (gdbarch, AMD64_RIP_REGNUM);
+   value->kind = axs_lvalue_memory;
+ }
+ 
  
  /* Signal trampolines.  */
  
*************** amd64_init_abi (struct gdbarch_info info
*** 2669,2674 ****
--- 2690,2697 ----
    set_gdbarch_get_longjmp_target (gdbarch, amd64_get_longjmp_target);
  
    set_gdbarch_relocate_instruction (gdbarch, amd64_relocate_instruction);
+ 
+   set_gdbarch_gen_return_address (gdbarch, amd64_gen_return_address);
  }
  
  /* Provide a prototype to silence -Wmissing-prototypes.  */
Index: arch-utils.c
===================================================================
RCS file: /cvs/src/src/gdb/arch-utils.c,v
retrieving revision 1.192
diff -p -r1.192 arch-utils.c
*** arch-utils.c	5 Jan 2011 22:22:47 -0000	1.192
--- arch-utils.c	21 Sep 2011 21:27:00 -0000
*************** default_remote_breakpoint_from_pc (struc
*** 786,791 ****
--- 786,799 ----
    gdbarch_breakpoint_from_pc (gdbarch, pcptr, kindptr);
  }
  
+ void
+ default_gen_return_address (struct gdbarch *gdbarch,
+ 			    struct agent_expr *ax, struct axs_value *value,
+ 			    CORE_ADDR scope)
+ {
+   error (_("This architecture has no method to collect a return address."));
+ }
+ 
  /* */
  
  /* -Wmissing-prototypes */
Index: arch-utils.h
===================================================================
RCS file: /cvs/src/src/gdb/arch-utils.h,v
retrieving revision 1.113
diff -p -r1.113 arch-utils.h
*** arch-utils.h	5 Jan 2011 22:22:47 -0000	1.113
--- arch-utils.h	21 Sep 2011 21:27:00 -0000
*************** extern int default_fast_tracepoint_valid
*** 164,169 ****
--- 164,174 ----
  extern void default_remote_breakpoint_from_pc (struct gdbarch *,
  					       CORE_ADDR *pcptr, int *kindptr);
  
+ extern void default_gen_return_address (struct gdbarch *gdbarch,
+ 					struct agent_expr *ax,
+ 					struct axs_value *value,
+ 					CORE_ADDR scope);
+ 
  extern const char *default_auto_charset (void);
  extern const char *default_auto_wide_charset (void);
  
Index: ax-gdb.c
===================================================================
RCS file: /cvs/src/src/gdb/ax-gdb.c,v
retrieving revision 1.88
diff -p -r1.88 ax-gdb.c
*** ax-gdb.c	17 Jun 2011 20:46:47 -0000	1.88
--- ax-gdb.c	21 Sep 2011 21:27:00 -0000
***************
*** 40,45 ****
--- 40,46 ----
  #include "breakpoint.h"
  #include "tracepoint.h"
  #include "cp-support.h"
+ #include "arch-utils.h"
  
  /* To make sense of this file, you should read doc/agentexpr.texi.
     Then look at the types and enums in ax-gdb.h.  For the code itself,
*************** gen_eval_for_expr (CORE_ADDR scope, stru
*** 2444,2449 ****
--- 2445,2476 ----
    return ax;
  }
  
+ struct agent_expr *
+ gen_trace_for_return_address (CORE_ADDR scope, struct gdbarch *gdbarch)
+ {
+   struct cleanup *old_chain = 0;
+   struct agent_expr *ax = new_agent_expr (gdbarch, scope);
+   struct axs_value value;
+ 
+   old_chain = make_cleanup_free_agent_expr (ax);
+ 
+   trace_kludge = 1;
+ 
+   gdbarch_gen_return_address (gdbarch, ax, &value, scope);
+ 
+   /* Make sure we record the final object, and get rid of it.  */
+   gen_traced_pop (gdbarch, ax, &value);
+ 
+   /* Oh, and terminate.  */
+   ax_simple (ax, aop_end);
+ 
+   /* We have successfully built the agent expr, so cancel the cleanup
+      request.  If we add more cleanups that we always want done, this
+      will have to get more complicated.  */
+   discard_cleanups (old_chain);
+   return ax;
+ }
+ 
  static void
  agent_command (char *exp, int from_tty)
  {
*************** agent_command (char *exp, int from_tty)
*** 2462,2471 ****
    if (exp == 0)
      error_no_arg (_("expression to translate"));
  
!   expr = parse_expression (exp);
!   old_chain = make_cleanup (free_current_contents, &expr);
!   agent = gen_trace_for_expr (get_frame_pc (fi), expr);
!   make_cleanup_free_agent_expr (agent);
    ax_reqs (agent);
    ax_print (gdb_stdout, agent);
  
--- 2489,2510 ----
    if (exp == 0)
      error_no_arg (_("expression to translate"));
  
!   /* Recognize the return address collection directive specially.  Note
!      that it is not really an expression of any sort.  */
!   if (strcmp (exp, "$_ret") == 0)
!     {
!       agent = gen_trace_for_return_address (get_frame_pc (fi),
! 					    get_current_arch ());
!       old_chain = make_cleanup_free_agent_expr (agent);
!     }
!   else
!     {
!       expr = parse_expression (exp);
!       old_chain = make_cleanup (free_current_contents, &expr);
!       agent = gen_trace_for_expr (get_frame_pc (fi), expr);
!       make_cleanup_free_agent_expr (agent);
!     }
! 
    ax_reqs (agent);
    ax_print (gdb_stdout, agent);
  
Index: ax-gdb.h
===================================================================
RCS file: /cvs/src/src/gdb/ax-gdb.h,v
retrieving revision 1.20
diff -p -r1.20 ax-gdb.h
*** ax-gdb.h	24 Feb 2011 07:39:48 -0000	1.20
--- ax-gdb.h	21 Sep 2011 21:27:00 -0000
*************** extern struct agent_expr *gen_trace_for_
*** 106,111 ****
--- 106,114 ----
  extern struct agent_expr *gen_trace_for_var (CORE_ADDR, struct gdbarch *,
  					     struct symbol *);
  
+ extern struct agent_expr *gen_trace_for_return_address (CORE_ADDR,
+ 							struct gdbarch *);
+ 
  extern struct agent_expr *gen_eval_for_expr (CORE_ADDR, struct expression *);
  
  extern int trace_kludge;
Index: gdbarch.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbarch.c,v
retrieving revision 1.477
diff -p -r1.477 gdbarch.c
*** gdbarch.c	22 Jul 2011 15:31:50 -0000	1.477
--- gdbarch.c	21 Sep 2011 21:27:00 -0000
*************** struct gdbarch
*** 270,275 ****
--- 270,276 ----
    gdbarch_auto_wide_charset_ftype *auto_wide_charset;
    const char * solib_symbols_extension;
    int has_dos_based_file_system;
+   gdbarch_gen_return_address_ftype *gen_return_address;
  };
  
  
*************** struct gdbarch startup_gdbarch =
*** 423,428 ****
--- 424,430 ----
    default_auto_wide_charset,  /* auto_wide_charset */
    0,  /* solib_symbols_extension */
    0,  /* has_dos_based_file_system */
+   default_gen_return_address,  /* gen_return_address */
    /* startup_gdbarch() */
  };
  
*************** gdbarch_alloc (const struct gdbarch_info
*** 513,518 ****
--- 515,521 ----
    gdbarch->fast_tracepoint_valid_at = default_fast_tracepoint_valid_at;
    gdbarch->auto_charset = default_auto_charset;
    gdbarch->auto_wide_charset = default_auto_wide_charset;
+   gdbarch->gen_return_address = default_gen_return_address;
    /* gdbarch_alloc() */
  
    return gdbarch;
*************** verify_gdbarch (struct gdbarch *gdbarch)
*** 707,712 ****
--- 710,716 ----
    /* Skip verify of auto_charset, invalid_p == 0 */
    /* Skip verify of auto_wide_charset, invalid_p == 0 */
    /* Skip verify of has_dos_based_file_system, invalid_p == 0 */
+   /* Skip verify of gen_return_address, invalid_p == 0 */
    buf = ui_file_xstrdup (log, &length);
    make_cleanup (xfree, buf);
    if (length > 0)
*************** gdbarch_dump (struct gdbarch *gdbarch, s
*** 947,952 ****
--- 951,959 ----
                        "gdbarch_dump: gcore_bfd_target = %s\n",
                        gdbarch->gcore_bfd_target);
    fprintf_unfiltered (file,
+                       "gdbarch_dump: gen_return_address = <%s>\n",
+                       host_address_to_string (gdbarch->gen_return_address));
+   fprintf_unfiltered (file,
                        "gdbarch_dump: gdbarch_get_longjmp_target_p() = %d\n",
                        gdbarch_get_longjmp_target_p (gdbarch));
    fprintf_unfiltered (file,
*************** set_gdbarch_has_dos_based_file_system (s
*** 3863,3868 ****
--- 3870,3892 ----
    gdbarch->has_dos_based_file_system = has_dos_based_file_system;
  }
  
+ void
+ gdbarch_gen_return_address (struct gdbarch *gdbarch, struct agent_expr *ax, struct axs_value *value, CORE_ADDR scope)
+ {
+   gdb_assert (gdbarch != NULL);
+   gdb_assert (gdbarch->gen_return_address != NULL);
+   if (gdbarch_debug >= 2)
+     fprintf_unfiltered (gdb_stdlog, "gdbarch_gen_return_address called\n");
+   gdbarch->gen_return_address (gdbarch, ax, value, scope);
+ }
+ 
+ void
+ set_gdbarch_gen_return_address (struct gdbarch *gdbarch,
+                                 gdbarch_gen_return_address_ftype gen_return_address)
+ {
+   gdbarch->gen_return_address = gen_return_address;
+ }
+ 
  
  /* Keep a registry of per-architecture data-pointers required by GDB
     modules.  */
Index: gdbarch.h
===================================================================
RCS file: /cvs/src/src/gdb/gdbarch.h,v
retrieving revision 1.425
diff -p -r1.425 gdbarch.h
*** gdbarch.h	22 Jul 2011 15:31:50 -0000	1.425
--- gdbarch.h	21 Sep 2011 21:27:00 -0000
*************** struct displaced_step_closure;
*** 54,59 ****
--- 54,60 ----
  struct core_regset_section;
  struct syscall;
  struct agent_expr;
+ struct axs_value;
  
  /* The architecture associated with the connection to the target.
   
*************** extern void set_gdbarch_solib_symbols_ex
*** 1014,1019 ****
--- 1015,1026 ----
  extern int gdbarch_has_dos_based_file_system (struct gdbarch *gdbarch);
  extern void set_gdbarch_has_dos_based_file_system (struct gdbarch *gdbarch, int has_dos_based_file_system);
  
+ /* Generate bytecodes to collect the return address in a frame. */
+ 
+ typedef void (gdbarch_gen_return_address_ftype) (struct gdbarch *gdbarch, struct agent_expr *ax, struct axs_value *value, CORE_ADDR scope);
+ extern void gdbarch_gen_return_address (struct gdbarch *gdbarch, struct agent_expr *ax, struct axs_value *value, CORE_ADDR scope);
+ extern void set_gdbarch_gen_return_address (struct gdbarch *gdbarch, gdbarch_gen_return_address_ftype *gen_return_address);
+ 
  /* Definition for an unknown syscall, used basically in error-cases.  */
  #define UNKNOWN_SYSCALL (-1)
  
Index: gdbarch.sh
===================================================================
RCS file: /cvs/src/src/gdb/gdbarch.sh,v
retrieving revision 1.523
diff -p -r1.523 gdbarch.sh
*** gdbarch.sh	22 Jul 2011 15:31:50 -0000	1.523
--- gdbarch.sh	21 Sep 2011 21:27:00 -0000
*************** v:const char *:solib_symbols_extension::
*** 820,825 ****
--- 820,829 ----
  # is, absolute paths include a drive name, and the backslash is
  # considered a directory separator.
  v:int:has_dos_based_file_system:::0:0::0
+ 
+ # Generate bytecodes to collect the return address in a frame.
+ m:void:gen_return_address:struct agent_expr *ax, struct axs_value *value, CORE_ADDR scope:ax, value, scope::default_gen_return_address::0
+ 
  EOF
  }
  
*************** struct displaced_step_closure;
*** 934,939 ****
--- 938,944 ----
  struct core_regset_section;
  struct syscall;
  struct agent_expr;
+ struct axs_value;
  
  /* The architecture associated with the connection to the target.
   
Index: i386-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/i386-tdep.c,v
retrieving revision 1.336
diff -p -r1.336 i386-tdep.c
*** i386-tdep.c	22 Jul 2011 15:31:51 -0000	1.336
--- i386-tdep.c	21 Sep 2011 21:27:00 -0000
***************
*** 60,65 ****
--- 60,68 ----
  #include "features/i386/i386-avx.c"
  #include "features/i386/i386-mmx.c"
  
+ #include "ax.h"
+ #include "ax-gdb.h"
+ 
  /* Register names.  */
  
  static const char *i386_register_names[] =
*************** static const struct frame_unwind i386_st
*** 2074,2079 ****
--- 2077,2100 ----
    i386_stack_tramp_frame_sniffer
  };
  
+ /* Generate a bytecode expression to get the value of the saved PC.
+    Since this is supposed to run on the target independently of GDB,
+    we don't have the full power of the unwinding machinery.  Instead,
+    make a guess as to the most likely location of the return address,
+    and issue byte codes for that.  */
+ 
+ void
+ i386_gen_return_address (struct gdbarch *gdbarch,
+ 			 struct agent_expr *ax, struct axs_value *value,
+ 			 CORE_ADDR scope)
+ {
+   ax_reg (ax, I386_EBP_REGNUM);
+   ax_const_l (ax, 4);
+   ax_simple (ax, aop_add);
+   value->type = register_type (gdbarch, I386_EIP_REGNUM);
+   value->kind = axs_lvalue_memory;
+ }
+ 
  
  /* Signal trampolines.  */
  
*************** i386_gdbarch_init (struct gdbarch_info i
*** 7400,7405 ****
--- 7421,7428 ----
  
    set_gdbarch_relocate_instruction (gdbarch, i386_relocate_instruction);
  
+   set_gdbarch_gen_return_address (gdbarch, i386_gen_return_address);
+ 
    /* Hook in ABI-specific overrides, if they have been registered.  */
    info.tdep_info = (void *) tdesc_data;
    gdbarch_init_osabi (info, gdbarch);
Index: tracepoint.c
===================================================================
RCS file: /cvs/src/src/gdb/tracepoint.c,v
retrieving revision 1.231
diff -p -r1.231 tracepoint.c
*** tracepoint.c	24 Aug 2011 09:24:10 -0000	1.231
--- tracepoint.c	21 Sep 2011 21:27:00 -0000
*************** validate_actionline (char **line, struct
*** 667,672 ****
--- 667,673 ----
  	      if (0 == strncasecmp ("reg", p + 1, 3)
  		  || 0 == strncasecmp ("arg", p + 1, 3)
  		  || 0 == strncasecmp ("loc", p + 1, 3)
+ 		  || 0 == strncasecmp ("_ret", p + 1, 4)
  		  || 0 == strncasecmp ("_sdata", p + 1, 6))
  		{
  		  p = strchr (p, ',');
*************** encode_actions_1 (struct command_line *a
*** 1344,1349 ****
--- 1345,1387 ----
  				     'L');
  		  action_exp = strchr (action_exp, ',');	/* more? */
  		}
+ 	      else if (0 == strncasecmp ("$_ret", action_exp, 5))
+ 		{
+ 		  struct cleanup *old_chain1 = NULL;
+ 
+ 		  aexpr = gen_trace_for_return_address (tloc->address,
+ 							t->gdbarch);
+ 
+ 		  old_chain1 = make_cleanup_free_agent_expr (aexpr);
+ 
+ 		  ax_reqs (aexpr);
+ 		  report_agent_reqs_errors (aexpr);
+ 
+ 		  discard_cleanups (old_chain1);
+ 		  add_aexpr (collect, aexpr);
+ 
+ 		  /* take care of the registers */
+ 		  if (aexpr->reg_mask_len > 0)
+ 		    {
+ 		      int ndx1, ndx2;
+ 
+ 		      for (ndx1 = 0; ndx1 < aexpr->reg_mask_len; ndx1++)
+ 			{
+ 			  QUIT;	/* allow user to bail out with ^C */
+ 			  if (aexpr->reg_mask[ndx1] != 0)
+ 			    {
+ 			      /* assume chars have 8 bits */
+ 			      for (ndx2 = 0; ndx2 < 8; ndx2++)
+ 				if (aexpr->reg_mask[ndx1] & (1 << ndx2))
+ 				  /* it's used -- record it */
+ 				  add_register (collect, 
+ 						ndx1 * 8 + ndx2);
+ 			    }
+ 			}
+ 		    }
+ 
+ 		  action_exp = strchr (action_exp, ',');	/* more? */
+ 		}
  	      else if (0 == strncasecmp ("$_sdata", action_exp, 7))
  		{
  		  add_static_trace_data (collect);
*************** trace_dump_actions (struct command_line 
*** 2555,2560 ****
--- 2593,2600 ----
  
  		  if (0 == strncasecmp (action_exp, "$reg", 4))
  		    registers_info (NULL, from_tty);
+ 		  else if (0 == strncasecmp (action_exp, "$_ret", 5))
+ 		    ;
  		  else if (0 == strncasecmp (action_exp, "$loc", 4))
  		    locals_info (NULL, from_tty);
  		  else if (0 == strncasecmp (action_exp, "$arg", 4))
Index: testsuite/gdb.trace/collection.exp
===================================================================
RCS file: /cvs/src/src/gdb/testsuite/gdb.trace/collection.exp,v
retrieving revision 1.26
diff -p -r1.26 collection.exp
*** testsuite/gdb.trace/collection.exp	8 Sep 2011 17:40:53 -0000	1.26
--- testsuite/gdb.trace/collection.exp	21 Sep 2011 21:27:01 -0000
*************** proc gdb_collect_global_in_pieces_test {
*** 588,593 ****
--- 588,624 ----
  	"collect global in pieces: cease trace debugging"
  }
  
+ proc gdb_collect_return_test { } {
+ 
+     prepare_for_trace_test
+ 
+     # We'll simply re-use the args_test_function for this test
+     gdb_test "trace args_test_func" \
+ 	    "Tracepoint \[0-9\]+ at .*" \
+ 	    "collect \$_ret: set tracepoint"
+     gdb_trace_setactions "collect \$_ret: define actions" \
+ 	    "" \
+ 	    "collect \$_ret" "^$"
+ 
+     # Begin the test.
+     run_trace_experiment \$_ret args_test_func
+ 
+     # Since we can't guarantee that $_ret will give us the caller,
+     # pass either way, but giving different messages.
+     gdb_test_multiple "backtrace" "" {
+ 	-re ".*#1 .* in main .*" {
+ 	    pass "collect \$_ret: backtrace lists main"
+ 	}
+ 	-re ".*#1 .* in ?? .*" {
+ 	    pass "collect \$_ret: backtrace not listing main"
+ 	}
+     }
+ 
+     gdb_test "tfind none" \
+ 	    "#0  end .*" \
+ 	    "collect \$_ret: cease trace debugging"
+ }
+ 
  proc gdb_trace_collection_test {} {
      global fpreg
      global spreg
*************** proc gdb_trace_collection_test {} {
*** 696,701 ****
--- 727,733 ----
      gdb_collect_expression_test globals_test_func \
  	    "globalarr\[\(l6, l7\)\]" "7"    "a\[\(b, c\)\]"
  
+     gdb_collect_return_test
  }
  
  clean_restart $executable