Fix PR19548: Breakpoint re-set inserts breakpoints when it shouldn't

PR19548 shows that we still have problems related to 13fd3ff34329:

 [PR17431: following execs with "breakpoint always-inserted on"]
 https://sourceware.org/ml/gdb-patches/2014-09/msg00733.html

The problem this time is that we currently update the global location
list and try to insert breakpoint locations after re-setting _each_
breakpoint in turn.

Say:

 - We have _more_ than one breakpoint set.  Let's assume 2.

 - There's a breakpoint with a pre-exec address that ends up being an
   unmapped address after the exec.

 - That breakpoint is NOT the first in the breakpoint list.

Then when handling an exec, and we re-set the first breakpoint in the
breakpoint list, we mistakently try to install the old pre-exec /
un-re-set locations of the other breakpoint, which fails:

 (gdb) continue
 Continuing.
 process 28295 is executing new program: (...)/execl-update-breakpoints2
 Error in re-setting breakpoint 1: Warning:
 Cannot insert breakpoint 2.
 Cannot access memory at address 0x1000764

 Breakpoint 1, main (argc=1, argv=0x7fffffffd368) at /home/pedro/gdb/mygit/src/gdb/testsuite/gdb.base/execl-update-breakpoints.c:34
 34        len = strlen (argv[0]);
 (gdb)

Fix this by deferring the global location list update till after all
breakpoints are re-set.

Tested on x86_64 Fedora 20, native and gdbserver.

gdb/ChangeLog:
2016-02-09  Pedro Alves  <palves@redhat.com>

	PR breakpoints/19548
	* breakpoint.c (create_overlay_event_breakpoint): Don't update
	global location list here.
	(create_longjmp_master_breakpoint)
	(create_std_terminate_master_breakpoint)
	(create_exception_master_breakpoint, create_jit_event_breakpoint)
	(update_breakpoint_locations):
	(breakpoint_re_set): Update global location list after all
	breakpoints are re-set.

gdb/testsuite/ChangeLog:
2016-02-09  Pedro Alves  <palves@redhat.com>

	PR breakpoints/19548
	* gdb.base/execl-update-breakpoints.c (some_function): New
	function.
	(main): Call it.
	* gdb.base/execl-update-breakpoints.exp: Add a second breakpoint.
	Tighten expected GDB output.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 6150f6c8aac794937dbc3101b46e2f7a552efe85..8e6e4ec2b25b101c47e87bfffbc3ab9e25ee1055 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,15 @@
+2016-02-09  Pedro Alves  <palves@redhat.com>
+
+       PR breakpoints/19548
+       * breakpoint.c (create_overlay_event_breakpoint): Don't update
+       global location list here.
+       (create_longjmp_master_breakpoint)
+       (create_std_terminate_master_breakpoint)
+       (create_exception_master_breakpoint, create_jit_event_breakpoint)
+       (update_breakpoint_locations):
+       (breakpoint_re_set): Update global location list after all
+       breakpoints are re-set.
+
 2016-02-08  Simon Marchi  <simon.marchi@ericsson.com>
 
        * remote.c (remote_register_number_and_offset): Remove unused

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index afd90651932f24c303a3ba11b87ffc3a3ad7cbc6..c059861138220639e88013fc45cfce2f36fdc1a7 100644 (file)
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -3488,7 +3488,6 @@ create_overlay_event_breakpoint (void)
          overlay_events_enabled = 0;
        }
     }
-  update_global_location_list (UGLL_MAY_INSERT);
 }
 
 static void
@@ -3602,7 +3601,6 @@ create_longjmp_master_breakpoint (void)
        }
     }
   }
-  update_global_location_list (UGLL_MAY_INSERT);
 
   do_cleanups (old_chain);
 }
@@ -3661,8 +3659,6 @@ create_std_terminate_master_breakpoint (void)
     }
   }
 
-  update_global_location_list (UGLL_MAY_INSERT);
-
   do_cleanups (old_chain);
 }
 
@@ -3766,8 +3762,6 @@ create_exception_master_breakpoint (void)
       b->location = new_explicit_location (&explicit_loc);
       b->enable_state = bp_disabled;
     }
-
-  update_global_location_list (UGLL_MAY_INSERT);
 }
 
 void
@@ -7807,12 +7801,8 @@ struct lang_and_radix
 struct breakpoint *
 create_jit_event_breakpoint (struct gdbarch *gdbarch, CORE_ADDR address)
 {
-  struct breakpoint *b;
-
-  b = create_internal_breakpoint (gdbarch, address, bp_jit_event,
-                                 &internal_breakpoint_ops);
-  update_global_location_list_nothrow (UGLL_MAY_INSERT);
-  return b;
+  return create_internal_breakpoint (gdbarch, address, bp_jit_event,
+                                    &internal_breakpoint_ops);
 }
 
 /* Remove JIT code registration and unregistration breakpoint(s).  */
@@ -14278,7 +14268,6 @@ update_breakpoint_locations (struct breakpoint *b,
       /* Ranged breakpoints have only one start location and one end
         location.  */
       b->enable_state = bp_disabled;
-      update_global_location_list (UGLL_MAY_INSERT);
       printf_unfiltered (_("Could not reset ranged breakpoint %d: "
                           "multiple locations found\n"),
                         b->number);
@@ -14376,8 +14365,6 @@ update_breakpoint_locations (struct breakpoint *b,
 
   if (!locations_are_equal (existing_locations, b->loc))
     observer_notify_breakpoint_modified (b);
-
-  update_global_location_list (UGLL_MAY_INSERT);
 }
 
 /* Find the SaL locations corresponding to the given LOCATION.
@@ -14617,6 +14604,11 @@ breakpoint_re_set (void)
   save_input_radix = input_radix;
   old_chain = save_current_space_and_thread ();
 
+  /* Note: we must not try to insert locations until after all
+     breakpoints have been re-set.  Otherwise, e.g., when re-setting
+     breakpoint 1, we'd insert the locations of breakpoint 2, which
+     hadn't been re-set yet, and thus may have stale locations.  */
+
   ALL_BREAKPOINTS_SAFE (b, b_tmp)
   {
     /* Format possible error msg.  */
@@ -14637,6 +14629,9 @@ breakpoint_re_set (void)
   create_longjmp_master_breakpoint ();
   create_std_terminate_master_breakpoint ();
   create_exception_master_breakpoint ();
+
+  /* Now we can insert.  */
+  update_global_location_list (UGLL_MAY_INSERT);
 }
 \f
 /* Reset the thread number of this breakpoint:

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 2a7193003a83bb7659dd73434568328f2e41515c..f8e080088066f17995c1c97a30c897d15a3a90d2 100644 (file)
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,12 @@
+2016-02-09  Pedro Alves  <palves@redhat.com>
+
+       PR breakpoints/19548
+       * gdb.base/execl-update-breakpoints.c (some_function): New
+       function.
+       (main): Call it.
+       * gdb.base/execl-update-breakpoints.exp: Add a second breakpoint.
+       Tighten expected GDB output.
+
 2016-02-08  Simon Marchi  <simon.marchi@ericsson.com>
 
        * Makefile.in (ALL_SUBDIRS): Remove.

diff --git a/gdb/testsuite/gdb.base/execl-update-breakpoints.c b/gdb/testsuite/gdb.base/execl-update-breakpoints.c
index 3978a70189c2086efa54f89dd8809af55a43276c..38f1cea6ea04ca22072a6c91c17a27735bd7766b 100644 (file)
--- a/gdb/testsuite/gdb.base/execl-update-breakpoints.c
+++ b/gdb/testsuite/gdb.base/execl-update-breakpoints.c
@@ -20,6 +20,11 @@
 #include <stdlib.h>
 #include <string.h>
 
+void
+some_function (void)
+{
+}
+
 int
 main (int argc, char **argv)
 {
@@ -34,5 +39,6 @@ main (int argc, char **argv)
 
   execl (bin, bin, (char *) NULL);
   perror ("execl failed");
+  some_function ();
   exit (1);
 }

diff --git a/gdb/testsuite/gdb.base/execl-update-breakpoints.exp b/gdb/testsuite/gdb.base/execl-update-breakpoints.exp
index 4f35999a256ed14a2060e5ff3362bcde3d459e25..47a848ea8483af2ee9149a1ae1537dcaeca26e49 100644 (file)
--- a/gdb/testsuite/gdb.base/execl-update-breakpoints.exp
+++ b/gdb/testsuite/gdb.base/execl-update-breakpoints.exp
@@ -96,6 +96,7 @@ if {!$cannot_access} {
 
 proc test { always_inserted } {
     global exec1
+    global gdb_prompt
 
     clean_restart ${exec1}
 
@@ -106,13 +107,39 @@ proc test { always_inserted } {
        return -1
     }
 
-    # On a buggy GDB, with always-inserted on, we'd see:
+    # Set a second breakpoint (whose original address also ends up
+    # unmmapped after the exec), for PR 19548.
+    gdb_test "break some_function" "Breakpoint .*"
+
+    # PR17431: with always-inserted on, we'd see:
     #  (gdb) continue
     #  Continuing.
     #  Warning:
     #  Cannot insert breakpoint 1.
     #  Cannot access memory at address 0x10000ff
-    gdb_test "continue" "Breakpoint 1, main.*" "continue across exec"
+
+    # PR 19548: with more than one breakpoint, we'd see:
+    #  (gdb) continue
+    #  Continuing.
+    #  process (...) is executing new program: (...)/execl-update-breakpoints2
+    #  Error in re-setting breakpoint 1: Warning:
+    #  Cannot insert breakpoint 2.
+    #  Cannot access memory at address 0x1000764
+    set not_nl "\[^\r\n\]*"
+    set regex ""
+    append regex \
+       "^continue\r\n" \
+       "Continuing\\.\r\n" \
+       "${not_nl} is executing new program: ${not_nl}\r\n" \
+       "(Reading ${not_nl} from remote target\\.\\.\\.\r\n)*" \
+       "\r\n" \
+       "Breakpoint 1, main.*$gdb_prompt $"
+    set message "continue across exec"
+    gdb_test_multiple "continue" $message {
+       -re $regex {
+           pass $message
+       }
+    }
 }
 
 foreach always_inserted { "off" "on" } {