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[PATCH] Fix 19548: Breakpoint re-set inserts breakpoints when it shouldn't
- From: Pedro Alves <palves at redhat dot com>
- To: gdb-patches at sourceware dot org
- Date: Mon, 1 Feb 2016 17:04:06 +0000
- Subject: [PATCH] Fix 19548: Breakpoint re-set inserts breakpoints when it shouldn't
- Authentication-results: sourceware.org; auth=none
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:
2016-02-01 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:
2016-02-01 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.
---
gdb/breakpoint.c | 25 +++++++----------
gdb/testsuite/gdb.base/execl-update-breakpoints.c | 6 +++++
.../gdb.base/execl-update-breakpoints.exp | 31 ++++++++++++++++++++--
3 files changed, 45 insertions(+), 17 deletions(-)
diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index afd9065..c059861 100644
--- 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);
}
/* Reset the thread number of this breakpoint:
diff --git a/gdb/testsuite/gdb.base/execl-update-breakpoints.c b/gdb/testsuite/gdb.base/execl-update-breakpoints.c
index 3978a70..38f1cea 100644
--- 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 4f35999..e7b276c 100644
--- 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 17227 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" } {
--
1.9.3