[v2,1/1] gdb, breakpoint: add a destructor to the watchpoint struct
Commit Message
Make sure to unlink the related breakpoint when the watchpoint instance
is deleted. This prevents having a wp-related breakpoint that is
linked to a NULL watchpoint (e.g. the watchpoint instance is being
deleted when the 'watch' command fails). With the below scenario,
having such a left out breakpoint will lead to a GDB hang, and this
is due to an infinite loop when deleting all inferior breakpoints.
Scenario:
(gdb) set can-use-hw-watchpoints 0
(gdb) awatch <SCOPE VAR>
Can't set read/access watchpoint when hardware watchpoints are disabled.
(gdb) rwatch <SCOPE VAR>
Can't set read/access watchpoint when hardware watchpoints are disabled.
(gdb) <continue the program until the end>
>> HANG <<
Signed-off-by: Mohamed Bouhaouel <mohamed.bouhaouel@intel.com>
---
gdb/breakpoint.c | 15 +++++++
gdb/breakpoint.h | 3 ++
.../gdb.base/scope-hw-watch-disable.c | 26 ++++++++++++
.../gdb.base/scope-hw-watch-disable.exp | 40 +++++++++++++++++++
4 files changed, 84 insertions(+)
create mode 100644 gdb/testsuite/gdb.base/scope-hw-watch-disable.c
create mode 100644 gdb/testsuite/gdb.base/scope-hw-watch-disable.exp
Comments
Dear all,
I kindly request that you review this patch.
Thanks,
-Mohamed
> -----Original Message-----
> From: Gdb-patches <gdb-patches-
> bounces+felix.willgerodt=intel.com@sourceware.org> On Behalf Of Mohamed
> Bouhaouel via Gdb-patches
> Sent: Wednesday, April 5, 2023 3:35 PM
> To: gdb-patches@sourceware.org
> Cc: tom@tromey.com; aburgess@redhat.com
> Subject: [PATCH v2 1/1] gdb, breakpoint: add a destructor to the watchpoint
> struct
>
> Make sure to unlink the related breakpoint when the watchpoint instance
> is deleted. This prevents having a wp-related breakpoint that is
> linked to a NULL watchpoint (e.g. the watchpoint instance is being
> deleted when the 'watch' command fails). With the below scenario,
> having such a left out breakpoint will lead to a GDB hang, and this
> is due to an infinite loop when deleting all inferior breakpoints.
>
> Scenario:
> (gdb) set can-use-hw-watchpoints 0
> (gdb) awatch <SCOPE VAR>
> Can't set read/access watchpoint when hardware watchpoints are
> disabled.
> (gdb) rwatch <SCOPE VAR>
> Can't set read/access watchpoint when hardware watchpoints are
> disabled.
> (gdb) <continue the program until the end>
> >> HANG <<
>
> Signed-off-by: Mohamed Bouhaouel <mohamed.bouhaouel@intel.com>
> ---
> gdb/breakpoint.c | 15 +++++++
> gdb/breakpoint.h | 3 ++
> .../gdb.base/scope-hw-watch-disable.c | 26 ++++++++++++
> .../gdb.base/scope-hw-watch-disable.exp | 40 +++++++++++++++++++
> 4 files changed, 84 insertions(+)
> create mode 100644 gdb/testsuite/gdb.base/scope-hw-watch-disable.c
> create mode 100644 gdb/testsuite/gdb.base/scope-hw-watch-disable.exp
>
> diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
> index ebe97940f54..862e9a372ab 100644
> --- a/gdb/breakpoint.c
> +++ b/gdb/breakpoint.c
> @@ -9594,6 +9594,21 @@ break_range_command (const char *arg, int
> from_tty)
> install_breakpoint (false, std::move (br), true);
> }
>
> +/* See breakpoint.h. */
> +
> +watchpoint::~watchpoint ()
> +{
> + /* Make sure to unlink the destroyed watchpoint from the related
> + breakpoint ring. */
> +
> + breakpoint *bpt = this;
> + breakpoint *related = bpt;
> + while (related->related_breakpoint != bpt)
> + related = related->related_breakpoint;
> +
> + related->related_breakpoint = bpt->related_breakpoint;
> +}
> +
> /* Return non-zero if EXP is verified as constant. Returned zero
> means EXP is variable. Also the constant detection may fail for
> some constant expressions and in such case still falsely return
> diff --git a/gdb/breakpoint.h b/gdb/breakpoint.h
> index 7c5cf3f2bef..cccd331e6e8 100644
> --- a/gdb/breakpoint.h
> +++ b/gdb/breakpoint.h
> @@ -933,6 +933,9 @@ struct watchpoint : public breakpoint
> void print_recreate (struct ui_file *fp) const override;
> bool explains_signal (enum gdb_signal) override;
>
> + /* Destructor for WATCHPOINT. */
> + ~watchpoint ();
> +
> /* String form of exp to use for displaying to the user (malloc'd),
> or NULL if none. */
> gdb::unique_xmalloc_ptr<char> exp_string;
> diff --git a/gdb/testsuite/gdb.base/scope-hw-watch-disable.c
> b/gdb/testsuite/gdb.base/scope-hw-watch-disable.c
> new file mode 100644
> index 00000000000..30956fe1b84
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/scope-hw-watch-disable.c
> @@ -0,0 +1,26 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> + Copyright 2023 Free Software Foundation, Inc.
> +
> + This program is free software; you can redistribute it and/or modify
> + it under the terms of the GNU General Public License as published by
> + the Free Software Foundation; either version 3 of the License, or
> + (at your option) any later version.
> +
> + This program is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + GNU General Public License for more details.
> +
> + You should have received a copy of the GNU General Public License
> + along with this program. If not, see <http://www.gnu.org/licenses/>. */
> +
> +int
> +main ()
> +{
> + int a = 0, b = 0;
> + b = a;
> + a = b + 10;
> +
> + return 0;
> +}
> diff --git a/gdb/testsuite/gdb.base/scope-hw-watch-disable.exp
> b/gdb/testsuite/gdb.base/scope-hw-watch-disable.exp
> new file mode 100644
> index 00000000000..54ebb4e4226
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/scope-hw-watch-disable.exp
> @@ -0,0 +1,40 @@
> +# Copyright 2023 Free Software Foundation, Inc.
> +
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program. If not, see <http://www.gnu.org/licenses/>.
> +
> +# Test that GDB displays the correct error message when hardware
> watchpoints
> +# are not supported or explicitly disabled. Test also that GDB terminates
> +# successfully after several attempts to insert a hardware watchpoint.
> +
> +standard_testfile
> +
> +if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile}]} {
> + return -1
> +}
> +
> +gdb_test_no_output "set can-use-hw-watchpoints 0"
> +
> +if {![runto_main]} {
> + return -1
> +}
> +
> +gdb_test "awatch a" \
> + "Can't set read/access watchpoint when hardware watchpoints are
> disabled." \
> + "unsuccessful attempt to create an access watchpoint"
> +gdb_test "rwatch b" \
> + "Can't set read/access watchpoint when hardware watchpoints are
> disabled." \
> + "unsuccessful attempt to create a read watchpoint"
> +
> +# The program continues until termination.
> +gdb_continue_to_end
> --
> 2.25.1
>
> Intel Deutschland GmbH
> Registered Address: Am Campeon 10, 85579 Neubiberg, Germany
> Tel: +49 89 99 8853-0, www.intel.de <http://www.intel.de>
> Managing Directors: Christin Eisenschmid, Sharon Heck, Tiffany Doon Silva
> Chairperson of the Supervisory Board: Nicole Lau
> Registered Office: Munich
> Commercial Register: Amtsgericht Muenchen HRB 186928
Intel Deutschland GmbH
Registered Address: Am Campeon 10, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de <http://www.intel.de>
Managing Directors: Christin Eisenschmid, Sharon Heck, Tiffany Doon Silva
Chairperson of the Supervisory Board: Nicole Lau
Registered Office: Munich
Commercial Register: Amtsgericht Muenchen HRB 186928
On 05/04/2023 15:34, Mohamed Bouhaouel via Gdb-patches wrote:
> Make sure to unlink the related breakpoint when the watchpoint instance
> is deleted. This prevents having a wp-related breakpoint that is
> linked to a NULL watchpoint (e.g. the watchpoint instance is being
> deleted when the 'watch' command fails). With the below scenario,
> having such a left out breakpoint will lead to a GDB hang, and this
> is due to an infinite loop when deleting all inferior breakpoints.
>
> Scenario:
> (gdb) set can-use-hw-watchpoints 0
> (gdb) awatch <SCOPE VAR>
> Can't set read/access watchpoint when hardware watchpoints are disabled.
> (gdb) rwatch <SCOPE VAR>
> Can't set read/access watchpoint when hardware watchpoints are disabled.
> (gdb) <continue the program until the end>
> >> HANG <<
>
> Signed-off-by: Mohamed Bouhaouel <mohamed.bouhaouel@intel.com>
Hi Mohamed!
Thank you for working on this!
I have tried it, your test reproduces the issue, and your changes fix
them. I only have one small nit inlined. Other than that:
Reviewed-By: Bruno Larsen <blarsen@redhat.com>
Do note that that tag is not enough to push, so here's hoping a
maintainer looks at it soon!
> ---
> gdb/breakpoint.c | 15 +++++++
> gdb/breakpoint.h | 3 ++
> .../gdb.base/scope-hw-watch-disable.c | 26 ++++++++++++
> .../gdb.base/scope-hw-watch-disable.exp | 40 +++++++++++++++++++
> 4 files changed, 84 insertions(+)
> create mode 100644 gdb/testsuite/gdb.base/scope-hw-watch-disable.c
> create mode 100644 gdb/testsuite/gdb.base/scope-hw-watch-disable.exp
>
> diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
> index ebe97940f54..862e9a372ab 100644
> --- a/gdb/breakpoint.c
> +++ b/gdb/breakpoint.c
> @@ -9594,6 +9594,21 @@ break_range_command (const char *arg, int from_tty)
> install_breakpoint (false, std::move (br), true);
> }
>
> +/* See breakpoint.h. */
> +
> +watchpoint::~watchpoint ()
> +{
> + /* Make sure to unlink the destroyed watchpoint from the related
> + breakpoint ring. */
> +
> + breakpoint *bpt = this;
The bpt variable seems unnecessary to me. you could remove this line and
substitute all occurrences of bpt in the following lines with "this"
> + breakpoint *related = bpt;
and in doing that, I think it might make sense to rename this to bpt?
This second one is just a suggestion, though, so no need to change if
you prefer it like this.
@@ -9594,6 +9594,21 @@ break_range_command (const char *arg, int from_tty)
install_breakpoint (false, std::move (br), true);
}
+/* See breakpoint.h. */
+
+watchpoint::~watchpoint ()
+{
+ /* Make sure to unlink the destroyed watchpoint from the related
+ breakpoint ring. */
+
+ breakpoint *bpt = this;
+ breakpoint *related = bpt;
+ while (related->related_breakpoint != bpt)
+ related = related->related_breakpoint;
+
+ related->related_breakpoint = bpt->related_breakpoint;
+}
+
/* Return non-zero if EXP is verified as constant. Returned zero
means EXP is variable. Also the constant detection may fail for
some constant expressions and in such case still falsely return
@@ -933,6 +933,9 @@ struct watchpoint : public breakpoint
void print_recreate (struct ui_file *fp) const override;
bool explains_signal (enum gdb_signal) override;
+ /* Destructor for WATCHPOINT. */
+ ~watchpoint ();
+
/* String form of exp to use for displaying to the user (malloc'd),
or NULL if none. */
gdb::unique_xmalloc_ptr<char> exp_string;
new file mode 100644
@@ -0,0 +1,26 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2023 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+int
+main ()
+{
+ int a = 0, b = 0;
+ b = a;
+ a = b + 10;
+
+ return 0;
+}
new file mode 100644
@@ -0,0 +1,40 @@
+# Copyright 2023 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+# Test that GDB displays the correct error message when hardware watchpoints
+# are not supported or explicitly disabled. Test also that GDB terminates
+# successfully after several attempts to insert a hardware watchpoint.
+
+standard_testfile
+
+if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile}]} {
+ return -1
+}
+
+gdb_test_no_output "set can-use-hw-watchpoints 0"
+
+if {![runto_main]} {
+ return -1
+}
+
+gdb_test "awatch a" \
+ "Can't set read/access watchpoint when hardware watchpoints are disabled." \
+ "unsuccessful attempt to create an access watchpoint"
+gdb_test "rwatch b" \
+ "Can't set read/access watchpoint when hardware watchpoints are disabled." \
+ "unsuccessful attempt to create a read watchpoint"
+
+# The program continues until termination.
+gdb_continue_to_end