+2021-06-01 Andrew Burgess <andrew.burgess@embecosm.com>
+ Richard Bunt <richard.bunt@arm.com>
+
+ * breakpoint.c (check_longjmp_breakpoint_for_call_dummy): Add
+ check for why the backtrace stopped.
+
2021-05-31 Simon Marchi <simon.marchi@polymtl.ca>
* dwarf2/read.h (struct structured_type) <signatured_type>: New.
TP. Remove those which can no longer be found in the current frame
stack.
- You should call this function only at places where it is safe to currently
- unwind the whole stack. Failed stack unwind would discard live dummy
- frames. */
+ If the unwind fails then there is not sufficient information to discard
+ dummy frames. In this case, elide the clean up and the dummy frames will
+ be cleaned up next time this function is called from a location where
+ unwinding is possible. */
void
check_longjmp_breakpoint_for_call_dummy (struct thread_info *tp)
{
struct breakpoint *dummy_b = b->related_breakpoint;
+ /* Find the bp_call_dummy breakpoint in the list of breakpoints
+ chained off b->related_breakpoint. */
while (dummy_b != b && dummy_b->type != bp_call_dummy)
dummy_b = dummy_b->related_breakpoint;
+
+ /* If there was no bp_call_dummy breakpoint then there's nothing
+ more to do. Or, if the dummy frame associated with the
+ bp_call_dummy is still on the stack then we need to leave this
+ bp_call_dummy in place. */
if (dummy_b->type != bp_call_dummy
|| frame_find_by_id (dummy_b->frame_id) != NULL)
continue;
-
+
+ /* We didn't find the dummy frame on the stack, this could be
+ because we have longjmp'd to a stack frame that is previous to
+ the dummy frame, or it could be because the stack unwind is
+ broken at some point between the longjmp frame and the dummy
+ frame.
+
+ Next we figure out why the stack unwind stopped. If it looks
+ like the unwind is complete then we assume the dummy frame has
+ been jumped over, however, if the unwind stopped for an
+ unexpected reason then we assume the stack unwind is currently
+ broken, and that we will (eventually) return to the dummy
+ frame.
+
+ It might be tempting to consider using frame_id_inner here, but
+ that is not safe. There is no guarantee that the stack frames
+ we are looking at here are even on the same stack as the
+ original dummy frame, hence frame_id_inner can't be used. See
+ the comments on frame_id_inner for more details. */
+ bool unwind_finished_unexpectedly = false;
+ for (struct frame_info *fi = get_current_frame (); fi != nullptr; )
+ {
+ struct frame_info *prev = get_prev_frame (fi);
+ if (prev == nullptr)
+ {
+ /* FI is the last stack frame. Why did this frame not
+ unwind further? */
+ auto stop_reason = get_frame_unwind_stop_reason (fi);
+ if (stop_reason != UNWIND_NO_REASON
+ && stop_reason != UNWIND_OUTERMOST)
+ unwind_finished_unexpectedly = true;
+ }
+ fi = prev;
+ }
+ if (unwind_finished_unexpectedly)
+ continue;
+
dummy_frame_discard (dummy_b->frame_id, tp);
while (b->related_breakpoint != b)
+2021-06-01 Andrew Burgess <andrew.burgess@embecosm.com>
+
+ * gdb.base/premature-dummy-frame-removal.c: New file.
+ * gdb.base/premature-dummy-frame-removal.exp: New file.
+ * gdb.base/premature-dummy-frame-removal.py: New file.
+
2021-05-27 Simon Marchi <simon.marchi@polymtl.ca>
* gdb.base/reverse-init-functions.exp: New.
--- /dev/null
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2021 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/>. */
+
+#include <stdlib.h>
+#include <setjmp.h>
+
+jmp_buf env;
+
+void
+worker (void)
+{
+ longjmp (env, 1);
+}
+
+void
+test_inner (void)
+{
+ if (setjmp (env) == 0)
+ {
+ /* Direct call. */
+ worker ();
+
+ /* Will never get here. */
+ abort ();
+ }
+ else
+ {
+ /* Called from longjmp. */
+ }
+}
+
+void
+break_bt_here (void)
+{
+ test_inner ();
+}
+
+int
+some_func (void)
+{
+ break_bt_here ();
+ return 0;
+}
+
+int
+main (void)
+{
+ some_func ();
+
+ return 0;
+}
--- /dev/null
+# Copyright 2021 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/>.
+
+# Make an inferior call to a function which uses longjmp. However,
+# the backtrace for the function that is called is broken at the point
+# where the longjmp is handled. This test is checking to see if the
+# inferior call still completes successfully.
+#
+# This test forces a broken backtrace using Python, but in real life a
+# broken backtrace can easily occur when calling through code for
+# which there is no debug information if the prologue unwinder fails,
+# which can often happen if the code has been optimized.
+#
+# The problem was that, due to the broken backtrace, GDB failed to
+# find the inferior call's dummy frame. GDB then concluded that the
+# inferior had longjmp'd backward past the dummy frame and so garbage
+# collected the dummy frame, this causes the breakpoint within the
+# dummy frame to be deleted.
+#
+# When the inferior continued, and eventually returned to the dummy
+# frame, it would try to execute instruction from the dummy frame
+# (which for most, or even all, targets, is on the stack), and then
+# experience undefined behaviuor, often a SIGSEGV.
+
+standard_testfile .c
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
+ return -1
+}
+
+if ![runto_main] then {
+ return 0
+}
+
+# Skip this test if Python scripting is not enabled.
+if { [skip_python_tests] } { continue }
+
+set pyfile [gdb_remote_download host ${srcdir}/${subdir}/${testfile}.py]
+gdb_test_no_output "source ${pyfile}" "load python file"
+
+gdb_test "p some_func ()" " = 0"
--- /dev/null
+# Copyright (C) 2021 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/>.
+
+# This dummy unwinder will break GDB's backtrce at the function called
+# 'break_bt_here'.
+
+import gdb
+from gdb.unwinder import Unwinder
+
+
+class FrameId(object):
+ def __init__(self, sp, pc):
+ self._sp = sp
+ self._pc = pc
+
+ @property
+ def sp(self):
+ return self._sp
+
+ @property
+ def pc(self):
+ return self._pc
+
+
+class TestUnwinder(Unwinder):
+ def __init__(self):
+ Unwinder.__init__(self, "break unwinding")
+
+ def __call__(self, pending_frame):
+ pc_desc = pending_frame.architecture().registers().find("pc")
+ pc = pending_frame.read_register(pc_desc)
+
+ sp_desc = pending_frame.architecture().registers().find("sp")
+ sp = pending_frame.read_register(sp_desc)
+
+ block = gdb.block_for_pc(int(pc))
+ if block == None:
+ return None
+ func = block.function
+ if func == None:
+ return None
+ if str(func) != "break_bt_here":
+ return None
+ fid = FrameId(pc, sp)
+ return pending_frame.create_unwind_info(fid)
+
+
+gdb.unwinder.register_unwinder(None, TestUnwinder(), True)
projects / deliverable / binutils-gdb.git / commitdiff
