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# 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 test checks for an edge case when unwinding inline frames which
# occur towards the older end of the stack when the stack ends with a
# cycle. Consider this well formed stack:
#
# main -> normal_frame -> inline_frame
#
# Now consider that, for whatever reason, the stack unwinding of
# "normal_frame" becomes corrupted, such that the stack appears to be
# this:
#
# .-> normal_frame -> inline_frame
# | |
# '------'
#
# When confronted with such a situation we would expect GDB to detect
# the stack frame cycle and terminate the backtrace at the first
# instance of "normal_frame" with a message:
#
# Backtrace stopped: previous frame identical to this frame (corrupt stack?)
#
# However, at one point there was a bug in GDB's inline frame
# mechanism such that the fact that "inline_frame" was inlined into
# "normal_frame" would cause GDB to trigger an assertion.
#
# This text makes use of a Python unwinder which can fake the cyclic
# stack cycle, further the test sets up multiple levels of normal and
# inline frames. At the point of testing the stack looks like this:
#
# main -> normal_func -> inline_func -> normal_func -> inline_func -> normal_func -> inline_func
#
# Where "normal_func" is a normal frame, and "inline_func" is an inline frame.
#
# The python unwinder is then used to force a stack cycle at each
# "normal_func" frame in turn, we then check that GDB can successfully unwind
# the stack.
standard_testfile
if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}]} {
return -1
}
# Skip this test if Python scripting is not enabled.
if { [skip_python_tests] } { continue }
if ![runto_main] then {
return 0
}
set pyfile [gdb_remote_download host ${srcdir}/${subdir}/${testfile}.py]
# Run to the breakpoint where we will carry out the test.
gdb_breakpoint [gdb_get_line_number "Break here"]
gdb_continue_to_breakpoint "stop at test breakpoint"
# Load the script containing the unwinder, this must be done at the
# testing point as the script will examine the stack as it is loaded.
gdb_test_no_output "source ${pyfile}"\
"import python scripts"
# Check the unbroken stack.
gdb_test_sequence "bt" "backtrace when the unwind is left unbroken" {
"\\r\\n#0 \[^\r\n\]* inline_func \\(\\) at "
"\\r\\n#1 \[^\r\n\]* normal_func \\(\\) at "
"\\r\\n#2 \[^\r\n\]* inline_func \\(\\) at "
"\\r\\n#3 \[^\r\n\]* normal_func \\(\\) at "
"\\r\\n#4 \[^\r\n\]* inline_func \\(\\) at "
"\\r\\n#5 \[^\r\n\]* normal_func \\(\\) at "
"\\r\\n#6 \[^\r\n\]* main \\(\\) at "
}
with_test_prefix "cycle at level 5" {
# Arrange to introduce a stack cycle at frame 5.
gdb_test_no_output "python stop_at_level=5"
gdb_test "maint flush register-cache" \
"Register cache flushed\\."
gdb_test_lines "bt" "backtrace when the unwind is broken at frame 5" \
[multi_line \
"#0 \[^\r\n\]* inline_func \\(\\) at \[^\r\n\]+" \
"#1 \[^\r\n\]* normal_func \\(\\) at \[^\r\n\]+" \
"#2 \[^\r\n\]* inline_func \\(\\) at \[^\r\n\]+" \
"#3 \[^\r\n\]* normal_func \\(\\) at \[^\r\n\]+" \
"#4 \[^\r\n\]* inline_func \\(\\) at \[^\r\n\]+" \
"#5 \[^\r\n\]* normal_func \\(\\) at \[^\r\n\]+" \
"Backtrace stopped: previous frame identical to this frame \\(corrupt stack\\?\\)"]
}
with_test_prefix "cycle at level 3" {
# Arrange to introduce a stack cycle at frame 3.
gdb_test_no_output "python stop_at_level=3"
gdb_test "maint flush register-cache" \
"Register cache flushed\\."
gdb_test_lines "bt" "backtrace when the unwind is broken at frame 3" \
[multi_line \
"#0 \[^\r\n\]* inline_func \\(\\) at \[^\r\n\]+" \
"#1 \[^\r\n\]* normal_func \\(\\) at \[^\r\n\]+" \
"#2 \[^\r\n\]* inline_func \\(\\) at \[^\r\n\]+" \
"#3 \[^\r\n\]* normal_func \\(\\) at \[^\r\n\]+" \
"Backtrace stopped: previous frame identical to this frame \\(corrupt stack\\?\\)"]
}
with_test_prefix "cycle at level 1" {
# Arrange to introduce a stack cycle at frame 1.
gdb_test_no_output "python stop_at_level=1"
gdb_test "maint flush register-cache" \
"Register cache flushed\\."
gdb_test_lines "bt" "backtrace when the unwind is broken at frame 1" \
[multi_line \
"#0 \[^\r\n\]* inline_func \\(\\) at \[^\r\n\]+" \
"#1 \[^\r\n\]* normal_func \\(\\) at \[^\r\n\]+" \
"Backtrace stopped: previous frame identical to this frame \\(corrupt stack\\?\\)"]
}
# Flush the register cache (which also flushes the frame cache) so we
# get a full backtrace again, then switch on frame debugging and try
# to back trace. At one point this triggered an assertion.
gdb_test "maint flush register-cache" \
"Register cache flushed\\." ""
gdb_test_no_output "set debug frame 1"
gdb_test_multiple "bt" "backtrace with debugging on" {
-re "^$gdb_prompt $" {
pass $gdb_test_name
}
-re "\[^\r\n\]+\r\n" {
exp_continue
}
}
gdb_test "p 1 + 2 + 3" " = 6" \
"ensure GDB is still alive"
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