# Copyright (C) 2015-2024 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/>.
import gdb
from gdb.unwinder import Unwinder, FrameId
# These are set to test whether invalid register names cause an error.
add_saved_register_errors = {}
read_register_error = False
class TestUnwinder(Unwinder):
AMD64_RBP = 6
AMD64_RSP = 7
AMD64_RIP = None
def __init__(self):
Unwinder.__init__(self, "test unwinder")
self.char_ptr_t = gdb.lookup_type("unsigned char").pointer()
self.char_ptr_ptr_t = self.char_ptr_t.pointer()
self._last_arch = None
# Update the register descriptor AMD64_RIP based on ARCH.
def _update_register_descriptors(self, arch):
if self._last_arch != arch:
TestUnwinder.AMD64_RIP = arch.registers().find("rip")
self._last_arch = arch
def _read_word(self, address):
return address.cast(self.char_ptr_ptr_t).dereference()
def __call__(self, pending_frame):
"""Test unwinder written in Python.
This unwinder can unwind the frames that have been deliberately
corrupted in a specific way (functions in the accompanying
py-unwind.c file do that.)
This code is only on AMD64.
On AMD64 $RBP points to the innermost frame (unless the code
was compiled with -fomit-frame-pointer), which contains the
address of the previous frame at offset 0. The functions
deliberately corrupt their frames as follows:
Before After
Corruption: Corruption:
+--------------+ +--------------+
RBP-8 | | | Previous RBP |
+--------------+ +--------------+
RBP + Previous RBP | | RBP |
+--------------+ +--------------+
RBP+8 | Return RIP | | Return RIP |
+--------------+ +--------------+
Old SP | | | |
This unwinder recognizes the corrupt frames by checking that
*RBP == RBP, and restores previous RBP from the word above it.
"""
# Check that we can access the architecture of the pending
# frame, and that this is the same architecture as for the
# currently selected inferior.
inf_arch = gdb.selected_inferior().architecture()
frame_arch = pending_frame.architecture()
if inf_arch != frame_arch:
raise gdb.GdbError("architecture mismatch")
self._update_register_descriptors(frame_arch)
try:
# NOTE: the registers in Unwinder API can be referenced
# either by name or by number. The code below uses both
# to achieve more coverage.
bp = pending_frame.read_register("rbp").cast(self.char_ptr_t)
if self._read_word(bp) != bp:
return None
# Found the frame that the test program has corrupted for us.
# The correct BP for the outer frame has been saved one word
# above, previous IP and SP are at the expected places.
previous_bp = self._read_word(bp - 8)
previous_ip = self._read_word(bp + 8)
previous_sp = bp + 16
try:
pending_frame.read_register("nosuchregister")
except ValueError as ve:
global read_register_error
read_register_error = str(ve)
frame_id = FrameId(
pending_frame.read_register(register=TestUnwinder.AMD64_RSP),
pending_frame.read_register(TestUnwinder.AMD64_RIP),
)
unwind_info = pending_frame.create_unwind_info(frame_id)
unwind_info.add_saved_register(TestUnwinder.AMD64_RBP, previous_bp)
unwind_info.add_saved_register(value=previous_ip, register="rip")
unwind_info.add_saved_register(register="rsp", value=previous_sp)
global add_saved_register_errors
try:
unwind_info.add_saved_register("nosuchregister", previous_sp)
except ValueError as ve:
add_saved_register_errors["unknown_name"] = str(ve)
try:
unwind_info.add_saved_register(999, previous_sp)
except ValueError as ve:
add_saved_register_errors["unknown_number"] = str(ve)
try:
unwind_info.add_saved_register("rsp", 1234)
except TypeError as ve:
add_saved_register_errors["bad_value"] = str(ve)
return unwind_info
except (gdb.error, RuntimeError):
return None
global_test_unwinder = TestUnwinder()
gdb.unwinder.register_unwinder(None, global_test_unwinder, True)
# These are filled in by the simple_unwinder class.
captured_pending_frame = None
captured_pending_frame_repr = None
captured_unwind_info = None
captured_unwind_info_repr = None
class simple_unwinder(Unwinder):
def __init__(self, name, sp=0x123, pc=0x456):
super().__init__(name)
self._sp = sp
self._pc = pc
def __call__(self, pending_frame):
global captured_pending_frame
global captured_pending_frame_repr
global captured_unwind_info
global captured_unwind_info_repr
assert pending_frame.is_valid()
if captured_pending_frame is None:
captured_pending_frame = pending_frame
captured_pending_frame_repr = repr(pending_frame)
fid = FrameId(self._sp, self._pc)
uw = pending_frame.create_unwind_info(frame_id=fid)
uw.add_saved_register("rip", gdb.Value(0x123))
uw.add_saved_register("rbp", gdb.Value(0x456))
uw.add_saved_register("rsp", gdb.Value(0x789))
captured_unwind_info = uw
captured_unwind_info_repr = repr(uw)
return None
# Return a dictionary of information about FRAME.
def capture_frame_information(frame):
name = frame.name()
level = frame.level()
language = frame.language()
function = frame.function()
architecture = frame.architecture()
pc = frame.pc()
sal = frame.find_sal()
try:
block = frame.block()
assert isinstance(block, gdb.Block)
except RuntimeError as rte:
assert str(rte) == "Cannot locate block for frame."
block = "RuntimeError: " + str(rte)
return {
"name": name,
"level": level,
"language": language,
"function": function,
"architecture": architecture,
"pc": pc,
"sal": sal,
"block": block,
}
# List of information about each frame. The index into this list is
# the frame level. This is populated by
# capture_all_frame_information.
all_frame_information = []
# Fill in the global ALL_FRAME_INFORMATION list.
def capture_all_frame_information():
global all_frame_information
all_frame_information = []
gdb.newest_frame().select()
frame = gdb.selected_frame()
count = 0
while frame is not None:
frame.select()
info = capture_frame_information(frame)
level = info["level"]
info["matched"] = False
while len(all_frame_information) <= level:
all_frame_information.append(None)
assert all_frame_information[level] is None
all_frame_information[level] = info
if frame.name == "main" or count > 10:
break
count += 1
frame = frame.older()
# Assert that every entry in the global ALL_FRAME_INFORMATION list was
# matched by the validating_unwinder.
def check_all_frame_information_matched():
global all_frame_information
for entry in all_frame_information:
assert entry["matched"]
# An unwinder that doesn't match any frames. What it does do is
# lookup information from the PendingFrame object and compare it
# against information stored in the global ALL_FRAME_INFORMATION list.
class validating_unwinder(Unwinder):
def __init__(self):
super().__init__("validating_unwinder")
def __call__(self, pending_frame):
info = capture_frame_information(pending_frame)
level = info["level"]
global all_frame_information
old_info = all_frame_information[level]
assert old_info is not None
assert not old_info["matched"]
for key, value in info.items():
assert key in old_info, key + " not in old_info"
assert type(value) == type(old_info[key])
if isinstance(value, gdb.Block):
assert value.start == old_info[key].start
assert value.end == old_info[key].end
assert value.is_static == old_info[key].is_static
assert value.is_global == old_info[key].is_global
else:
assert str(value) == str(old_info[key])
old_info["matched"] = True
return None
print("Python script imported")