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GH-120754: Add a strace helper and test set of syscalls for open().read() (#121143)

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Cody Maloney 2024-08-24 13:42:41 -07:00 • committed by GitHub
parent 86f06cb3fb
commit e38d0afe35
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4 changed files with 280 additions and 33 deletions
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53
Lib/test/test_subprocess.py
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@ -4,6 +4,7 @@ from test import support
from test.support import check_sanitizer
from test.support import import_helper
from test.support import os_helper
from test.support import strace_helper
from test.support import warnings_helper
from test.support.script_helper import assert_python_ok
import subprocess
@ -3415,7 +3416,7 @@ class POSIXProcessTestCase(BaseTestCase):
@unittest.skipIf(not sysconfig.get_config_var("HAVE_VFORK"),
"vfork() not enabled by configure.")
@unittest.skipIf(sys.platform != "linux", "Linux only, requires strace.")
@strace_helper.requires_strace()
@mock.patch("subprocess._USE_POSIX_SPAWN", new=False)
def test_vfork_used_when_expected(self):
# This is a performance regression test to ensure we default to using
@ -3423,36 +3424,25 @@ class POSIXProcessTestCase(BaseTestCase):
# Technically this test could pass when posix_spawn is used as well
# because libc tends to implement that internally using vfork. But
# that'd just be testing a libc+kernel implementation detail.
strace_binary = "/usr/bin/strace"
# The only system calls we are interested in.
strace_filter = "--trace=clone,clone2,clone3,fork,vfork,exit,exit_group"
true_binary = "/bin/true"
strace_command = [strace_binary, strace_filter]
try:
does_strace_work_process = subprocess.run(
strace_command + [true_binary],
stderr=subprocess.PIPE,
stdout=subprocess.DEVNULL,
)
rc = does_strace_work_process.returncode
stderr = does_strace_work_process.stderr
except OSError:
rc = -1
stderr = ""
if rc or (b"+++ exited with 0 +++" not in stderr):
self.skipTest("strace not found or not working as expected.")
# Are intersted in the system calls:
# clone,clone2,clone3,fork,vfork,exit,exit_group
# Unfortunately using `--trace` with that list to strace fails because
# not all are supported on all platforms (ex. clone2 is ia64 only...)
# So instead use `%process` which is recommended by strace, and contains
# the above.
true_binary = "/bin/true"
strace_args = ["--trace=%process"]
with self.subTest(name="default_is_vfork"):
vfork_result = assert_python_ok(
"-c",
textwrap.dedent(f"""\
import subprocess
subprocess.check_call([{true_binary!r}])"""),
__run_using_command=strace_command,
vfork_result = strace_helper.strace_python(
f"""\
import subprocess
subprocess.check_call([{true_binary!r}])""",
strace_args
)
# Match both vfork() and clone(..., flags=...|CLONE_VFORK|...)
self.assertRegex(vfork_result.err, br"(?i)vfork")
self.assertRegex(vfork_result.event_bytes, br"(?i)vfork")
# Do NOT check that fork() or other clones did not happen.
# If the OS denys the vfork it'll fallback to plain fork().
@ -3465,9 +3455,8 @@ class POSIXProcessTestCase(BaseTestCase):
("setgroups", "", "extra_groups=[]", True),
):
with self.subTest(name=sub_name):
non_vfork_result = assert_python_ok(
"-c",
textwrap.dedent(f"""\
non_vfork_result = strace_helper.strace_python(
f"""\
import subprocess
{preamble}
try:
@ -3475,11 +3464,11 @@ class POSIXProcessTestCase(BaseTestCase):
[{true_binary!r}], **dict({sp_kwarg}))
except PermissionError:
if not {expect_permission_error}:
raise"""),
__run_using_command=strace_command,
raise""",
strace_args
)
# Ensure neither vfork() or clone(..., flags=...|CLONE_VFORK|...).
self.assertNotRegex(non_vfork_result.err, br"(?i)vfork")
self.assertNotRegex(non_vfork_result.event_bytes, br"(?i)vfork")
@unittest.skipUnless(mswindows, "Windows specific tests")