test_signals.py

# Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
# SPDX-License-Identifier: Apache-2.0
"""Tests scenarios for Firecracker signal handling."""

importjson
importos
importresourceasres
fromsignalimportSIGBUS, SIGHUP, SIGILL, SIGPIPE, SIGSEGV, SIGSYS, SIGXCPU, SIGXFSZ
fromtimeimportsleep

importpytest

signum_str= {
SIGBUS: "sigbus",
SIGSEGV: "sigsegv",
SIGXFSZ: "sigxfsz",
SIGXCPU: "sigxcpu",
SIGPIPE: "sigpipe",
SIGHUP: "sighup",
SIGILL: "sigill",
SIGSYS: "sigsys",
}


@pytest.mark.parametrize(
"signum", [SIGBUS, SIGSEGV, SIGXFSZ, SIGXCPU, SIGPIPE, SIGHUP, SIGILL, SIGSYS]
)
deftest_generic_signal_handler(uvm_plain, signum):
"""
 Test signal handling for all handled signals.
 """
microvm=uvm_plain
microvm.spawn()

# We don't need to monitor the memory for this test.
microvm.memory_monitor=None

microvm.basic_config()
microvm.start()
sleep(0.5)

metrics_jail_path=microvm.metrics_file
metrics_fd=open(metrics_jail_path, encoding="utf-8")
line_metrics=metrics_fd.readlines()
assertlen(line_metrics) ==1

os.kill(microvm.firecracker_pid, signum)
# Firecracker gracefully handles SIGPIPE (doesn't terminate).
ifsignum==int(SIGPIPE):
msg="Received signal 13"
# Flush metrics to file, so we can see the SIGPIPE at bottom assert.
# This is going to fail if process has exited.
microvm.api.actions.put(action_type="FlushMetrics")
else:
msg="Shutting down VM after intercepting signal {}".format(signum)

microvm.mark_killed()

microvm.check_log_message(msg)

ifsignum!=SIGSYS:
metric_line=json.loads(metrics_fd.readlines()[0])
assertmetric_line["signals"][signum_str[signum]] ==1


deftest_sigxfsz_handler(uvm_plain_rw):
"""
 Test intercepting and handling SIGXFSZ.
 """
microvm=uvm_plain_rw
microvm.spawn()

# We don't need to monitor the memory for this test.
microvm.memory_monitor=None

# We need to use the Sync file engine type. If we use io_uring we will not
# get a SIGXFSZ. We'll instead get an errno 27 File too large as the
# completed entry status code.
microvm.basic_config(rootfs_io_engine="Sync")
microvm.start()

metrics_jail_path=microvm.metrics_file
metrics_fd=open(metrics_jail_path, encoding="utf-8")
line_metrics=metrics_fd.readlines()
assertlen(line_metrics) ==1

firecracker_pid=microvm.firecracker_pid
size=os.path.getsize(metrics_jail_path)
# The SIGXFSZ is triggered because the size of rootfs is bigger than
# the size of metrics file times 3. Since the metrics file is flushed
# twice we have to make sure that the limit is bigger than that
# in order to make sure the SIGXFSZ metric is logged
res.prlimit(firecracker_pid, res.RLIMIT_FSIZE, (size*3, res.RLIM_INFINITY))

microvm.mark_killed()

msg="Shutting down VM after intercepting signal 25, code 0"
microvm.check_log_message(msg)
metric_line=json.loads(metrics_fd.readlines()[0])
assertmetric_line["signals"]["sigxfsz"] ==1


deftest_handled_signals(uvm_plain):
"""
 Test that handled signals don't kill the microVM.
 """
microvm=uvm_plain
microvm.spawn()

# We don't need to monitor the memory for this test.
microvm.memory_monitor=None

microvm.basic_config(vcpu_count=2)
microvm.add_net_iface()
microvm.start()

# Open a SSH connection to validate the microVM stays alive.
# Just validate a simple command: `nproc`
cmd="nproc"
_, stdout, stderr=microvm.ssh.run(cmd)
assertstderr==""
assertint(stdout) ==2

# We have a handler installed for this signal.
# The 35 is the SIGRTMIN for musl libc.
# We hardcode this value since the SIGRTMIN python reports
# is 34, which is likely the one for glibc.
os.kill(microvm.firecracker_pid, 35)

# Validate the microVM is still up and running.
_, stdout, stderr=microvm.ssh.run(cmd)
assertstderr==""
assertint(stdout) ==2