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# Copyright (c) Meta Platforms, Inc. and affiliates.
# SPDX-License-Identifier: LGPL-2.1-or-later
import ctypes
import os
import re
import subprocess
import sys
from _drgn_util.platform import NORMALIZED_MACHINE_NAME, SYS
KEXEC_FILE_ON_CRASH = 2
KEXEC_FILE_NO_INITRAMFS = 4
def main() -> None:
with open("/proc/cmdline", "rb") as f:
cmdline = f.read().rstrip(b"\n")
cmdline = re.sub(rb"(^|\s)crashkernel=\S+", b"", cmdline)
# `nokaslr` is required to avoid sporadically failing to reserve space for the
# capture kernel
cmdline += b" nokaslr"
if os.getenv("KDUMP_NEEDS_NOSMP"):
# `nosmp` is required to avoid QEMU sporadically failing an internal
# assertion when using emulation.
cmdline += b" nosmp"
# On RISC-V, kexec_file_load() is supported for Image (vmlinuz) files only
# since Linux kernel commit 809a11eea8e8 ("riscv: kexec_file: Support
# loading Image binary file") (in v6.16), but for ELF files since Linux
# kernel commit 6261586e0c91 ("RISC-V: Add kexec_file support") (in v5.19).
if NORMALIZED_MACHINE_NAME == "riscv64":
kernel_image = f"/lib/modules/{os.uname().release}/build/vmlinux"
else:
kernel_image = f"/lib/modules/{os.uname().release}/vmlinuz"
# On x86-64 and RISC-V, kexec_file_load() is supported on all kernel
# versions we care about, and it's simple enough to call ourselves. On
# other architectures, we just use kexec(8).
if NORMALIZED_MACHINE_NAME in {"x86_64", "riscv64"}:
syscall = ctypes.CDLL(None, use_errno=True).syscall
syscall.restype = ctypes.c_long
with open(kernel_image, "rb") as kernel:
if syscall(
ctypes.c_long(SYS["kexec_file_load"]),
ctypes.c_int(kernel.fileno()),
ctypes.c_int(-1),
ctypes.c_ulong(len(cmdline) + 1),
ctypes.c_char_p(cmdline + b"\0"),
ctypes.c_ulong(KEXEC_FILE_ON_CRASH | KEXEC_FILE_NO_INITRAMFS),
):
errno = ctypes.get_errno()
raise OSError(errno, os.strerror(errno))
else:
subprocess.check_call(
[
"kexec",
"--load-panic",
"--kexec-syscall-auto",
"--command-line=" + cmdline.decode(),
kernel_image,
]
)
with open("/proc/self/comm", "w") as f:
f.write("selfdestruct")
# Avoid panicking from CPU 0 on s390x. See _skip_if_cpu0_on_s390x().
if NORMALIZED_MACHINE_NAME == "s390x":
cpus = os.sched_getaffinity(0)
cpus.remove(0)
if cpus:
os.sched_setaffinity(0, cpus)
# Try the drgn_test kmod crash method first.
try:
with open("/sys/kernel/drgn_test/crash", "w") as f:
f.write("1")
except FileNotFoundError:
pass
# Fall back to sysrq-trigger.
with open("/proc/sysrq-trigger", "w") as f:
f.write("c")
if __name__ == "__main__":
if os.path.exists("/proc/vmcore") and len(sys.argv) > 1:
# We're in the kdump kernel already. Assume the user wanted to run
# a command within it.
os.execvp(sys.argv[1], sys.argv[1:])
main()
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