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Hedy88 2026-08-27 22:50:44 +01:00
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151
tools/run_vm.py
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@ -11,12 +11,19 @@ examples:
python3 tools/run_vm.py --fetch-busybox --nographic
python3 tools/run_vm.py --kernel /boot/vmlinuz-$(uname -r) --gdb
python3 tools/run_vm.py --config my-init.rc
python3 tools/run_vm.py --selinux # boot with the host SELinux policy (permissive)
inside the guest: log in as `root` (passwordless by default, or use
--root-password), then `kill -TERM 1` -> reboot path, `kill -INT 1` ->
--root-password). `bctl status` / `bctl shutdown poweroff` drive the
init over its control socket; `kill -TERM 1` -> reboot path, `kill -INT 1` ->
poweroff path.
bajia is built statically by default: a dynamic binary cannot exec inside the
initramfs (no libc there). Use --no-static only if you ship the libs too.
--selinux flips bajia to a dynamic build (there is no static libselinux on
Fedora), bundles libselinux/libpcre2/glibc + the loader into the initramfs,
and copies the host's /etc/selinux/<type> policy (loaded permissively). This
is the first stage of bootstrapping a real policy: boot, read the `avc:
denied` lines, refine, then flip to enforcing.
"""
from __future__ import annotations
@ -60,11 +67,11 @@ on shutdown
service console-serial /bin/getty -L ttyS0 115200 vt100
console
respawn always
respawn = always
service console-tty1 /bin/getty -L 38400 tty1 vt100
console
respawn always
respawn = always
"""
# source tarballs of busybox (github.com/mirror/busybox); a pinned tag is
@ -77,18 +84,19 @@ BUSYBOX_URLS = [
BUSYBOX_APPLETS = ["sh", "getty", "mount", "sync", "ls", "cat", "kill", "ps",
"poweroff", "reboot", "mkdir", "mknod", "login"]
def run(cmd, **kw) -> subprocess.CompletedProcess:
print("$", " ".join(str(c) for c in cmd))
return subprocess.run(cmd, **kw)
def build_bajia(static: bool) -> Path:
def build_bajia(static: bool, selinux: bool = False) -> Path:
env = dict(os.environ)
cfg = ["python3", "configure.py"]
if selinux:
cfg.append("--selinux")
if static:
print("building bajia (statically linked)...")
env["CXX"] = env.get("CXX", "g++") + " -static"
r = run(["python3", "configure.py"], env=env)
r = run(cfg, env=env)
if r.returncode != 0:
sys.exit("configure.py failed")
r = run(["ninja", "-C", str(BUILD)])
@ -96,6 +104,64 @@ def build_bajia(static: bool) -> Path:
sys.exit("ninja build failed")
return BAJIA
SELINUX_CONFIG = Path("/etc/selinux/config")
def host_selinux_type() -> str:
if not SELINUX_CONFIG.is_file():
return "targeted"
for line in SELINUX_CONFIG.read_text().splitlines():
line = line.strip()
if line.startswith("SELINUXTYPE="):
return line.split("=", 1)[1].strip().strip('"')
return "targeted"
def selinux_policy_files() -> list[tuple[Path, str]]:
"""Return (host_path, initramfs_relative_path) pairs for the policy payload."""
typ = host_selinux_type()
base = Path("/etc/selinux") / typ
pols = sorted((base / "policy").glob("policy.*"))
if not pols:
sys.exit(f"--selinux: no policy under {base / 'policy'}/ "
"(install selinux-policy-targeted, a Fedora SELinux host is assumed)")
# libselinux 3.x looks for the restorecon table at contexts/files/file_contexts
# (older versions used contexts/file_contexts); bundle whichever exists.
fc = next((p for p in (base / "contexts" / "files" / "file_contexts",
base / "contexts" / "file_contexts") if p.is_file()), None)
if not fc:
sys.exit(f"--selinux: missing file_contexts under {base / 'contexts'}/")
fc_rel = "etc/selinux/" + typ + "/" + str(fc.relative_to(base))
prefix = f"etc/selinux/{typ}/"
return [(pols[-1], prefix + f"policy/{pols[-1].name}"),
(fc, fc_rel)]
def bundle_dynamic_libs(init: Path, root: Path) -> None:
"""Copy the dynamic loader + resolved .so deps into the initramfs,
mirroring their absolute paths so the interpreter finds them."""
out = run(["ldd", str(init)], capture_output=True, text=True)
if out.returncode != 0:
sys.exit("ldd failed on " + str(init))
libs: list[str] = []
for line in out.stdout.splitlines():
line = line.strip()
if "=>" in line:
path = line.split("=>", 1)[1].strip().split(" ", 1)[0].strip()
else: # "linux-vdso" or the loader line "/lib64/ld-linux-x86-64.so.2 (0x...)"
path = line.split(" ", 1)[0].strip()
if path.startswith("/") and Path(path).is_file():
libs.append(path)
seen: set[str] = set()
for lib in libs: # preserve first-seen order
if lib in seen:
continue
seen.add(lib)
dst = root / lib.lstrip("/")
dst.parent.mkdir(parents=True, exist_ok=True)
shutil.copy(lib, dst)
dst.chmod(0o755)
print("bundled dynamic libs:", ", ".join(seen))
if not seen:
sys.exit("ldd reported no libraries - unexpected for a dynamic binary")
def find_kernel() -> Path | None:
p = Path("/boot/vmlinuz-" + os.uname().release)
if p.is_file():
@ -194,8 +260,20 @@ def root_passwd_line(password: str | None) -> str:
field = crypt_password(password) if password else ""
return f"root:{field}:0:0:root:/:/bin/sh\n"
# appended to the test init.rc; started on boot, prints the exec context of a
# seclabel'd service and of init itself, then exits.
SELINUX_RC_PROBE = """
service selinux-probe /bin/sh -c "echo probe-ctx=$(cat /proc/self/attr/current) init-ctx=$(cat /proc/1/attr/current)"
console
seclabel = system_u:system_r:init_t:s0
respawn = never
on boot
start selinux-probe
"""
def build_initramfs(init: Path, busybox: Path, rc_text: str, root_password: str | None,
keep: bool) -> Path:
selinux: bool, keep: bool) -> Path:
if not shutil.which("cpio"):
sys.exit("cpio not found (install cpio)")
root = Path(tempfile.mkdtemp(prefix="bajia-root-"))
@ -204,19 +282,52 @@ def build_initramfs(init: Path, busybox: Path, rc_text: str, root_password: str
"dev", "proc", "sys", "run", "tmp"):
(root / sub).mkdir(parents=True)
if selinux:
for src, rel in selinux_policy_files():
dst = root / rel
dst.parent.mkdir(parents=True, exist_ok=True)
shutil.copy(src, dst)
selcfg = root / "etc" / "selinux" / "config"
selcfg.write_text(f"SELINUX=permissive\nSELINUXTYPE={host_selinux_type()}\n")
bundle_dynamic_libs(init, root)
elif not is_static(init):
print("warning: bajia is dynamically linked; /init will fail to exec "
"inside the initramfs (error -2). Rebuild with --no-static "
"unset (static is the default) or drop --no-build.")
if selinux:
rc_text = rc_text + SELINUX_RC_PROBE
shutil.copy(init, root / "init")
(root / "init").chmod(0o755)
ctl = BUILD / "bctl"
if ctl.is_file():
shutil.copy(ctl, root / "bin" / "bctl")
(root / "bin" / "bctl").chmod(0o755)
shutil.copy(busybox, root / "bin" / "busybox")
(root / "bin" / "busybox").chmod(0o755)
for applet in BUSYBOX_APPLETS:
(root / "bin" / applet).symlink_to("busybox")
(root / "etc" / "bajia" / "init.rc").write_text(rc_text)
(root / "etc" / "passwd").write_text(root_passwd_line(root_password))
(root / "etc" / "passwd").write_text(
root_passwd_line(root_password) +
"nobody:x:65534:65534:nobody:/:/bin/sh\n")
(root / "etc" / "group").write_text(
"root:x:0:\n"
"nobody:x:65534:\n"
"daemon:x:1:\n")
# The staging tree is owned by the host user and mkdtemp makes the
# top dir 0700; GNU cpio preserves both, so without this the guest's
# "/" would be mode 0700 owned by uid 1000 -- fine for root services,
# but dropped-privilege services couldn't traverse it. Stamp owner
# root:root (no host chown needed) and make the root traversable.
p = run(["bash", "-c",
"cd \"$1\" && find . -print0 | cpio --null -o -H newc",
"cd \"$1\" && chmod 0755 . && "
"find . -print0 | cpio --null -o -H newc --owner=0:0",
"bajia-initramfs", str(root)], stdout=subprocess.PIPE)
if p.returncode != 0:
sys.exit("cpio packing failed")
@ -235,6 +346,9 @@ def qemu_command(kernel: Path, initrd: Path, args: argparse.Namespace) -> list[s
display = args.display
if display is None:
display = "gtk" if os.environ.get("DISPLAY") else "none"
append = (f"console=tty1 console=ttyS0 rdinit=/init loglevel={args.loglevel}")
if args.selinux:
append += " selinux=1 enforcing=0"
cmd = [
qemu,
"-M", args.machine,
@ -242,13 +356,15 @@ def qemu_command(kernel: Path, initrd: Path, args: argparse.Namespace) -> list[s
"-smp", str(args.smp),
"-kernel", str(kernel),
"-initrd", str(initrd),
"-append",
f"console=tty1 console=ttyS0 rdinit=/init loglevel={args.loglevel}",
"-append", append,
"-display", display,
"-serial", "stdio",
]
if args.nographic:
cmd[cmd.index("-display") + 1] = "none"
if args.serial_log:
cmd[cmd.index("-display") + 1] = "none"
cmd[cmd.index("-serial") + 1] = f"file:{args.serial_log}"
if args.gdb or args.wait_gdb:
cmd += ["-gdb", "tcp::1234", "-S"] if args.wait_gdb else ["-s"]
cmd += ["-no-reboot", "-no-shutdown"]
@ -287,12 +403,17 @@ def main() -> int:
help="pause the machine until a gdb client attaches")
ap.add_argument("--keep-initramfs", action="store_true",
help="don't delete the initramfs staging tree")
ap.add_argument("--selinux", action="store_true",
help="bundle the host SELinux policy + libs, boot permissive")
ap.add_argument("--serial-log", type=Path,
help="write the serial console to this file (forces -display none)")
args = ap.parse_args()
init = BAJIA if args.no_build else build_bajia(not args.no_static)
static = not args.no_static and not args.selinux
init = BAJIA if args.no_build else build_bajia(static, args.selinux)
if not init.is_file():
sys.exit(f"bajia not built at {init} (drop --no-build)")
if not is_static(init):
if not static and not args.selinux and not is_static(init):
print("warning: bajia is dynamically linked; /init will fail to exec "
"inside the initramfs (error -2). Rebuild with --no-static "
"unset (static is the default) or drop --no-build.")
@ -315,7 +436,7 @@ def main() -> int:
rc_text = args.config.read_text() if args.config else DEFAULT_RC
initrd = build_initramfs(init, busybox, rc_text, args.root_password,
keep=args.keep_initramfs)
selinux=args.selinux, keep=args.keep_initramfs)
print("initramfs:", initrd, f"({initrd.stat().st_size / 1024:.0f} KB)")
cmd = qemu_command(kernel, initrd, args)