mmdebstrap/ldconfig.fakechroot

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#!/usr/bin/env python3
#
# This script is in the public domain
#
# Author: Johannes Schauer Marin Rodrigues <josch@mister-muffin.de>
#
# This is command substitution for ldconfig under fakechroot:
#
# export FAKECHROOT_CMD_SUBST=/sbin/ldconfig=/path/to/ldconfig.fakechroot
#
# Statically linked binaries cannot work with fakechroot and thus have to be
# replaced by either /bin/true or a more clever solution like this one. The
# ldconfig command supports the -r option which allows passing a chroot
# directory for ldconfig to work in. This can be used to run ldconfig without
# fakechroot but still let it create /etc/ld.so.cache inside the chroot.
#
# Since absolute symlinks are broken without fakechroot to translate them,
# we read /etc/ld.so.conf and turn all absolute symlink shared libraries into
# relative ones. At program exit, the original state is restored.
import os
import sys
import subprocess
import atexit
import glob
from pathlib import Path
symlinks = []
def restore_symlinks():
for (link, target, atime, mtime) in symlinks:
link.unlink()
link.symlink_to(target)
os.utime(link, times=None, ns=(atime, mtime), follow_symlinks=False)
atexit.register(restore_symlinks)
def get_libdirs(chroot, configs):
res = []
for conf in configs:
for line in (Path(conf)).read_text().splitlines():
line = line.strip()
if not line:
continue
if line.startswith("#"):
continue
if line.startswith("include "):
assert line.startswith("include /")
res.extend(
get_libdirs(chroot, chroot.glob(line.removeprefix("include /")))
)
continue
assert line.startswith("/"), line
line = line.lstrip("/")
if not (chroot / Path(line)).is_dir():
continue
for f in (chroot / Path(line)).iterdir():
if not f.is_symlink():
continue
linktarget = f.readlink()
# make sure that the linktarget is an absolute path inside the
# chroot
if not str(linktarget).startswith("/"):
continue
if chroot not in linktarget.parents:
continue
# store original link so that we can restore it later
symlinks.append(
(f, linktarget, f.lstat().st_atime_ns, f.lstat().st_mtime_ns)
)
# replace absolute symlink by relative link
relative = os.path.relpath(linktarget, f.parent)
f.unlink()
f.symlink_to(relative)
return res
def main():
if "FAKECHROOT_BASE_ORIG" not in os.environ:
print("FAKECHROOT_BASE_ORIG is not set", file=sys.stderr)
print(
"must be executed under fakechroot using FAKECHROOT_CMD_SUBST",
file=sys.stderr,
)
sys.exit(1)
chroot = Path(os.environ["FAKECHROOT_BASE_ORIG"])
2021-09-23 04:07:48 +00:00
# if chrootless mode is used from within a fakechroot chroot, then
# FAKECHROOT_BASE_ORIG will point at the outer chroot. We want to use
# the path from DPKG_ROOT inside of that instead
if os.environ.get("DPKG_ROOT", "") not in ["", "/"]:
chroot /= os.environ["DPKG_ROOT"].lstrip("/")
if not (chroot / "sbin" / "ldconfig").exists():
sys.exit(0)
(chroot / "var" / "cache" / "ldconfig").mkdir(
mode=0o700, parents=True, exist_ok=True
)
for d in get_libdirs(chroot, [chroot / "etc" / "ld.so.conf"]):
make_relative(d)
# we add any additional arguments before "-r" such that any other "-r"
# option will be overwritten by the one we set
subprocess.check_call(
[chroot / "sbin" / "ldconfig"] + sys.argv[1:] + ["-r", chroot]
)
if __name__ == "__main__":
main()