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cmake,cpio: Move cpio(5) archive generation mechanism into script
Move the process of constructing an archive out into a new Python script
`make_cpio.py', and simplify the mechanism by directly using libarchive
to generate a file with the desired properties.
(I've previously run afoul of GNU cpio(1)'s `--reproducible' flag and
the detection machinery thereof; and of subtle and tricky-to-debug build
failures that occur partway through the generated command line. I opted
to rework the CMake into Python; the result is that the CMake here
simplifies to the invocation of a single, fairly simple tool with
appropriate arguments, instead of the composition of a fairly involved
shell script.)
r2: `cmake-format'.
r3: rebased, and reworded commit message to more clearly explain the
rationale for the change, as this was open to misinterpretation.
Signed-off-by: Jashank Jeremy <[email protected]>- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,221 @@ | ||
| #!/usr/bin/env python3 | ||
| #- | ||
| # SPDX-License-Identifier: BSD-2-Clause | ||
| # | ||
| # Copyright 2020, Data61 | ||
| # Commonwealth Scientific and Industrial Research Organisation (CSIRO) | ||
| # ABN 41 687 119 230. | ||
| # | ||
| # This software may be distributed and modified according to the terms | ||
| # of the BSD 2-Clause license. Note that NO WARRANTY is provided. | ||
| # See "LICENSE_BSD2.txt" for details. | ||
| # | ||
| # @TAG(DATA61_BSD) | ||
| # | ||
|
|
||
| # | ||
| # make_cpio --- create a newc-style cpio(5) archive without metadata | ||
| # | ||
| # previously, in an attempt to create a ``reproducible'' cpio(5) archive | ||
| # (i.e., without any especially-variable metadata), and as described in | ||
| # `cmake-tool/helpers/cpio.cmake': | ||
| # | ||
| # > Try and generate reproducible cpio meta-data as we do this: | ||
| # > - touch -d @0 file sets the modified time to 0 | ||
| # > - --owner=root:root sets user and group values to 0:0 | ||
| # > - --reproducible creates reproducible archives with consistent | ||
| # > inodes and device numbering | ||
| # | ||
| # that is, for every file to be archived: a copy was made, to archive to | ||
| # throw away its partially- or fully-qualified path name; a GNU | ||
| # extension to touch(1) threw its timestamps away, and, via a GNU | ||
| # extension to cpio(1), its owner, group, device, and inode number were | ||
| # thrown away. | ||
| # | ||
| # there must be a better way! | ||
| # | ||
| # % make_cpio archive.cpio ../kernel.elf ../kernel.dtb | ||
| # | ||
| # (I wrote this in C first, and then was defeated by the cmake build | ||
| # system in my attempt to add it to the build. this is a very literal | ||
| # translation of that C into Python, which I don't know very well.) | ||
| # | ||
| # 2020-09-03 Jashank Jeremy <[email protected]> | ||
| # | ||
|
|
||
| import ctypes | ||
| import ctypes.util | ||
| from ctypes import c_char_p, c_int, c_int64, c_longlong, c_size_t, c_ssize_t, c_uint, c_void_p, c_wchar_p | ||
| import os | ||
| import stat | ||
| import sys | ||
| from typing import Any, List, NoReturn, Optional | ||
|
|
||
| # constants from <sysexits.h>: | ||
| EX_USAGE : int = 64 | ||
| EX_SOFTWARE : int = 70 | ||
|
|
||
| # constants from <archive.h> | ||
| ARCHIVE_EOF = 1 # Found end of archive. | ||
| ARCHIVE_OK = 0 # Operation was successful. | ||
| ARCHIVE_RETRY = -10 # Retry might succeed. | ||
| ARCHIVE_WARN = -20 # Partial success. | ||
| ARCHIVE_FAILED = -25 # Current operation cannot complete. | ||
| ARCHIVE_FATAL = -30 # No more operations are possible. | ||
|
|
||
| def main (args: List[str]) -> int: | ||
| if len(args) < 2: | ||
| errx(EX_USAGE, "usage: make_cpio archive-file file...") | ||
| argv0, archive_file, *files = args | ||
|
|
||
| A = load_libarchive() | ||
|
|
||
| ark = A.archive_write_new() | ||
| if ark is None: | ||
| err (EX_SOFTWARE, "couldn't write archive object") | ||
|
|
||
| if A.archive_write_set_format_cpio_newc(ark) != ARCHIVE_OK or \ | ||
| A.archive_write_open_filename_w(ark, archive_file) != ARCHIVE_OK: | ||
| warnx(f'{archive_file}: {A.archive_error_string(ark)}') | ||
| A.archive_write_fail(ark) | ||
| A.archive_write_free(ark) | ||
| return -1 | ||
|
|
||
| for i, file in enumerate(files): | ||
| basename_idx = file.rfind('/') | ||
| if basename_idx == -1 or file[basename_idx:] == '/': | ||
| warnx(f'skipping {file}: nonsense filename') | ||
| continue | ||
|
|
||
| basename = file[basename_idx + 1:] | ||
| entry = A.archive_entry_new() | ||
| if entry is None: | ||
| warnx(f"skipping {file}: couldn't make archive entry object") | ||
| continue | ||
|
|
||
| fd = os.open(file, os.O_RDONLY) | ||
| if fd == -1: | ||
| warnx(f"skipping {file}: couldn't open") | ||
| A.archive_entry_free(entry) | ||
| continue | ||
|
|
||
| sb = os.fstat(fd) | ||
| # what if it failed, Python? | ||
|
|
||
| if not stat.S_ISREG(sb.st_mode): | ||
| warnx(f'skipping {file}: not a regular file') | ||
| A.archive_entry_free(entry) | ||
| os.close(fd) | ||
| continue | ||
|
|
||
| # | ||
| # Surprise! `os.fstat' returns a `stat_result', which is some | ||
| # weirdo class that doesn't derive from `ctypes.Structure' --- | ||
| # which it *should* --- and therefore you cannot pass it around | ||
| # as if it were a `struct stat *'. | ||
| # | ||
| # This means we can't just use `archive_entry_copy_stat(3)', | ||
| # because we cannot pass it the results of the `fstat(2)' we | ||
| # just did. Arrrrgh! | ||
| # | ||
| # A.archive_entry_copy_stat (entry, &sbuf); | ||
|
|
||
| A.archive_entry_set_size (entry, sb.st_size); | ||
| A.archive_entry_set_mode (entry, sb.st_mode); | ||
| A.archive_entry_update_pathname_utf8 (entry, c_char_p(basename.encode('utf8'))); | ||
| A.archive_entry_set_uid (entry, 0); | ||
| A.archive_entry_set_gid (entry, 0); | ||
| A.archive_entry_unset_ctime (entry); | ||
| A.archive_entry_unset_birthtime (entry); | ||
| A.archive_entry_unset_mtime (entry); | ||
| A.archive_entry_unset_atime (entry); | ||
| A.archive_entry_set_dev (entry, 0); | ||
| A.archive_entry_set_ino64 (entry, 0); | ||
|
|
||
| if A.archive_write_header (ark, entry) != ARCHIVE_OK: | ||
| warnx(f"abandoning {file}: couldn't write header: {A.archive_error_string(ark)}") | ||
| A.archive_entry_free(entry) | ||
| os.close(fd) | ||
| continue | ||
|
|
||
| bufsiz = 4096 | ||
| while True: | ||
| buf = os.read(fd, bufsiz) | ||
| if not buf or len(buf) == 0: break | ||
| assert len(buf) > 0 | ||
| A.archive_write_data(ark, buf, len(buf)) | ||
|
|
||
| if A.archive_write_finish_entry(ark) != ARCHIVE_OK: | ||
| warnx(f"finishing '{file}': {A.archive_error_string(ark)}"); | ||
| os.close(fd) | ||
| A.archive_entry_free(entry) | ||
|
|
||
| A.archive_write_close(ark) | ||
| A.archive_write_free(ark) | ||
| return 0 | ||
|
|
||
|
|
||
| def load_libarchive(): | ||
| libarchive_path \ | ||
| = os.environ.get('LIBARCHIVE') \ | ||
| or ctypes.util.find_library('archive') | ||
| if libarchive_path is None: | ||
| errx(EX_SOFTWARE, "cannot find libarchive") | ||
| libarchive = ctypes.cdll.LoadLibrary(libarchive_path) | ||
| declare_libarchive_types(libarchive) | ||
| return libarchive | ||
|
|
||
| # | ||
| # the python binding doesn't expose parts of the `libarchive' api. | ||
| # because why would you ever want to write python. | ||
| # | ||
|
|
||
| c_archive_p = c_void_p | ||
| c_archive_entry_p = c_void_p | ||
|
|
||
| def declare_libarchive_types(a: ctypes.CDLL): | ||
| def typesig (a: ctypes.CDLL, f: str, argty: List[Any], retty: Any): | ||
| fn = getattr(a, 'archive_' + f) | ||
| fn.argtypes = argty | ||
| fn.restype = retty | ||
| return fn | ||
|
|
||
| typesig(a, 'write_new', [], c_archive_p) | ||
| typesig(a, 'write_set_format_cpio_newc', [c_archive_p], c_int) | ||
| typesig(a, 'write_open_filename_w', [c_archive_p, c_wchar_p], c_int) | ||
| typesig(a, 'entry_new', [], c_archive_entry_p) | ||
| typesig(a, 'entry_free', [], c_archive_entry_p) | ||
| typesig(a, 'entry_set_size', [c_archive_entry_p, c_longlong], None) | ||
| typesig(a, 'entry_set_mode', [c_archive_entry_p, c_int], None) | ||
| typesig(a, 'entry_update_pathname_utf8', [c_archive_entry_p, c_char_p], None) | ||
| typesig(a, 'entry_set_uid', [c_archive_entry_p, c_longlong], None) | ||
| typesig(a, 'entry_set_gid', [c_archive_entry_p, c_longlong], None) | ||
| typesig(a, 'entry_unset_ctime', [c_archive_entry_p], None) | ||
| typesig(a, 'entry_unset_birthtime', [c_archive_entry_p], None) | ||
| typesig(a, 'entry_unset_mtime', [c_archive_entry_p], None) | ||
| typesig(a, 'entry_unset_atime', [c_archive_entry_p], None) | ||
| typesig(a, 'entry_set_dev', [c_archive_entry_p, c_uint], None) | ||
| typesig(a, 'entry_set_ino64', [c_archive_entry_p, c_int64], None) | ||
| typesig(a, 'write_header', [c_archive_p, c_archive_entry_p], c_int) | ||
| typesig(a, 'write_data', [c_archive_p, c_void_p, c_size_t], c_ssize_t) | ||
| typesig(a, 'write_finish_entry', [c_archive_p], c_int) | ||
| typesig(a, 'entry_free', [c_archive_entry_p], None) | ||
| typesig(a, 'error_string', [c_archive_p], c_char_p) | ||
| typesig(a, 'write_close', [c_archive_p], c_int) | ||
| typesig(a, 'write_fail', [c_archive_p], None) | ||
| typesig(a, 'write_free', [c_archive_p], None) | ||
|
|
||
|
|
||
| ######################################################################## | ||
|
|
||
| def warnx (message: str) -> None: | ||
| sys.stderr.write(message + "\n") | ||
| def warn (message: str) -> None: | ||
| warnx(f'{message}: <errno>') | ||
| def errx (code: int, message: str) -> NoReturn: | ||
| warnx(message); sys.exit(code) | ||
| def err (code: int, message: str) -> NoReturn: | ||
| warn(message); sys.exit(code) | ||
|
|
||
| if __name__ == "__main__": | ||
| sys.exit(main(sys.argv)) |