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183 lines
8.0 KiB
Plaintext
183 lines
8.0 KiB
Plaintext
Busybox TODO
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Stuff that needs to be done
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tr - missing SuS3 features in busybox 1.0pre10
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tr doesnt support [:blank:], [:digit:] or other predefined classes, [=equiv=]
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support is also missing.
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----
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find
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doesn't understand () or -exec, and these are actually used out in the real
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world. The "make uninstall" of lots of things (including busybox itself)
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breaks because of this, and sometimes even "make install" (like udev).
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----
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sh
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The command shell situation is a big mess. We have three or four different
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shells that don't really share any code, and the "standalone shell" doesn't
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work all that well (especially not in a chroot environment), due to apps not
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being reentrant. Unifying the various shells and figuring out a configurable
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way of adding the minimal set of bash features a given script uses is a big
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job, but it be a big improvement.
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Note: Rob Landley (rob@landley.net) is working on this one, but very slowly...
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---
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gzip
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Can't handle compressing multiple files at once. (I don't mean making a
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multiple file archive, I mean compressing more than one file at a time.)
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Some global variables aren't re-initialized between runs.
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---
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gunzip
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same problem as gzip. "gunzip one.gz two.gz three.gz" doesn't work for
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two.gz and three.gz due to global variables not getting reset.
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---
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diff
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We should have a diff -u command. We have patch, we should have diff
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(we only need to support unified diffs though).
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---
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fuser
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Would be nice. The basic susv3 options, plus fuser -k.
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---
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patch
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should have simple fuzz factor support to apply patches at an offset which
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shouldn't take up too much space.
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---
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man
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It would be nice to have a man command. Not one that handles troff or
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anything, just one that can handle preformatted ascii man pages, possibly
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compressed. This could probably be a script in the extras directory that
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calls cat/zcatbzcat | more
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---
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bzip2
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Compression-side support.
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Architectural issues:
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Do a SUSv3 audit
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Look at the full Single Unix Specification version 3 (available online at
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"http://www.opengroup.org/onlinepubs/009695399/nfindex.html") and
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figure out which of our apps are compliant, and what we're missing that
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we might actually care about.
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Even better would be some kind of automated compliance test harness that
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exercises each command line option and the various corner cases.
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--
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Unify archivers
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Lots of archivers have the same general infrastructure. The directory
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traversal code should be factored out, and the guts of each archiver could
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be some setup code and a series of callbacks for "add this file",
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"add this directory", "add this symlink" and so on.
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This could clean up tar and zip, and make it cheaper to add cpio and ar
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write support, and possibly even cheaply add things like mkisofs someday,
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if it becomes relevant.
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---
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Text buffer support.
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Several existing applets and potential additions (sort, vi, less...) read
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a whole file into memory and act on it. There might be an opportunity
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for shared code in there that could be moved into libbb...
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---
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Individual compilation of applets.
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It would be nice if busybox had the option to compile to individual applets,
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for people who want an alternate implementation less bloated than the gnu
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utils (or simply with less political baggage), but without it being one big
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executable.
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Turning libbb into a real dll is another possibility, especially if libbb
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could export some of the other library interfaces we've already more or less
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got the code for (like zlib).
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---
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buildroot - Make a "dogfood" option
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Busybox is now capable of replacing most gnu packages for real world use,
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such as developing software or in a live CD. A system built from busybox
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(1.00 with updated sort.c), uclibc 0.9.27, gcc, binutils, make, and a few
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other development tools (http://www.landley.net/code/firmware has an example
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system using autoconf, automake, bison, flex, libtools, m4, zlib,
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and groff: dunno what subset of that is actually necessary) is capable of
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rebuilding itself, from scratch, under itself.
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It would be a good "eating our own dogfood" test if buildroot had the option
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of using busybox instead of bzip2, coreutils, file, findutils, gawk, grep,
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inetutils, modutils, net-tools, procps, sed, shadow, sysklogd, sysvinit, tar,
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util-linux, and vim. Anything that's wrong with the resulting system, we
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can fix. (It would be nice to be able to upgrade busybox to be able to
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replace bash, diffutils, gzip, less, and patch as well.)
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---
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Memory Allocation
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We have a CONFIG_BUFFER mechanism that lets us select whether to do memory
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allocation on the stack or the heap. Unfortunately, we're not using it much.
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We need to audit our memory allocations and turn a lot of malloc/free calls
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into RESERVE_CONFIG_BUFFER/RELEASE_CONFIG_BUFFER.
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And while we're at it, many of the CONFIG_FEATURE_CLEAN_UP #ifdefs will be
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optimized out by the compiler in the stack allocation case (since there's no
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free for an alloca()), and this means that various cleanup loops that just
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call free might also be optimized out by the compiler if written right, so
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we can yank those #ifdefs too, and generally clean up the code.
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---
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Switch CONFIG_SYMBOLS to ENABLE_SYMBOLS
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In busybox 1.0 and earlier, configuration was done by CONFIG_SYMBOLS
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that were either defined or undefined to indicate whether the symbol was
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selected in the .config file. They were used with #ifdefs, ala:
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#ifdef CONFIG_SYMBOL
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if (other_test) {
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do_code();
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}
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#endif
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In 1.1, we have new ENABLE_SYMBOLS which are always defined (as 0 or 1),
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meaning you can still use them for preprocessor tests by replacing
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"#ifdef CONFIG_SYMBOL" with "#if ENABLE_SYMBOL". But more importantly, we
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can use them as a true or false test in normal C code:
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if (ENABLE_SYMBOL && other_test) {
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do_code();
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}
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(Optimizing away if() statements that resolve to a constant value
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is known as "dead code elimination", an optimization so old and simple that
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Turbo Pascal for DOS did it twenty years ago. Even modern mini-compilers
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like the Tiny C Compiler (tcc) and the Small Device C Compiler (SDCC)
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perform dead code elimination.)
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Right now, busybox.h is #including both "config.h" (defining the
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CONFIG_SYMBOLS) and "bb_config.h" (defining the ENABLE_SYMBOLS). At some
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point in the future, it would be nice to wean ourselves off of the
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CONFIG versions. (Among other things, some defective build environments
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leak the Linux kernel's CONFIG_SYMBOLS into the system's standard #include
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files. We've experienced collisions before.)
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---
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FEATURE_CLEAN_UP
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This is more an unresolved issue than a to-do item. More thought is needed.
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Normally we rely on exit() to free memory, close files, and unmap segments
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for us. This makes most calls to free(), close(), and unmap() optional in
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busybox applets that don't intend to run for very long, and optional stuff
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can be omitted to save size.
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The idea was raised that we could simulate fork/exit with setjmp/longjmp
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for _really_ brainless embedded systems, or speed up the standalone shell
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by not forking. Doing so would require a reliable FEATURE_CLEAN_UP.
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Unfortunately, this isn't as easy as it sounds.
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The problem is, lots of things exit(), sometimes unexpectedly (xmalloc())
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and sometimes reliably (bb_perror_msg_and_die() or show_usage()). This
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jumps out of the normal flow control and bypasses any cleanup code we
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put at the end of our applets.
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It's possible to add hooks to libbb functions like xmalloc() and bb_xopen()
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to add their entries to a linked list, which could be traversed and
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freed/closed automatically. (This would need to be able to free just the
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entries after a checkpoint to be usable for a forkless standalone shell.
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You don't want to free the shell's own resources.)
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Right now, FEATURE_CLEAN_UP is more or less a debugging aid, to make things
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like valgrind happy. It's also documentation of _what_ we're trusting
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exit() to clean up for us. But new infrastructure to auto-free stuff would
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render the existing FEATURE_CLEAN_UP code redundant.
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For right now, exit() handles it just fine.
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