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Makes tail -f for multiple files display the header only if another (ie. not currently displayed) file changed. Signed-off-by: Bartosz Golaszewski <bartekgola@gmail.com> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
263 lines
11 KiB
Plaintext
263 lines
11 KiB
Plaintext
Busybox TODO
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Harvest patches from
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http://git.openembedded.org/cgit.cgi/openembedded/tree/recipes/busybox/
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https://dev.openwrt.org/browser/trunk/package/busybox/patches/
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Stuff that needs to be done. This is organized by who plans to get around to
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doing it eventually, but that doesn't mean they "own" the item. If you want to
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do one of these bounce an email off the person it's listed under to see if they
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have any suggestions how they plan to go about it, and to minimize conflicts
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between your work and theirs. But otherwise, all of these are fair game.
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Rob Landley suggested this:
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Implement bb_realpath() that can handle NULL on non-glibc.
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sh
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The command shell situation is a mess. We have two 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.
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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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Internationalization
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How much internationalization should we do?
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The low hanging fruit is UTF-8 character set support. We should do this.
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See TODO_unicode file.
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We also have lots of hardwired english text messages. Consolidating this
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into some kind of message table not only makes translation easier, but
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also allows us to consolidate redundant (or close) strings.
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We probably don't want to be bloated with locale support. (Not unless we
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can cleanly export it from our underlying C library without having to
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concern ourselves with it directly. Perhaps a few specific things like a
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config option for "date" are low hanging fruit here?)
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What level should things happen at? How much do we care about
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internationalizing the text console when X11 and xterms are so much better
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at it? (There's some infrastructure here we don't implement: The
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"unicode_start" and "unicode_stop" shell scripts need "vt-is-UTF8" and a
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--unicode option to loadkeys. That implies a real loadkeys/dumpkeys
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implementation to replace loadkmap/dumpkmap. Plus messing with console font
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loading. Is it worth it, or do we just say "use X"?)
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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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buildroot - Make a "dogfood" option
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Busybox 1.1 will be capable of replacing most gnu packages for real world
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use, such as developing software or in a live CD. It needs wider testing.
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Busybox should now be able to replace bzip2, coreutils, e2fsprogs, file,
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findutils, gawk, grep, inetutils, less, modutils, net-tools, patch, procps,
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sed, shadow, sysklogd, sysvinit, tar, util-linux, and vim. The resulting
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system should be self-hosting (I.E. able to rebuild itself from source
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code). This means it would need (at least) binutils, gcc, and make, or
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equivalents.
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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 a "make allyesconfig" busybox instead of the all of the above
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packages. Anything that's wrong with the resulting system, we can fix. (It
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would be nice to be able to upgrade busybox to be able to replace bash and
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diffutils as well, but we're not there yet.)
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One example of an existing system that does this already is Firmware Linux:
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http://www.landley.net/code/firmware
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initramfs
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Busybox should have a sample initramfs build script. This depends on
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shell, mdev, and switch_root.
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mkdep
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Write a mkdep that doesn't segfault if there's a directory it doesn't
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have permission to read, isn't based on manually editing the output of
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lexx and yacc, doesn't make such a mess under include/config, etc.
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Group globals into unions of structures.
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Go through and turn all the global and static variables into structures,
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and have all those structures be in a big union shared between processes,
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so busybox uses less bss. (This is a big win on nommu machines.) See
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sed.c and mdev.c for examples.
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Go through bugs.busybox.net and close out all of that somehow.
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This one's open to everybody, but I'll wind up doing it...
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Bernhard Reutner-Fischer <busybox@busybox.net> suggests to look at these:
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New debug options:
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-Wlarger-than-127
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Cleanup any big users
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Collate BUFSIZ IOBUF_SIZE MY_BUF_SIZE PIPE_PROGRESS_SIZE BUFSIZE PIPESIZE
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make bb_common_bufsiz1 configurable, size wise.
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make pipesize configurable, size wise.
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Use bb_common_bufsiz1 throughout applets!
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As yet unclaimed:
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----
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diff
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Make sure we handle empty files properly:
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From the patch man page:
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you can remove a file by sending out a context diff that compares
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the file to be deleted with an empty file dated the Epoch. The
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file will be removed unless patch is conforming to POSIX and the
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-E or --remove-empty-files option is not given.
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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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And while we're at it, a new patch filename quoting format is apparently
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coming soon: http://marc.theaimsgroup.com/?l=git&m=112927316408690&w=2
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Architectural issues:
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bb_close() with fsync()
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We should have a bb_close() in place of normal close, with a CONFIG_ option
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to not just check the return value of close() for an error, but fsync().
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Close can't reliably report anything useful because if write() accepted the
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data then it either went out to the network or it's in cache or a pipe
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buffer. Either way, there's no guarantee it'll make it to its final
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destination before close() gets called, so there's no guarantee that any
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error will be reported.
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You need to call fsync() if you care about errors that occur after write(),
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but that can have a big performance impact. So make it a config option.
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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 or
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mksquashfs someday, if they become relevant.
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---
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Text buffer support.
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Several existing applets (sort, vi, less...) read
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a whole file into memory and act on it. Use open_read_close().
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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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For a start, see e.g. make EXTRA_CFLAGS=-Wlarger-than-64
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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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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 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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Minor stuff:
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watchdog.c could autodetect the timer duration via:
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if(!ioctl (fd, WDIOC_GETTIMEOUT, &tmo)) timer_duration = 1 + (tmo / 2);
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Unfortunately, that needs linux/watchdog.h and that contains unfiltered
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kernel types on some distros, which breaks the build.
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---
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use bb_error_msg where appropriate: See
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egrep "(printf.*\([[:space:]]*(stderr|2)|[^_]write.*\([[:space:]]*(stderr|2))"
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---
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use bb_perror_msg where appropriate: See
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egrep "[^_]perror"
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---
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possible code duplication ingroup() and is_a_group_member()
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---
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Move __get_hz() to a better place and (re)use it in route.c, ash.c
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---
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See grep -r strtod
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Alot of duplication that wants cleanup.
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---
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unify progress_meter. wget, flash_eraseall, pipe_progress, fbsplash, setfiles.
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---
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support start-stop-daemon -d <chdir-path>
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---
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vdprintf() -> similar sized functionality
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---
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(TODO list after discussion 11.05.2009)
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* shrink tc/brctl/ip
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tc/brctl seem like fairly large things to try and tackle in your timeframe,
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and i think people have posted attempts in the past. Adding additional
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options to ip though seems reasonable.
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* add tests for some applets
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* implement POSIX utilities and audit them for POSIX conformance. then
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audit them for GNU conformance. then document all your findings in a new
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doc/conformance.txt file while perhaps implementing some of the missing
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features.
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you can find the latest POSIX documentation (1003.1-2008) here:
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http://www.opengroup.org/onlinepubs/9699919799/
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and the complete list of all utilities that POSIX covers:
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http://www.opengroup.org/onlinepubs/9699919799/idx/utilities.html
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The first step would to generate a file/matrix what is already archived
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(also IPV6)
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* implement 'at'
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* rpcbind (former portmap) or equivalent
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so that we don't have to use -o nolock on nfs mounts
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* check IPV6 compliance
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* generate a mini example using kernel+busybox only (+libc) for example
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* more support for advanced linux 2.6.x features, see: iotop
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most likely there is more
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* even more support for statistics: mpstat, iostat, powertop....
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