source: MondoRescue/branches/stable/mindi-busybox/docs/nofork_noexec.txt @ 1770

Last change on this file since 1770 was 1770, checked in by Bruno Cornec, 12 years ago
  • Better output for mindi-busybox revision
  • Remove dummy file created on NFS - report from Arnaud Tiger <arnaud.tiger_at_hp.com>
  • strace useful for debug
  • fix new versions for pb (2.0.0 for mindi and 1.7.2 for mindi-busybox)
  • fix build process for mindi-busybox + options used in that version (dd for label-partitions-as-necessary)
  • fix typo in label-partitions-as-necessary which doesn't seem to work
  • Update to busybox 1.7.2
  • perl is now required at restore time to support uuid swap partitions (and will be used for many other thigs

in the future for sure)

  • next mindi version will be 2.0.0 due to all the changes made in it (udev may break working distros)
  • small optimization in mindi on keyboard handling (one single find instead of multiple)
  • better interaction for USB device when launching mindi manually
  • attempt to automatically guess block disk size for ramdisk
  • fix typos in bkphw
  • Fix the remaining problem with UUID support for swap partitions
  • Updates mondoarchive man page for USB support
  • Adds preliminary Hardware support to mindi (Proliant SSSTK)
  • Tries to add udev support also for rhel4
  • Fix UUID support which was still broken.
  • Be conservative in test for the start-nfs script
  • Update config file for mindi-busybox for 1.7.2 migration
  • Try to run around a busybox bug (1.2.2 pb on inexistant links)
  • Add build content for mindi-busybox in pb
  • Remove distributions content for mindi-busybox
  • Fix a warning on inexistant raidtab
  • Solve problem on tmpfs in restore init (Problem of inexistant symlink and busybox)
  • Create MONDO_CACHE and use it everywhere + creation at start
  • Really never try to eject a USB device
  • Fix a issue with &> usage (replaced with 1> and 2>)
  • Adds magic file to depllist in order to have file working + ldd which helps for debugging issues
  • tty modes correct to avoid sh error messages
  • Use ext3 normally and not ext2 instead
  • USB device should be corrected after reading (take 1st part)
  • Adds a mount_USB_here function derived from mount_CDROM_here
  • usb detection place before /dev detection in device name at restore time
  • Fix when restoring from USB: media is asked in interactive mode
  • Adds USB support for mondorestore
  • mount_cdrom => mount_media
  • elilo.efi is now searched throughout /boot/efi and not in a fixed place as there is no standard
  • untar-and-softlink => untar (+ interface change)
  • suppress useless softlinks creation/removal in boot process
  • avoids udevd messages on groups
  • Increase # of disks to 99 as in mindi at restore time (should be a conf file parameter)
  • skip existing big file creation
  • seems to work correctly for USB mindi boot
  • Adds group and tty link to udev conf
  • Always load usb-torage (even 2.6) to initiate USB bus discovery
  • Better printing of messages
  • Attempt to fix a bug in supporting OpenSusE 10.3 kernel for initramfs (mindi may now use multiple regex for kernel initrd detection)
  • Links were not correctly done as non relative for modules in mindi
  • exclusion of modules denied now works
  • Also create modules in their ordinary place, so that classical modprobe works + copy modules.dep
  • Fix bugs for DENY_MODS handling
  • Add device /dev/console for udev
  • ide-generic should now really be excluded
  • Fix a bug in major number for tty
  • If udev then adds modprobe/insmod to rootfs
  • tty0 is also cretaed with udev
  • ide-generic put rather in DENY_MODS
  • udevd remove from deplist s handled in mindi directly
  • better default for mindi when using --usb
  • Handles dynamically linked busybox (in case we want to use it soon ;-)
  • Adds fixed devices to create for udev
  • ide-generic should not be part of the initrd when using libata v2
  • support a dynamically linked udev (case on Ubuntu 7.10 and Mandriva 2008.0 so should be quite generic) This will give incitation to move to dyn. linked binaries in the initrd which will help for other tasks (ia6 4)
  • Improvement in udev support (do not use cl options not available in busybox)
  • Udev in mindi
    • auto creation of the right links at boot time with udev-links.conf(from Mandriva 2008.0)
    • rework startup of udev as current makes kernel crash (from Mandriva 2008.0)
    • add support for 64 bits udev
  • Try to render MyInsmod? silent at boot time
  • Adds udev support (mandatory for newest distributions to avoid remapping of devices in a different way as on the original system)
  • We also need vaft format support for USB boot
  • Adds libusual support (Ubuntu 7.10 needs it for USB)
  • Improve Ubuntu/Debian? keyboard detection and support
  • pbinit adapted to new pb (0.8.10). Filtering of docs done in it
  • Suppress some mondo warnings and errors on USB again
  • Tries to fix lack of files in deb mindi package
  • Verify should now work for USB devices
  • More log/mesages improvement for USB support
  • - Supress g_erase_tmpdir_and_scratchdir
  • Improve some log messages for USB support
  • Try to improve install in mindi to avoid issues with isolinux.cfg not installed vene if in the pkg :-(
  • Improve mindi-busybox build
  • In conformity with pb 0.8.9
  • Add support for Ubuntu 7.10 in build process
  • Add USB Key button to Menu UI (CD streamer removed)
  • Attempt to fix error messages on tmp/scratch files at the end by removing those dir at the latest possible.
  • Fix a bug linked to the size of the -E param which could be used (Arnaud Tiger/René? Ribaud).
  • Integrate ~/.pbrc content into mondorescue.pb (required project-builder >= 0.8.7)
  • Put mondorescue in conformity with new pb filtering rules
  • Add USB support at restore time (no test done yet). New start-usb script PB varibale added where useful
  • Unmounting USB device before removal of temporary scratchdir
  • Stil refining USB copy back to mondo (one command was not executed)
  • No need to have the image subdor in the csratchdir when USB.
  • umount the USB partition before attempting to use it
  • Remove useless copy from mindi to mondo at end of USB handling

(risky merge, we are raising the limits of 2 diverging branches. The status of stable is not completely sure as such. Will need lots of tests, but it's not yet done :-()
(merge -r1692:1769 $SVN_M/branches/2.2.5)

  • Property svn:eol-style set to native
File size: 3.0 KB
Line 
1    NOEXEC and NOFORK applets.
2
3Unix shells traditionally execute some commands internally in the attempt
4to dramatically speed up execution. It will be slow as hell if for every
5"echo blah" shell will fork and exec /bin/echo. For this end, shells
6have to _reimplement_ these commands internally.
7
8Busybox is unique in this regard because it already is a collection
9of reimplemented Unix commands, and we can do the same trick
10for speeding up busybox shells, and more. NOEXEC and NOFORK applets
11are exactly those applets which are eligible for these tricks.
12
13Applet will be subject to NOFORK/NOEXEC tricks if it is marked as such
14in applets.h. CONFIG_FEATURE_PREFER_APPLETS is a config option which
15globally enables usage of NOFORK/NOEXEC tricks.
16
17If you want to call a program and wait for it, use spawn_and_wait(argv).
18It will check whether argv[0] is an applet name and will optionally
19do NOFORK/NOEXEC thing.
20
21NOEXEC
22
23NOEXEC applet should work correctly if another applet forks and then
24executes exit(<applet>_main(argc,argv)) in the child. The rules
25roughly are:
26
27* do not expect shared global variables/buffers to be in their
28  "initialized" state. Examples: xfunc_error_retval can be != 1,
29  bb_common_bufsiz1 can be scribbled over, ...
30* do not expect that stdio wasn't used before. Calling set[v]buf()
31  can be disastrous.
32* ...
33
34NOEXEC applets save only one half of fork+exec overhead.
35NOEXEC trick is disabled for NOMMU compile.
36
37NOFORK
38
39NOFORK applet should work correctly if another applet simply runs
40<applet>_main(argc,argv) and then continues with its business (xargs,
41find, shells can do it). This poses much more serious limitations
42on what applet can/cannot do:
43
44* all NOEXEC limitations apply.
45* do not ever exit() or exec().
46  - xfuncs are okay. They are using special trick to return
47    to the caller applet instead of dying when they detect "x" condition.
48  - you may "exit" to caller applet by calling xfunc_die(). Return value
49    is taken from xfunc_error_retval.
50  - fflush_stdout_and_exit(n) is ok to use.
51* do not use shared global data, or save/restore shared global data
52  prior to returning. (e.g. bb_common_bufsiz1 is off-limits).
53  - getopt32() is ok to use. You do not need to save/restore option_mask32,
54    it is already done by core code.
55* if you allocate memory, you can use xmalloc() only on the very first
56  allocation. All other allocations should use malloc[_or_warn]().
57  After first allocation, you cannot use any xfuncs.
58* All allocated data, opened files, signal handlers, termios settings,
59  O_NONBLOCK flags etc should be freed/closed/restored prior to return.
60* ...
61
62NOFORK applets give the most of speed advantage, but are trickiest
63to implement. In order to minimize amount of bugs and maintenance,
64prime candidates for NOFORK-ification are those applets which
65are small and easy to audit, and those which are more likely to be
66frequently executed from shell/find/xargs, particularly in shell
67script loops. Applets which mess with signal handlers, termios etc
68are probably not worth the effort.
69
70Any NOFORK applet is also a NOEXEC applet.
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