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authorDenys Vlasenko2017-01-26 00:27:53 +0100
committerDenys Vlasenko2017-01-26 00:27:53 +0100
commit06f20bf675cdd415c2f796ebea9fc55030ef49cc (patch)
tree04aa11f7829e346b630b2e8cb62a52d3b488d330 /docs/nofork_noexec.txt
parent7dd906a3884a31458d30fc43eb9885c5adf4bbea (diff)
downloadbusybox-06f20bf675cdd415c2f796ebea9fc55030ef49cc.zip
busybox-06f20bf675cdd415c2f796ebea9fc55030ef49cc.tar.gz
link: new applet
coreutils grew itself a tiny simplistic alternative to ln: Usage: link FILE LINK Create hard LINK to FILE function old new delta link_main - 75 +75 packed_usage 31114 31131 +17 applet_names 2564 2569 +5 applet_main 1480 1484 +4 applet_install_loc 185 186 +1 ------------------------------------------------------------------------------ (add/remove: 1/0 grow/shrink: 4/0 up/down: 102/0) Total: 102 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'docs/nofork_noexec.txt')
-rw-r--r--docs/nofork_noexec.txt32
1 files changed, 26 insertions, 6 deletions
diff --git a/docs/nofork_noexec.txt b/docs/nofork_noexec.txt
index c58f5a8..2fb184a 100644
--- a/docs/nofork_noexec.txt
+++ b/docs/nofork_noexec.txt
@@ -33,6 +33,7 @@ roughly are:
* do not expect shared global variables/buffers to be in their
"initialized" state. Examples: xfunc_error_retval can be != 1,
bb_common_bufsiz1 can be scribbled over, ...
+ (although usually xfunc_error_retval's state is not a problem).
* do not expect that stdio wasn't used before. Calling set[v]buf()
can be disastrous.
* ...
@@ -81,18 +82,37 @@ are probably not worth the effort.
Any NOFORK applet is also a NOEXEC applet.
+ Calling NOFORK applets
+
+API to call NOFORK applets is two functions:
+
+ run_nofork_applet(appno, argv)
+ spawn_and_wait(argv) // only if FEATURE_PREFER_APPLETS=y
+
+First one is directly used by shells if FEATURE_SH_NOFORK=y.
+Second one is used by many applets, but main users are xargs and find.
+It itself calls run_nofork_applet(), if argv[0] turned out to be a name
+of a NOFORK applet.
+
+run_nofork_applet() saves/inits/restores option parsing, xfunc_error_retval,
+applet_name. Thus, for example, caller does not need to worry about
+option_mask32 getting trashed.
+
+
Relevant CONFIG options
FEATURE_PREFER_APPLETS
BB_EXECVP(cmd, argv) will try to exec /proc/self/exe
- if command's name matches some applet name
- applet tables will contain NOFORK/NOEXEC bits
+ if command's name matches some applet name;
spawn_and_wait(argv) will do NOFORK/NOEXEC tricks
-FEATURE_SH_STANDALONE (needs FEATURE_PREFER_APPLETS=y)
+//TODO: the above two things probably should have separate options?
+
+FEATURE_SH_STANDALONE
shells will try to exec /proc/self/exe if command's name matches
- some applet name
- shells will do NOEXEC trick on NOEXEC applets
+ some applet name; shells will do NOEXEC trick on NOEXEC applets
+
+//TODO: split (same as for PREFER_APPLETS)
-FEATURE_SH_NOFORK (needs FEATURE_PREFER_APPLETS=y)
+FEATURE_SH_NOFORK
shells will do NOFORK trick on NOFORK applets