emo/busybox
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Tweak outdated documentation and comments

Browse Source 
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
2017-08-06 14:03:27 +02:00
parent 9a58cc0f7f
commit fbecca1bed
3 changed files with 37 additions and 35 deletions
Download Patch File Download Diff File Expand all files Collapse all files

53
docs/nofork_noexec.txt
View File

@@ -10,13 +10,8 @@ of reimplemented Unix commands, and we can do the same trick
for speeding up busybox shells, and more. NOEXEC and NOFORK applets
are exactly those applets which are eligible for these tricks.
Applet will be subject to NOFORK/NOEXEC tricks if it is marked as such
in applets.h. FEATURE_PREFER_APPLETS is a config option which
globally enables usage of NOFORK/NOEXEC tricks.
If it is enabled, FEATURE_SH_STANDALONE can be enabled too,
and then shells will use NOFORK/NOEXEC tricks for ordinary commands.
NB: shell builtins use these tricks regardless of FEATURE_SH_STANDALONE
or FEATURE_PREFER_APPLETS.
Applet will be subject to NOFORK/NOEXEC tricks only if it is marked
as such in applets.src.h or in their inline "//applet:" directives.
In C, if you want to call a program and wait for it, use
spawn_and_wait(argv), BB_EXECVP(prog,argv) or BB_EXECLP(prog,argv0,...).
@@ -24,6 +19,31 @@ They check whether program name is an applet name and optionally
do NOFORK/NOEXEC thing depending on configuration.
Relevant CONFIG options
FEATURE_PREFER_APPLETS
Globally enables NOFORK/NOEXEC tricks for such programs as xargs
and find:
BB_EXECVP(cmd, argv) will try to exec /proc/self/exe
if command's name matches some applet name;
spawn_and_wait(argv) will do NOFORK/NOEXEC tricks
//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
//TODO: split (same as for PREFER_APPLETS)
FEATURE_SH_NOFORK
shells will do NOFORK trick on NOFORK applets
NB: shell builtins use these tricks regardless of FEATURE_SH_STANDALONE,
FEATURE_PREFER_APPLETS or FEATURE_SH_NOFORK. In effect, builtins
are "always NOFORK".
NOEXEC
NOEXEC applet should work correctly if another applet forks and then
@@ -121,22 +141,3 @@ option_mask32 getting trashed.
It's the same trusty spawn_and_wait(argv). If FEATURE_PREFER_APPLETS=y,
it does NOEXEC trick. It resets xfunc_error_retval = 1 and
logmode = LOGMODE_STDIO in the child.
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;
spawn_and_wait(argv) will do NOFORK/NOEXEC tricks
//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
//TODO: split (same as for PREFER_APPLETS)
FEATURE_SH_NOFORK
shells will do NOFORK trick on NOFORK applets