Tweak outdated documentation and comments

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

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@ -147,10 +147,6 @@ Placement / Directory
Find the appropriate directory for your new applet. Find the appropriate directory for your new applet.
Add the kbuild snippet to the .c file:
//kbuild:lib-$(CONFIG_MU) += mu.o
Add the config snippet to the .c file: Add the config snippet to the .c file:
//config:config MU //config:config MU
@ -159,6 +155,10 @@ Add the config snippet to the .c file:
//config: help //config: help
//config: Returns an indeterminate value. //config: Returns an indeterminate value.
Add the kbuild snippet to the .c file:
//kbuild:lib-$(CONFIG_MU) += mu.o
Usage String(s) Usage String(s)
--------------- ---------------
@ -168,8 +168,9 @@ This should look like the following:
//usage:#define mu_trivial_usage //usage:#define mu_trivial_usage
//usage: "[-abcde] FILE..." //usage: "[-abcde] FILE..."
//usage:#define mu_full_usage //usage:#define mu_full_usage "\n\n"
//usage: "Returns an indeterminate value\n" //usage: "Returns an indeterminate value"
//usage: "\n"
//usage: "\n -a First function" //usage: "\n -a First function"
//usage: "\n -b Second function" //usage: "\n -b Second function"
//usage: ... //usage: ...

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@ -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 for speeding up busybox shells, and more. NOEXEC and NOFORK applets
are exactly those applets which are eligible for these tricks. are exactly those applets which are eligible for these tricks.
Applet will be subject to NOFORK/NOEXEC tricks if it is marked as such Applet will be subject to NOFORK/NOEXEC tricks only if it is marked
in applets.h. FEATURE_PREFER_APPLETS is a config option which as such in applets.src.h or in their inline "//applet:" directives.
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.
In C, if you want to call a program and wait for it, use 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,...). 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. 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
NOEXEC applet should work correctly if another applet forks and then 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's the same trusty spawn_and_wait(argv). If FEATURE_PREFER_APPLETS=y,
it does NOEXEC trick. It resets xfunc_error_retval = 1 and it does NOEXEC trick. It resets xfunc_error_retval = 1 and
logmode = LOGMODE_STDIO in the child. 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

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@ -295,8 +295,8 @@ int arping_main(int argc UNUSED_PARAM, char **argv)
sock_fd = xsocket(AF_PACKET, SOCK_DGRAM, 0); sock_fd = xsocket(AF_PACKET, SOCK_DGRAM, 0);
// Drop suid root privileges // If you ever change BB_SUID_DROP to BB_SUID_REQUIRE,
// Need to remove SUID_NEVER from applets.h for this to work // drop suid root privileges here:
//xsetuid(getuid()); //xsetuid(getuid());
{ {