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Code Issues Releases Activity

Add init_exec kenv(1) variable, to make init(8) execute a file

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after opening the console, replacing init as PID 1.

From the user point of view, it makes it possible to run eg the
shell as PID 1, using 'set init_exec=/bin/sh' at the loader(8)
prompt.

Reviewed by:	kib
MFC after:	2 weeks
Relnotes:	yes
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D16625
This commit is contained in:
Edward Tomasz Napierala 2018-08-14 11:01:52 +00:00
parent 398810619c
commit 335fe94f90
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=337740
3 changed files with 37 additions and 2 deletions
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12
sbin/init/init.8
View File

@ -31,7 +31,7 @@
.\" @(#)init.8 8.3 (Berkeley) 4/18/94
.\" $FreeBSD$
.\"
.Dd August 7, 2018
.Dd August 14, 2018
.Dt INIT 8
.Os
.Sh NAME
@ -316,6 +316,14 @@ See
.Xr reboot 8
.Fl r
for details.
.It Va init_exec
If set to a valid file name in the root file system,
instructs
.Nm
to directly execute that file as the very first action,
replacing
.Nm
as PID 1.
.It Va init_script
If set to a valid file name in the root file system,
instructs
@ -341,6 +349,8 @@ Defines the shell binary to be used for executing the various shell scripts.
The default is
.Dq Li /bin/sh .
It is used for running the
.Va init_exec
or
.Va init_script
if set, as well as for the
.Pa /etc/rc

22
sbin/init/init.c
View File

@ -149,6 +149,7 @@ static state_t current_state = death_single;
static void execute_script(char *argv[]);
static void open_console(void);
static const char *get_shell(void);
static void replace_init(char *path);
static void write_stderr(const char *message);
typedef struct init_session {
@ -330,6 +331,11 @@ main(int argc, char *argv[])
close(1);
close(2);
if (kenv(KENV_GET, "init_exec", kenv_value, sizeof(kenv_value)) > 0) {
replace_init(kenv_value);
_exit(0); /* reboot */
}
if (kenv(KENV_GET, "init_script", kenv_value, sizeof(kenv_value)) > 0) {
state_func_t next_transition;
@ -1087,6 +1093,22 @@ execute_script(char *argv[])
stall("can't exec %s for %s: %m", shell, script);
}
/*
* Execute binary, replacing init(8) as PID 1.
*/
static void
replace_init(char *path)
{
char *argv[3];
char sh[] = "sh";
argv[0] = sh;
argv[1] = path;
argv[2] = NULL;
execute_script(argv);
}
/*
* Run a shell script.
* Returns 0 on success, otherwise the next transition to enter:

5
stand/man/loader.8
View File

@ -24,7 +24,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd August 13, 2018
.Dd August 14, 2018
.Dt LOADER 8
.Os
.Sh NAME
@ -492,6 +492,9 @@ of boot to be captured.
.It Va init_chroot
See
.Xr init 8 .
.It Va init_exec
See
.Xr init 8 .
.It Va init_path
Sets the list of binaries which the kernel will try to run as the initial
process.