stand: create common set_currdev

Pull together the nearly identical copies of set_currdev in i386,
userboot and efi. Other boot loaders have variances that might be fine
to use the common routine, or not. Since they are harder to test for me,
and ofw and uboot do handle these setting differently, leave them be for
now.

Sponsored by:		Netflix
Reviewed by:		kevans
Differential Revision:	https://reviews.freebsd.org/D38005

stand/common/bootstrap.h

@@ -415,6 +415,7 @@ int nvstore_unset_var(void *, const char *);
 /* common code to set currdev variable. */
 int gen_setcurrdev(struct env_var *ev, int flags, const void *value);
 int mount_currdev(struct env_var *, int, const void *);
+void set_currdev(const char *devname);
 
 #ifndef CTASSERT
 #define	CTASSERT(x)	_Static_assert(x, "compile-time assertion failed")

stand/common/misc.c

@@ -206,3 +206,20 @@ gen_setcurrdev(struct env_var *ev, int flags, const void *value)
 
 	return (mount_currdev(ev, flags, value));
 }
+
+/*
+ * Wrapper to set currdev and loaddev at the same time.
+ */
+void
+set_currdev(const char *devname)
+{
+
+	env_setenv("currdev", EV_VOLATILE, devname, gen_setcurrdev,
+	    env_nounset);
+	/*
+	 * Don't execute hook here; the loaddev hook makes it immutable
+	 * once we've determined what the proper currdev is.
+	 */
+	env_setenv("loaddev", EV_VOLATILE | EV_NOHOOK, devname, env_noset,
+	    env_nounset);
+}

stand/efi/loader/main.c

@@ -185,20 +185,6 @@ has_keyboard(void)
 	return retval;
 }
 
-static void
-set_currdev(const char *devname)
-{
-
-	env_setenv("currdev", EV_VOLATILE, devname, gen_setcurrdev,
-	    env_nounset);
-	/*
-	 * Don't execute hook here; the loaddev hook makes it immutable
-	 * once we've determined what the proper currdev is.
-	 */
-	env_setenv("loaddev", EV_VOLATILE | EV_NOHOOK, devname, env_noset,
-	    env_nounset);
-}
-
 static void
 set_currdev_devdesc(struct devdesc *currdev)
 {

stand/i386/loader/main.c

@@ -383,10 +383,7 @@ extract_currdev(void)
 		init_zfs_boot_options(devformat(&new_currdev.dd));
 #endif
 
-	env_setenv("currdev", EV_VOLATILE, devformat(&new_currdev.dd),
-	    gen_setcurrdev, env_nounset);
-	env_setenv("loaddev", EV_VOLATILE, devformat(&new_currdev.dd),
-	    env_noset, env_nounset);
+	set_currdev(devformat(&new_currdev.dd));
 }
 
 COMMAND_SET(reboot, "reboot", "reboot the system", command_reboot);

stand/userboot/userboot/main.c

@@ -224,16 +224,6 @@ loader_main(struct loader_callbacks *cb, void *arg, int version, int ndisks)
 	exit(0);
 }
 
-static void
-set_currdev(const char *devname)
-{
-
-	env_setenv("currdev", EV_VOLATILE, devname,
-	    gen_setcurrdev, env_nounset);
-	env_setenv("loaddev", EV_VOLATILE, devname,
-	    env_noset, env_nounset);
-}
-
 /*
  * Set the 'current device' by (if possible) recovering the boot device as 
  * supplied by the initial bootstrap.