Make linux(4) create /dev/shm. Linux applications often expect

a tmpfs to be mounted there, and because they like to verify it's
actually a mountpoint, a symlink won't do.

Reviewed by:	dchagin (earlier version)
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D20333

3 files changed, 32 insertions, 0 deletions

diff --git a/sys/compat/linux/linux.c b/sys/compat/linux/linux.c
index fa1e8f315f9e..621efaf3a4ab 100644
--- a/sys/compat/linux/linux.c
+++ b/sys/compat/linux/linux.c
@@ -31,6 +31,7 @@ __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/conf.h>
 #include <sys/ctype.h>
 #include <sys/jail.h>
 #include <sys/lock.h>
@@ -129,6 +130,12 @@ static int linux_to_bsd_sigtbl[LINUX_SIGTBLSZ] = {
 	SIGSYS		/* LINUX_SIGSYS */
 };
 
+static struct cdev *dev_shm_cdev;
+static struct cdevsw dev_shm_cdevsw = {
+     .d_version = D_VERSION,
+     .d_name    = "dev_shm",
+};
+
 /*
  * Map Linux RT signals to the FreeBSD RT signals.
  */
@@ -524,3 +531,23 @@ out:
 	free(kosa, M_SONAME);
 	return (error);
 }
+
+void
+linux_dev_shm_create(void)
+{
+	int error;
+
+	error = make_dev_p(MAKEDEV_CHECKNAME | MAKEDEV_WAITOK, &dev_shm_cdev,
+	    &dev_shm_cdevsw, NULL, UID_ROOT, GID_WHEEL, 0, "shm/.mountpoint");
+	if (error != 0) {
+		printf("%s: failed to create device node, error %d\n",
+		    __func__, error);
+	}
+}
+
+void
+linux_dev_shm_destroy(void)
+{
+
+	destroy_dev(dev_shm_cdev);
+}
diff --git a/sys/compat/linux/linux.h b/sys/compat/linux/linux.h
index 2959c1dfe320..00650d075837 100644
--- a/sys/compat/linux/linux.h
+++ b/sys/compat/linux/linux.h
@@ -143,4 +143,7 @@ int bsd_to_linux_signal(int sig);
 extern LIST_HEAD(futex_list, futex) futex_list;
 extern struct mtx futex_mtx;
 
+void linux_dev_shm_create(void);
+void linux_dev_shm_destroy(void);
+
 #endif /* _LINUX_MI_H_ */
diff --git a/sys/compat/linux/linux_common.c b/sys/compat/linux/linux_common.c
index 2bb11c279761..a6c780bd5e10 100644
--- a/sys/compat/linux/linux_common.c
+++ b/sys/compat/linux/linux_common.c
@@ -68,6 +68,7 @@ linux_common_modevent(module_t mod, int type, void *data)
 
 	switch(type) {
 	case MOD_LOAD:
+		linux_dev_shm_create();
 		linux_osd_jail_register();
 		linux_exit_tag = EVENTHANDLER_REGISTER(process_exit,
 		    linux_proc_exit, NULL, 1000);
@@ -81,6 +82,7 @@ linux_common_modevent(module_t mod, int type, void *data)
 		mtx_init(&futex_mtx, "ftllk", NULL, MTX_DEF);
 		break;
 	case MOD_UNLOAD:
+		linux_dev_shm_destroy();
 		linux_osd_jail_deregister();
 		SET_FOREACH(ldhp, linux_device_handler_set)
 			linux_device_unregister_handler(*ldhp);