Add an automatic kernel module version dependency to prevent loading

modules using invalid ABI versions (e.g. a 7.x module with an 8.x kernel)
for a given kernel:
- Add a 'kernel' module version whose value is __FreeBSD_version.
- Add a version dependency on 'kernel' in every module that has an
  acceptable version range of __FreeBSD_version up to the end of the
  branch __FreeBSD_version is part of.  E.g. a module compiled on 701000
  would work on kernels with versions between 701000 and 799999 inclusive.

Discussed on:	arch@
MFC after:	1 week

1 files changed, 2 insertions, 0 deletions

diff --git a/sys/kern/kern_module.c b/sys/kern/kern_module.c
index 9a1f159..72a6991 100644
--- a/sys/kern/kern_module.c
+++ b/sys/kern/kern_module.c
@@ -414,6 +414,8 @@ modfind(struct thread *td, struct modfind_args *uap)
 	return (error);
 }
 
+MODULE_VERSION(kernel, __FreeBSD_version);
+
 #ifdef COMPAT_IA32
 #include <sys/mount.h>
 #include <sys/socket.h>