kern_linker: Handle module-loading failures in preloaded .ko files

The runtime kernel loader, linker_load_file, unloads kernel files that
failed to load all of their modules. For consistency, treat preloaded
(loader.conf loaded) kernel files in the same way.

Reviewed by:	kib
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D8200

2 files changed, 38 insertions, 1 deletions

diff --git a/sys/kern/kern_linker.c b/sys/kern/kern_linker.c
index 4758cdc2072a..1bd3ad077fdd 100644
--- a/sys/kern/kern_linker.c
+++ b/sys/kern/kern_linker.c
@@ -1599,7 +1599,6 @@ restart:
 			if (error)
 				panic("cannot add dependency");
 		}
-		lf->userrefs++;	/* so we can (try to) kldunload it */
 		error = linker_file_lookup_set(lf, MDT_SETNAME, &start,
 		    &stop, NULL);
 		if (!error) {
@@ -1637,6 +1636,8 @@ restart:
 			goto fail;
 		}
 		linker_file_register_modules(lf);
+		if (!TAILQ_EMPTY(&lf->modules))
+			lf->flags |= LINKER_FILE_MODULES;
 		if (linker_file_lookup_set(lf, "sysinit_set", &si_start,
 		    &si_stop, NULL) == 0)
 			sysinit_add(si_start, si_stop);
@@ -1654,6 +1655,41 @@ fail:
 SYSINIT(preload, SI_SUB_KLD, SI_ORDER_MIDDLE, linker_preload, 0);
 
 /*
+ * Handle preload files that failed to load any modules.
+ */
+static void
+linker_preload_finish(void *arg)
+{
+	linker_file_t lf, nlf;
+
+	sx_xlock(&kld_sx);
+	TAILQ_FOREACH_SAFE(lf, &linker_files, link, nlf) {
+		/*
+		 * If all of the modules in this file failed to load, unload
+		 * the file and return an error of ENOEXEC.  (Parity with
+		 * linker_load_file.)
+		 */
+		if ((lf->flags & LINKER_FILE_MODULES) != 0 &&
+		    TAILQ_EMPTY(&lf->modules)) {
+			linker_file_unload(lf, LINKER_UNLOAD_FORCE);
+			continue;
+		}
+
+		lf->flags &= ~LINKER_FILE_MODULES;
+		lf->userrefs++;	/* so we can (try to) kldunload it */
+	}
+	sx_xunlock(&kld_sx);
+}
+
+/*
+ * Attempt to run after all DECLARE_MODULE SYSINITs.  Unfortunately they can be
+ * scheduled at any subsystem and order, so run this as late as possible.  init
+ * becomes runnable in SI_SUB_KTHREAD_INIT, so go slightly before that.
+ */
+SYSINIT(preload_finish, SI_SUB_KTHREAD_INIT - 100, SI_ORDER_MIDDLE,
+    linker_preload_finish, 0);
+
+/*
  * Search for a not-loaded module by name.
  *
  * Modules may be found in the following locations:
diff --git a/sys/sys/linker.h b/sys/sys/linker.h
index 42253a7758ab..e650967cecb1 100644
--- a/sys/sys/linker.h
+++ b/sys/sys/linker.h
@@ -73,6 +73,7 @@ struct linker_file {
     int			userrefs;	/* kldload(2) count */
     int			flags;
 #define LINKER_FILE_LINKED	0x1	/* file has been fully linked */
+#define LINKER_FILE_MODULES	0x2	/* file has >0 modules at preload */
     TAILQ_ENTRY(linker_file) link;	/* list of all loaded files */
     char*		filename;	/* file which was loaded */
     char*		pathname;	/* file name with full path */