svn commit: r348866 - in stable/11/stand: common i386/zfsboot

[Kyle Evans]

Author: kevans
Date: Mon Jun 10 15:55:38 2019
New Revision: 348866
URL: https://svnweb.freebsd.org/changeset/base/348866

Log:
  MFC r348569: [zfsboot] Fix boot env back compat (#190)
  
  * Fix boot env back compat
  
  zfsboot must try zfsloader before loader in order to remain compatible
  with boot environments created prior to zfs functionality being rolled
  into loader proper.
  
  * Improve comments in zfsboot
  
  Explain the significance of the load path order, and put the comment
  about looping through the paths in the appropriate scope.
  
  Approved by:	re (gjb)

Modified:
  stable/11/stand/common/paths.h
  stable/11/stand/i386/zfsboot/zfsboot.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/stand/common/paths.h
==============================================================================
--- stable/11/stand/common/paths.h	Mon Jun 10 15:46:19 2019	(r348865)
+++ stable/11/stand/common/paths.h	Mon Jun 10 15:55:38 2019	(r348866)
@@ -33,6 +33,7 @@
 #define PATH_CONFIG	"/boot/config"
 #define PATH_LOADER	"/boot/loader"
 #define PATH_LOADER_EFI	"/boot/loader.efi"
+#define PATH_LOADER_ZFS	"/boot/zfsloader"
 #define PATH_KERNEL	"/boot/kernel/kernel"
 
 #endif /* _PATHS_H_ */

Modified: stable/11/stand/i386/zfsboot/zfsboot.c
==============================================================================
--- stable/11/stand/i386/zfsboot/zfsboot.c	Mon Jun 10 15:46:19 2019	(r348865)
+++ stable/11/stand/i386/zfsboot/zfsboot.c	Mon Jun 10 15:55:38 2019	(r348866)
@@ -87,6 +87,24 @@ static const unsigned char flags[NOPT] = {
 };
 uint32_t opts;
 
+/*
+ * Paths to try loading before falling back to the boot2 prompt.
+ *
+ * /boot/zfsloader must be tried before /boot/loader in order to remain
+ * backward compatible with ZFS boot environments where /boot/loader exists
+ * but does not have ZFS support, which was the case before FreeBSD 12.
+ *
+ * If no loader is found, try to load a kernel directly instead.
+ */
+static const struct string {
+    const char *p;
+    size_t len;
+} loadpath[] = {
+    { PATH_LOADER_ZFS, sizeof(PATH_LOADER_ZFS) },
+    { PATH_LOADER, sizeof(PATH_LOADER) },
+    { PATH_KERNEL, sizeof(PATH_KERNEL) },
+};
+
 static const unsigned char dev_maj[NDEV] = {30, 4, 2};
 
 static char cmd[512];
@@ -838,16 +856,17 @@ main(void)
     if (nextboot && !autoboot)
 	reboot();
 
-    /*
-     * Try to exec /boot/loader. If interrupted by a keypress,
-     * or in case of failure, try to load a kernel directly instead.
-     */
-
     if (autoboot && !*kname) {
-	memcpy(kname, PATH_LOADER, sizeof(PATH_LOADER));
-	if (!keyhit(3)) {
+	/*
+	 * Iterate through the list of loader and kernel paths, trying to load.
+	 * If interrupted by a keypress, or in case of failure, drop the user
+	 * to the boot2 prompt.
+	 */
+	for (i = 0; i < nitems(loadpath); i++) {
+	    memcpy(kname, loadpath[i].p, loadpath[i].len);
+	    if (keyhit(3))
+		break;
 	    load();
-	    memcpy(kname, PATH_KERNEL, sizeof(PATH_KERNEL));
 	}
     }