Add comments describing the bootargs handoff between loader(8) and gptboot

or zfsboot, when loader(8) is the BTX loader.  No functional changes.

1 files changed, 5 insertions, 0 deletions

diff --git a/stand/i386/zfsboot/zfsboot.c b/stand/i386/zfsboot/zfsboot.c
index e88527757158..2369276f5e69 100644
--- a/stand/i386/zfsboot/zfsboot.c
+++ b/stand/i386/zfsboot/zfsboot.c
@@ -1005,6 +1005,11 @@ load(void)
 	zfsargs.primary_vdev = primary_vdev->v_guid;
     else
 	printf("failed to detect primary vdev\n");
+    /*
+     * Note that the zfsargs struct is passed by value, not by pointer.  Code in
+     * btxldr.S copies the values from the entry stack to a fixed location
+     * within loader(8) at startup due to the presence of KARGS_FLAGS_EXTARG.
+     */
     __exec((caddr_t)addr, RB_BOOTINFO | (opts & RBX_MASK),
 	   bootdev,
 	   KARGS_FLAGS_ZFS | KARGS_FLAGS_EXTARG,