Eliminate duplicated code and struct member definitions in the handoff

of args data between gptboot/zfsboot and loader(8).

Despite what seems like a lot of changes here, there are no actual
changes in behavior, or in the data layout in the structures involved.
This is just eliminating identical code pasted into multiple locations.

In detail, the changes are...

- Move struct zfs_boot_args definition from libsa/zfs/libzfs.h to
  i386/common/bootargs.h because it is specific to x86 booting and the
  handoff between zfsboot and loader, and has no relation to the zfs
  library code in general.

- The geli_boot_args and zfs_boot_args structs both contain an identical
  set of member variables containing geli information.  Extract this out
  to a new geli_boot_data struct, and embed it in the arg-passing structs.

- Provide new routines geli_import_boot_data() and geli_export_boot_data()
  that can be shared between gptboot, zfsboot, and loader instead of
  pasting identical code into several different .c files.

- Remove some checks for a NULL pointer that can never be true because the
  pointer being tested was set using pointer math (kargs + 1) and that can
  never result in NULL in this code.

stand/i386/common/bootargs.h

@@ -84,11 +84,15 @@ struct bootargs
 
 #ifdef LOADER_GELI_SUPPORT
 #include <crypto/intake.h>
+#include "geliboot.h"
 #endif
 
-struct geli_boot_args
+/*
+ * geli_boot_data is embedded in geli_boot_args (passed from gptboot to loader)
+ * and in zfs_boot_args (passed from zfsboot and gptzfsboot to loader).
+ */
+struct geli_boot_data
 {
-    uint32_t		size;
     union {
         char            gelipw[256];
         struct {
@@ -106,6 +110,49 @@ struct geli_boot_args
     };
 };
 
+#ifdef LOADER_GELI_SUPPORT
+
+static inline void
+export_geli_boot_data(struct geli_boot_data *gbdata)
+{
+
+	gbdata->notapw = '\0';
+	gbdata->keybuf_sentinel = KEYBUF_SENTINEL;
+	gbdata->keybuf = malloc(sizeof(struct keybuf) +
+	    (GELI_MAX_KEYS * sizeof(struct keybuf_ent)));
+	geli_export_key_buffer(gbdata->keybuf);
+}
+
+static inline void
+import_geli_boot_data(struct geli_boot_data *gbdata)
+{
+
+	if (gbdata->gelipw[0] != '\0') {
+	    setenv("kern.geom.eli.passphrase", gbdata->gelipw, 1);
+	    explicit_bzero(gbdata->gelipw, sizeof(gbdata->gelipw));
+	} else if (gbdata->keybuf_sentinel == KEYBUF_SENTINEL) {
+	    geli_import_key_buffer(gbdata->keybuf);
+	}
+}
+#endif /* LOADER_GELI_SUPPORT */
+
+struct geli_boot_args
+{
+	uint32_t		size;
+	struct geli_boot_data	gelidata;
+};
+
+struct zfs_boot_args
+{
+	uint32_t		size;
+	uint32_t		reserved;
+	uint64_t		pool;
+	uint64_t		root;
+	uint64_t		primary_pool;
+	uint64_t		primary_vdev;
+	struct geli_boot_data	gelidata;
+};
+
 #endif /*__ASSEMBLER__*/
 
 #endif	/* !_BOOT_I386_ARGS_H_ */

stand/i386/gptboot/gptboot.c

@@ -114,7 +114,6 @@ static int vdev_read(void *vdev __unused, void *priv, off_t off, void *buf,
 #ifdef LOADER_GELI_SUPPORT
 #include "geliboot.h"
 static char gelipw[GELI_PW_MAXLEN];
-static struct keybuf *gelibuf;
 #endif
 
 struct gptdsk {
@@ -480,12 +479,7 @@ load(void)
 #ifdef LOADER_GELI_SUPPORT
 	geliargs.size = sizeof(geliargs);
 	explicit_bzero(gelipw, sizeof(gelipw));
-	gelibuf = malloc(sizeof(struct keybuf) +
-	    (GELI_MAX_KEYS * sizeof(struct keybuf_ent)));
-	geli_export_key_buffer(gelibuf);
-	geliargs.notapw = '\0';
-	geliargs.keybuf_sentinel = KEYBUF_SENTINEL;
-	geliargs.keybuf = gelibuf;
+	export_geli_boot_data(&geliargs.gelidata);
 #endif
 	/*
 	 * Note that the geliargs struct is passed by value, not by pointer.

stand/i386/loader/main.c

@@ -172,15 +172,8 @@ main(void)
 #ifdef LOADER_GELI_SUPPORT
     if ((kargs->bootflags & KARGS_FLAGS_EXTARG) != 0) {
 	zargs = (struct zfs_boot_args *)(kargs + 1);
-	if (zargs != NULL && zargs->size >= offsetof(struct zfs_boot_args, gelipw)) {
-	    if (zargs->size >= offsetof(struct zfs_boot_args, keybuf_sentinel) &&
-	      zargs->keybuf_sentinel == KEYBUF_SENTINEL) {
-		geli_import_key_buffer(zargs->keybuf);
-	    }
-	    if (zargs->gelipw[0] != '\0') {
-		setenv("kern.geom.eli.passphrase", zargs->gelipw, 1);
-		explicit_bzero(zargs->gelipw, sizeof(zargs->gelipw));
-	    }
+	if (zargs->size > offsetof(struct zfs_boot_args, gelidata)) {
+	    import_geli_boot_data(&zargs->gelidata);
 	}
     }
 #endif /* LOADER_GELI_SUPPORT */
@@ -188,14 +181,8 @@ main(void)
 #ifdef LOADER_GELI_SUPPORT
     if ((kargs->bootflags & KARGS_FLAGS_EXTARG) != 0) {
 	gargs = (struct geli_boot_args *)(kargs + 1);
-	if (gargs != NULL && gargs->size >= offsetof(struct geli_boot_args, gelipw)) {
-	    if (gargs->keybuf_sentinel == KEYBUF_SENTINEL) {
-		geli_import_key_buffer(gargs->keybuf);
-	    }
-	    if (gargs->gelipw[0] != '\0') {
-		setenv("kern.geom.eli.passphrase", gargs->gelipw, 1);
-		explicit_bzero(gargs->gelipw, sizeof(gargs->gelipw));
-	    }
+	if (gargs->size >= offsetof(struct geli_boot_args, gelidata)) {
+	    import_geli_boot_data(&gargs->gelidata);
 	}
     }
 #endif /* LOADER_GELI_SUPPORT */

stand/i386/zfsboot/zfsboot.c

@@ -129,7 +129,6 @@ int main(void);
 #ifdef LOADER_GELI_SUPPORT
 #include "geliboot.h"
 static char gelipw[GELI_PW_MAXLEN];
-static struct keybuf *gelibuf;
 #endif
 
 struct zfsdsk {
@@ -993,13 +992,7 @@ load(void)
     zfsargs.primary_pool = primary_spa->spa_guid;
 #ifdef LOADER_GELI_SUPPORT
     explicit_bzero(gelipw, sizeof(gelipw));
-    gelibuf = malloc(sizeof(struct keybuf) + (GELI_MAX_KEYS * sizeof(struct keybuf_ent)));
-    geli_export_key_buffer(gelibuf);
-    zfsargs.notapw = '\0';
-    zfsargs.keybuf_sentinel = KEYBUF_SENTINEL;
-    zfsargs.keybuf = gelibuf;
-#else
-    zfsargs.gelipw[0] = '\0';
+    export_geli_boot_data(&zfsargs.gelidata);
 #endif
     if (primary_vdev != NULL)
 	zfsargs.primary_vdev = primary_vdev->v_guid;

stand/libsa/zfs/libzfs.h

@@ -44,31 +44,6 @@ struct zfs_devdesc {
 #include <crypto/intake.h>
 #endif
 
-struct zfs_boot_args
-{
-    uint32_t		size;
-    uint32_t		reserved;
-    uint64_t		pool;
-    uint64_t		root;
-    uint64_t		primary_pool;
-    uint64_t		primary_vdev;
-    union {
-	char		gelipw[256];
-	struct {
-            char                notapw;	/* 
-					 * single null byte to stop keybuf
-					 * being interpreted as a password
-					 */
-	    uint32_t		keybuf_sentinel;
-#ifdef LOADER_GELI_SUPPORT
-	    struct keybuf	*keybuf;
-#else
-	    void		*keybuf;
-#endif
-	};
-    };
-};
-
 int	zfs_parsedev(struct zfs_devdesc *dev, const char *devspec,
 		     const char **path);
 char	*zfs_fmtdev(void *vdev);