re: ioctl VNDIOCSET vs netbsd32

[matthew green <mrg%eterna.com.au@localhost>]

> /*
>  * The next two structures are marked "__packed" as they normally end up
>  * being padded in 64-bit mode.
>  */
> struct netbsd32_vnd_ioctl {
>         netbsd32_charp  vnd_file;       /* pathname of file to mount */  
>         int             vnd_flags;      /* flags; see below */   
>         struct vndgeom  vnd_geom;       /* geometry to emulate */
>         unsigned int    vnd_osize;      /* (returned) size of disk */
>         uint64_t        vnd_size;       /* (returned) size of disk */
> } __packed;
> 
> where the __packed makes the bogus difference.
> 
> I don't understand the comment. Of course they end up being padded
> (2 bytes after vnd_flags, 2 bytes after vnd_osize), but that applies to
> both the 64bit and the 32bit ABI.
> 
> For which architectures is this __packed important? We need to somehow
> conditionalize it. Or am I missing something?

the packed makes it work on x86-64 where the alignment of
vnd_size is at 7 * 4 bytes, and plain uint64_t will get
padded for 8 byte alignment.

this is bogus (thanks, 9 year old me.)  can you try this?
it removes the __packed and replaces references to the
properly aligned types.  compile tested only.

thanks.


.mrg.


Index: netbsd32_ioctl.h
===================================================================
RCS file: /cvsroot/src/sys/compat/netbsd32/netbsd32_ioctl.h,v
retrieving revision 1.68
diff -p -u -r1.68 netbsd32_ioctl.h
--- netbsd32_ioctl.h	20 Aug 2019 09:32:21 -0000	1.68
+++ netbsd32_ioctl.h	3 Sep 2019 18:48:44 -0000
@@ -473,23 +473,19 @@ struct netbsd32_sioc_sg_req {
 /* from <sys/sockio.h> */
 #define	SIOCGETSGCNT32	_IOWR('u', 52, struct netbsd32_sioc_sg_req) /* sg pkt cnt */
 
-/*
- * The next two structures are marked "__packed" as they normally end up
- * being padded in 64-bit mode.
- */
 struct netbsd32_vnd_ioctl {
 	netbsd32_charp	vnd_file;	/* pathname of file to mount */
 	int		vnd_flags;	/* flags; see below */
 	struct vndgeom	vnd_geom;	/* geometry to emulate */
 	unsigned int	vnd_osize;	/* (returned) size of disk */
-	uint64_t	vnd_size;	/* (returned) size of disk */
-} __packed;
+	netbsd32_uint64	vnd_size;	/* (returned) size of disk */
+};
 
 struct netbsd32_vnd_user {
 	int		vnu_unit;	/* which vnd unit */
-	dev_t		vnu_dev;	/* file is on this device... */
-	ino_t		vnu_ino;	/* ...at this inode */
-} __packed;
+	netbsd32_dev_t	vnu_dev;	/* file is on this device... */
+	netbsd32_ino_t	vnu_ino;	/* ...at this inode */
+};
 
 /* from <dev/vndvar.h> */
 #define VNDIOCSET32	_IOWR('F', 0, struct netbsd32_vnd_ioctl)	/* enable disk */