On Sat, Jun 10, 2017 at 05:18:16 +0200, Emmanuel Dreyfus wrote:
> I just upgraded an HP Jornada 720 from NetBSD 2.0 to NetBSD 7.1, and
> discovered the wscons keymaps were broken in the meantime: it is impossible to
> change the keymap using wsconsctl encoding or wsconsctl map. Both commands
> succeed but have no effect.
>
> After poking a few printf in the kernel, I found this in
> src/sys/dev/hpc/hpckbd.c:
>
> /* fix keydesc table */
> /*
> * XXX The way this is done is really wrong. The __UNCONST()
> * is a hint as to what is wrong. This actually ends up modifying
> * initialized data which is marked "const".
> * The reason we get away with it here is apparently that text
> * and read-only data gets mapped read/write on the platforms
> * using this code.
> */
> desc = (struct wscons_keydesc *)__UNCONST(hpckbd_keymapdata.keydesc);
> for (i = 0; desc[i].name != 0; i++) {
> if ((desc[i].name & KB_MACHDEP) && desc[i].map == NULL) {
> desc[i].map = map;
> desc[i].map_size = mapsize;
> }
> }
>
> I managed to restore wscons keymaps by copying hpckbd_keymapdata.keydesc into
> a malloc() buffer and changing the hpckbd_keymapdata.keydesc to the new
> location, which is mapped read/write.
>
> The offending code did not change since NetBSD 2.0, except the XXX comment
> added in 2015. That suggests the compiler behavior changed about initalized
> const data, which was still mapped R/W in the ancient time and is now really
> read-only, altough it accepts nilpotent writes without raising an exception.
The constness in the MI wskbd code looks wrong:
/* KBD_NULLMAP generates a entry for machine native variant.
the entry will be modified by machine dependent keyboard driver. */
#define KBD_NULLMAP() ...
const struct wscons_keydesc pckbd_keydesctab[] = {
...
/* placeholders */
KBD_NULLMAP(KB_US | KB_MACHDEP, KB_US),
...
};
Which is obviously self-contradictory.
This is probably b/c induced by const in:
struct wskbd_mapdata {
const struct wscons_keydesc *keydesc;
kbd_t layout;
};
> + for (sz = 0; hpckbd_keymapdata.keydesc[sz].name != 0; sz++);
/usr/share/misc/style requires explicit no-op "continue" here.
-uwe
