Re: _bus_dmamap_sync fires assertion

On Thu, Sep 11, 2025 at 03:29:24PM +0000, Emmanuel Dreyfus wrote:
> Hello
> 
> I am still working on ucom console. boot -a works, DDB works, exitting DDB
> crashes.
> 
> There is an assertion in _bus_dmamap_sync() that fires:
> 829                     KASSERTMSG(len <= map->dm_mapsize - offset,
> 830                         "bad length 0x%"PRIxBUSADDR" + 0x%"PRIxBUSSIZE
> 831                         " > 0x%"PRIxBUSSIZE,
> 832                         offset, len, map->dm_mapsize);
> 
> Values are len = 472, map->dm_mapsize = 4096, offset = 3712.
> 

~~~~~

> The 3712 comes from the USB xfer: ux_dmabuf.udma_offs = 3712
> The error is cryptic. What am I doing wrong?

It's simple buffer overflow.  The sum of 3712 and 472 is greater (by 88)
than 4096.