> PAGE_OFFSET definitely works for me, but a quick scan of the headers
> suggests that non-sun3 m68k builds define PAGE_OFFSET as 0, as does
> s390.
Hum - is there no simple way to determine whether a pointer is
a valid pointer to something returned by __get_free_pages ()? You are
right, S390 in particular seems to allow arbitrary addresses starting from
0.
> Sure, the overloading is self-admittedly hacky, but (again I assume)
> the motivation was to avoid breaking the clients, many of which are
> not in the kernel.org tree. Your proposed change overloads a third
> interpretation on start, namely an arbitrary pointer, outside the
> page allocation.
For some reason I was convinced that this was the originally intended
use of start. The only quotes I find right now are Ori Pomerantz'
Module Programming Guide (http://www.linuxdoc.org/LDP/lkmpg/node16.html)
and Rubini's "Writing Device Drivers", chapter 4. Also, the comment in the
code
if (!start) {
/*
* For proc files that are less than 4k
*/
...
}
supports this notion somehow (start only set if data size > page size).
After all, unless you want to mangle the file position as intended by
the hack, there is no point in touching start at all in proc_read (),
ppos will be updated automatically.
Perhaps I have misunderstood something here.
Who wrote the original code, after all?
Martin
-- Martin Wilck <Martin.Wilck@fujitsu-siemens.com> FSC EP PS DS1, Paderborn Tel. +49 5251 8 15113- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Sat Jun 30 2001 - 21:00:17 EST