On Fri Mar 18 06:32:08 EDT 2011, al...@pbrane.org wrote:
> I've read through the MMU code more than
> a few times and never noticed this. Who
> reads past tmpunmap anyways? ;)
>
> Anthony
>
> diff -c /sys/src/9/pc/mmu.c /tmp/mmu.c
> /sys/src/9/pc/mmu.c:934,940 - /tmp/mmu.c:934,940
> void*
> kaddr(ulong pa)
> {
> - if(pa > (ulong)-KZERO)
> + if(pa >= (ulong)-KZERO)
> panic("kaddr: pa=%#.8lux", pa);
> return (void*)(pa+KZERO);
> }
of course, this would allow one to KADDR(-KZERO).
and get 0. good call. cf. cankaddr().
unfortunately, xalloc() is not playing along. if you have
a kernel that's using a full -KZERO, then your kernel
will panic in xinit() when it tries to set m->klimit to
KADDR(m->base+n*BY2PG), since m->base+n*BY2PG =
-KZERO.
perhaps the correct fix is to store the Confmem
range as [a,b] not [a, b). so
../port/devproc.c:754: if(cm->kbase <= offset && offset <=
cm->klimit-1){
../port/devproc.c:755: if(offset+n >= cm->klimit-1)
../port/devproc.c:756: n = cm->klimit - offset;
../port/xalloc.c:75: m->klimit =
(ulong)KADDR(m->base+n*BY2PG);
would be
../port/devproc.c:753: if(cm->kbase <= offset && offset <=
cm->klimit){
../port/devproc.c:754: if(offset+n >= cm->klimit)
../port/devproc.c:755: n = cm->klimit - offset
+ 1;
../port/xalloc.c:72: m->klimit =
(ulong)KADDR(m->base+n*BY2PG-1);
there's even a comment you can remove
/* klimit-1 because klimit might be zero! */
- erik
