Hi Wolfgang, On Tue, Oct 16, 2012 at 9:43 PM, Wolfgang Denk <[email protected]> wrote: > Dear Marek Vasut, > > In message <[email protected]> you wrote: >> >> > In short, returning non-NULL from malloc(0) and expecting a CPU exception >> > when it is de-referenced is not going to fly. > > We should not expect to have support for any exceptions for any kind > of illegal accesses. In general, behaviours is undetermined. > >> > [1] Apparently the way do do it is to reserve the entire first 4kB page and >> > mark it as 'not-present' so any access causes a page-fault. >> >> Ok, I don't mean to reopen this can of worms again ... but what're we going >> to >> do about this patch? > > NAK it.
That was my thought > It is perfectly valid on most systems to dereference a pointer to > address 0 (which in almost all cases looks the same as a NULL > pointer). In an OS environment, it is valid to dereference _physical_ address 0 but not _virtual_ address 0. To achieve this, you need to configure the MMU accordingly. For x86, this means enabling paging and configuring the physical/virtual address map... > I object against patches that will make access to this data impossible > (or even more complicated than it is now). Exactly - way too complicated for the (questionable) benefit it provides. Regards, Graeme _______________________________________________ U-Boot mailing list [email protected] http://lists.denx.de/mailman/listinfo/u-boot
