Messages in this thread | | | Date | Mon, 5 Jul 2004 20:11:58 +0100 | From | Jamie Lokier <> | Subject | Re: A question about PROT_NONE on PPC and PPC64 |
| |
Hi Paul,
Gabriel Paubert tells me that PROT_NONE _might_ have the bug described below on the PPC 4xx and 8xx architectures, because their MMUs don't implement "Ks = Kp = 1" segments.
Can you or someone else confirm whether the potential bug occurs on PPC 4xx/8xx?
Thanks, -- Jamie
Paul Mackerras wrote: > > It appears the only difference betwen PROT_READ and PROT_NONE is > > whether _PAGE_USER is set. > > > > Thus PROT_NONE pages aren't readable from userspace, but it appears > > they _are_ readable from kernel space. Is this correct? > > No. Kernel accesses to pages in the user portion of the address space > (0 .. TASK_SIZE-1) are done using the user permissions. On classic > PPC this is implemented (in part) by setting Ks = Kp = 1 in the > segment descriptors for the user segments, which tells the hardware to > check the access as if it was a user access even in supervisor mode. - 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/
| |