Messages in this thread | | | Date | Tue, 10 Oct 2006 04:58:21 +0200 | From | Nick Piggin <> | Subject | Re: ptrace and pfn mappings |
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On Tue, Oct 10, 2006 at 12:47:46PM +1000, Benjamin Herrenschmidt wrote: > > > Switch the mm and do a copy_from_user? (rather than the GUP). > > Sounds pretty ugly :P > > > > Can you do a get_user_pfns, and do a copy_from_user on the pfn > > addresses? In other words, is the memory / mmio at the end of a > > given address the same from the perspective of any process? It > > is for physical memory of course, which is why get_user_pages > > works... > > Doesn't help with the racyness.
I don't understand what the racyness is that you can solve by accessing it from the target process's mm?
> > What if you hold your per-object lock over the operation? (I guess > > it would have to nest *inside* mmap_sem, but that should be OK). > > Over the ptrace operation ? how so ?
You just have to hold it over access_process_vm, AFAIKS. Once it is copied into the kernel buffer that's done. Maybe I misunderstood what the race is? - 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/
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