Messages in this thread | | | From | "David S. Miller" <> | Date | Tue, 10 Apr 2001 11:07:06 -0700 (PDT) | Subject | Re: [CHECKER] amusing copy_from_user bug |
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Petru Paler writes: > On Tue, Apr 10, 2001 at 06:41:28AM -0400, Jakub Jelinek wrote: > > some architectures don't care at all, because verify_area is a noop > > (sparc64). > > Why (and how) is this?
On sparc64, the user lives in an entirely different address space. The user cannot even generate addresses in kernel space. Basically, addresses are prefix'd by an 8-bit tag called an ASI (Address Space Identifier), which tells the cpu which TLB context to use etc. When running in user space or accessing user space in kernel mode we make the cpu use the special userspace ASI.
In fact the user can be given the complete 32-bit or 64-bit virtual address space, the kernel takes up none of it.
Later, David S. Miller davem@redhat.com - 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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