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SubjectRe: Linux 2.4.1-ac15


On Fri, 23 Feb 2001, Andrea Arcangeli wrote:
>
> I think that can't happen. Infact I think the whole section:
>
> pmd = pmd_offset(pgd, address);
> pmd_k = pmd_offset(pgd_k, address);
>
> if (pmd_present(*pmd) || !pmd_present(*pmd_k))
> goto bad_area_nosemaphore;
> set_pmd(pmd, *pmd_k);
> return;
>
> is superflows.

No. Think about the differences in PAE and non-PAE mode.

> The middle pagetable is shared and the pmd_t entry is set by vmalloc itself (it
> just points to the as well shared pte), it's only the pgd that is setup lazily

In non-PAE mode, the pgd entry doesn't exist. pgd_present() returns a
unconditional 1. Its' the pmd functions that kick in then.

Linus

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