Messages in this thread | | | Date | Mon, 30 Jul 2007 23:42:52 -0700 (PDT) | Subject | Re: [SPARC32] NULL pointer derefference | From | David Miller <> |
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From: Mark Fortescue <mark@mtfhpc.demon.co.uk> Date: Tue, 31 Jul 2007 06:35:29 +0100 (BST)
> The original code did a job lot of pte stuf in install_arg_page. The > new code seems to replace this using get_user_pages but I have not > worked out how get_user_pages gets to the point at which it > allocated pte's i.e. maps the stack memory it is about to put the > arguments into.
get_user_pages() essentially walks through the requested user address space, faults in pages if necessary, and returns references to those pages.
The logic of get_user_pages() you need to be concerned about is this inner loop:
while (!(page = follow_page(vma, start, foll_flags))) { int ret; ret = handle_mm_fault(mm, vma, start, foll_flags & FOLL_WRITE); ... }
handle_mm_fault() does all the dirty work of a page fault, and is how we get to update_mmu_cache(), the sun4c implementation of which is where you see the crash. - 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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