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    SubjectRe: [PATCH] x86: NX protection for kernel data
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    On Sun, Jul 19, 2009 at 4:18 PM, Arjan van de Ven<arjan@infradead.org> wrote:
    > On Sun, 19 Jul 2009 15:43:06 -0400
    > Siarhei Liakh <sliakh.lkml@gmail.com> wrote:
    >
    >> This patch expands functionality of CONFIG_DEBUG_RODATA to set main
    >> (static) kernel data area as NX.
    >> The following steps are taken to achieve this:
    >> 1. Linker scripts are adjusted so .text always starts and end on a
    >> page boundary 2. Linker scripts are adjusted so .rodata and .data
    >> always starts and end on a page boundary
    >> 3. void mark_nxdata_nx(void) added to arch/x86/mm/init_64.c and
    >> arch/x86/mm/init_32.c with actual functionality: NX is set for all
    >> pages from _etext through _edata
    >> 4. mark_nxdata_nx() called from init_post(void) in init/main.c
    >>
    >> The patch have been developed for Linux 2.6.30 x86 by Siarhei Liakh
    >> <sliakh.lkml@gmail.com> and Xuxian Jiang <jiang@cs.ncsu.edu>.
    >
    > I like the idea, and am happy to see the lack of ifdefs ;)

    I was thinking about ifdefs, but could not find a place to put them in ;)

    > I wonder if we should have a testcase for this though similar to
    > how stackprotector and rodata get tested already....

    We probably should. In addition, after looking at the code for a
    while, it seems to me that the proper place to enable protection would
    be kernel_physical_mapping_init(). This way the kernel could enjoy
    protection from the very beginning of init, instead of turning it on
    at the end.


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