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    SubjectRe: [PATCH] x86: NX protection for kernel data
    On Sun, Jul 19, 2009 at 03:43:06PM -0400, Siarhei Liakh 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>.


    The patch no longer applies.
    The file vmlinux_32.lds.S and vmlinux_64.lds.S has been unified
    into one file.


    > --- a/arch/x86/kernel/vmlinux_32.lds.S
    > +++ b/arch/x86/kernel/vmlinux_32.lds.S
    > @@ -47,6 +47,7 @@ SECTIONS
    > IRQENTRY_TEXT
    > *(.fixup)
    > *(.gnu.warning)
    > + . = ALIGN(PAGE_SIZE); /* .text should occupy whole number of pages */
    > _etext = .; /* End of text section */

    So _etext cover until page boundary - makes sense.

    > } :text = 0x9090
    >
    > @@ -93,6 +94,7 @@ SECTIONS
    > *(.data.read_mostly)
    > _edata = .; /* End of data section */
    > }
    > + . = ALIGN(PAGE_SIZE); /* needed so we can set NX for .data */

    But here _edata does not cover until page boundary.
    And alignmnet is located outside the output section
    definition.
    It would be better/more consistent to follow the style you use for .text here.


    Sam


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