Subject: Re: [PATCH 2/3 V8] [tip:x86/mm] NX protection for kernel data

From: Konrad Rzeszutek Wilk <[email-masked]>
Date: Tue, 21 Sep 2010 15:00:06 -0400

On Tue, Sep 14, 2010 at 07:51:18PM +0200, matthieu castet wrote:
> Hi,
> any feedback on that ?

I was hoping to run your patch through a Xen guest. In the past modifications
in that area caused unbootable kernels :-( But I am still suffering from
post-vacation-amnesia and e-mails so haven't gotten to look at this.

> 
> Thanks,
> 
> Matthieu
> 
> 
> matthieu castet a écrit :
> >   Note: this patch depends on "Correct improper large page
> >preservation" patch
> >      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 script is adjusted so .text always starts and ends on
> >a page bound
> >   2. Linker script is adjusted so .rodata always start and
> >   end on a page boundary
> >   3. NX is set for all pages from _etext through _end in mark_rodata_ro.
> >   4. free_init_pages() sets released memory NX in arch/x86/mm/init.c
> >   5. bios rom is set to x when pcibios is used.
> >      The results of patch application may be observed in the diff
> >of kernel page
> >   table dumps.
> >   pcibios :
> >   --- data_nx_pt_before.txt       2009-10-13 07:48:59.000000000 -0400
> >   +++ data_nx_pt_after.txt        2009-10-13 07:26:46.000000000 -0400
> >   @@ -2,8 +2,9 @@
> >    0x00000000-0xc0000000           3G                           pmd
> >    ---[ Kernel Mapping ]---
> >   -0xc0000000-0xc0100000           1M     RW             GLB x  pte
> >   +0xc0000000-0xc00a0000         640K     RW             GLB NX pte
> >   +0xc00a0000-0xc0100000         384K     RW             GLB x  pte
> >   -0xc0100000-0xc03d7000        2908K     ro             GLB x  pte
> >   +0xc0100000-0xc0318000        2144K     ro             GLB x  pte
> >   +0xc0318000-0xc03d7000         764K     ro             GLB NX pte
> >   -0xc03d7000-0xc0600000        2212K     RW             GLB x  pte
> >   +0xc03d7000-0xc0600000        2212K     RW             GLB NX pte
> >    0xc0600000-0xf7a00000         884M     RW         PSE GLB NX pmd
> >    0xf7a00000-0xf7bfe000        2040K     RW             GLB NX pte
> >    0xf7bfe000-0xf7c00000           8K                           pte
> >      no pcibios :
> >   --- data_nx_pt_before.txt       2009-10-13 07:48:59.000000000 -0400
> >   +++ data_nx_pt_after.txt        2009-10-13 07:26:46.000000000 -0400
> >   @@ -2,8 +2,9 @@
> >    0x00000000-0xc0000000           3G                           pmd
> >    ---[ Kernel Mapping ]---
> >   -0xc0000000-0xc0100000           1M     RW             GLB x  pte
> >   +0xc0000000-0xc0100000           1M     RW             GLB NX pte
> >   -0xc0100000-0xc03d7000        2908K     ro             GLB x  pte
> >   +0xc0100000-0xc0318000        2144K     ro             GLB x  pte
> >   +0xc0318000-0xc03d7000         764K     ro             GLB NX pte
> >   -0xc03d7000-0xc0600000        2212K     RW             GLB x  pte
> >   +0xc03d7000-0xc0600000        2212K     RW             GLB NX pte
> >    0xc0600000-0xf7a00000         884M     RW         PSE GLB NX pmd
> >    0xf7a00000-0xf7bfe000        2040K     RW             GLB NX pte
> >    0xf7bfe000-0xf7c00000           8K                           pte
> >      The patch have been developed for Linux 2.6.34-rc2 x86 by
> >Siarhei Liakh
> >   <[email-masked]> and Xuxian Jiang <[email-masked]>.
> >      V1:  initial patch for 2.6.30
> >   V2:  patch for 2.6.31-rc7
> >   V3:  moved all code into arch/x86, adjusted credits
> >   V4:  fixed ifdef, removed credits from CREDITS
> >   V5:  fixed an address calculation bug in mark_nxdata_nx()
> >   V6:  added acked-by and PT dump diff to commit log
> >   V7:  minor adjustments for -tip
> >   V8:  rework with the merge of "Set first MB as RW+NX"
> >      Signed-off-by: Siarhei Liakh <[email-masked]>
> >   Signed-off-by: Xuxian Jiang <[email-masked]>
> >   Signed-off-by: Matthieu CASTET <[email-masked]>
> >
> 
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