• Matthieu Castet's avatar
    x86: Add NX protection for kernel data · 5bd5a452
    Matthieu Castet authored
    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
      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
      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 has been originally developed for Linux 2.6.34-rc2 x86 by
    Siarhei Liakh <sliakh.lkml@gmail.com> and Xuxian Jiang <jiang@cs.ncsu.edu>.
    
     -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: default avatarSiarhei Liakh <sliakh.lkml@gmail.com>
    Signed-off-by: default avatarXuxian Jiang <jiang@cs.ncsu.edu>
    Signed-off-by: default avatarMatthieu CASTET <castet.matthieu@free.fr>
    Cc: Arjan van de Ven <arjan@infradead.org>
    Cc: James Morris <jmorris@namei.org>
    Cc: Andi Kleen <ak@muc.de>
    Cc: Rusty Russell <rusty@rustcorp.com.au>
    Cc: Stephen Rothwell <sfr@canb.auug.org.au>
    Cc: Dave Jones <davej@redhat.com>
    Cc: Kees Cook <kees.cook@canonical.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    LKML-Reference: <4CE2F82E.60601@free.fr>
    [ minor cleanliness edits ]
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    5bd5a452
pcbios.c 10.9 KB