On Fri, Nov 14, 2014 at 6:29 PM, Yinghai Lu <ying...@kernel.org> wrote:
> On Fri, Nov 14, 2014 at 5:29 PM, Yinghai Lu <ying...@kernel.org> wrote:
>> On Fri, Nov 14, 2014 at 12:45 PM, Kees Cook <keesc...@chromium.org> wrote:
>>> v2:
>>> - added call to free_init_pages(), as suggested by tglx
>
>> something is wrong:
>>
>> [ 7.842479] Freeing unused kernel memory: 3844K (ffffffff82e52000 -
>> ffffffff83213000)
>> [ 7.843305] Write protecting the kernel read-only data: 28672k
>
> ....
> should use attached one instead.
>
> 1. should use _brk_end instead of &end, as we only use partial of
> brk.
> 2. [_brk_end, pm_end) page range is already converted. aka
> is not wasted.
Are you sure? For me, _brk_end isn't far enough:
[ 1.475572] all_end: 0xffffffff82df5000
[ 1.476736] _brk_end: 0xffffffff82dd6000
>
> ---
> arch/x86/mm/init_64.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> Index: linux-2.6/arch/x86/mm/init_64.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/mm/init_64.c
> +++ linux-2.6/arch/x86/mm/init_64.c
> @@ -1124,7 +1124,8 @@ void mark_rodata_ro(void)
> unsigned long end = (unsigned long) &__end_rodata_hpage_align;
> unsigned long text_end = PFN_ALIGN(&__stop___ex_table);
> unsigned long rodata_end = PFN_ALIGN(&__end_rodata);
> - unsigned long all_end = PFN_ALIGN(&_end);
> + unsigned long all_end = PFN_ALIGN(_brk_end);
> + unsigned long pmd_end = roundup(all_end, PMD_SIZE);
>
> printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n",
> (end - start) >> 10);
> @@ -1136,7 +1137,7 @@ void mark_rodata_ro(void)
> * The rodata/data/bss/brk section (but not the kernel text!)
> * should also be not-executable.
> */
> - set_memory_nx(rodata_start, (all_end - rodata_start) >> PAGE_SHIFT);
> + set_memory_nx(rodata_start, (pmd_end - rodata_start) >> PAGE_SHIFT);
>
> rodata_test();
>
> @@ -1148,6 +1149,7 @@ void mark_rodata_ro(void)
> set_memory_ro(start, (end-start) >> PAGE_SHIFT);
> #endif
>
> + /* all_end to pmd_end is handled via free_all_bootmem() */
> free_init_pages("unused kernel",
> (unsigned long) __va(__pa_symbol(text_end)),
> (unsigned long) __va(__pa_symbol(rodata_start)));
This patch produces the same results as my v1 patch:
0xffffffff8202d000-0xffffffff82200000 1868K RW GLB NX pte
0xffffffff82200000-0xffffffff82e00000 12M RW PSE GLB NX pmd
0xffffffff82e00000-0xffffffffc0000000 978M pmd
Is this correct? It sounded like tglx wanted the pmd split, like this:
0xffffffff82200000-0xffffffff82c00000 10M RW PSE GLB NX pmd
0xffffffff82c00000-0xffffffff82df5000 2004K RW GLB NX pte
0xffffffff82df5000-0xffffffff82e00000 44K RW NX pte
0xffffffff82e00000-0xffffffffc0000000 978M pmd
-Kees
--
Kees Cook
Chrome OS Security
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