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Date: Thu, 13 Jul 2017 15:58:29 +0300
From: Andrey Ryabinin <aryabinin@...tuozzo.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: "Kirill A. Shutemov" <kirill@...temov.name>,
Andy Lutomirski <luto@...nel.org>,
Dmitry Vyukov <dvyukov@...gle.com>,
Alexander Potapenko <glider@...gle.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
"x86@...nel.org" <x86@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...ux.intel.com>,
Dave Hansen <dave.hansen@...el.com>,
linux-arch <linux-arch@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>,
kasan-dev <kasan-dev@...glegroups.com>
Subject: Re: KASAN vs. boot-time switching between 4- and 5-level paging
On 07/11/2017 10:05 PM, Kirill A. Shutemov wrote:
>>> Can use your Signed-off-by for a [cleaned up version of your] patch?
>>
>> Sure.
>
> Another KASAN-releated issue: dumping page tables for KASAN shadow memory
> region takes unreasonable time due to kasan_zero_p?? mapped there.
>
> The patch below helps. Any objections?
>
Well, page tables dump doesn't work at all on 5-level paging.
E.g. I've got this nonsense:
....
---[ Kernel Space ]---
0xffff800000000000-0xffff808000000000 512G pud
---[ Low Kernel Mapping ]---
0xffff808000000000-0xffff810000000000 512G pud
---[ vmalloc() Area ]---
0xffff810000000000-0xffff818000000000 512G pud
---[ Vmemmap ]---
0xffff818000000000-0xffffff0000000000 128512G pud
---[ ESPfix Area ]---
0xffffff0000000000-0x0000000000000000 1T pud
0x0000000000000000-0x0000000000000000 0E pgd
0x0000000000000000-0x0000000000001000 4K RW PCD GLB NX pte
0x0000000000001000-0x0000000000002000 4K pte
0x0000000000002000-0x0000000000003000 4K ro GLB NX pte
0x0000000000003000-0x0000000000004000 4K pte
0x0000000000004000-0x0000000000007000 12K RW GLB NX pte
0x0000000000007000-0x0000000000008000 4K pte
0x0000000000008000-0x0000000000108000 1M RW GLB NX pte
0x0000000000108000-0x0000000000109000 4K pte
0x0000000000109000-0x0000000000189000 512K RW GLB NX pte
0x0000000000189000-0x000000000018a000 4K pte
0x000000000018a000-0x000000000018e000 16K RW GLB NX pte
0x000000000018e000-0x000000000018f000 4K pte
0x000000000018f000-0x0000000000193000 16K RW GLB NX pte
0x0000000000193000-0x0000000000194000 4K pte
... 304 entries skipped ...
---[ EFI Runtime Services ]---
0xffffffef00000000-0xffffffff80000000 66G pud
---[ High Kernel Mapping ]---
0xffffffff80000000-0xffffffffc0000000 1G pud
...
As for KASAN, I think it would be better just to make it work faster, the patch below demonstrates the idea.
---
arch/x86/mm/dump_pagetables.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 0470826d2bdc..36515fba86b0 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -13,6 +13,7 @@
*/
#include <linux/debugfs.h>
+#include <linux/kasan.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/sched.h>
@@ -307,16 +308,19 @@ static void walk_pte_level(struct seq_file *m, struct pg_state *st, pmd_t addr,
static void walk_pmd_level(struct seq_file *m, struct pg_state *st, pud_t addr, unsigned long P)
{
int i;
- pmd_t *start;
+ pmd_t *start, *pmd_addr;
pgprotval_t prot;
- start = (pmd_t *)pud_page_vaddr(addr);
+ pmd_addr = start = (pmd_t *)pud_page_vaddr(addr);
for (i = 0; i < PTRS_PER_PMD; i++) {
st->current_address = normalize_addr(P + i * PMD_LEVEL_MULT);
if (!pmd_none(*start)) {
if (pmd_large(*start) || !pmd_present(*start)) {
prot = pmd_flags(*start);
note_page(m, st, __pgprot(prot), 3);
+ } else if (__pa(pmd_addr) == __pa(kasan_zero_pmd)) {
+ prot = pte_flags(kasan_zero_pte[0]);
+ note_page(m, st, __pgprot(prot), 4);
} else {
walk_pte_level(m, st, *start,
P + i * PMD_LEVEL_MULT);
@@ -349,11 +353,11 @@ static bool pud_already_checked(pud_t *prev_pud, pud_t *pud, bool checkwx)
static void walk_pud_level(struct seq_file *m, struct pg_state *st, p4d_t addr, unsigned long P)
{
int i;
- pud_t *start;
+ pud_t *start, *pud_addr;
pgprotval_t prot;
pud_t *prev_pud = NULL;
- start = (pud_t *)p4d_page_vaddr(addr);
+ pud_addr = start = (pud_t *)p4d_page_vaddr(addr);
for (i = 0; i < PTRS_PER_PUD; i++) {
st->current_address = normalize_addr(P + i * PUD_LEVEL_MULT);
@@ -362,6 +366,9 @@ static void walk_pud_level(struct seq_file *m, struct pg_state *st, p4d_t addr,
if (pud_large(*start) || !pud_present(*start)) {
prot = pud_flags(*start);
note_page(m, st, __pgprot(prot), 2);
+ } else if (__pa(pud_addr) == __pa(kasan_zero_pud)) {
+ prot = pte_flags(kasan_zero_pte[0]);
+ note_page(m, st, __pgprot(prot), 4);
} else {
walk_pmd_level(m, st, *start,
P + i * PUD_LEVEL_MULT);
@@ -385,10 +392,10 @@ static void walk_pud_level(struct seq_file *m, struct pg_state *st, p4d_t addr,
static void walk_p4d_level(struct seq_file *m, struct pg_state *st, pgd_t addr, unsigned long P)
{
int i;
- p4d_t *start;
+ p4d_t *start, *p4d_addr;
pgprotval_t prot;
- start = (p4d_t *)pgd_page_vaddr(addr);
+ p4d_addr = start = (p4d_t *)pgd_page_vaddr(addr);
for (i = 0; i < PTRS_PER_P4D; i++) {
st->current_address = normalize_addr(P + i * P4D_LEVEL_MULT);
@@ -396,6 +403,9 @@ static void walk_p4d_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
if (p4d_large(*start) || !p4d_present(*start)) {
prot = p4d_flags(*start);
note_page(m, st, __pgprot(prot), 2);
+ } else if (__pa(p4d_addr) == __pa(kasan_zero_p4d)) {
+ prot = pte_flags(kasan_zero_pte[0]);
+ note_page(m, st, __pgprot(prot), 4);
} else {
walk_pud_level(m, st, *start,
P + i * P4D_LEVEL_MULT);
--
2.13.0
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