* [PATCH v2] x86/mm/pti: remove dead logic during user pagetable population
@ 2018-01-07 10:33 Jike Song
2018-01-07 11:36 ` Borislav Petkov
0 siblings, 1 reply; 6+ messages in thread
From: Jike Song @ 2018-01-07 10:33 UTC (permalink / raw)
To: tglx
Cc: linux-kernel, Jike Song, David Woodhouse, Alan Cox, Jiri Koshina,
Linus Torvalds, Tim Chen, Andi Lutomirski, Andi Kleen,
Peter Zijlstra, Paul Turner, Tom Lendacky, Greg KH, Dave Hansen,
Kees Cook, stable
Look at one of the code snippets:
162 if (pgd_none(*pgd)) {
163 unsigned long new_p4d_page = __get_free_page(gfp);
164 if (!new_p4d_page)
165 return NULL;
166
167 if (pgd_none(*pgd)) {
168 set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
169 new_p4d_page = 0;
170 }
171 if (new_p4d_page)
172 free_page(new_p4d_page);
173 }
There can't be any difference between two pgd_none(*pgd) at L162 and L167,
so it's always false at L171.
v2: add the commit message above.
Signed-off-by: Jike Song <albcamus@gmail.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: Jiri Koshina <jikos@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Andi Lutomirski <luto@amacapital.net>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Turner <pjt@google.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Greg KH <gregkh@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kees Cook <keescook@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jike Song <albcamus@gmail.com>
---
arch/x86/mm/pti.c | 28 ++++------------------------
1 file changed, 4 insertions(+), 24 deletions(-)
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 43d4a4a29037..dc611d039bd5 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -164,12 +164,7 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
if (!new_p4d_page)
return NULL;
- if (pgd_none(*pgd)) {
- set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
- new_p4d_page = 0;
- }
- if (new_p4d_page)
- free_page(new_p4d_page);
+ set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
}
BUILD_BUG_ON(pgd_large(*pgd) != 0);
@@ -194,12 +189,7 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
if (!new_pud_page)
return NULL;
- if (p4d_none(*p4d)) {
- set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page)));
- new_pud_page = 0;
- }
- if (new_pud_page)
- free_page(new_pud_page);
+ set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page)));
}
pud = pud_offset(p4d, address);
@@ -213,12 +203,7 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
if (!new_pmd_page)
return NULL;
- if (pud_none(*pud)) {
- set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page)));
- new_pmd_page = 0;
- }
- if (new_pmd_page)
- free_page(new_pmd_page);
+ set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page)));
}
return pmd_offset(pud, address);
@@ -251,12 +236,7 @@ static __init pte_t *pti_user_pagetable_walk_pte(unsigned long address)
if (!new_pte_page)
return NULL;
- if (pmd_none(*pmd)) {
- set_pmd(pmd, __pmd(_KERNPG_TABLE | __pa(new_pte_page)));
- new_pte_page = 0;
- }
- if (new_pte_page)
- free_page(new_pte_page);
+ set_pmd(pmd, __pmd(_KERNPG_TABLE | __pa(new_pte_page)));
}
pte = pte_offset_kernel(pmd, address);
--
2.14.3
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2] x86/mm/pti: remove dead logic during user pagetable population
2018-01-07 10:33 [PATCH v2] x86/mm/pti: remove dead logic during user pagetable population Jike Song
@ 2018-01-07 11:36 ` Borislav Petkov
2018-01-07 12:05 ` Thomas Gleixner
0 siblings, 1 reply; 6+ messages in thread
From: Borislav Petkov @ 2018-01-07 11:36 UTC (permalink / raw)
To: Jike Song
Cc: tglx, linux-kernel, David Woodhouse, Alan Cox, Jiri Koshina,
Linus Torvalds, Tim Chen, Andi Lutomirski, Andi Kleen,
Peter Zijlstra, Paul Turner, Tom Lendacky, Greg KH, Dave Hansen,
Kees Cook, stable
On Sun, Jan 07, 2018 at 06:33:17PM +0800, Jike Song wrote:
> Look at one of the code snippets:
>
> 162 if (pgd_none(*pgd)) {
> 163 unsigned long new_p4d_page = __get_free_page(gfp);
> 164 if (!new_p4d_page)
> 165 return NULL;
> 166
> 167 if (pgd_none(*pgd)) {
> 168 set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
> 169 new_p4d_page = 0;
> 170 }
> 171 if (new_p4d_page)
> 172 free_page(new_p4d_page);
> 173 }
>
> There can't be any difference between two pgd_none(*pgd) at L162 and L167,
> so it's always false at L171.
I think this is a remnant from the kaiser version which did this:
if (pud_none(*pud)) {
unsigned long new_pmd_page = __get_free_page(gfp);
if (!new_pmd_page)
return NULL;
spin_lock(&shadow_table_allocation_lock);
if (pud_none(*pud))
set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page)));
else
free_page(new_pmd_page);
spin_unlock(&shadow_table_allocation_lock);
}
I was wondering too, why the duplicated checks.
Which has this explanation about the need for the locking:
/*
* At runtime, the only things we map are some things for CPU
* hotplug, and stacks for new processes. No two CPUs will ever
* be populating the same addresses, so we only need to ensure
* that we protect between two CPUs trying to allocate and
* populate the same page table page.
*
* Only take this lock when doing a set_p[4um]d(), but it is not
* needed for doing a set_pte(). We assume that only the *owner*
* of a given allocation will be doing this for _their_
* allocation.
*
* This ensures that once a system has been running for a while
* and there have been stacks all over and these page tables
* are fully populated, there will be no further acquisitions of
* this lock.
*/
static DEFINE_SPINLOCK(shadow_table_allocation_lock);
Now I have my suspicions why that's not needed anymore upstream but I'd
let tglx explain better.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] x86/mm/pti: remove dead logic during user pagetable population
2018-01-07 11:36 ` Borislav Petkov
@ 2018-01-07 12:05 ` Thomas Gleixner
2018-01-07 18:34 ` Dave Hansen
2018-01-08 16:03 ` [PATCH v3] " Jike Song
0 siblings, 2 replies; 6+ messages in thread
From: Thomas Gleixner @ 2018-01-07 12:05 UTC (permalink / raw)
To: Borislav Petkov
Cc: Jike Song, linux-kernel, David Woodhouse, Alan Cox, Jiri Koshina,
Linus Torvalds, Tim Chen, Andi Lutomirski, Andi Kleen,
Peter Zijlstra, Paul Turner, Tom Lendacky, Greg KH, Dave Hansen,
Kees Cook, stable
On Sun, 7 Jan 2018, Borislav Petkov wrote:
> On Sun, Jan 07, 2018 at 06:33:17PM +0800, Jike Song wrote:
> > Look at one of the code snippets:
> >
> > 162 if (pgd_none(*pgd)) {
> > 163 unsigned long new_p4d_page = __get_free_page(gfp);
> > 164 if (!new_p4d_page)
> > 165 return NULL;
> > 166
> > 167 if (pgd_none(*pgd)) {
> > 168 set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
> > 169 new_p4d_page = 0;
> > 170 }
> > 171 if (new_p4d_page)
> > 172 free_page(new_p4d_page);
> > 173 }
> >
> > There can't be any difference between two pgd_none(*pgd) at L162 and L167,
> > so it's always false at L171.
>
> I think this is a remnant from the kaiser version which did this:
>
> if (pud_none(*pud)) {
> unsigned long new_pmd_page = __get_free_page(gfp);
> if (!new_pmd_page)
> return NULL;
> spin_lock(&shadow_table_allocation_lock);
> if (pud_none(*pud))
> set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page)));
> else
> free_page(new_pmd_page);
> spin_unlock(&shadow_table_allocation_lock);
> }
>
> I was wondering too, why the duplicated checks.
>
> Which has this explanation about the need for the locking:
>
> /*
> * At runtime, the only things we map are some things for CPU
> * hotplug, and stacks for new processes. No two CPUs will ever
> * be populating the same addresses, so we only need to ensure
> * that we protect between two CPUs trying to allocate and
> * populate the same page table page.
> *
> * Only take this lock when doing a set_p[4um]d(), but it is not
> * needed for doing a set_pte(). We assume that only the *owner*
> * of a given allocation will be doing this for _their_
> * allocation.
> *
> * This ensures that once a system has been running for a while
> * and there have been stacks all over and these page tables
> * are fully populated, there will be no further acquisitions of
> * this lock.
> */
> static DEFINE_SPINLOCK(shadow_table_allocation_lock);
>
> Now I have my suspicions why that's not needed anymore upstream but I'd
> let tglx explain better.
We got rid of all that runtime mapping stuff and the functions are only
called from pti_init(). So the locking and therefor the tests above are not
needed anymore. While at it we should mark all those function __init.
Thanks,
tglx
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] x86/mm/pti: remove dead logic during user pagetable population
2018-01-07 12:05 ` Thomas Gleixner
@ 2018-01-07 18:34 ` Dave Hansen
2018-01-08 16:03 ` [PATCH v3] " Jike Song
1 sibling, 0 replies; 6+ messages in thread
From: Dave Hansen @ 2018-01-07 18:34 UTC (permalink / raw)
To: Thomas Gleixner, Borislav Petkov
Cc: Jike Song, linux-kernel, David Woodhouse, Alan Cox, Jiri Koshina,
Linus Torvalds, Tim Chen, Andi Lutomirski, Andi Kleen,
Peter Zijlstra, Paul Turner, Tom Lendacky, Greg KH, Kees Cook,
stable
On 01/07/2018 04:05 AM, Thomas Gleixner wrote:
>> static DEFINE_SPINLOCK(shadow_table_allocation_lock);
>>
>> Now I have my suspicions why that's not needed anymore upstream but I'd
>> let tglx explain better.
> We got rid of all that runtime mapping stuff and the functions are only
> called from pti_init(). So the locking and therefor the tests above are not
> needed anymore. While at it we should mark all those function __init.
Yes, the double-test was part of an optimization where we attempted to
avoid using a global spinlock in the fork() path. We would check for
unallocated mid-level page tables without the lock. The lock was only
taken it when we needed to *make* an entry to avoid collisions.
Now that it is all single-threaded, there is no chance of a collision,
no need for a lock, and no need for the re-check.
^^ Just in case someone wants to include a bit more first-hand
information about wtf that code was doing there.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v3] x86/mm/pti: remove dead logic during user pagetable population
2018-01-07 12:05 ` Thomas Gleixner
2018-01-07 18:34 ` Dave Hansen
@ 2018-01-08 16:03 ` Jike Song
2018-01-08 20:43 ` [tip:x86/pti] x86/mm/pti: Remove dead logic in pti_user_pagetable_walk*() tip-bot for Jike Song
1 sibling, 1 reply; 6+ messages in thread
From: Jike Song @ 2018-01-08 16:03 UTC (permalink / raw)
To: tglx
Cc: linux-kernel, Jike Song, David Woodhouse, Alan Cox, Jiri Koshina,
Linus Torvalds, Tim Chen, Andi Lutomirski, Andi Kleen,
Peter Zijlstra, Paul Turner, Tom Lendacky, Greg KH, Dave Hansen,
Kees Cook, Borislav Petkov, stable
Look at one of the code snippets:
162 if (pgd_none(*pgd)) {
163 unsigned long new_p4d_page = __get_free_page(gfp);
164 if (!new_p4d_page)
165 return NULL;
166
167 if (pgd_none(*pgd)) {
168 set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
169 new_p4d_page = 0;
170 }
171 if (new_p4d_page)
172 free_page(new_p4d_page);
173 }
There can't be any difference between two pgd_none(*pgd) at L162 and L167,
so it's always false at L171.
To quote Dave Hansen:
> Yes, the double-test was part of an optimization where we attempted to
> avoid using a global spinlock in the fork() path. We would check for
> unallocated mid-level page tables without the lock. The lock was only
> taken it when we needed to *make* an entry to avoid collisions.
>
> Now that it is all single-threaded, there is no chance of a collision,
> no need for a lock, and no need for the re-check.
v3: mark functions __init; add first-hand explanation
v2: add commit message.
Signed-off-by: Jike Song <albcamus@gmail.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: Jiri Koshina <jikos@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Andi Lutomirski <luto@amacapital.net>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Turner <pjt@google.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Greg KH <gregkh@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kees Cook <keescook@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: stable@vger.kernel.org
---
arch/x86/mm/pti.c | 32 ++++++--------------------------
1 file changed, 6 insertions(+), 26 deletions(-)
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 43d4a4a29037..ce38f165489b 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -149,7 +149,7 @@ pgd_t __pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd)
*
* Returns a pointer to a P4D on success, or NULL on failure.
*/
-static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
+static __init p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
{
pgd_t *pgd = kernel_to_user_pgdp(pgd_offset_k(address));
gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO);
@@ -164,12 +164,7 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
if (!new_p4d_page)
return NULL;
- if (pgd_none(*pgd)) {
- set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
- new_p4d_page = 0;
- }
- if (new_p4d_page)
- free_page(new_p4d_page);
+ set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
}
BUILD_BUG_ON(pgd_large(*pgd) != 0);
@@ -182,7 +177,7 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
*
* Returns a pointer to a PMD on success, or NULL on failure.
*/
-static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
+static __init pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
{
gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO);
p4d_t *p4d = pti_user_pagetable_walk_p4d(address);
@@ -194,12 +189,7 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
if (!new_pud_page)
return NULL;
- if (p4d_none(*p4d)) {
- set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page)));
- new_pud_page = 0;
- }
- if (new_pud_page)
- free_page(new_pud_page);
+ set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page)));
}
pud = pud_offset(p4d, address);
@@ -213,12 +203,7 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
if (!new_pmd_page)
return NULL;
- if (pud_none(*pud)) {
- set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page)));
- new_pmd_page = 0;
- }
- if (new_pmd_page)
- free_page(new_pmd_page);
+ set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page)));
}
return pmd_offset(pud, address);
@@ -251,12 +236,7 @@ static __init pte_t *pti_user_pagetable_walk_pte(unsigned long address)
if (!new_pte_page)
return NULL;
- if (pmd_none(*pmd)) {
- set_pmd(pmd, __pmd(_KERNPG_TABLE | __pa(new_pte_page)));
- new_pte_page = 0;
- }
- if (new_pte_page)
- free_page(new_pte_page);
+ set_pmd(pmd, __pmd(_KERNPG_TABLE | __pa(new_pte_page)));
}
pte = pte_offset_kernel(pmd, address);
--
2.14.3
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [tip:x86/pti] x86/mm/pti: Remove dead logic in pti_user_pagetable_walk*()
2018-01-08 16:03 ` [PATCH v3] " Jike Song
@ 2018-01-08 20:43 ` tip-bot for Jike Song
0 siblings, 0 replies; 6+ messages in thread
From: tip-bot for Jike Song @ 2018-01-08 20:43 UTC (permalink / raw)
To: linux-tip-commits
Cc: hpa, ak, mingo, dwmw, bp, thomas.lendacky, jikos, albcamus,
gregkh, dave.hansen, pjt, linux-kernel, peterz, torvalds, gnomes,
tglx, keescook, tim.c.chen, luto
Commit-ID: 8d56eff266f3e41a6c39926269c4c3f58f881a8e
Gitweb: https://git.kernel.org/tip/8d56eff266f3e41a6c39926269c4c3f58f881a8e
Author: Jike Song <albcamus@gmail.com>
AuthorDate: Tue, 9 Jan 2018 00:03:41 +0800
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Mon, 8 Jan 2018 17:42:13 +0100
x86/mm/pti: Remove dead logic in pti_user_pagetable_walk*()
The following code contains dead logic:
162 if (pgd_none(*pgd)) {
163 unsigned long new_p4d_page = __get_free_page(gfp);
164 if (!new_p4d_page)
165 return NULL;
166
167 if (pgd_none(*pgd)) {
168 set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
169 new_p4d_page = 0;
170 }
171 if (new_p4d_page)
172 free_page(new_p4d_page);
173 }
There can't be any difference between two pgd_none(*pgd) at L162 and L167,
so it's always false at L171.
Dave Hansen explained:
Yes, the double-test was part of an optimization where we attempted to
avoid using a global spinlock in the fork() path. We would check for
unallocated mid-level page tables without the lock. The lock was only
taken when we needed to *make* an entry to avoid collisions.
Now that it is all single-threaded, there is no chance of a collision,
no need for a lock, and no need for the re-check.
As all these functions are only called during init, mark them __init as
well.
Fixes: 03f4424f348e ("x86/mm/pti: Add functions to clone kernel PMDs")
Signed-off-by: Jike Song <albcamus@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Jiri Koshina <jikos@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Kees Cook <keescook@google.com>
Cc: Andi Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg KH <gregkh@linux-foundation.org>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Paul Turner <pjt@google.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180108160341.3461-1-albcamus@gmail.com
---
arch/x86/mm/pti.c | 32 ++++++--------------------------
1 file changed, 6 insertions(+), 26 deletions(-)
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 43d4a4a..ce38f16 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -149,7 +149,7 @@ pgd_t __pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd)
*
* Returns a pointer to a P4D on success, or NULL on failure.
*/
-static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
+static __init p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
{
pgd_t *pgd = kernel_to_user_pgdp(pgd_offset_k(address));
gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO);
@@ -164,12 +164,7 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
if (!new_p4d_page)
return NULL;
- if (pgd_none(*pgd)) {
- set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
- new_p4d_page = 0;
- }
- if (new_p4d_page)
- free_page(new_p4d_page);
+ set_pgd(pgd, __pgd(_KERNPG_TABLE | __pa(new_p4d_page)));
}
BUILD_BUG_ON(pgd_large(*pgd) != 0);
@@ -182,7 +177,7 @@ static p4d_t *pti_user_pagetable_walk_p4d(unsigned long address)
*
* Returns a pointer to a PMD on success, or NULL on failure.
*/
-static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
+static __init pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
{
gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO);
p4d_t *p4d = pti_user_pagetable_walk_p4d(address);
@@ -194,12 +189,7 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
if (!new_pud_page)
return NULL;
- if (p4d_none(*p4d)) {
- set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page)));
- new_pud_page = 0;
- }
- if (new_pud_page)
- free_page(new_pud_page);
+ set_p4d(p4d, __p4d(_KERNPG_TABLE | __pa(new_pud_page)));
}
pud = pud_offset(p4d, address);
@@ -213,12 +203,7 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address)
if (!new_pmd_page)
return NULL;
- if (pud_none(*pud)) {
- set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page)));
- new_pmd_page = 0;
- }
- if (new_pmd_page)
- free_page(new_pmd_page);
+ set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page)));
}
return pmd_offset(pud, address);
@@ -251,12 +236,7 @@ static __init pte_t *pti_user_pagetable_walk_pte(unsigned long address)
if (!new_pte_page)
return NULL;
- if (pmd_none(*pmd)) {
- set_pmd(pmd, __pmd(_KERNPG_TABLE | __pa(new_pte_page)));
- new_pte_page = 0;
- }
- if (new_pte_page)
- free_page(new_pte_page);
+ set_pmd(pmd, __pmd(_KERNPG_TABLE | __pa(new_pte_page)));
}
pte = pte_offset_kernel(pmd, address);
^ permalink raw reply related [flat|nested] 6+ messages in thread
end of thread, other threads:[~2018-01-08 20:50 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-01-07 10:33 [PATCH v2] x86/mm/pti: remove dead logic during user pagetable population Jike Song
2018-01-07 11:36 ` Borislav Petkov
2018-01-07 12:05 ` Thomas Gleixner
2018-01-07 18:34 ` Dave Hansen
2018-01-08 16:03 ` [PATCH v3] " Jike Song
2018-01-08 20:43 ` [tip:x86/pti] x86/mm/pti: Remove dead logic in pti_user_pagetable_walk*() tip-bot for Jike Song
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