[PATCH 0/3] arm64: Add support for handling memory corruption

[PATCH 0/3] arm64: Add support for handling memory corruption

[Punit Agrawal]

Hi,

With support for contiguous hugepages being turned off[0], some of the
problems arising from swap entries go away[1]. This simplifies the
changes needed to enable memory corruption handling for arm64 (done in
this seris).

In this series, we updates huge_pte_offset() to correctly deal with
swap entries (Patch 1). This function will need to be updated when
contiguous hugepages are re-enabled.

Patch 2 adds support to send SIGBUS to processes that have their
memory corrupted. With the prerequisites in place, enable memory
corruption handling for arm64 (patch 3).

Thanks,
Punit

[0] https://lkml.org/lkml/2017/4/7/486
[1] https://lkml.org/lkml/2017/4/5/402

Jonathan (Zhixiong) Zhang (2):
  arm64: hwpoison: add VM_FAULT_HWPOISON[_LARGE] handling
  arm64: kconfig: allow support for memory failure handling

Punit Agrawal (1):
  arm64: hugetlb: Fix huge_pte_offset to return poisoned page table
    entries

 arch/arm64/Kconfig          |  1 +
 arch/arm64/mm/fault.c       | 22 +++++++++++++++++++---
 arch/arm64/mm/hugetlbpage.c | 20 +++++++++++++++-----
 3 files changed, 35 insertions(+), 8 deletions(-)

-- 
2.11.0

[PATCH 1/3] arm64: hugetlb: Fix huge_pte_offset to return poisoned page table entries

[Punit Agrawal]

When memory failure is enabled, a poisoned hugepage pte is marked as a
swap entry. huge_pte_offset() does not return the poisoned page table
entries when it encounters PUD/PMD hugepages.

This behaviour of huge_pte_offset() leads to error such as below when
munmap is called on poisoned hugepages.

[  344.165544] mm/pgtable-generic.c:33: bad pmd 000000083af00074.

Fix huge_pte_offset() to return the poisoned pte which is then
appropriately handled by the generic layer code.

Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Steve Capper <steve.capper@arm.com>
Cc: David Woods <dwoods@mellanox.com>
---
 arch/arm64/mm/hugetlbpage.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 7514a000e361..5f1832165d69 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -143,15 +143,24 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
 	pr_debug("%s: addr:0x%lx pgd:%p\n", __func__, addr, pgd);
 	if (!pgd_present(*pgd))
 		return NULL;
-	pud = pud_offset(pgd, addr);
-	if (!pud_present(*pud))
-		return NULL;
 
-	if (pud_huge(*pud))
+	pud = pud_offset(pgd, addr);
+	/*
+	 * In case of HW Poisoning, a hugepage pud/pmd can contain
+	 * poisoned entries. Poisoned entries are marked as swap
+	 * entries.
+	 *
+	 * For puds/pmds that are not present, check to see if it
+	 * could be a swap entry (!present and !none).
+	 */
+	if ((!pte_present(pud_pte(*pud)) && !pud_none(*pud)) || pud_huge(*pud))
 		return (pte_t *)pud;
+
 	pmd = pmd_offset(pud, addr);
-	if (!pmd_present(*pmd))
+	if (pmd_none(*pmd))
 		return NULL;
+	if (!pmd_present(*pmd) && !pmd_none(*pmd))
+		return (pte_t *)pmd;
 
 	if (pte_cont(pmd_pte(*pmd))) {
 		pmd = pmd_offset(
@@ -160,6 +169,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
 	}
 	if (pmd_huge(*pmd))
 		return (pte_t *)pmd;
+
 	pte = pte_offset_kernel(pmd, addr);
 	if (pte_present(*pte) && pte_cont(*pte)) {
 		pte = pte_offset_kernel(
-- 
2.11.0

Re: [PATCH 1/3] arm64: hugetlb: Fix huge_pte_offset to return poisoned page table entries

[Baicar, Tyler]

On 4/12/2017 8:04 AM, Punit Agrawal wrote:
> When memory failure is enabled, a poisoned hugepage pte is marked as a
> swap entry. huge_pte_offset() does not return the poisoned page table
> entries when it encounters PUD/PMD hugepages.
>
> This behaviour of huge_pte_offset() leads to error such as below when
> munmap is called on poisoned hugepages.
>
> [  344.165544] mm/pgtable-generic.c:33: bad pmd 000000083af00074.
>
> Fix huge_pte_offset() to return the poisoned pte which is then
> appropriately handled by the generic layer code.
>
> Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Steve Capper <steve.capper@arm.com>
> Cc: David Woods <dwoods@mellanox.com>
Tested-by: Tyler Baicar <tbaicar@codeaurora.org>

Thanks,
Tyler
> ---
>   arch/arm64/mm/hugetlbpage.c | 20 +++++++++++++++-----
>   1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> index 7514a000e361..5f1832165d69 100644
> --- a/arch/arm64/mm/hugetlbpage.c
> +++ b/arch/arm64/mm/hugetlbpage.c
> @@ -143,15 +143,24 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
>   	pr_debug("%s: addr:0x%lx pgd:%p\n", __func__, addr, pgd);
>   	if (!pgd_present(*pgd))
>   		return NULL;
> -	pud = pud_offset(pgd, addr);
> -	if (!pud_present(*pud))
> -		return NULL;
>   
> -	if (pud_huge(*pud))
> +	pud = pud_offset(pgd, addr);
> +	/*
> +	 * In case of HW Poisoning, a hugepage pud/pmd can contain
> +	 * poisoned entries. Poisoned entries are marked as swap
> +	 * entries.
> +	 *
> +	 * For puds/pmds that are not present, check to see if it
> +	 * could be a swap entry (!present and !none).
> +	 */
> +	if ((!pte_present(pud_pte(*pud)) && !pud_none(*pud)) || pud_huge(*pud))
>   		return (pte_t *)pud;
> +
>   	pmd = pmd_offset(pud, addr);
> -	if (!pmd_present(*pmd))
> +	if (pmd_none(*pmd))
>   		return NULL;
> +	if (!pmd_present(*pmd) && !pmd_none(*pmd))
> +		return (pte_t *)pmd;
>   
>   	if (pte_cont(pmd_pte(*pmd))) {
>   		pmd = pmd_offset(
> @@ -160,6 +169,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
>   	}
>   	if (pmd_huge(*pmd))
>   		return (pte_t *)pmd;
> +
>   	pte = pte_offset_kernel(pmd, addr);
>   	if (pte_present(*pte) && pte_cont(*pte)) {
>   		pte = pte_offset_kernel(

-- 
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.

Re: [PATCH 1/3] arm64: hugetlb: Fix huge_pte_offset to return poisoned page table entries

[Catalin Marinas]

On Wed, Apr 12, 2017 at 03:04:57PM +0100, Punit Agrawal wrote:
> When memory failure is enabled, a poisoned hugepage pte is marked as a
> swap entry. huge_pte_offset() does not return the poisoned page table
> entries when it encounters PUD/PMD hugepages.
> 
> This behaviour of huge_pte_offset() leads to error such as below when
> munmap is called on poisoned hugepages.
> 
> [  344.165544] mm/pgtable-generic.c:33: bad pmd 000000083af00074.
> 
> Fix huge_pte_offset() to return the poisoned pte which is then
> appropriately handled by the generic layer code.
> 
> Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Steve Capper <steve.capper@arm.com>
> Cc: David Woods <dwoods@mellanox.com>
> ---
>  arch/arm64/mm/hugetlbpage.c | 20 +++++++++++++++-----
>  1 file changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> index 7514a000e361..5f1832165d69 100644
> --- a/arch/arm64/mm/hugetlbpage.c
> +++ b/arch/arm64/mm/hugetlbpage.c
> @@ -143,15 +143,24 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
>  	pr_debug("%s: addr:0x%lx pgd:%p\n", __func__, addr, pgd);
>  	if (!pgd_present(*pgd))
>  		return NULL;
> -	pud = pud_offset(pgd, addr);
> -	if (!pud_present(*pud))
> -		return NULL;
>  
> -	if (pud_huge(*pud))
> +	pud = pud_offset(pgd, addr);
> +	/*
> +	 * In case of HW Poisoning, a hugepage pud/pmd can contain
> +	 * poisoned entries. Poisoned entries are marked as swap
> +	 * entries.
> +	 *
> +	 * For puds/pmds that are not present, check to see if it
> +	 * could be a swap entry (!present and !none).
> +	 */
> +	if ((!pte_present(pud_pte(*pud)) && !pud_none(*pud)) || pud_huge(*pud))
>  		return (pte_t *)pud;

Since we use puds as huge pages, can we just change pud_present() to
match the pmd_present()? I'd like to see similar checks for pud and pmd,
it would be easier to follow. Something like (unchecked):

	if (pud_none(*pud))
		return NULL;
	/* swap or huge page */
	if (!pud_present(*pud) || pud_huge(*pud))
		return (pte_t *)pud;
	/* table; check the next level */

> +
>  	pmd = pmd_offset(pud, addr);
> -	if (!pmd_present(*pmd))
> +	if (pmd_none(*pmd))
>  		return NULL;
> +	if (!pmd_present(*pmd) && !pmd_none(*pmd))
> +		return (pte_t *)pmd;

At this point, we already know that pmd_none(*pmd) is false, no ned to
check it again.

-- 
Catalin

Re: [PATCH 1/3] arm64: hugetlb: Fix huge_pte_offset to return poisoned page table entries

[Punit Agrawal]

Catalin Marinas <catalin.marinas@arm.com> writes:

> On Wed, Apr 12, 2017 at 03:04:57PM +0100, Punit Agrawal wrote:
>> When memory failure is enabled, a poisoned hugepage pte is marked as a
>> swap entry. huge_pte_offset() does not return the poisoned page table
>> entries when it encounters PUD/PMD hugepages.
>> 
>> This behaviour of huge_pte_offset() leads to error such as below when
>> munmap is called on poisoned hugepages.
>> 
>> [  344.165544] mm/pgtable-generic.c:33: bad pmd 000000083af00074.
>> 
>> Fix huge_pte_offset() to return the poisoned pte which is then
>> appropriately handled by the generic layer code.
>> 
>> Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Cc: Steve Capper <steve.capper@arm.com>
>> Cc: David Woods <dwoods@mellanox.com>
>> ---
>>  arch/arm64/mm/hugetlbpage.c | 20 +++++++++++++++-----
>>  1 file changed, 15 insertions(+), 5 deletions(-)
>> 
>> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
>> index 7514a000e361..5f1832165d69 100644
>> --- a/arch/arm64/mm/hugetlbpage.c
>> +++ b/arch/arm64/mm/hugetlbpage.c
>> @@ -143,15 +143,24 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
>>  	pr_debug("%s: addr:0x%lx pgd:%p\n", __func__, addr, pgd);
>>  	if (!pgd_present(*pgd))
>>  		return NULL;
>> -	pud = pud_offset(pgd, addr);
>> -	if (!pud_present(*pud))
>> -		return NULL;
>>  
>> -	if (pud_huge(*pud))
>> +	pud = pud_offset(pgd, addr);
>> +	/*
>> +	 * In case of HW Poisoning, a hugepage pud/pmd can contain
>> +	 * poisoned entries. Poisoned entries are marked as swap
>> +	 * entries.
>> +	 *
>> +	 * For puds/pmds that are not present, check to see if it
>> +	 * could be a swap entry (!present and !none).
>> +	 */
>> +	if ((!pte_present(pud_pte(*pud)) && !pud_none(*pud)) || pud_huge(*pud))
>>  		return (pte_t *)pud;
>
> Since we use puds as huge pages, can we just change pud_present() to
> match the pmd_present()? I'd like to see similar checks for pud and pmd,
> it would be easier to follow. Something like (unchecked):
>
> 	if (pud_none(*pud))
> 		return NULL;
> 	/* swap or huge page */
> 	if (!pud_present(*pud) || pud_huge(*pud))
> 		return (pte_t *)pud;
> 	/* table; check the next level */
>
>> +
>>  	pmd = pmd_offset(pud, addr);
>> -	if (!pmd_present(*pmd))
>> +	if (pmd_none(*pmd))
>>  		return NULL;
>> +	if (!pmd_present(*pmd) && !pmd_none(*pmd))
>> +		return (pte_t *)pmd;
>
> At this point, we already know that pmd_none(*pmd) is false, no ned to
> check it again.

Indeed - I was avoiding changing the function to drop contiguous
hugepage support which follows this hunk.

I've made changes locally based on your suggestion and will post a
revised version after the merge window.

Thanks,
Punit

Re: [PATCH 1/3] arm64: hugetlb: Fix huge_pte_offset to return poisoned page table entries

[Timur Tabi]

On Thu, May 4, 2017 at 10:55 AM, Punit Agrawal <punit.agrawal@arm.com> wrote:
> Indeed - I was avoiding changing the function to drop contiguous
> hugepage support which follows this hunk.
>
> I've made changes locally based on your suggestion and will post a
> revised version after the merge window.

Punit, will you be able to post a new version that could be a
candidate for 4.13?

-- 
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.

Re: [PATCH 1/3] arm64: hugetlb: Fix huge_pte_offset to return poisoned page table entries

[Punit Agrawal]

Timur Tabi <timur@codeaurora.org> writes:

> On Thu, May 4, 2017 at 10:55 AM, Punit Agrawal <punit.agrawal@arm.com> wrote:
>> Indeed - I was avoiding changing the function to drop contiguous
>> hugepage support which follows this hunk.
>>
>> I've made changes locally based on your suggestion and will post a
>> revised version after the merge window.
>
> Punit, will you be able to post a new version that could be a
> candidate for 4.13?

Hi Timur,

I've just posted v2 for this series. I was testing the patches on rc1
when I saw your mail come through.

Please shout out if you notice any problems with the new version.

Thanks,
Punit

[PATCH 2/3] arm64: hwpoison: add VM_FAULT_HWPOISON[_LARGE] handling

[Punit Agrawal]

From: "Jonathan (Zhixiong) Zhang" <zjzhang@codeaurora.org>

Add VM_FAULT_HWPOISON[_LARGE] handling to the arm64 page fault
handler. Handling of VM_FAULT_HWPOISON[_LARGE] is very similar
to VM_FAULT_OOM, the only difference is that a different si_code
(BUS_MCEERR_AR) is passed to user space and si_addr_lsb field is
initialized.

Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@codeaurora.org>
Signed-off-by: Tyler Baicar <tbaicar@codeaurora.org>
(fix new __do_user_fault call-site)
Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
---
 arch/arm64/mm/fault.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 1b35b8bddbfb..7684219d8cc4 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -31,6 +31,7 @@
 #include <linux/highmem.h>
 #include <linux/perf_event.h>
 #include <linux/preempt.h>
+#include <linux/hugetlb.h>
 
 #include <asm/bug.h>
 #include <asm/cpufeature.h>
@@ -207,10 +208,11 @@ static void __do_kernel_fault(struct mm_struct *mm, unsigned long addr,
  */
 static void __do_user_fault(struct task_struct *tsk, unsigned long addr,
 			    unsigned int esr, unsigned int sig, int code,
-			    struct pt_regs *regs)
+			    struct pt_regs *regs, int fault)
 {
 	struct siginfo si;
 	const struct fault_info *inf;
+	unsigned int lsb = 0;
 
 	if (unhandled_signal(tsk, sig) && show_unhandled_signals_ratelimited()) {
 		inf = esr_to_fault_info(esr);
@@ -227,6 +229,17 @@ static void __do_user_fault(struct task_struct *tsk, unsigned long addr,
 	si.si_errno = 0;
 	si.si_code = code;
 	si.si_addr = (void __user *)addr;
+	/*
+	 * Either small page or large page may be poisoned.
+	 * In other words, VM_FAULT_HWPOISON_LARGE and
+	 * VM_FAULT_HWPOISON are mutually exclusive.
+	 */
+	if (fault & VM_FAULT_HWPOISON_LARGE)
+		lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
+	else if (fault & VM_FAULT_HWPOISON)
+		lsb = PAGE_SHIFT;
+	si.si_addr_lsb = lsb;
+
 	force_sig_info(sig, &si, tsk);
 }
 
@@ -242,7 +255,7 @@ static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *re
 	 */
 	if (user_mode(regs)) {
 		inf = esr_to_fault_info(esr);
-		__do_user_fault(tsk, addr, esr, inf->sig, inf->code, regs);
+		__do_user_fault(tsk, addr, esr, inf->sig, inf->code, regs, 0);
 	} else
 		__do_kernel_fault(mm, addr, esr, regs);
 }
@@ -444,6 +457,9 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
 		 */
 		sig = SIGBUS;
 		code = BUS_ADRERR;
+	} else if (fault & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE)) {
+		sig = SIGBUS;
+		code = BUS_MCEERR_AR;
 	} else {
 		/*
 		 * Something tried to access memory that isn't in our memory
@@ -454,7 +470,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
 			SEGV_ACCERR : SEGV_MAPERR;
 	}
 
-	__do_user_fault(tsk, addr, esr, sig, code, regs);
+	__do_user_fault(tsk, addr, esr, sig, code, regs, fault);
 	return 0;
 
 no_context:
-- 
2.11.0

[PATCH 3/3] arm64: kconfig: allow support for memory failure handling

[Punit Agrawal]

From: "Jonathan (Zhixiong) Zhang" <zjzhang@codeaurora.org>

Declare ARCH_SUPPORTS_MEMORY_FAILURE, as arm64 does support
memory failure recovery attempt.

Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@codeaurora.org>
Signed-off-by: Tyler Baicar <tbaicar@codeaurora.org>
(Dropped changes to ACPI APEI Kconfig and updated commit log)
Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
---
 arch/arm64/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 3741859765cf..993a5fd85452 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -19,6 +19,7 @@ config ARM64
 	select ARCH_HAS_STRICT_MODULE_RWX
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_USE_CMPXCHG_LOCKREF
+	select ARCH_SUPPORTS_MEMORY_FAILURE
 	select ARCH_SUPPORTS_ATOMIC_RMW
 	select ARCH_SUPPORTS_NUMA_BALANCING
 	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
-- 
2.11.0