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Date: Sun, 24 Apr 2022 12:10:07 +0800
From: Tong Tiangen <tongtiangen@...wei.com>
To: Anshuman Khandual <anshuman.khandual@....com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, <x86@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>,
Pasha Tatashin <pasha.tatashin@...een.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>
CC: <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-riscv@...ts.infradead.org>,
Kefeng Wang <wangkefeng.wang@...wei.com>,
Guohanjun <guohanjun@...wei.com>
Subject: Re: [PATCH -next v5 3/5] mm: page_table_check: add hooks to public
helpers
在 2022/4/22 14:05, Anshuman Khandual 写道:
>
>
> On 4/21/22 13:50, Tong Tiangen wrote:
>> Move ptep_clear() to the include/linux/pgtable.h and add page table check
>> relate hooks to some helpers, it's prepare for support page table check
>> feature on new architecture.
>
> Could instrumenting generic page table helpers (fallback instances when its
> corresponding __HAVE_ARCH_XXX is not defined on the platform), might add all
> the page table check hooks into paths on platforms which have not subscribed
> ARCH_SUPPORTS_PAGE_TABLE_CHECK in the first place ? Although these looks have
> !CONFIG_PAGE_TABLE_CHECK fallback stubs in the header, hence a build problem
> gets avoided.
Right, build problems are avoided by fallback stubs in the header file.
>
>>
>> Signed-off-by: Tong Tiangen <tongtiangen@...wei.com>
>> Acked-by: Pasha Tatashin <pasha.tatashin@...een.com>
>> ---
>> arch/x86/include/asm/pgtable.h | 10 ----------
>> include/linux/pgtable.h | 26 ++++++++++++++++++--------
>> 2 files changed, 18 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
>> index 564abe42b0f7..51cd39858f81 100644
>> --- a/arch/x86/include/asm/pgtable.h
>> +++ b/arch/x86/include/asm/pgtable.h
>> @@ -1073,16 +1073,6 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
>> return pte;
>> }
>>
>> -#define __HAVE_ARCH_PTEP_CLEAR
>
> AFICS X86 is the only platform subscribing __HAVE_ARCH_PTEP_CLEAR. Hence if
> this is getting dropped for generic ptep_clear(), then no need to add back
> #ifnded __HAVE_ARCH_PTEP_CLEAR construct. Generic ptep_clear() is the only
> definition for all platforms ?
>
> Also if this patch is trying to drop off __HAVE_ARCH_PTEP_CLEAR along with
> other page table check related changes, it needs to be done via a separate
> patch instead.
Agreed.
IMO, this fix can be patched later.
>
>> -static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
>> - pte_t *ptep)
>> -{
>> - if (IS_ENABLED(CONFIG_PAGE_TABLE_CHECK))
>> - ptep_get_and_clear(mm, addr, ptep);
>> - else
>> - pte_clear(mm, addr, ptep);
>> -}
>> -
>> #define __HAVE_ARCH_PTEP_SET_WRPROTECT
>> static inline void ptep_set_wrprotect(struct mm_struct *mm,
>> unsigned long addr, pte_t *ptep)
>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
>> index 49ab8ee2d6d7..10d2d91edf20 100644
>> --- a/include/linux/pgtable.h
>> +++ b/include/linux/pgtable.h
>> @@ -12,6 +12,7 @@
>> #include <linux/bug.h>
>> #include <linux/errno.h>
>> #include <asm-generic/pgtable_uffd.h>
>> +#include <linux/page_table_check.h>
>>
>> #if 5 - defined(__PAGETABLE_P4D_FOLDED) - defined(__PAGETABLE_PUD_FOLDED) - \
>> defined(__PAGETABLE_PMD_FOLDED) != CONFIG_PGTABLE_LEVELS
>> @@ -272,14 +273,6 @@ static inline bool arch_has_hw_pte_young(void)
>> }
>> #endif
>>
>> -#ifndef __HAVE_ARCH_PTEP_CLEAR
>> -static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
>> - pte_t *ptep)
>> -{
>> - pte_clear(mm, addr, ptep);
>> -}
>> -#endif
>> -
>> #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR
>> static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
>> unsigned long address,
>> @@ -287,10 +280,22 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
>> {
>> pte_t pte = *ptep;
>> pte_clear(mm, address, ptep);
>> + page_table_check_pte_clear(mm, address, pte);
>> return pte;
>> }
>> #endif
>>
>> +#ifndef __HAVE_ARCH_PTEP_CLEAR
>> +static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
>> + pte_t *ptep)
>> +{
>> + if (IS_ENABLED(CONFIG_PAGE_TABLE_CHECK))
>> + ptep_get_and_clear(mm, addr, ptep);
>> + else
>> + pte_clear(mm, addr, ptep);
>
> Could not this be reworked to avoid IS_ENABLED() ? This is confusing. If the page
> table hooks can be added to all potential page table paths via generic helpers,
> irrespective of CONFIG_PAGE_TABLE_CHECK option, there is no rationale for doing
> a IS_ENABLED() check here.
>
From the perspective of code logic, we need to check the pte before
being cleared. Whether pte check is required depends on IS_ENABLED().
Are there any suggestions for better implementation?
Thank you,
Tong.
>> +}
>> +#endif
>> +
>> #ifndef __HAVE_ARCH_PTEP_GET
>> static inline pte_t ptep_get(pte_t *ptep)
>> {
>> @@ -360,7 +365,10 @@ static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
>> pmd_t *pmdp)
>> {
>> pmd_t pmd = *pmdp;
>> +
>> pmd_clear(pmdp);
>> + page_table_check_pmd_clear(mm, address, pmd);
>> +
>> return pmd;
>> }
>> #endif /* __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR */
>> @@ -372,6 +380,8 @@ static inline pud_t pudp_huge_get_and_clear(struct mm_struct *mm,
>> pud_t pud = *pudp;
>>
>> pud_clear(pudp);
>> + page_table_check_pud_clear(mm, address, pud);
>> +
>> return pud;
>> }
>> #endif /* __HAVE_ARCH_PUDP_HUGE_GET_AND_CLEAR */
> .
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