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Message-ID: <ae74ea7c-9014-b162-f1e7-a66f402aee49@arm.com>
Date:   Fri, 29 Apr 2022 11:48:18 +0530
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Subject: Re: [PATCH -next v6 5/6] arm64/mm: Enable
 ARCH_SUPPORTS_PAGE_TABLE_CHECK
Content-Language: en-US
To:     Tong Tiangen <tongtiangen@huawei.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        Pasha Tatashin <pasha.tatashin@soleen.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linux-arm-kernel@lists.infradead.org,
        linux-riscv@lists.infradead.org,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        Guohanjun <guohanjun@huawei.com>
References: <20220426081036.1374452-1-tongtiangen@huawei.com>
 <20220426081036.1374452-6-tongtiangen@huawei.com>
From:   Anshuman Khandual <anshuman.khandual@arm.com>
In-Reply-To: <20220426081036.1374452-6-tongtiangen@huawei.com>
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Precedence: bulk


On 4/26/22 13:40, Tong Tiangen wrote:
> From: Kefeng Wang <wangkefeng.wang@huawei.com>
> 
> As commit d283d422c6c4 ("x86: mm: add x86_64 support for page table check")
> , enable ARCH_SUPPORTS_PAGE_TABLE_CHECK on arm64.
> 
> Add additional page table check stubs for page table helpers, these stubs
> can be used to check the existing page table entries.
> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
> Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> ---
>  arch/arm64/Kconfig               |  1 +
>  arch/arm64/include/asm/pgtable.h | 59 +++++++++++++++++++++++++++++---
>  2 files changed, 55 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 18a18a0e855d..c1509525ab8e 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -92,6 +92,7 @@ config ARM64
>  	select ARCH_SUPPORTS_ATOMIC_RMW
>  	select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
>  	select ARCH_SUPPORTS_NUMA_BALANCING
> +	select ARCH_SUPPORTS_PAGE_TABLE_CHECK
>  	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION if COMPAT
>  	select ARCH_WANT_DEFAULT_BPF_JIT
>  	select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index ad9b221963d4..fe17788a6885 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -33,6 +33,7 @@
>  #include <linux/mmdebug.h>
>  #include <linux/mm_types.h>
>  #include <linux/sched.h>
> +#include <linux/page_table_check.h>
>  
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  #define __HAVE_ARCH_FLUSH_PMD_TLB_RANGE
> @@ -96,6 +97,7 @@ static inline pteval_t __phys_to_pte_val(phys_addr_t phys)
>  #define pte_young(pte)		(!!(pte_val(pte) & PTE_AF))
>  #define pte_special(pte)	(!!(pte_val(pte) & PTE_SPECIAL))
>  #define pte_write(pte)		(!!(pte_val(pte) & PTE_WRITE))
> +#define pte_user(pte)		(!!(pte_val(pte) & PTE_USER))
>  #define pte_user_exec(pte)	(!(pte_val(pte) & PTE_UXN))
>  #define pte_cont(pte)		(!!(pte_val(pte) & PTE_CONT))
>  #define pte_devmap(pte)		(!!(pte_val(pte) & PTE_DEVMAP))
> @@ -312,7 +314,7 @@ static inline void __check_racy_pte_update(struct mm_struct *mm, pte_t *ptep,
>  		     __func__, pte_val(old_pte), pte_val(pte));
>  }
>  
> -static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
> +static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
>  			      pte_t *ptep, pte_t pte)

A small nit. Subsequent line containing the arguments "pte_t *ptep ..."
needs to be aligned properly, after '__' got added into set_pte_at().

>  {
>  	if (pte_present(pte) && pte_user_exec(pte) && !pte_special(pte))
> @@ -343,6 +345,13 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
>  	set_pte(ptep, pte);
>  }
>  
> +static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
> +			      pte_t *ptep, pte_t pte)
> +{
> +	page_table_check_pte_set(mm, addr, ptep, pte);
> +	return __set_pte_at(mm, addr, ptep, pte);
> +}
> +
>  /*
>   * Huge pte definitions.
>   */
> @@ -454,6 +463,8 @@ static inline int pmd_trans_huge(pmd_t pmd)
>  #define pmd_dirty(pmd)		pte_dirty(pmd_pte(pmd))
>  #define pmd_young(pmd)		pte_young(pmd_pte(pmd))
>  #define pmd_valid(pmd)		pte_valid(pmd_pte(pmd))
> +#define pmd_user(pmd)		pte_user(pmd_pte(pmd))
> +#define pmd_user_exec(pmd)	pte_user_exec(pmd_pte(pmd))
>  #define pmd_cont(pmd)		pte_cont(pmd_pte(pmd))
>  #define pmd_wrprotect(pmd)	pte_pmd(pte_wrprotect(pmd_pte(pmd)))
>  #define pmd_mkold(pmd)		pte_pmd(pte_mkold(pmd_pte(pmd)))
> @@ -501,8 +512,19 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
>  #define pud_pfn(pud)		((__pud_to_phys(pud) & PUD_MASK) >> PAGE_SHIFT)
>  #define pfn_pud(pfn,prot)	__pud(__phys_to_pud_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
>  
> -#define set_pmd_at(mm, addr, pmdp, pmd)	set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd))
> -#define set_pud_at(mm, addr, pudp, pud)	set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud))
> +static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
> +			      pmd_t *pmdp, pmd_t pmd)
> +{
> +	page_table_check_pmd_set(mm, addr, pmdp, pmd);
> +	return __set_pte_at(mm, addr, (pte_t *)pmdp, pmd_pte(pmd));
> +}
> +
> +static inline void set_pud_at(struct mm_struct *mm, unsigned long addr,
> +			      pud_t *pudp, pud_t pud)
> +{
> +	page_table_check_pud_set(mm, addr, pudp, pud);
> +	return __set_pte_at(mm, addr, (pte_t *)pudp, pud_pte(pud));
> +}
>  
>  #define __p4d_to_phys(p4d)	__pte_to_phys(p4d_pte(p4d))
>  #define __phys_to_p4d_val(phys)	__phys_to_pte_val(phys)
> @@ -643,6 +665,24 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd)
>  #define pud_present(pud)	pte_present(pud_pte(pud))
>  #define pud_leaf(pud)		pud_sect(pud)
>  #define pud_valid(pud)		pte_valid(pud_pte(pud))
> +#define pud_user(pud)		pte_user(pud_pte(pud))
> +
> +#ifdef CONFIG_PAGE_TABLE_CHECK
> +static inline bool pte_user_accessible_page(pte_t pte)
> +{
> +	return pte_present(pte) && (pte_user(pte) || pte_user_exec(pte));
> +}
> +
> +static inline bool pmd_user_accessible_page(pmd_t pmd)
> +{
> +	return pmd_present(pmd) && (pmd_user(pmd) || pmd_user_exec(pmd));
> +}
> +
> +static inline bool pud_user_accessible_page(pud_t pud)
> +{
> +	return pud_present(pud) && pud_user(pud);
> +}
> +#endif
>  
>  static inline void set_pud(pud_t *pudp, pud_t pud)
>  {
> @@ -876,7 +916,11 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
>  static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
>  				       unsigned long address, pte_t *ptep)
>  {
> -	return __pte(xchg_relaxed(&pte_val(*ptep), 0));
> +	pte_t pte = __pte(xchg_relaxed(&pte_val(*ptep), 0));
> +
> +	page_table_check_pte_clear(mm, address, pte);
> +
> +	return pte;
>  }
>  
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> @@ -884,7 +928,11 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
>  static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
>  					    unsigned long address, pmd_t *pmdp)
>  {
> -	return pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp));
> +	pmd_t pmd = pte_pmd(__pte(xchg_relaxed(&pte_val(*(pte_t *)pmdp), 0)));

Why there is any change here ? Why not just the following instead, like what you did
in ptep_get_and_clear() above. The page table entry return value here just needs to
be preserved for subsequent page table check helpers.

	pmd_t pmd = pte_pmd(ptep_get_and_clear(mm, address, (pte_t *)pmdp));

> +
> +	page_table_check_pmd_clear(mm, address, pmd);
> +
> +	return pmd;
>  }
>  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  
> @@ -918,6 +966,7 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm,
>  static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
>  		unsigned long address, pmd_t *pmdp, pmd_t pmd)
>  {
> +	page_table_check_pmd_set(vma->vm_mm, address, pmdp, pmd);
>  	return __pmd(xchg_relaxed(&pmd_val(*pmdp), pmd_val(pmd)));
>  }
>  #endif