Re: [PATCH -next v6 5/6] arm64/mm: Enable ARCH_SUPPORTS_PAGE_TABLE_CHECK

From: Anshuman Khandual
Date: Fri Apr 29 2022 - 02:17:40 EST

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In reply to: Tong Tiangen: "[PATCH -next v6 5/6] arm64/mm: Enable ARCH_SUPPORTS_PAGE_TABLE_CHECK"
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On 4/26/22 13:40, Tong Tiangen wrote:
> From: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> Signed-off-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
> Reviewed-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
> ---
> 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

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Previous message: Baolu Lu: "Re: [PATCH v4 10/12] iommu: Prepare IOMMU domain for IOPF"
In reply to: Tong Tiangen: "[PATCH -next v6 5/6] arm64/mm: Enable ARCH_SUPPORTS_PAGE_TABLE_CHECK"
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