Messages in this thread | | | Date | Fri, 18 Mar 2022 11:58:22 +0800 | Subject | Re: [PATCH -next 3/4] arm64: mm: add support for page table check | From | Tong Tiangen <> |
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在 2022/3/18 3:00, Catalin Marinas 写道: > On Thu, Mar 17, 2022 at 02:12:02PM +0000, Tong Tiangen wrote: >> @@ -628,6 +647,25 @@ static inline unsigned long pmd_page_vaddr(pmd_t pmd) >> #define pud_leaf(pud) pud_sect(pud) >> #define pud_valid(pud) pte_valid(pud_pte(pud)) >> >> +#ifdef CONFIG_PAGE_TABLE_CHECK >> +static inline bool pte_user_accessible_page(pte_t pte) >> +{ >> + return (pte_val(pte) & PTE_VALID) && (pte_val(pte) & PTE_USER); >> +} > > There is another class of user mappings, execute-only, that have both > PTE_USER and PTE_UXN cleared. So this logic should be: > > pte_valid(pte) && (pte_user(pte) || pte_user_exec(pte)) > > with pte_user() as: > > #define pte_user(pte) (!!(pte_val(pte) & PTE_USER))
Good suggestion, the PTC(page table check) can cover UXN page and pte_user(pte) helper is required.
> > Do we care about PROT_NONE mappings here? They have the valid bit > cleared but pte_present() is true. >
PTC will not check this special type(PROT_NONE) of page.
>> +static inline bool pmd_user_accessible_page(pmd_t pmd) >> +{ >> + return pmd_leaf(pmd) && (pmd_val(pmd) & PTE_VALID) && >> + (pmd_val(pmd) & PTE_USER); >> +} > > pmd_leaf() implies valid, so you can skip it if that's the aim.
PTC only checks whether the memory block corresponding to the pmd_leaf type can access, for !pmd_leaf, PTC checks at the pte level. So i think this is necessary.
> > Similar comment to the pte variant on execute-only and PROT_NONE > mappings
Same considerations as above.
Thanks. Tong >
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