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Fri, 19 Apr 2024 00:43:58 -0700 (PDT) From: Ryan Roberts To: Catalin Marinas , Will Deacon , Andrew Morton , Shuah Khan , Joey Gouly , Ard Biesheuvel , Mark Rutland , Anshuman Khandual , David Hildenbrand , Shivansh Vij Cc: Ryan Roberts , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: [PATCH v1 2/5] arm64/mm: Add uffd write-protect support Date: Fri, 19 Apr 2024 08:43:41 +0100 Message-Id: <20240419074344.2643212-3-ryan.roberts@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20240419074344.2643212-1-ryan.roberts@arm.com> References: <20240419074344.2643212-1-ryan.roberts@arm.com> MIME-Version: 1.0 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 418B81A000A X-Stat-Signature: 8wuq7thrgydie6mid4tagb94i4wzph7y X-Rspam-User: X-HE-Tag: 1713512641-12746 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Let's use the newly-free PTE SW bit (58) to add support for uffd-wp. The standard handlers are implemented for set/test/clear for both pte and pmd. Additionally we must also track the uffd-wp state as a pte swp bit, so use a free swap entry pte bit (3). Signed-off-by: Ryan Roberts --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/pgtable-prot.h | 8 ++++ arch/arm64/include/asm/pgtable.h | 55 +++++++++++++++++++++++++++ 3 files changed, 64 insertions(+) -- 2.25.1 diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 7b11c98b3e84..763e221f2169 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -255,6 +255,7 @@ config ARM64 select SYSCTL_EXCEPTION_TRACE select THREAD_INFO_IN_TASK select HAVE_ARCH_USERFAULTFD_MINOR if USERFAULTFD + select HAVE_ARCH_USERFAULTFD_WP if USERFAULTFD select TRACE_IRQFLAGS_SUPPORT select TRACE_IRQFLAGS_NMI_SUPPORT select HAVE_SOFTIRQ_ON_OWN_STACK diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h index ef952d69fd04..f1e1f6306e03 100644 --- a/arch/arm64/include/asm/pgtable-prot.h +++ b/arch/arm64/include/asm/pgtable-prot.h @@ -20,6 +20,14 @@ #define PTE_DEVMAP (_AT(pteval_t, 1) << 57) #define PTE_PROT_NONE (PTE_UXN) /* Reuse PTE_UXN; only when !PTE_VALID */ +#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP +#define PTE_UFFD_WP (_AT(pteval_t, 1) << 58) /* uffd-wp tracking */ +#define PTE_SWP_UFFD_WP (_AT(pteval_t, 1) << 3) /* only for swp ptes */ +#else +#define PTE_UFFD_WP (_AT(pteval_t, 0)) +#define PTE_SWP_UFFD_WP (_AT(pteval_t, 0)) +#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */ + /* * This bit indicates that the entry is present i.e. pmd_page() * still points to a valid huge page in memory even if the pmd diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 23aabff4fa6f..3f4748741fdb 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -271,6 +271,34 @@ static inline pte_t pte_mkdevmap(pte_t pte) return set_pte_bit(pte, __pgprot(PTE_DEVMAP | PTE_SPECIAL)); } +#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP +static inline int pte_uffd_wp(pte_t pte) +{ + bool wp = !!(pte_val(pte) & PTE_UFFD_WP); + +#ifdef CONFIG_DEBUG_VM + /* + * Having write bit for wr-protect-marked present ptes is fatal, because + * it means the uffd-wp bit will be ignored and write will just go + * through. See comment in x86 implementation. + */ + WARN_ON_ONCE(wp && pte_write(pte)); +#endif + + return wp; +} + +static inline pte_t pte_mkuffd_wp(pte_t pte) +{ + return pte_wrprotect(set_pte_bit(pte, __pgprot(PTE_UFFD_WP))); +} + +static inline pte_t pte_clear_uffd_wp(pte_t pte) +{ + return clear_pte_bit(pte, __pgprot(PTE_UFFD_WP)); +} +#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */ + static inline void __set_pte(pte_t *ptep, pte_t pte) { WRITE_ONCE(*ptep, pte); @@ -463,6 +491,23 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte) return clear_pte_bit(pte, __pgprot(PTE_SWP_EXCLUSIVE)); } +#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP +static inline pte_t pte_swp_mkuffd_wp(pte_t pte) +{ + return set_pte_bit(pte, __pgprot(PTE_SWP_UFFD_WP)); +} + +static inline int pte_swp_uffd_wp(pte_t pte) +{ + return !!(pte_val(pte) & PTE_SWP_UFFD_WP); +} + +static inline pte_t pte_swp_clear_uffd_wp(pte_t pte) +{ + return clear_pte_bit(pte, __pgprot(PTE_SWP_UFFD_WP)); +} +#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */ + #ifdef CONFIG_NUMA_BALANCING /* * See the comment in include/linux/pgtable.h @@ -508,6 +553,15 @@ static inline int pmd_trans_huge(pmd_t pmd) #define pmd_mkclean(pmd) pte_pmd(pte_mkclean(pmd_pte(pmd))) #define pmd_mkdirty(pmd) pte_pmd(pte_mkdirty(pmd_pte(pmd))) #define pmd_mkyoung(pmd) pte_pmd(pte_mkyoung(pmd_pte(pmd))) +#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_WP +#define pmd_uffd_wp(pmd) pte_uffd_wp(pmd_pte(pmd)) +#define pmd_mkuffd_wp(pmd) pte_pmd(pte_mkuffd_wp(pmd_pte(pmd))) +#define pmd_clear_uffd_wp(pmd) pte_pmd(pte_clear_uffd_wp(pmd_pte(pmd))) +#define pmd_swp_uffd_wp(pmd) pte_swp_uffd_wp(pmd_pte(pmd)) +#define pmd_swp_mkuffd_wp(pmd) pte_pmd(pte_swp_mkuffd_wp(pmd_pte(pmd))) +#define pmd_swp_clear_uffd_wp(pmd) \ + pte_pmd(pte_swp_clear_uffd_wp(pmd_pte(pmd))) +#endif /* CONFIG_HAVE_ARCH_USERFAULTFD_WP */ static inline pmd_t pmd_mkinvalid(pmd_t pmd) { @@ -1248,6 +1302,7 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma, * Encode and decode a swap entry: * bits 0-1: present (must be zero) * bits 2: remember PG_anon_exclusive + * bit 3: remember uffd-wp state * bits 4-53: swap offset * bit 54: PTE_PROT_NONE (overlays PTE_UXN) (must be zero) * bits 55-59: swap type