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Mon, 21 Sep 2026 04:00:58 -0700 (PDT) Date: Mon, 21 Sep 2026 12:00:44 +0100 In-Reply-To: <20260921110050.3977591-1-vdonnefort@google.com> Mime-Version: 1.0 References: <20260921110050.3977591-1-vdonnefort@google.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Message-ID: <20260921110050.3977591-3-vdonnefort@google.com> Subject: [PATCH v2 2/8] arm64: Introduce can_set_direct_map_range() From: Vincent Donnefort To: catalin.marinas@arm.com, will@kernel.org, rppt@kernel.org, akpm@linux-foundation.org, sudeep.holla@kernel.org, jenswi@kernel.org, robh@kernel.org Cc: mark.rutland@arm.com, sumit.garg@kernel.org, ardb@kernel.org, thierry.reding@kernel.org, david@kernel.org, danielmentz@google.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, op-tee@lists.trustedfirmware.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Vincent Donnefort Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260921_120101_074120_571CF037 X-CRM114-Status: GOOD ( 13.07 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org For systems where can_set_direct_map() is false, it is still possible that a subregion of the direct map can be modified if it is mapped at the last-level. Add an implementation for can_set_direct_map_range(). It falls back to a page table walk to verify the mapping level if can_set_direct_map() is false. Signed-off-by: Vincent Donnefort --- arch/arm64/include/asm/set_memory.h | 3 ++ arch/arm64/mm/pageattr.c | 50 +++++++++++++++++++++++++++++ 2 files changed, 53 insertions(+) diff --git a/arch/arm64/include/asm/set_memory.h b/arch/arm64/include/asm/set_memory.h index 0091ba12200e..80bb94a340fd 100644 --- a/arch/arm64/include/asm/set_memory.h +++ b/arch/arm64/include/asm/set_memory.h @@ -9,6 +9,9 @@ bool can_set_direct_map(void); #define can_set_direct_map can_set_direct_map +bool can_set_direct_map_range(struct page *page, unsigned long numpages); +#define can_set_direct_map_range can_set_direct_map_range + int set_memory_valid(unsigned long addr, int numpages, int enable); int set_direct_map_invalid_noflush(struct page *page, unsigned int numpages); diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c index 132938b32eb1..5fcdb292905f 100644 --- a/arch/arm64/mm/pageattr.c +++ b/arch/arm64/mm/pageattr.c @@ -102,6 +102,56 @@ bool can_set_direct_map(void) arm64_kfence_can_set_direct_map() || is_realm_world(); } +static int can_set_direct_map_pud_entry(pud_t *pud, unsigned long addr, + unsigned long next, struct mm_walk *walk) +{ + if (pud_leaf(pudp_get(pud))) + return -EINVAL; + + return 0; +} + +static int can_set_direct_map_pmd_entry(pmd_t *pmd, unsigned long addr, + unsigned long next, struct mm_walk *walk) +{ + if (pmd_leaf(pmdp_get(pmd))) + return -EINVAL; + + return 0; +} + +static int can_set_direct_map_pte_hole(unsigned long addr, unsigned long next, + int depth, struct mm_walk *walk) +{ + return -EINVAL; +} + +static const struct mm_walk_ops can_set_direct_map_ops = { + .pud_entry = can_set_direct_map_pud_entry, + .pmd_entry = can_set_direct_map_pmd_entry, + .pte_hole = can_set_direct_map_pte_hole, +}; + +bool can_set_direct_map_range(struct page *page, unsigned long numpages) +{ + unsigned long addr = (unsigned long)page_address(page); + unsigned long end = addr + numpages * PAGE_SIZE; + + if (can_set_direct_map()) + return true; + + if (!numpages) + return false; + + /* + * If !can_set_direct_map() then no one can split blocks and it is safe + * to walk the page-table lockless. + */ + return !walk_kernel_page_table_range_lockless(addr, end, + &can_set_direct_map_ops, + NULL, NULL); +} + static int update_range_prot(unsigned long start, unsigned long size, pgprot_t set_mask, pgprot_t clear_mask) { -- 2.55.0.1082.g2b9226bbc0-goog