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 vdonnefort@google.com --- 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) {