Re: [PATCH] arm64: remove page granularity limitation from KFENCE

Signed-off-by: Liu Shixin <redacted>
---
 arch/arm64/include/asm/kfence.h | 69 ++++++++++++++++++++++++++++++++-
 arch/arm64/mm/mmu.c             |  4 +-
 2 files changed, 70 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/kfence.h b/arch/arm64/include/asm/kfence.h
index aa855c6a0ae6..bee101eced0b 100644
--- a/arch/arm64/include/asm/kfence.h
+++ b/arch/arm64/include/asm/kfence.h

@@ -8,9 +8,76 @@
 #ifndef __ASM_KFENCE_H
 #define __ASM_KFENCE_H

+#include <linux/kfence.h>
 #include <asm/set_memory.h>
+#include <asm/pgalloc.h>

-static inline bool arch_kfence_init_pool(void) { return true; }
+static inline int split_pud_page(pud_t *pud, unsigned long addr)
+{
+       int i;
+       pmd_t *pmd = pmd_alloc_one(&init_mm, addr);
+       unsigned long pfn = PFN_DOWN(__pa(addr));
+
+       if (!pmd)
+               return -ENOMEM;
+
+       for (i = 0; i < PTRS_PER_PMD; i++)
+               set_pmd(pmd + i, pmd_mkhuge(pfn_pmd(pfn + i * PTRS_PER_PTE, PAGE_KERNEL)));
+
+       smp_wmb(); /* See comment in __pte_alloc */
+       pud_populate(&init_mm, pud, pmd);
+       flush_tlb_kernel_range(addr, addr + PUD_SIZE);
+       return 0;
+}
+
+static inline int split_pmd_page(pmd_t *pmd, unsigned long addr)
+{
+       int i;
+       pte_t *pte = pte_alloc_one_kernel(&init_mm);
+       unsigned long pfn = PFN_DOWN(__pa(addr));
+
+       if (!pte)
+               return -ENOMEM;
+
+       for (i = 0; i < PTRS_PER_PTE; i++)
+               set_pte(pte + i, pfn_pte(pfn + i, PAGE_KERNEL));
+
+       smp_wmb(); /* See comment in __pte_alloc */
+       pmd_populate_kernel(&init_mm, pmd, pte);
+
+       flush_tlb_kernel_range(addr, addr + PMD_SIZE);
+       return 0;
+}
+
+static inline bool arch_kfence_init_pool(void)
+{
+       unsigned long addr;
+       pgd_t *pgd;
+       p4d_t *p4d;
+       pud_t *pud;
+       pmd_t *pmd;
+
+       for (addr = (unsigned long)__kfence_pool; is_kfence_address((void *)addr);
+            addr += PAGE_SIZE) {
+               pgd = pgd_offset(&init_mm, addr);
+               if (pgd_leaf(*pgd))
+                       return false;
+               p4d = p4d_offset(pgd, addr);
+               if (p4d_leaf(*p4d))
+                       return false;
+               pud = pud_offset(p4d, addr);
+               if (pud_leaf(*pud)) {
+                       if (split_pud_page(pud, addr & PUD_MASK))
+                               return false;
+               }
+               pmd = pmd_offset(pud, addr);
+               if (pmd_leaf(*pmd)) {
+                       if (split_pmd_page(pmd, addr & PMD_MASK))
+                               return false;
+               }
+       }
+       return true;
+}

 static inline bool kfence_protect_page(unsigned long addr, bool protect)
 {

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index cfd9deb347c3..b2c79ccfb1c5 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c

@@ -516,7 +516,7 @@ static void __init map_mem(pgd_t *pgdp)
         */
        BUILD_BUG_ON(pgd_index(direct_map_end - 1) == pgd_index(direct_map_end));

-       if (can_set_direct_map() || crash_mem_map || IS_ENABLED(CONFIG_KFENCE))
+       if (can_set_direct_map() || crash_mem_map)
                flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;

        /*

@@ -1485,7 +1485,7 @@ int arch_add_memory(int nid, u64 start, u64 size,
         * KFENCE requires linear map to be mapped at page granularity, so that
         * it is possible to protect/unprotect single pages in the KFENCE pool.
         */
-       if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE))
+       if (can_set_direct_map())
                flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS;

        __create_pgd_mapping(swapper_pg_dir, start, __phys_to_virt(start),
--

2.18.0.huawei.25

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