mm/debug_vm_pgtable: avoid none pte in pte_clear_test

pte_clear_tests operate on an existing pte entry.  Make sure that is not a
none pte entry.

[aneesh.kumar@linux.ibm.com: avoid kernel crash with riscv]
Link: https://lkml.kernel.org/r/20201015033206.140550-1-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nathan Chancellor <natechancellor@gmail.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Link: https://lkml.kernel.org/r/20200902114222.181353-14-aneesh.kumar@linux.ibm.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index bfc9c65..9a0a42a 100644 (file)
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -540,12 +540,15 @@ static void __init pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp,
 #endif /* PAGETABLE_P4D_FOLDED */
 
 static void __init pte_clear_tests(struct mm_struct *mm, pte_t *ptep,
-                                  unsigned long vaddr)
+                                  unsigned long pfn, unsigned long vaddr,
+                                  pgprot_t prot)
 {
-       pte_t pte = ptep_get(ptep);
+       pte_t pte = pfn_pte(pfn, prot);
 
        pr_debug("Validating PTE clear\n");
+#ifndef CONFIG_RISCV
        pte = __pte(pte_val(pte) | RANDOM_ORVALUE);
+#endif
        set_pte_at(mm, vaddr, ptep, pte);
        barrier();
        pte_clear(mm, vaddr, ptep);
@@ -996,7 +999,7 @@ static int __init debug_vm_pgtable(void)
 
        ptl = pte_lockptr(mm, pmdp);
        spin_lock(ptl);
-       pte_clear_tests(mm, ptep, vaddr);
+       pte_clear_tests(mm, ptep, pte_aligned, vaddr, prot);
        pte_advanced_tests(mm, vma, ptep, pte_aligned, vaddr, prot);
        pte_unmap_unlock(ptep, ptl);