[PATCH v2 16/32] mm/debug_vm_pgtable,page_table_check: warn pte map fails

Hugh Dickins
2023-06-09T01:28:02Z

Failures here would be surprising: pte_advanced_tests() and
pte_clear_tests() and __page_table_check_pte_clear_range() each
issue a warning if pte_offset_map() or pte_offset_map_lock() fails.

Signed-off-by: Hugh Dickins <hughd@google.com>
---
mm/debug_vm_pgtable.c | 9 ++++++++-
mm/page_table_check.c | 2 ++
2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index c54177aabebd..ee119e33fef1 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -138,6 +138,9 @@ static void __init pte_advanced_tests(struct pgtable_debug_args *args)
return;

pr_debug("Validating PTE advanced\n");
+ if (WARN_ON(!args->ptep))
+ return;
+
pte = pfn_pte(args->pte_pfn, args->page_prot);
set_pte_at(args->mm, args->vaddr, args->ptep, pte);
flush_dcache_page(page);
@@ -619,6 +622,9 @@ static void __init pte_clear_tests(struct pgtable_debug_args *args)
* the unexpected overhead of cache flushing is acceptable.
*/
pr_debug("Validating PTE clear\n");
+ if (WARN_ON(!args->ptep))
+ return;
+
#ifndef CONFIG_RISCV
pte = __pte(pte_val(pte) | RANDOM_ORVALUE);
#endif
@@ -1377,7 +1383,8 @@ static int __init debug_vm_pgtable(void)
args.ptep = pte_offset_map_lock(args.mm, args.pmdp, args.vaddr, &ptl);
pte_clear_tests(&args);
pte_advanced_tests(&args);
- pte_unmap_unlock(args.ptep, ptl);
+ if (args.ptep)
+ pte_unmap_unlock(args.ptep, ptl);

ptl = pmd_lock(args.mm, args.pmdp);
pmd_clear_tests(&args);
diff --git a/mm/page_table_check.c b/mm/page_table_check.c
index f2baf97d5f38..b743a2f6bce0 100644
--- a/mm/page_table_check.c
+++ b/mm/page_table_check.c
@@ -246,6 +246,8 @@ void __page_table_check_pte_clear_range(struct mm_struct *mm,
pte_t *ptep = pte_offset_map(&pmd, addr);
unsigned long i;

+ if (WARN_ON(!ptep))
+ return;
for (i = 0; i < PTRS_PER_PTE; i++) {
__page_table_check_pte_clear(mm, addr, *ptep);
addr += PAGE_SIZE;
--
2.35.3