arm64: Improve error reporting on set_pte_at() checks

Currently the BUG_ON() checks do not give enough information about the
PTEs being set. This patch changes BUG_ON to WARN_ONCE and dumps the
values of the old and new PTEs. In addition, the checks are only made if
the new PTE entry is valid.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Ming Lei <tom.leiming@gmail.com>
Cc: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 7e074f93f383fea1891ce79d4048c22f647841a7..63f52b55defe1041a7913217db490528c441c6f3 100644 (file)
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -276,10 +276,14 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
         * hardware updates of the pte (ptep_set_access_flags safely changes
         * valid ptes without going through an invalid entry).
         */
-       if (IS_ENABLED(CONFIG_DEBUG_VM) && IS_ENABLED(CONFIG_ARM64_HW_AFDBM) &&
-           pte_valid(*ptep)) {
-               BUG_ON(!pte_young(pte));
-               BUG_ON(pte_write(*ptep) && !pte_dirty(pte));
+       if (IS_ENABLED(CONFIG_ARM64_HW_AFDBM) &&
+           pte_valid(*ptep) && pte_valid(pte)) {
+               VM_WARN_ONCE(!pte_young(pte),
+                            "%s: racy access flag clearing: 0x%016llx -> 0x%016llx",
+                            __func__, pte_val(*ptep), pte_val(pte));
+               VM_WARN_ONCE(pte_write(*ptep) && !pte_dirty(pte),
+                            "%s: racy dirty state clearing: 0x%016llx -> 0x%016llx",
+                            __func__, pte_val(*ptep), pte_val(pte));
        }
 
        set_pte(ptep, pte);