[PATCH] arm64: mm: Fix dead assignment of old_pte
From: Nathan Huckleberry
Date: Tue Jul 02 2019 - 21:08:04 EST
When analyzed with the clang static analyzer the
following warning occurs
line 251, column 2
Value stored to 'old_pte' is never read
This warning is repeated every time pgtable.h is
included by another file and produces ~3500
extra warnings.
Moving old_pte into preprocessor guard.
Cc: clang-built-linux@xxxxxxxxxxxxxxxx
Signed-off-by: Nathan Huckleberry <nhuck@xxxxxxxxxx>
---
arch/arm64/include/asm/pgtable.h | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index fca26759081a..42ca4fc67f27 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -238,8 +238,6 @@ extern void __sync_icache_dcache(pte_t pteval);
static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
pte_t *ptep, pte_t pte)
{
- pte_t old_pte;
-
if (pte_present(pte) && pte_user_exec(pte) && !pte_special(pte))
__sync_icache_dcache(pte);
@@ -248,8 +246,11 @@ 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)
+ pte_t old_pte;
+
old_pte = READ_ONCE(*ptep);
- if (IS_ENABLED(CONFIG_DEBUG_VM) && pte_valid(old_pte) && pte_valid(pte) &&
+ if (pte_valid(old_pte) && pte_valid(pte) &&
(mm == current->active_mm || atomic_read(&mm->mm_users) > 1)) {
VM_WARN_ONCE(!pte_young(pte),
"%s: racy access flag clearing: 0x%016llx -> 0x%016llx",
@@ -258,6 +259,7 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
"%s: racy dirty state clearing: 0x%016llx -> 0x%016llx",
__func__, pte_val(old_pte), pte_val(pte));
}
+ #endif
set_pte(ptep, pte);
}
--
2.22.0.410.gd8fdbe21b5-goog