arm64: mm: Use READ_ONCE/WRITE_ONCE when accessing page tables

In many cases, page tables can be accessed concurrently by either another
CPU (due to things like fast gup) or by the hardware page table walker
itself, which may set access/dirty bits. In such cases, it is important
to use READ_ONCE/WRITE_ONCE when accessing page table entries so that
entries cannot be torn, merged or subject to apparent loss of coherence
due to compiler transformations.

Whilst there are some scenarios where this cannot happen (e.g. pinned
kernel mappings for the linear region), the overhead of using READ_ONCE
/WRITE_ONCE everywhere is minimal and makes the code an awful lot easier
to reason about. This patch consistently uses these macros in the arch
code, as well as explicitly namespacing pointers to page table entries
from the entries themselves by using adopting a 'p' suffix for the former
(as is sometimes used elsewhere in the kernel source).

Tested-by: Yury Norov <ynorov@caviumnetworks.com>
Tested-by: Richard Ruigrok <rruigrok@codeaurora.org>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 22 insertions, 22 deletions

diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h
index e9d9f1b006ef..2e05bcd944c8 100644
--- a/arch/arm64/include/asm/pgalloc.h
+++ b/arch/arm64/include/asm/pgalloc.h
@@ -36,23 +36,23 @@ static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long addr)
 	return (pmd_t *)__get_free_page(PGALLOC_GFP);
 }
 
-static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
+static inline void pmd_free(struct mm_struct *mm, pmd_t *pmdp)
 {
-	BUG_ON((unsigned long)pmd & (PAGE_SIZE-1));
-	free_page((unsigned long)pmd);
+	BUG_ON((unsigned long)pmdp & (PAGE_SIZE-1));
+	free_page((unsigned long)pmdp);
 }
 
-static inline void __pud_populate(pud_t *pud, phys_addr_t pmd, pudval_t prot)
+static inline void __pud_populate(pud_t *pudp, phys_addr_t pmdp, pudval_t prot)
 {
-	set_pud(pud, __pud(__phys_to_pud_val(pmd) | prot));
+	set_pud(pudp, __pud(__phys_to_pud_val(pmdp) | prot));
 }
 
-static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
+static inline void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmdp)
 {
-	__pud_populate(pud, __pa(pmd), PMD_TYPE_TABLE);
+	__pud_populate(pudp, __pa(pmdp), PMD_TYPE_TABLE);
 }
 #else
-static inline void __pud_populate(pud_t *pud, phys_addr_t pmd, pudval_t prot)
+static inline void __pud_populate(pud_t *pudp, phys_addr_t pmdp, pudval_t prot)
 {
 	BUILD_BUG();
 }
@@ -65,30 +65,30 @@ static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr)
 	return (pud_t *)__get_free_page(PGALLOC_GFP);
 }
 
-static inline void pud_free(struct mm_struct *mm, pud_t *pud)
+static inline void pud_free(struct mm_struct *mm, pud_t *pudp)
 {
-	BUG_ON((unsigned long)pud & (PAGE_SIZE-1));
-	free_page((unsigned long)pud);
+	BUG_ON((unsigned long)pudp & (PAGE_SIZE-1));
+	free_page((unsigned long)pudp);
 }
 
-static inline void __pgd_populate(pgd_t *pgdp, phys_addr_t pud, pgdval_t prot)
+static inline void __pgd_populate(pgd_t *pgdp, phys_addr_t pudp, pgdval_t prot)
 {
-	set_pgd(pgdp, __pgd(__phys_to_pgd_val(pud) | prot));
+	set_pgd(pgdp, __pgd(__phys_to_pgd_val(pudp) | prot));
 }
 
-static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, pud_t *pud)
+static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgdp, pud_t *pudp)
 {
-	__pgd_populate(pgd, __pa(pud), PUD_TYPE_TABLE);
+	__pgd_populate(pgdp, __pa(pudp), PUD_TYPE_TABLE);
 }
 #else
-static inline void __pgd_populate(pgd_t *pgdp, phys_addr_t pud, pgdval_t prot)
+static inline void __pgd_populate(pgd_t *pgdp, phys_addr_t pudp, pgdval_t prot)
 {
 	BUILD_BUG();
 }
 #endif	/* CONFIG_PGTABLE_LEVELS > 3 */
 
 extern pgd_t *pgd_alloc(struct mm_struct *mm);
-extern void pgd_free(struct mm_struct *mm, pgd_t *pgd);
+extern void pgd_free(struct mm_struct *mm, pgd_t *pgdp);
 
 static inline pte_t *
 pte_alloc_one_kernel(struct mm_struct *mm, unsigned long addr)
@@ -114,10 +114,10 @@ pte_alloc_one(struct mm_struct *mm, unsigned long addr)
 /*
  * Free a PTE table.
  */
-static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte)
+static inline void pte_free_kernel(struct mm_struct *mm, pte_t *ptep)
 {
-	if (pte)
-		free_page((unsigned long)pte);
+	if (ptep)
+		free_page((unsigned long)ptep);
 }
 
 static inline void pte_free(struct mm_struct *mm, pgtable_t pte)
@@ -126,10 +126,10 @@ static inline void pte_free(struct mm_struct *mm, pgtable_t pte)
 	__free_page(pte);
 }
 
-static inline void __pmd_populate(pmd_t *pmdp, phys_addr_t pte,
+static inline void __pmd_populate(pmd_t *pmdp, phys_addr_t ptep,
 				  pmdval_t prot)
 {
-	set_pmd(pmdp, __pmd(__phys_to_pmd_val(pte) | prot));
+	set_pmd(pmdp, __pmd(__phys_to_pmd_val(ptep) | prot));
 }
 
 /*