[PATCH v1 01/14] arm64/mm: set_pte(): New layer to manage contig bit

[Ryan Roberts <ryan.roberts@arm.com>]

Create a new layer for the in-table PTE manipulation APIs. For now, The
existing API is prefixed with double underscore to become the
arch-private API and the public API is just a simple wrapper that calls
the private API.

The public API implementation will subsequently be used to transparently
manipulate the contiguous bit where appropriate. But since there are
already some contig-aware users (e.g. hugetlb, kernel mapper), we must
first ensure those users use the private API directly so that the future
contig-bit manipulations in the public API do not interfere with those
existing uses.

No behavioural changes intended.

Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
---
 arch/arm64/include/asm/pgtable.h | 23 ++++++++++++++++++++---
 arch/arm64/kernel/efi.c          |  2 +-
 arch/arm64/mm/fixmap.c           |  2 +-
 arch/arm64/mm/kasan_init.c       |  4 ++--
 arch/arm64/mm/mmu.c              |  2 +-
 arch/arm64/mm/pageattr.c         |  2 +-
 arch/arm64/mm/trans_pgd.c        |  4 ++--
 7 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 6fd012663a01..7f5ce5687466 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -93,7 +93,8 @@ static inline pteval_t __phys_to_pte_val(phys_addr_t phys)
 	__pte(__phys_to_pte_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
 
 #define pte_none(pte)		(!pte_val(pte))
-#define pte_clear(mm,addr,ptep)	set_pte(ptep, __pte(0))
+#define pte_clear(mm, addr, ptep) \
+				__set_pte(ptep, __pte(0))
 #define pte_page(pte)		(pfn_to_page(pte_pfn(pte)))
 
 /*
@@ -260,7 +261,7 @@ static inline pte_t pte_mkdevmap(pte_t pte)
 	return set_pte_bit(pte, __pgprot(PTE_DEVMAP | PTE_SPECIAL));
 }
 
-static inline void set_pte(pte_t *ptep, pte_t pte)
+static inline void __set_pte(pte_t *ptep, pte_t pte)
 {
 	WRITE_ONCE(*ptep, pte);
 
@@ -352,7 +353,7 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
 
 	__check_safe_pte_update(mm, ptep, pte);
 
-	set_pte(ptep, pte);
+	__set_pte(ptep, pte);
 }
 
 static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
@@ -1117,6 +1118,22 @@ extern pte_t ptep_modify_prot_start(struct vm_area_struct *vma,
 extern void ptep_modify_prot_commit(struct vm_area_struct *vma,
 				    unsigned long addr, pte_t *ptep,
 				    pte_t old_pte, pte_t new_pte);
+
+/*
+ * The below functions constitute the public API that arm64 presents to the
+ * core-mm to manipulate PTE entries within the their page tables (or at least
+ * this is the subset of the API that arm64 needs to implement). These public
+ * versions will automatically and transparently apply the contiguous bit where
+ * it makes sense to do so. Therefore any users that are contig-aware (e.g.
+ * hugetlb, kernel mapper) should NOT use these APIs, but instead use the
+ * private versions, which are prefixed with double underscore.
+ */
+
+static inline void set_pte(pte_t *ptep, pte_t pte)
+{
+	__set_pte(ptep, pte);
+}
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_PGTABLE_H */
diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index baab8dd3ead3..7a28b6a08a82 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -115,7 +115,7 @@ static int __init set_permissions(pte_t *ptep, unsigned long addr, void *data)
 	else if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) &&
 		 system_supports_bti() && spd->has_bti)
 		pte = set_pte_bit(pte, __pgprot(PTE_GP));
-	set_pte(ptep, pte);
+	__set_pte(ptep, pte);
 	return 0;
 }
 
diff --git a/arch/arm64/mm/fixmap.c b/arch/arm64/mm/fixmap.c
index c0a3301203bd..51cd4501816d 100644
--- a/arch/arm64/mm/fixmap.c
+++ b/arch/arm64/mm/fixmap.c
@@ -121,7 +121,7 @@ void __set_fixmap(enum fixed_addresses idx,
 	ptep = fixmap_pte(addr);
 
 	if (pgprot_val(flags)) {
-		set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, flags));
+		__set_pte(ptep, pfn_pte(phys >> PAGE_SHIFT, flags));
 	} else {
 		pte_clear(&init_mm, addr, ptep);
 		flush_tlb_kernel_range(addr, addr+PAGE_SIZE);
diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index e969e68de005..40125b217195 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -112,7 +112,7 @@ static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
 		if (!early)
 			memset(__va(page_phys), KASAN_SHADOW_INIT, PAGE_SIZE);
 		next = addr + PAGE_SIZE;
-		set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
+		__set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
 	} while (ptep++, addr = next, addr != end && pte_none(READ_ONCE(*ptep)));
 }
 
@@ -275,7 +275,7 @@ static void __init kasan_init_shadow(void)
 	 * so we should make sure that it maps the zero page read-only.
 	 */
 	for (i = 0; i < PTRS_PER_PTE; i++)
-		set_pte(&kasan_early_shadow_pte[i],
+		__set_pte(&kasan_early_shadow_pte[i],
 			pfn_pte(sym_to_pfn(kasan_early_shadow_page),
 				PAGE_KERNEL_RO));
 
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index af6bc8403ee4..c84dc87d08b9 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -178,7 +178,7 @@ static void init_pte(pmd_t *pmdp, unsigned long addr, unsigned long end,
 	do {
 		pte_t old_pte = READ_ONCE(*ptep);
 
-		set_pte(ptep, pfn_pte(__phys_to_pfn(phys), prot));
+		__set_pte(ptep, pfn_pte(__phys_to_pfn(phys), prot));
 
 		/*
 		 * After the PTE entry has been populated once, we
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index 8e2017ba5f1b..057097acf9e0 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -41,7 +41,7 @@ static int change_page_range(pte_t *ptep, unsigned long addr, void *data)
 	pte = clear_pte_bit(pte, cdata->clear_mask);
 	pte = set_pte_bit(pte, cdata->set_mask);
 
-	set_pte(ptep, pte);
+	__set_pte(ptep, pte);
 	return 0;
 }
 
diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c
index 4ea2eefbc053..f9997b226614 100644
--- a/arch/arm64/mm/trans_pgd.c
+++ b/arch/arm64/mm/trans_pgd.c
@@ -40,7 +40,7 @@ static void _copy_pte(pte_t *dst_ptep, pte_t *src_ptep, unsigned long addr)
 		 * read only (code, rodata). Clear the RDONLY bit from
 		 * the temporary mappings we use during restore.
 		 */
-		set_pte(dst_ptep, pte_mkwrite(pte));
+		__set_pte(dst_ptep, pte_mkwrite(pte));
 	} else if (debug_pagealloc_enabled() && !pte_none(pte)) {
 		/*
 		 * debug_pagealloc will removed the PTE_VALID bit if
@@ -53,7 +53,7 @@ static void _copy_pte(pte_t *dst_ptep, pte_t *src_ptep, unsigned long addr)
 		 */
 		BUG_ON(!pfn_valid(pte_pfn(pte)));
 
-		set_pte(dst_ptep, pte_mkpresent(pte_mkwrite(pte)));
+		__set_pte(dst_ptep, pte_mkpresent(pte_mkwrite(pte)));
 	}
 }
 
-- 
2.25.1