[RFC PATCH] mm: introduce alloc hook to apply PTE_CONT

[Huangzhaoyang <huangzhaoyang@xxxxxxxxx>]

From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>

Since there is no PTE_CONT when rodata_full in ARM64, introducing a
hook function to apply PTE_CONT on the proper page blocks.

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
---
 arch/arm64/include/asm/page.h |  5 +++++
 arch/arm64/mm/pageattr.c      | 45 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h
index f98c91b..53cdd09 100644
--- a/arch/arm64/include/asm/page.h
+++ b/arch/arm64/include/asm/page.h
@@ -46,6 +46,11 @@ struct page *alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma,
 
 #include <asm/memory.h>
 
+#define HAVE_ARCH_ALLOC_PAGE
+#define HAVE_ARCH_FREE_PAGE
+
+extern void arch_alloc_page(struct page *page, int order);
+extern void arch_free_page(struct page *page, int order);
 #endif /* !__ASSEMBLY__ */
 
 #define VM_DATA_DEFAULT_FLAGS	(VM_DATA_FLAGS_TSK_EXEC | VM_MTE_ALLOWED)
diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
index a3bacd7..815a06d 100644
--- a/arch/arm64/mm/pageattr.c
+++ b/arch/arm64/mm/pageattr.c
@@ -239,3 +239,48 @@ bool kernel_page_present(struct page *page)
 	ptep = pte_offset_kernel(pmdp, addr);
 	return pte_valid(READ_ONCE(*ptep));
 }
+
+void arch_alloc_page(struct page *page, int order)
+{
+	unsigned long addr;
+	unsigned long cont_pte_low_bound;
+
+	if (!rodata_full)
+		return;
+
+	addr = (u64)page_address(page);
+	if ((order >= 4) && (addr & ~CONT_PTE_MASK) == 0) {
+		order -= 4;
+		do {
+			cont_pte_low_bound = addr & CONT_PTE_MASK;
+			__change_memory_common(cont_pte_low_bound,
+					(~CONT_PTE_MASK + 1), __pgprot(PTE_CONT), __pgprot(0));
+			addr = (u64)page_address(page);
+			page += 4;
+			order--;
+		}while (order >= 0);
+	}
+}
+
+void arch_free_page(struct page *page, int order)
+{
+	unsigned long addr;
+	unsigned long cont_pte_low_bound;
+
+	if (!rodata_full)
+		return;
+
+	addr = (u64)page_address(page);
+	if ((order >= 4) && (addr & ~CONT_PTE_MASK) == 0) {
+		order -= 4;
+		do {
+			cont_pte_low_bound = addr & CONT_PTE_MASK;
+			__change_memory_common(cont_pte_low_bound,
+					(~CONT_PTE_MASK + 1), __pgprot(0), __pgprot(PTE_CONT));
+			addr = (u64)page_address(page);
+			page += 4;
+			order--;
+		}while (order >= 0);
+	}
+}
+
-- 
1.9.1