arm64/mm: wire up CONFIG_ARCH_HAS_SET_DIRECT_MAP

Wire up the special helper functions to manipulate aliases of vmalloc
regions in the linear map.
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/Kconfig

@@ -26,6 +26,7 @@ config ARM64
 	select ARCH_HAS_MEMBARRIER_SYNC_CORE
 	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_SETUP_DMA_OPS
+	select ARCH_HAS_SET_DIRECT_MAP
 	select ARCH_HAS_SET_MEMORY
 	select ARCH_HAS_STRICT_KERNEL_RWX
 	select ARCH_HAS_STRICT_MODULE_RWX

arch/arm64/include/asm/cacheflush.h

@@ -187,4 +187,7 @@ static inline void flush_cache_vunmap(unsigned long start, unsigned long end)
 
 int set_memory_valid(unsigned long addr, int numpages, int enable);
 
+int set_direct_map_invalid_noflush(struct page *page);
+int set_direct_map_default_noflush(struct page *page);
+
 #endif

arch/arm64/mm/pageattr.c

@@ -159,17 +159,48 @@ int set_memory_valid(unsigned long addr, int numpages, int enable)
 					__pgprot(PTE_VALID));
 }
 
-#ifdef CONFIG_DEBUG_PAGEALLOC
+int set_direct_map_invalid_noflush(struct page *page)
+{
+	struct page_change_data data = {
+		.set_mask = __pgprot(0),
+		.clear_mask = __pgprot(PTE_VALID),
+	};
+
+	if (!rodata_full)
+		return 0;
+
+	return apply_to_page_range(&init_mm,
+				   (unsigned long)page_address(page),
+				   PAGE_SIZE, change_page_range, &data);
+}
+
+int set_direct_map_default_noflush(struct page *page)
+{
+	struct page_change_data data = {
+		.set_mask = __pgprot(PTE_VALID | PTE_WRITE),
+		.clear_mask = __pgprot(PTE_RDONLY),
+	};
+
+	if (!rodata_full)
+		return 0;
+
+	return apply_to_page_range(&init_mm,
+				   (unsigned long)page_address(page),
+				   PAGE_SIZE, change_page_range, &data);
+}
+
 void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
+	if (!debug_pagealloc_enabled() && !rodata_full)
+		return;
+
 	set_memory_valid((unsigned long)page_address(page), numpages, enable);
 }
-#ifdef CONFIG_HIBERNATION
+
 /*
- * When built with CONFIG_DEBUG_PAGEALLOC and CONFIG_HIBERNATION, this function
- * is used to determine if a linear map page has been marked as not-valid by
- * CONFIG_DEBUG_PAGEALLOC. Walk the page table and check the PTE_VALID bit.
- * This is based on kern_addr_valid(), which almost does what we need.
+ * This function is used to determine if a linear map page has been marked as
+ * not-valid. Walk the page table and check the PTE_VALID bit. This is based
+ * on kern_addr_valid(), which almost does what we need.
  *
  * Because this is only called on the kernel linear map,  p?d_sect() implies
  * p?d_present(). When debug_pagealloc is enabled, sections mappings are
@@ -183,6 +214,9 @@ bool kernel_page_present(struct page *page)
 	pte_t *ptep;
 	unsigned long addr = (unsigned long)page_address(page);
 
+	if (!debug_pagealloc_enabled() && !rodata_full)
+		return true;
+
 	pgdp = pgd_offset_k(addr);
 	if (pgd_none(READ_ONCE(*pgdp)))
 		return false;
@@ -204,5 +238,3 @@ bool kernel_page_present(struct page *page)
 	ptep = pte_offset_kernel(pmdp, addr);
 	return pte_valid(READ_ONCE(*ptep));
 }
-#endif /* CONFIG_HIBERNATION */
-#endif /* CONFIG_DEBUG_PAGEALLOC */

mm/vmalloc.c

@@ -2128,17 +2128,6 @@ static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages)
 	int flush_reset = area->flags & VM_FLUSH_RESET_PERMS;
 	int i;
 
-	/*
-	 * The below block can be removed when all architectures that have
-	 * direct map permissions also have set_direct_map_() implementations.
-	 * This is concerned with resetting the direct map any an vm alias with
-	 * execute permissions, without leaving a RW+X window.
-	 */
-	if (flush_reset && !IS_ENABLED(CONFIG_ARCH_HAS_SET_DIRECT_MAP)) {
-		set_memory_nx(addr, area->nr_pages);
-		set_memory_rw(addr, area->nr_pages);
-	}
-
 	remove_vm_area(area->addr);
 
 	/* If this is not VM_FLUSH_RESET_PERMS memory, no need for the below. */