arm64: vdso: Use only one single vvar mapping

The vvar mapping is the same for all processes. Use a single mapping to
simplify the logic and align it with the other architectures.

In addition this will enable the move of the vvar handling into generic code.

Signed-off-by: Thomas Weißschuh <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Will Deacon <[email protected]>
Acked-by: Will Deacon <[email protected]>
Link: https://lore.kernel.org/all/[email protected]

Author: t-8ch

arch/arm64/kernel/vdso.c

@@ -38,8 +38,6 @@ struct vdso_abi_info {
 	const char *vdso_code_start;
 	const char *vdso_code_end;
 	unsigned long vdso_pages;
-	/* Data Mapping */
-	struct vm_special_mapping *dm;
 	/* Code Mapping */
 	struct vm_special_mapping *cm;
 };
@@ -112,6 +110,8 @@ struct vdso_data *arch_get_vdso_data(void *vvar_page)
 	return (struct vdso_data *)(vvar_page);
 }
 
+static const struct vm_special_mapping vvar_map;
+
 /*
  * The vvar mapping contains data for a specific time namespace, so when a task
  * changes namespace we must unmap its vvar data for the old namespace.
@@ -128,12 +128,8 @@ int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
 	mmap_read_lock(mm);
 
 	for_each_vma(vmi, vma) {
-		if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm))
-			zap_vma_pages(vma);
-#ifdef CONFIG_COMPAT_VDSO
-		if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm))
+		if (vma_is_special_mapping(vma, &vvar_map))
 			zap_vma_pages(vma);
-#endif
 	}
 
 	mmap_read_unlock(mm);
@@ -175,6 +171,11 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 	return vmf_insert_pfn(vma, vmf->address, pfn);
 }
 
+static const struct vm_special_mapping vvar_map = {
+	.name   = "[vvar]",
+	.fault = vvar_fault,
+};
+
 static int __setup_additional_pages(enum vdso_abi abi,
 				    struct mm_struct *mm,
 				    struct linux_binprm *bprm,
@@ -198,7 +199,7 @@ static int __setup_additional_pages(enum vdso_abi abi,
 
 	ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
 				       VM_READ|VM_MAYREAD|VM_PFNMAP,
-				       vdso_info[abi].dm);
+				       &vvar_map);
 	if (IS_ERR(ret))
 		goto up_fail;
 
@@ -228,7 +229,6 @@ static int __setup_additional_pages(enum vdso_abi abi,
 enum aarch32_map {
 	AA32_MAP_VECTORS, /* kuser helpers */
 	AA32_MAP_SIGPAGE,
-	AA32_MAP_VVAR,
 	AA32_MAP_VDSO,
 };
 
@@ -253,10 +253,6 @@ static struct vm_special_mapping aarch32_vdso_maps[] = {
 		.pages	= &aarch32_sig_page,
 		.mremap	= aarch32_sigpage_mremap,
 	},
-	[AA32_MAP_VVAR] = {
-		.name = "[vvar]",
-		.fault = vvar_fault,
-	},
 	[AA32_MAP_VDSO] = {
 		.name = "[vdso]",
 		.mremap = vdso_mremap,
@@ -306,7 +302,6 @@ static int __init __aarch32_alloc_vdso_pages(void)
 	if (!IS_ENABLED(CONFIG_COMPAT_VDSO))
 		return 0;
 
-	vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
 	vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];
 
 	return __vdso_init(VDSO_ABI_AA32);
@@ -401,26 +396,14 @@ int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 }
 #endif /* CONFIG_COMPAT */
 
-enum aarch64_map {
-	AA64_MAP_VVAR,
-	AA64_MAP_VDSO,
-};
-
-static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
-	[AA64_MAP_VVAR] = {
-		.name	= "[vvar]",
-		.fault = vvar_fault,
-	},
-	[AA64_MAP_VDSO] = {
-		.name	= "[vdso]",
-		.mremap = vdso_mremap,
-	},
+static struct vm_special_mapping aarch64_vdso_map __ro_after_init = {
+	.name	= "[vdso]",
+	.mremap = vdso_mremap,
 };
 
 static int __init vdso_init(void)
 {
-	vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
-	vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];
+	vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_map;
 
 	return __vdso_init(VDSO_ABI_AA64);
 }