[05/28] arm64: vdso: Use only one single vvar mapping

Commit Message

Thomas Weißschuh Oct. 10, 2024, 7:01 a.m. UTC

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 <[e-mail]>
---
 arch/arm64/kernel/vdso.c | 43 +++++++++++++------------------------------
 1 file changed, 13 insertions(+), 30 deletions(-)

Comments

Will Deacon Oct. 28, 2024, 6:39 p.m. UTC | #1

On Thu, Oct 10, 2024 at 09:01:07AM +0200, Thomas Weißschuh wrote:
> 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 <[e-mail]>
> ---
>  arch/arm64/kernel/vdso.c | 43 +++++++++++++------------------------------
>  1 file changed, 13 insertions(+), 30 deletions(-)

I took this for a spin in qemu to double-check that compat and native
tasks can peacefully co-exist while using the vDSO. It all seems ok, so:

Acked-by: Will Deacon <[e-mail]>
Tested-by: Will Deacon <[e-mail]>

Will

Patch

diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 706c9c3a7a50a4574e77da296e9c83e1e2a9f5ab..2d7f8502953bbcf5c9d32f970d92fed71894b5a9 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -39,8 +39,6 @@  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;
 };
@@ -113,6 +111,8 @@  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.
@@ -129,12 +129,8 @@  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);
@@ -176,6 +172,11 @@  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,
@@ -199,7 +200,7 @@  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;
 
@@ -229,7 +230,6 @@  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,
 };
 
@@ -254,10 +254,6 @@  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,
@@ -307,7 +303,6 @@  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);
@@ -402,26 +397,14 @@  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);
 }