[PATCH 1/6] arm64/vdso: use the fault callback to map vvar pages

From: Andrei Vagin
Date: Tue Jun 02 2020 - 14:03:18 EST


This is required to support time namespaces where a time namespace data
page is different for each namespace.

Reviewed-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Signed-off-by: Andrei Vagin <avagin@xxxxxxxxx>
---
arch/arm64/kernel/vdso.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 033a48f30dbb..031ee1a8d4a8 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -114,28 +114,32 @@ static int __vdso_init(enum arch_vdso_type arch_index)
PAGE_SHIFT;

/* Allocate the vDSO pagelist, plus a page for the data. */
- vdso_pagelist = kcalloc(vdso_lookup[arch_index].vdso_pages + 1,
+ vdso_pagelist = kcalloc(vdso_lookup[arch_index].vdso_pages,
sizeof(struct page *),
GFP_KERNEL);
if (vdso_pagelist == NULL)
return -ENOMEM;

- /* Grab the vDSO data page. */
- vdso_pagelist[0] = phys_to_page(__pa_symbol(vdso_data));
-
-
/* Grab the vDSO code pages. */
pfn = sym_to_pfn(vdso_lookup[arch_index].vdso_code_start);

for (i = 0; i < vdso_lookup[arch_index].vdso_pages; i++)
- vdso_pagelist[i + 1] = pfn_to_page(pfn + i);
+ vdso_pagelist[i] = pfn_to_page(pfn + i);

- vdso_lookup[arch_index].dm->pages = &vdso_pagelist[0];
- vdso_lookup[arch_index].cm->pages = &vdso_pagelist[1];
+ vdso_lookup[arch_index].cm->pages = vdso_pagelist;

return 0;
}

+static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
+ struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+ if (vmf->pgoff == 0)
+ return vmf_insert_pfn(vma, vmf->address,
+ sym_to_pfn(vdso_data));
+ return VM_FAULT_SIGBUS;
+}
+
static int __setup_additional_pages(enum arch_vdso_type arch_index,
struct mm_struct *mm,
struct linux_binprm *bprm,
@@ -155,7 +159,7 @@ static int __setup_additional_pages(enum arch_vdso_type arch_index,
}

ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE,
- VM_READ|VM_MAYREAD,
+ VM_READ|VM_MAYREAD|VM_PFNMAP,
vdso_lookup[arch_index].dm);
if (IS_ERR(ret))
goto up_fail;
@@ -215,6 +219,7 @@ static struct vm_special_mapping aarch32_vdso_spec[C_PAGES] = {
#ifdef CONFIG_COMPAT_VDSO
{
.name = "[vvar]",
+ .fault = vvar_fault,
},
{
.name = "[vdso]",
@@ -385,6 +390,7 @@ static int vdso_mremap(const struct vm_special_mapping *sm,
static struct vm_special_mapping vdso_spec[A_PAGES] __ro_after_init = {
{
.name = "[vvar]",
+ .fault = vvar_fault,
},
{
.name = "[vdso]",
--
2.24.1