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

[Andrei Vagin]

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

Reviewed-by: Vincenzo Frascino <vincenzo.frasc...@arm.com>
Signed-off-by: Andrei Vagin <ava...@gmail.com>
---
 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