On Fri, Aug 26, 2016 at 10:13 AM, Dmitry Safonov <dsafo...@virtuozzo.com> wrote:
> Add API to change vdso blob type with arch_prctl.
> As this is usefull only by needs of CRIU, expose
> this interface under CONFIG_CHECKPOINT_RESTORE.
>
> Cc: Andy Lutomirski <l...@kernel.org>
> Cc: Oleg Nesterov <o...@redhat.com>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: "H. Peter Anvin" <h...@zytor.com>
> Cc: Ingo Molnar <mi...@redhat.com>
> Cc: linux...@kvack.org
> Cc: x...@kernel.org
> Cc: Cyrill Gorcunov <gorcu...@openvz.org>
> Cc: Pavel Emelyanov <xe...@virtuozzo.com>
> Signed-off-by: Dmitry Safonov <dsafo...@virtuozzo.com>
> ---
> arch/x86/entry/vdso/vma.c | 45
> ++++++++++++++++++++++++++++++---------
> arch/x86/include/asm/vdso.h | 2 ++
> arch/x86/include/uapi/asm/prctl.h | 6 ++++++
> arch/x86/kernel/process_64.c | 25 ++++++++++++++++++++++
> 4 files changed, 68 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
> index 5bcb25a9e573..dad2b2d8ff03 100644
> --- a/arch/x86/entry/vdso/vma.c
> +++ b/arch/x86/entry/vdso/vma.c
> @@ -176,6 +176,16 @@ static int vvar_fault(const struct vm_special_mapping
> *sm,
> return VM_FAULT_SIGBUS;
> }
>
> +static const struct vm_special_mapping vdso_mapping = {
> + .name = "[vdso]",
> + .fault = vdso_fault,
> + .mremap = vdso_mremap,
> +};
> +static const struct vm_special_mapping vvar_mapping = {
> + .name = "[vvar]",
> + .fault = vvar_fault,
> +};
> +
> /*
> * Add vdso and vvar mappings to current process.
> * @image - blob to map
> @@ -188,16 +198,6 @@ static int map_vdso(const struct vdso_image *image,
> unsigned long addr)
> unsigned long text_start;
> int ret = 0;
>
> - static const struct vm_special_mapping vdso_mapping = {
> - .name = "[vdso]",
> - .fault = vdso_fault,
> - .mremap = vdso_mremap,
> - };
> - static const struct vm_special_mapping vvar_mapping = {
> - .name = "[vvar]",
> - .fault = vvar_fault,
> - };
> -
> if (down_write_killable(&mm->mmap_sem))
> return -EINTR;
>
> @@ -256,6 +256,31 @@ static int map_vdso_randomized(const struct vdso_image
> *image)
> return map_vdso(image, addr);
> }
>
> +int map_vdso_once(const struct vdso_image *image, unsigned long addr)
> +{
> + struct mm_struct *mm = current->mm;
> + struct vm_area_struct *vma;
> +
> + down_write(&mm->mmap_sem);
> + /*
> + * Check if we have already mapped vdso blob - fail to prevent
> + * abusing from userspace install_speciall_mapping, which may
> + * not do accounting and rlimit right.
> + * We could search vma near context.vdso, but it's a slowpath,
> + * so let's explicitely check all VMAs to be completely sure.
> + */
> + for (vma = mm->mmap; vma; vma = vma->vm_next) {
> + if (vma->vm_private_data == &vdso_mapping ||
> + vma->vm_private_data == &vvar_mapping) {
Should probably also check that vm_ops == &special_mapping_vmops,
which means that maybe there should be a:
static inline bool vma_is_special_mapping(const struct vm_area_struct
*vma, const struct vm_special_mapping &sm);
--Andy
