On 08/31/2016 06:00 PM, Andy Lutomirski wrote:
On Fri, Aug 26, 2016 at 10:13 AM, Dmitry Safonov <dsafonov@xxxxxxxxxxxxx> 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 <luto@xxxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: linux-mm@xxxxxxxxx Cc: x86@xxxxxxxxxx Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> Signed-off-by: Dmitry Safonov <dsafonov@xxxxxxxxxxxxx> --- 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);
Well, yep, I thought about it, but left without it to not touch additional headers. Will do for the next version, thanks! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>