1 // SPDX-License-Identifier: GPL-2.0-only 2 3 #include <linux/linkage.h> 4 #include <linux/mmap_lock.h> 5 #include <linux/mm.h> 6 #include <linux/time_namespace.h> 7 #include <linux/types.h> 8 #include <linux/vdso_datastore.h> 9 #include <vdso/datapage.h> 10 11 /* 12 * The vDSO data page. 13 */ 14 #ifdef CONFIG_HAVE_GENERIC_VDSO 15 static union vdso_data_store vdso_time_data_store __page_aligned_data; 16 struct vdso_time_data *vdso_k_time_data = vdso_time_data_store.data; 17 static_assert(sizeof(vdso_time_data_store) == PAGE_SIZE); 18 #endif /* CONFIG_HAVE_GENERIC_VDSO */ 19 20 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 21 struct vm_area_struct *vma, struct vm_fault *vmf) 22 { 23 struct page *timens_page = find_timens_vvar_page(vma); 24 unsigned long addr, pfn; 25 vm_fault_t err; 26 27 switch (vmf->pgoff) { 28 case VDSO_TIME_PAGE_OFFSET: 29 if (!IS_ENABLED(CONFIG_HAVE_GENERIC_VDSO)) 30 return VM_FAULT_SIGBUS; 31 pfn = __phys_to_pfn(__pa_symbol(vdso_k_time_data)); 32 if (timens_page) { 33 /* 34 * Fault in VVAR page too, since it will be accessed 35 * to get clock data anyway. 36 */ 37 addr = vmf->address + VDSO_TIMENS_PAGE_OFFSET * PAGE_SIZE; 38 err = vmf_insert_pfn(vma, addr, pfn); 39 if (unlikely(err & VM_FAULT_ERROR)) 40 return err; 41 pfn = page_to_pfn(timens_page); 42 } 43 break; 44 case VDSO_TIMENS_PAGE_OFFSET: 45 /* 46 * If a task belongs to a time namespace then a namespace 47 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and 48 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET 49 * offset. 50 * See also the comment near timens_setup_vdso_data(). 51 */ 52 if (!IS_ENABLED(CONFIG_TIME_NS) || !timens_page) 53 return VM_FAULT_SIGBUS; 54 pfn = __phys_to_pfn(__pa_symbol(vdso_k_time_data)); 55 break; 56 default: 57 return VM_FAULT_SIGBUS; 58 } 59 60 return vmf_insert_pfn(vma, vmf->address, pfn); 61 } 62 63 const struct vm_special_mapping vdso_vvar_mapping = { 64 .name = "[vvar]", 65 .fault = vvar_fault, 66 }; 67 68 struct vm_area_struct *vdso_install_vvar_mapping(struct mm_struct *mm, unsigned long addr) 69 { 70 return _install_special_mapping(mm, addr, VDSO_NR_PAGES * PAGE_SIZE, 71 VM_READ | VM_MAYREAD | VM_IO | VM_DONTDUMP | VM_PFNMAP, 72 &vdso_vvar_mapping); 73 } 74 75 #ifdef CONFIG_TIME_NS 76 /* 77 * The vvar page layout depends on whether a task belongs to the root or 78 * non-root time namespace. Whenever a task changes its namespace, the VVAR 79 * page tables are cleared and then they will be re-faulted with a 80 * corresponding layout. 81 * See also the comment near timens_setup_vdso_data() for details. 82 */ 83 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) 84 { 85 struct mm_struct *mm = task->mm; 86 struct vm_area_struct *vma; 87 VMA_ITERATOR(vmi, mm, 0); 88 89 mmap_read_lock(mm); 90 for_each_vma(vmi, vma) { 91 if (vma_is_special_mapping(vma, &vdso_vvar_mapping)) 92 zap_vma_pages(vma); 93 } 94 mmap_read_unlock(mm); 95 96 return 0; 97 } 98 99 struct vdso_time_data *arch_get_vdso_data(void *vvar_page) 100 { 101 return (struct vdso_time_data *)vvar_page; 102 } 103 #endif 104