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 #ifdef CONFIG_VDSO_GETRANDOM 21 static union { 22 struct vdso_rng_data data; 23 u8 page[PAGE_SIZE]; 24 } vdso_rng_data_store __page_aligned_data; 25 struct vdso_rng_data *vdso_k_rng_data = &vdso_rng_data_store.data; 26 static_assert(sizeof(vdso_rng_data_store) == PAGE_SIZE); 27 #endif /* CONFIG_VDSO_GETRANDOM */ 28 29 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 30 struct vm_area_struct *vma, struct vm_fault *vmf) 31 { 32 struct page *timens_page = find_timens_vvar_page(vma); 33 unsigned long addr, pfn; 34 vm_fault_t err; 35 36 switch (vmf->pgoff) { 37 case VDSO_TIME_PAGE_OFFSET: 38 if (!IS_ENABLED(CONFIG_HAVE_GENERIC_VDSO)) 39 return VM_FAULT_SIGBUS; 40 pfn = __phys_to_pfn(__pa_symbol(vdso_k_time_data)); 41 if (timens_page) { 42 /* 43 * Fault in VVAR page too, since it will be accessed 44 * to get clock data anyway. 45 */ 46 addr = vmf->address + VDSO_TIMENS_PAGE_OFFSET * PAGE_SIZE; 47 err = vmf_insert_pfn(vma, addr, pfn); 48 if (unlikely(err & VM_FAULT_ERROR)) 49 return err; 50 pfn = page_to_pfn(timens_page); 51 } 52 break; 53 case VDSO_TIMENS_PAGE_OFFSET: 54 /* 55 * If a task belongs to a time namespace then a namespace 56 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and 57 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET 58 * offset. 59 * See also the comment near timens_setup_vdso_data(). 60 */ 61 if (!IS_ENABLED(CONFIG_TIME_NS) || !timens_page) 62 return VM_FAULT_SIGBUS; 63 pfn = __phys_to_pfn(__pa_symbol(vdso_k_time_data)); 64 break; 65 case VDSO_RNG_PAGE_OFFSET: 66 if (!IS_ENABLED(CONFIG_VDSO_GETRANDOM)) 67 return VM_FAULT_SIGBUS; 68 pfn = __phys_to_pfn(__pa_symbol(vdso_k_rng_data)); 69 break; 70 default: 71 return VM_FAULT_SIGBUS; 72 } 73 74 return vmf_insert_pfn(vma, vmf->address, pfn); 75 } 76 77 const struct vm_special_mapping vdso_vvar_mapping = { 78 .name = "[vvar]", 79 .fault = vvar_fault, 80 }; 81 82 struct vm_area_struct *vdso_install_vvar_mapping(struct mm_struct *mm, unsigned long addr) 83 { 84 return _install_special_mapping(mm, addr, VDSO_NR_PAGES * PAGE_SIZE, 85 VM_READ | VM_MAYREAD | VM_IO | VM_DONTDUMP | VM_PFNMAP, 86 &vdso_vvar_mapping); 87 } 88 89 #ifdef CONFIG_TIME_NS 90 /* 91 * The vvar page layout depends on whether a task belongs to the root or 92 * non-root time namespace. Whenever a task changes its namespace, the VVAR 93 * page tables are cleared and then they will be re-faulted with a 94 * corresponding layout. 95 * See also the comment near timens_setup_vdso_data() for details. 96 */ 97 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) 98 { 99 struct mm_struct *mm = task->mm; 100 struct vm_area_struct *vma; 101 VMA_ITERATOR(vmi, mm, 0); 102 103 mmap_read_lock(mm); 104 for_each_vma(vmi, vma) { 105 if (vma_is_special_mapping(vma, &vdso_vvar_mapping)) 106 zap_vma_pages(vma); 107 } 108 mmap_read_unlock(mm); 109 110 return 0; 111 } 112 113 struct vdso_time_data *arch_get_vdso_data(void *vvar_page) 114 { 115 return (struct vdso_time_data *)vvar_page; 116 } 117 #endif 118