datastore.c

  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_GENERIC_GETTIMEOFDAY
 15static union {
 16	struct vdso_time_data	data;
 17	u8			page[PAGE_SIZE];
 18} vdso_time_data_store __page_aligned_data;
 19struct vdso_time_data *vdso_k_time_data = &vdso_time_data_store.data;
 20static_assert(sizeof(vdso_time_data_store) == PAGE_SIZE);
 21#endif /* CONFIG_GENERIC_GETTIMEOFDAY */
 22
 23#ifdef CONFIG_VDSO_GETRANDOM
 24static union {
 25	struct vdso_rng_data	data;
 26	u8			page[PAGE_SIZE];
 27} vdso_rng_data_store __page_aligned_data;
 28struct vdso_rng_data *vdso_k_rng_data = &vdso_rng_data_store.data;
 29static_assert(sizeof(vdso_rng_data_store) == PAGE_SIZE);
 30#endif /* CONFIG_VDSO_GETRANDOM */
 31
 32#ifdef CONFIG_ARCH_HAS_VDSO_ARCH_DATA
 33static union {
 34	struct vdso_arch_data	data;
 35	u8			page[VDSO_ARCH_DATA_SIZE];
 36} vdso_arch_data_store __page_aligned_data;
 37struct vdso_arch_data *vdso_k_arch_data = &vdso_arch_data_store.data;
 38#endif /* CONFIG_ARCH_HAS_VDSO_ARCH_DATA */
 39
 40static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 41			     struct vm_area_struct *vma, struct vm_fault *vmf)
 42{
 43	struct page *timens_page = find_timens_vvar_page(vma);
 44	unsigned long addr, pfn;
 45	vm_fault_t err;
 46
 47	switch (vmf->pgoff) {
 48	case VDSO_TIME_PAGE_OFFSET:
 49		if (!IS_ENABLED(CONFIG_GENERIC_GETTIMEOFDAY))
 50			return VM_FAULT_SIGBUS;
 51		pfn = __phys_to_pfn(__pa_symbol(vdso_k_time_data));
 52		if (timens_page) {
 53			/*
 54			 * Fault in VVAR page too, since it will be accessed
 55			 * to get clock data anyway.
 56			 */
 57			addr = vmf->address + VDSO_TIMENS_PAGE_OFFSET * PAGE_SIZE;
 58			err = vmf_insert_pfn(vma, addr, pfn);
 59			if (unlikely(err & VM_FAULT_ERROR))
 60				return err;
 61			pfn = page_to_pfn(timens_page);
 62		}
 63		break;
 64	case VDSO_TIMENS_PAGE_OFFSET:
 65		/*
 66		 * If a task belongs to a time namespace then a namespace
 67		 * specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
 68		 * the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
 69		 * offset.
 70		 * See also the comment near timens_setup_vdso_data().
 71		 */
 72		if (!IS_ENABLED(CONFIG_TIME_NS) || !timens_page)
 73			return VM_FAULT_SIGBUS;
 74		pfn = __phys_to_pfn(__pa_symbol(vdso_k_time_data));
 75		break;
 76	case VDSO_RNG_PAGE_OFFSET:
 77		if (!IS_ENABLED(CONFIG_VDSO_GETRANDOM))
 78			return VM_FAULT_SIGBUS;
 79		pfn = __phys_to_pfn(__pa_symbol(vdso_k_rng_data));
 80		break;
 81	case VDSO_ARCH_PAGES_START ... VDSO_ARCH_PAGES_END:
 82		if (!IS_ENABLED(CONFIG_ARCH_HAS_VDSO_ARCH_DATA))
 83			return VM_FAULT_SIGBUS;
 84		pfn = __phys_to_pfn(__pa_symbol(vdso_k_arch_data)) +
 85			vmf->pgoff - VDSO_ARCH_PAGES_START;
 86		break;
 87	default:
 88		return VM_FAULT_SIGBUS;
 89	}
 90
 91	return vmf_insert_pfn(vma, vmf->address, pfn);
 92}
 93
 94const struct vm_special_mapping vdso_vvar_mapping = {
 95	.name	= "[vvar]",
 96	.fault	= vvar_fault,
 97};
 98
 99struct vm_area_struct *vdso_install_vvar_mapping(struct mm_struct *mm, unsigned long addr)
100{
101	return _install_special_mapping(mm, addr, VDSO_NR_PAGES * PAGE_SIZE,
102					VM_READ | VM_MAYREAD | VM_IO | VM_DONTDUMP |
103					VM_PFNMAP | VM_SEALED_SYSMAP,
104					&vdso_vvar_mapping);
105}
106
107#ifdef CONFIG_TIME_NS
108/*
109 * The vvar page layout depends on whether a task belongs to the root or
110 * non-root time namespace. Whenever a task changes its namespace, the VVAR
111 * page tables are cleared and then they will be re-faulted with a
112 * corresponding layout.
113 * See also the comment near timens_setup_vdso_clock_data() for details.
114 */
115int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
116{
117	struct mm_struct *mm = task->mm;
118	struct vm_area_struct *vma;
119	VMA_ITERATOR(vmi, mm, 0);
120
121	mmap_read_lock(mm);
122	for_each_vma(vmi, vma) {
123		if (vma_is_special_mapping(vma, &vdso_vvar_mapping))
124			zap_vma_pages(vma);
125	}
126	mmap_read_unlock(mm);
127
128	return 0;
129}
130#endif