1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright 2007 Andi Kleen, SUSE Labs.
4 *
5 * This contains most of the x86 vDSO kernel-side code.
6 */
7 #include <linux/mm.h>
8 #include <linux/err.h>
9 #include <linux/sched.h>
10 #include <linux/sched/task_stack.h>
11 #include <linux/slab.h>
12 #include <linux/init.h>
13 #include <linux/random.h>
14 #include <linux/elf.h>
15 #include <linux/cpu.h>
16 #include <linux/ptrace.h>
17 #include <linux/vdso_datastore.h>
18
19 #include <asm/pvclock.h>
20 #include <asm/vgtod.h>
21 #include <asm/proto.h>
22 #include <asm/vdso.h>
23 #include <asm/tlb.h>
24 #include <asm/page.h>
25 #include <asm/desc.h>
26 #include <asm/cpufeature.h>
27 #include <asm/vdso/vsyscall.h>
28 #include <clocksource/hyperv_timer.h>
29
30 static_assert(VDSO_NR_PAGES + VDSO_NR_VCLOCK_PAGES == __VDSO_PAGES);
31
32 unsigned int vclocks_used __read_mostly;
33
34 #if defined(CONFIG_X86_64)
35 unsigned int __read_mostly vdso64_enabled = 1;
36 #endif
37
init_vdso_image(const struct vdso_image * image)38 int __init init_vdso_image(const struct vdso_image *image)
39 {
40 BUILD_BUG_ON(VDSO_CLOCKMODE_MAX >= 32);
41 BUG_ON(image->size % PAGE_SIZE != 0);
42
43 apply_alternatives((struct alt_instr *)(image->data + image->alt),
44 (struct alt_instr *)(image->data + image->alt +
45 image->alt_len));
46
47 return 0;
48 }
49
50 struct linux_binprm;
51
vdso_fault(const struct vm_special_mapping * sm,struct vm_area_struct * vma,struct vm_fault * vmf)52 static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
53 struct vm_area_struct *vma, struct vm_fault *vmf)
54 {
55 const struct vdso_image *image = vma->vm_mm->context.vdso_image;
56
57 if (!image || (vmf->pgoff << PAGE_SHIFT) >= image->size)
58 return VM_FAULT_SIGBUS;
59
60 vmf->page = virt_to_page(image->data + (vmf->pgoff << PAGE_SHIFT));
61 get_page(vmf->page);
62 return 0;
63 }
64
vdso_fix_landing(const struct vdso_image * image,struct vm_area_struct * new_vma)65 static void vdso_fix_landing(const struct vdso_image *image,
66 struct vm_area_struct *new_vma)
67 {
68 if (in_ia32_syscall() && image == &vdso_image_32) {
69 struct pt_regs *regs = current_pt_regs();
70 unsigned long vdso_land = image->sym_int80_landing_pad;
71 unsigned long old_land_addr = vdso_land +
72 (unsigned long)current->mm->context.vdso;
73
74 /* Fixing userspace landing - look at do_fast_syscall_32 */
75 if (regs->ip == old_land_addr)
76 regs->ip = new_vma->vm_start + vdso_land;
77 }
78 }
79
vdso_mremap(const struct vm_special_mapping * sm,struct vm_area_struct * new_vma)80 static int vdso_mremap(const struct vm_special_mapping *sm,
81 struct vm_area_struct *new_vma)
82 {
83 const struct vdso_image *image = current->mm->context.vdso_image;
84
85 vdso_fix_landing(image, new_vma);
86 current->mm->context.vdso = (void __user *)new_vma->vm_start;
87
88 return 0;
89 }
90
vvar_vclock_fault(const struct vm_special_mapping * sm,struct vm_area_struct * vma,struct vm_fault * vmf)91 static vm_fault_t vvar_vclock_fault(const struct vm_special_mapping *sm,
92 struct vm_area_struct *vma, struct vm_fault *vmf)
93 {
94 switch (vmf->pgoff) {
95 #ifdef CONFIG_PARAVIRT_CLOCK
96 case VDSO_PAGE_PVCLOCK_OFFSET:
97 {
98 struct pvclock_vsyscall_time_info *pvti =
99 pvclock_get_pvti_cpu0_va();
100
101 if (pvti && vclock_was_used(VDSO_CLOCKMODE_PVCLOCK))
102 return vmf_insert_pfn_prot(vma, vmf->address,
103 __pa(pvti) >> PAGE_SHIFT,
104 pgprot_decrypted(vma->vm_page_prot));
105 break;
106 }
107 #endif /* CONFIG_PARAVIRT_CLOCK */
108 #ifdef CONFIG_HYPERV_TIMER
109 case VDSO_PAGE_HVCLOCK_OFFSET:
110 {
111 unsigned long pfn = hv_get_tsc_pfn();
112 if (pfn && vclock_was_used(VDSO_CLOCKMODE_HVCLOCK))
113 return vmf_insert_pfn(vma, vmf->address, pfn);
114 break;
115 }
116 #endif /* CONFIG_HYPERV_TIMER */
117 }
118
119 return VM_FAULT_SIGBUS;
120 }
121
122 static const struct vm_special_mapping vdso_mapping = {
123 .name = "[vdso]",
124 .fault = vdso_fault,
125 .mremap = vdso_mremap,
126 };
127 static const struct vm_special_mapping vvar_vclock_mapping = {
128 .name = "[vvar_vclock]",
129 .fault = vvar_vclock_fault,
130 };
131
132 /*
133 * Add vdso and vvar mappings to current process.
134 * @image - blob to map
135 * @addr - request a specific address (zero to map at free addr)
136 */
map_vdso(const struct vdso_image * image,unsigned long addr)137 static int map_vdso(const struct vdso_image *image, unsigned long addr)
138 {
139 struct mm_struct *mm = current->mm;
140 struct vm_area_struct *vma;
141 unsigned long text_start;
142 int ret = 0;
143
144 if (mmap_write_lock_killable(mm))
145 return -EINTR;
146
147 addr = get_unmapped_area(NULL, addr,
148 image->size + __VDSO_PAGES * PAGE_SIZE, 0, 0);
149 if (IS_ERR_VALUE(addr)) {
150 ret = addr;
151 goto up_fail;
152 }
153
154 text_start = addr + __VDSO_PAGES * PAGE_SIZE;
155
156 /*
157 * MAYWRITE to allow gdb to COW and set breakpoints
158 */
159 vma = _install_special_mapping(mm,
160 text_start,
161 image->size,
162 VM_READ|VM_EXEC|
163 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
164 VM_SEALED_SYSMAP,
165 &vdso_mapping);
166
167 if (IS_ERR(vma)) {
168 ret = PTR_ERR(vma);
169 goto up_fail;
170 }
171
172 vma = vdso_install_vvar_mapping(mm, addr);
173 if (IS_ERR(vma)) {
174 ret = PTR_ERR(vma);
175 do_munmap(mm, text_start, image->size, NULL);
176 goto up_fail;
177 }
178
179 vma = _install_special_mapping(mm,
180 VDSO_VCLOCK_PAGES_START(addr),
181 VDSO_NR_VCLOCK_PAGES * PAGE_SIZE,
182 VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|
183 VM_PFNMAP|VM_SEALED_SYSMAP,
184 &vvar_vclock_mapping);
185
186 if (IS_ERR(vma)) {
187 ret = PTR_ERR(vma);
188 do_munmap(mm, text_start, image->size, NULL);
189 do_munmap(mm, addr, image->size, NULL);
190 goto up_fail;
191 }
192
193 current->mm->context.vdso = (void __user *)text_start;
194 current->mm->context.vdso_image = image;
195
196 up_fail:
197 mmap_write_unlock(mm);
198 return ret;
199 }
200
map_vdso_once(const struct vdso_image * image,unsigned long addr)201 int map_vdso_once(const struct vdso_image *image, unsigned long addr)
202 {
203 struct mm_struct *mm = current->mm;
204 struct vm_area_struct *vma;
205 VMA_ITERATOR(vmi, mm, 0);
206
207 mmap_write_lock(mm);
208 /*
209 * Check if we have already mapped vdso blob - fail to prevent
210 * abusing from userspace install_special_mapping, which may
211 * not do accounting and rlimit right.
212 * We could search vma near context.vdso, but it's a slowpath,
213 * so let's explicitly check all VMAs to be completely sure.
214 */
215 for_each_vma(vmi, vma) {
216 if (vma_is_special_mapping(vma, &vdso_mapping) ||
217 vma_is_special_mapping(vma, &vdso_vvar_mapping) ||
218 vma_is_special_mapping(vma, &vvar_vclock_mapping)) {
219 mmap_write_unlock(mm);
220 return -EEXIST;
221 }
222 }
223 mmap_write_unlock(mm);
224
225 return map_vdso(image, addr);
226 }
227
load_vdso32(void)228 static int load_vdso32(void)
229 {
230 if (vdso32_enabled != 1) /* Other values all mean "disabled" */
231 return 0;
232
233 return map_vdso(&vdso_image_32, 0);
234 }
235
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)236 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
237 {
238 if (IS_ENABLED(CONFIG_X86_64)) {
239 if (!vdso64_enabled)
240 return 0;
241
242 return map_vdso(&vdso_image_64, 0);
243 }
244
245 return load_vdso32();
246 }
247
248 #ifdef CONFIG_COMPAT
compat_arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp,bool x32)249 int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
250 int uses_interp, bool x32)
251 {
252 if (IS_ENABLED(CONFIG_X86_X32_ABI) && x32) {
253 if (!vdso64_enabled)
254 return 0;
255 return map_vdso(&vdso_image_x32, 0);
256 }
257
258 if (IS_ENABLED(CONFIG_IA32_EMULATION))
259 return load_vdso32();
260
261 return 0;
262 }
263 #endif
264
arch_syscall_is_vdso_sigreturn(struct pt_regs * regs)265 bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)
266 {
267 const struct vdso_image *image = current->mm->context.vdso_image;
268 unsigned long vdso = (unsigned long) current->mm->context.vdso;
269
270 if (in_ia32_syscall() && image == &vdso_image_32) {
271 if (regs->ip == vdso + image->sym_vdso32_sigreturn_landing_pad ||
272 regs->ip == vdso + image->sym_vdso32_rt_sigreturn_landing_pad)
273 return true;
274 }
275 return false;
276 }
277
278 #ifdef CONFIG_X86_64
vdso_setup(char * s)279 static __init int vdso_setup(char *s)
280 {
281 vdso64_enabled = simple_strtoul(s, NULL, 0);
282 return 1;
283 }
284 __setup("vdso=", vdso_setup);
285 #endif /* CONFIG_X86_64 */
286