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/time_namespace.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 struct vdso_data *arch_get_vdso_data(void *vvar_page) 31 { 32 return (struct vdso_data *)vvar_page; 33 } 34 35 static union vdso_data_store vdso_data_store __page_aligned_data; 36 struct vdso_data *vdso_data = vdso_data_store.data; 37 38 unsigned int vclocks_used __read_mostly; 39 40 #if defined(CONFIG_X86_64) 41 unsigned int __read_mostly vdso64_enabled = 1; 42 #endif 43 44 int __init init_vdso_image(const struct vdso_image *image) 45 { 46 BUILD_BUG_ON(VDSO_CLOCKMODE_MAX >= 32); 47 BUG_ON(image->size % PAGE_SIZE != 0); 48 49 apply_alternatives((struct alt_instr *)(image->data + image->alt), 50 (struct alt_instr *)(image->data + image->alt + 51 image->alt_len), 52 NULL); 53 54 return 0; 55 } 56 57 static const struct vm_special_mapping vvar_mapping; 58 struct linux_binprm; 59 60 static vm_fault_t vdso_fault(const struct vm_special_mapping *sm, 61 struct vm_area_struct *vma, struct vm_fault *vmf) 62 { 63 const struct vdso_image *image = vma->vm_mm->context.vdso_image; 64 65 if (!image || (vmf->pgoff << PAGE_SHIFT) >= image->size) 66 return VM_FAULT_SIGBUS; 67 68 vmf->page = virt_to_page(image->data + (vmf->pgoff << PAGE_SHIFT)); 69 get_page(vmf->page); 70 return 0; 71 } 72 73 static void vdso_fix_landing(const struct vdso_image *image, 74 struct vm_area_struct *new_vma) 75 { 76 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION 77 if (in_ia32_syscall() && image == &vdso_image_32) { 78 struct pt_regs *regs = current_pt_regs(); 79 unsigned long vdso_land = image->sym_int80_landing_pad; 80 unsigned long old_land_addr = vdso_land + 81 (unsigned long)current->mm->context.vdso; 82 83 /* Fixing userspace landing - look at do_fast_syscall_32 */ 84 if (regs->ip == old_land_addr) 85 regs->ip = new_vma->vm_start + vdso_land; 86 } 87 #endif 88 } 89 90 static int vdso_mremap(const struct vm_special_mapping *sm, 91 struct vm_area_struct *new_vma) 92 { 93 const struct vdso_image *image = current->mm->context.vdso_image; 94 95 vdso_fix_landing(image, new_vma); 96 current->mm->context.vdso = (void __user *)new_vma->vm_start; 97 98 return 0; 99 } 100 101 #ifdef CONFIG_TIME_NS 102 /* 103 * The vvar page layout depends on whether a task belongs to the root or 104 * non-root time namespace. Whenever a task changes its namespace, the VVAR 105 * page tables are cleared and then they will re-faulted with a 106 * corresponding layout. 107 * See also the comment near timens_setup_vdso_data() for details. 108 */ 109 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns) 110 { 111 struct mm_struct *mm = task->mm; 112 struct vm_area_struct *vma; 113 VMA_ITERATOR(vmi, mm, 0); 114 115 mmap_read_lock(mm); 116 for_each_vma(vmi, vma) { 117 if (vma_is_special_mapping(vma, &vvar_mapping)) 118 zap_vma_pages(vma); 119 } 120 mmap_read_unlock(mm); 121 122 return 0; 123 } 124 #endif 125 126 static vm_fault_t vvar_fault(const struct vm_special_mapping *sm, 127 struct vm_area_struct *vma, struct vm_fault *vmf) 128 { 129 const struct vdso_image *image = vma->vm_mm->context.vdso_image; 130 unsigned long pfn; 131 long sym_offset; 132 133 if (!image) 134 return VM_FAULT_SIGBUS; 135 136 sym_offset = (long)(vmf->pgoff << PAGE_SHIFT) + 137 image->sym_vvar_start; 138 139 /* 140 * Sanity check: a symbol offset of zero means that the page 141 * does not exist for this vdso image, not that the page is at 142 * offset zero relative to the text mapping. This should be 143 * impossible here, because sym_offset should only be zero for 144 * the page past the end of the vvar mapping. 145 */ 146 if (sym_offset == 0) 147 return VM_FAULT_SIGBUS; 148 149 if (sym_offset == image->sym_vvar_page) { 150 struct page *timens_page = find_timens_vvar_page(vma); 151 152 pfn = __pa_symbol(vdso_data) >> PAGE_SHIFT; 153 154 /* 155 * If a task belongs to a time namespace then a namespace 156 * specific VVAR is mapped with the sym_vvar_page offset and 157 * the real VVAR page is mapped with the sym_timens_page 158 * offset. 159 * See also the comment near timens_setup_vdso_data(). 160 */ 161 if (timens_page) { 162 unsigned long addr; 163 vm_fault_t err; 164 165 /* 166 * Optimization: inside time namespace pre-fault 167 * VVAR page too. As on timens page there are only 168 * offsets for clocks on VVAR, it'll be faulted 169 * shortly by VDSO code. 170 */ 171 addr = vmf->address + (image->sym_timens_page - sym_offset); 172 err = vmf_insert_pfn(vma, addr, pfn); 173 if (unlikely(err & VM_FAULT_ERROR)) 174 return err; 175 176 pfn = page_to_pfn(timens_page); 177 } 178 179 return vmf_insert_pfn(vma, vmf->address, pfn); 180 181 } else if (sym_offset == image->sym_timens_page) { 182 struct page *timens_page = find_timens_vvar_page(vma); 183 184 if (!timens_page) 185 return VM_FAULT_SIGBUS; 186 187 pfn = __pa_symbol(vdso_data) >> PAGE_SHIFT; 188 return vmf_insert_pfn(vma, vmf->address, pfn); 189 } 190 191 return VM_FAULT_SIGBUS; 192 } 193 194 static vm_fault_t vvar_vclock_fault(const struct vm_special_mapping *sm, 195 struct vm_area_struct *vma, struct vm_fault *vmf) 196 { 197 switch (vmf->pgoff) { 198 #ifdef CONFIG_PARAVIRT_CLOCK 199 case VDSO_PAGE_PVCLOCK_OFFSET: 200 { 201 struct pvclock_vsyscall_time_info *pvti = 202 pvclock_get_pvti_cpu0_va(); 203 204 if (pvti && vclock_was_used(VDSO_CLOCKMODE_PVCLOCK)) 205 return vmf_insert_pfn_prot(vma, vmf->address, 206 __pa(pvti) >> PAGE_SHIFT, 207 pgprot_decrypted(vma->vm_page_prot)); 208 break; 209 } 210 #endif /* CONFIG_PARAVIRT_CLOCK */ 211 #ifdef CONFIG_HYPERV_TIMER 212 case VDSO_PAGE_HVCLOCK_OFFSET: 213 { 214 unsigned long pfn = hv_get_tsc_pfn(); 215 216 if (pfn && vclock_was_used(VDSO_CLOCKMODE_HVCLOCK)) 217 return vmf_insert_pfn(vma, vmf->address, pfn); 218 break; 219 } 220 #endif /* CONFIG_HYPERV_TIMER */ 221 } 222 223 return VM_FAULT_SIGBUS; 224 } 225 226 static const struct vm_special_mapping vdso_mapping = { 227 .name = "[vdso]", 228 .fault = vdso_fault, 229 .mremap = vdso_mremap, 230 }; 231 static const struct vm_special_mapping vvar_mapping = { 232 .name = "[vvar]", 233 .fault = vvar_fault, 234 }; 235 static const struct vm_special_mapping vvar_vclock_mapping = { 236 .name = "[vvar_vclock]", 237 .fault = vvar_vclock_fault, 238 }; 239 240 /* 241 * Add vdso and vvar mappings to current process. 242 * @image - blob to map 243 * @addr - request a specific address (zero to map at free addr) 244 */ 245 static int map_vdso(const struct vdso_image *image, unsigned long addr) 246 { 247 struct mm_struct *mm = current->mm; 248 struct vm_area_struct *vma; 249 unsigned long text_start; 250 int ret = 0; 251 252 if (mmap_write_lock_killable(mm)) 253 return -EINTR; 254 255 addr = get_unmapped_area(NULL, addr, 256 image->size - image->sym_vvar_start, 0, 0); 257 if (IS_ERR_VALUE(addr)) { 258 ret = addr; 259 goto up_fail; 260 } 261 262 text_start = addr - image->sym_vvar_start; 263 264 /* 265 * MAYWRITE to allow gdb to COW and set breakpoints 266 */ 267 vma = _install_special_mapping(mm, 268 text_start, 269 image->size, 270 VM_READ|VM_EXEC| 271 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC, 272 &vdso_mapping); 273 274 if (IS_ERR(vma)) { 275 ret = PTR_ERR(vma); 276 goto up_fail; 277 } 278 279 vma = _install_special_mapping(mm, 280 addr, 281 (__VVAR_PAGES - VDSO_NR_VCLOCK_PAGES) * PAGE_SIZE, 282 VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP| 283 VM_PFNMAP, 284 &vvar_mapping); 285 286 if (IS_ERR(vma)) { 287 ret = PTR_ERR(vma); 288 do_munmap(mm, text_start, image->size, NULL); 289 goto up_fail; 290 } 291 292 vma = _install_special_mapping(mm, 293 addr + (__VVAR_PAGES - VDSO_NR_VCLOCK_PAGES) * PAGE_SIZE, 294 VDSO_NR_VCLOCK_PAGES * PAGE_SIZE, 295 VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP| 296 VM_PFNMAP, 297 &vvar_vclock_mapping); 298 299 if (IS_ERR(vma)) { 300 ret = PTR_ERR(vma); 301 do_munmap(mm, text_start, image->size, NULL); 302 do_munmap(mm, addr, image->size, NULL); 303 goto up_fail; 304 } 305 306 current->mm->context.vdso = (void __user *)text_start; 307 current->mm->context.vdso_image = image; 308 309 up_fail: 310 mmap_write_unlock(mm); 311 return ret; 312 } 313 314 int map_vdso_once(const struct vdso_image *image, unsigned long addr) 315 { 316 struct mm_struct *mm = current->mm; 317 struct vm_area_struct *vma; 318 VMA_ITERATOR(vmi, mm, 0); 319 320 mmap_write_lock(mm); 321 /* 322 * Check if we have already mapped vdso blob - fail to prevent 323 * abusing from userspace install_special_mapping, which may 324 * not do accounting and rlimit right. 325 * We could search vma near context.vdso, but it's a slowpath, 326 * so let's explicitly check all VMAs to be completely sure. 327 */ 328 for_each_vma(vmi, vma) { 329 if (vma_is_special_mapping(vma, &vdso_mapping) || 330 vma_is_special_mapping(vma, &vvar_mapping) || 331 vma_is_special_mapping(vma, &vvar_vclock_mapping)) { 332 mmap_write_unlock(mm); 333 return -EEXIST; 334 } 335 } 336 mmap_write_unlock(mm); 337 338 return map_vdso(image, addr); 339 } 340 341 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) 342 static int load_vdso32(void) 343 { 344 if (vdso32_enabled != 1) /* Other values all mean "disabled" */ 345 return 0; 346 347 return map_vdso(&vdso_image_32, 0); 348 } 349 #endif 350 351 #ifdef CONFIG_X86_64 352 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 353 { 354 if (!vdso64_enabled) 355 return 0; 356 357 return map_vdso(&vdso_image_64, 0); 358 } 359 360 #ifdef CONFIG_COMPAT 361 int compat_arch_setup_additional_pages(struct linux_binprm *bprm, 362 int uses_interp, bool x32) 363 { 364 #ifdef CONFIG_X86_X32_ABI 365 if (x32) { 366 if (!vdso64_enabled) 367 return 0; 368 return map_vdso(&vdso_image_x32, 0); 369 } 370 #endif 371 #ifdef CONFIG_IA32_EMULATION 372 return load_vdso32(); 373 #else 374 return 0; 375 #endif 376 } 377 #endif 378 #else 379 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 380 { 381 return load_vdso32(); 382 } 383 #endif 384 385 bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs) 386 { 387 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) 388 const struct vdso_image *image = current->mm->context.vdso_image; 389 unsigned long vdso = (unsigned long) current->mm->context.vdso; 390 391 if (in_ia32_syscall() && image == &vdso_image_32) { 392 if (regs->ip == vdso + image->sym_vdso32_sigreturn_landing_pad || 393 regs->ip == vdso + image->sym_vdso32_rt_sigreturn_landing_pad) 394 return true; 395 } 396 #endif 397 return false; 398 } 399 400 #ifdef CONFIG_X86_64 401 static __init int vdso_setup(char *s) 402 { 403 vdso64_enabled = simple_strtoul(s, NULL, 0); 404 return 1; 405 } 406 __setup("vdso=", vdso_setup); 407 #endif /* CONFIG_X86_64 */ 408