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