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 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 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 65 static void vdso_fix_landing(const struct vdso_image *image, 66 struct vm_area_struct *new_vma) 67 { 68 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION 69 if (in_ia32_syscall() && image == &vdso_image_32) { 70 struct pt_regs *regs = current_pt_regs(); 71 unsigned long vdso_land = image->sym_int80_landing_pad; 72 unsigned long old_land_addr = vdso_land + 73 (unsigned long)current->mm->context.vdso; 74 75 /* Fixing userspace landing - look at do_fast_syscall_32 */ 76 if (regs->ip == old_land_addr) 77 regs->ip = new_vma->vm_start + vdso_land; 78 } 79 #endif 80 } 81 82 static int vdso_mremap(const struct vm_special_mapping *sm, 83 struct vm_area_struct *new_vma) 84 { 85 const struct vdso_image *image = current->mm->context.vdso_image; 86 87 vdso_fix_landing(image, new_vma); 88 current->mm->context.vdso = (void __user *)new_vma->vm_start; 89 90 return 0; 91 } 92 93 static vm_fault_t vvar_vclock_fault(const struct vm_special_mapping *sm, 94 struct vm_area_struct *vma, struct vm_fault *vmf) 95 { 96 switch (vmf->pgoff) { 97 #ifdef CONFIG_PARAVIRT_CLOCK 98 case VDSO_PAGE_PVCLOCK_OFFSET: 99 { 100 struct pvclock_vsyscall_time_info *pvti = 101 pvclock_get_pvti_cpu0_va(); 102 103 if (pvti && vclock_was_used(VDSO_CLOCKMODE_PVCLOCK)) 104 return vmf_insert_pfn_prot(vma, vmf->address, 105 __pa(pvti) >> PAGE_SHIFT, 106 pgprot_decrypted(vma->vm_page_prot)); 107 break; 108 } 109 #endif /* CONFIG_PARAVIRT_CLOCK */ 110 #ifdef CONFIG_HYPERV_TIMER 111 case VDSO_PAGE_HVCLOCK_OFFSET: 112 { 113 unsigned long pfn = hv_get_tsc_pfn(); 114 if (pfn && vclock_was_used(VDSO_CLOCKMODE_HVCLOCK)) 115 return vmf_insert_pfn(vma, vmf->address, pfn); 116 break; 117 } 118 #endif /* CONFIG_HYPERV_TIMER */ 119 } 120 121 return VM_FAULT_SIGBUS; 122 } 123 124 static const struct vm_special_mapping vdso_mapping = { 125 .name = "[vdso]", 126 .fault = vdso_fault, 127 .mremap = vdso_mremap, 128 }; 129 static const struct vm_special_mapping vvar_vclock_mapping = { 130 .name = "[vvar_vclock]", 131 .fault = vvar_vclock_fault, 132 }; 133 134 /* 135 * Add vdso and vvar mappings to current process. 136 * @image - blob to map 137 * @addr - request a specific address (zero to map at free addr) 138 */ 139 static int map_vdso(const struct vdso_image *image, unsigned long addr) 140 { 141 struct mm_struct *mm = current->mm; 142 struct vm_area_struct *vma; 143 unsigned long text_start; 144 int ret = 0; 145 146 if (mmap_write_lock_killable(mm)) 147 return -EINTR; 148 149 addr = get_unmapped_area(NULL, addr, 150 image->size + __VDSO_PAGES * PAGE_SIZE, 0, 0); 151 if (IS_ERR_VALUE(addr)) { 152 ret = addr; 153 goto up_fail; 154 } 155 156 text_start = addr + __VDSO_PAGES * PAGE_SIZE; 157 158 /* 159 * MAYWRITE to allow gdb to COW and set breakpoints 160 */ 161 vma = _install_special_mapping(mm, 162 text_start, 163 image->size, 164 VM_READ|VM_EXEC| 165 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| 166 VM_SEALED_SYSMAP, 167 &vdso_mapping); 168 169 if (IS_ERR(vma)) { 170 ret = PTR_ERR(vma); 171 goto up_fail; 172 } 173 174 vma = vdso_install_vvar_mapping(mm, addr); 175 if (IS_ERR(vma)) { 176 ret = PTR_ERR(vma); 177 do_munmap(mm, text_start, image->size, NULL); 178 goto up_fail; 179 } 180 181 vma = _install_special_mapping(mm, 182 VDSO_VCLOCK_PAGES_START(addr), 183 VDSO_NR_VCLOCK_PAGES * PAGE_SIZE, 184 VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP| 185 VM_PFNMAP|VM_SEALED_SYSMAP, 186 &vvar_vclock_mapping); 187 188 if (IS_ERR(vma)) { 189 ret = PTR_ERR(vma); 190 do_munmap(mm, text_start, image->size, NULL); 191 do_munmap(mm, addr, image->size, NULL); 192 goto up_fail; 193 } 194 195 current->mm->context.vdso = (void __user *)text_start; 196 current->mm->context.vdso_image = image; 197 198 up_fail: 199 mmap_write_unlock(mm); 200 return ret; 201 } 202 203 int map_vdso_once(const struct vdso_image *image, unsigned long addr) 204 { 205 struct mm_struct *mm = current->mm; 206 struct vm_area_struct *vma; 207 VMA_ITERATOR(vmi, mm, 0); 208 209 mmap_write_lock(mm); 210 /* 211 * Check if we have already mapped vdso blob - fail to prevent 212 * abusing from userspace install_special_mapping, which may 213 * not do accounting and rlimit right. 214 * We could search vma near context.vdso, but it's a slowpath, 215 * so let's explicitly check all VMAs to be completely sure. 216 */ 217 for_each_vma(vmi, vma) { 218 if (vma_is_special_mapping(vma, &vdso_mapping) || 219 vma_is_special_mapping(vma, &vdso_vvar_mapping) || 220 vma_is_special_mapping(vma, &vvar_vclock_mapping)) { 221 mmap_write_unlock(mm); 222 return -EEXIST; 223 } 224 } 225 mmap_write_unlock(mm); 226 227 return map_vdso(image, addr); 228 } 229 230 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) 231 static int load_vdso32(void) 232 { 233 if (vdso32_enabled != 1) /* Other values all mean "disabled" */ 234 return 0; 235 236 return map_vdso(&vdso_image_32, 0); 237 } 238 #endif 239 240 #ifdef CONFIG_X86_64 241 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 242 { 243 if (!vdso64_enabled) 244 return 0; 245 246 return map_vdso(&vdso_image_64, 0); 247 } 248 249 #ifdef CONFIG_COMPAT 250 int compat_arch_setup_additional_pages(struct linux_binprm *bprm, 251 int uses_interp, bool x32) 252 { 253 #ifdef CONFIG_X86_X32_ABI 254 if (x32) { 255 if (!vdso64_enabled) 256 return 0; 257 return map_vdso(&vdso_image_x32, 0); 258 } 259 #endif 260 #ifdef CONFIG_IA32_EMULATION 261 return load_vdso32(); 262 #else 263 return 0; 264 #endif 265 } 266 #endif 267 #else 268 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 269 { 270 return load_vdso32(); 271 } 272 #endif 273 274 bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs) 275 { 276 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION) 277 const struct vdso_image *image = current->mm->context.vdso_image; 278 unsigned long vdso = (unsigned long) current->mm->context.vdso; 279 280 if (in_ia32_syscall() && image == &vdso_image_32) { 281 if (regs->ip == vdso + image->sym_vdso32_sigreturn_landing_pad || 282 regs->ip == vdso + image->sym_vdso32_rt_sigreturn_landing_pad) 283 return true; 284 } 285 #endif 286 return false; 287 } 288 289 #ifdef CONFIG_X86_64 290 static __init int vdso_setup(char *s) 291 { 292 vdso64_enabled = simple_strtoul(s, NULL, 0); 293 return 1; 294 } 295 __setup("vdso=", vdso_setup); 296 #endif /* CONFIG_X86_64 */ 297