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 struct pt_regs *regs = current_pt_regs(); 69 unsigned long ipoffset = regs->ip - 70 (unsigned long)current->mm->context.vdso; 71 72 if (ipoffset < image->size) 73 regs->ip = new_vma->vm_start + ipoffset; 74 } 75 76 static int vdso_mremap(const struct vm_special_mapping *sm, 77 struct vm_area_struct *new_vma) 78 { 79 const struct vdso_image *image = current->mm->context.vdso_image; 80 81 vdso_fix_landing(image, new_vma); 82 current->mm->context.vdso = (void __user *)new_vma->vm_start; 83 84 return 0; 85 } 86 87 static vm_fault_t vvar_vclock_fault(const struct vm_special_mapping *sm, 88 struct vm_area_struct *vma, struct vm_fault *vmf) 89 { 90 switch (vmf->pgoff) { 91 #ifdef CONFIG_PARAVIRT_CLOCK 92 case VDSO_PAGE_PVCLOCK_OFFSET: 93 { 94 struct pvclock_vsyscall_time_info *pvti = 95 pvclock_get_pvti_cpu0_va(); 96 97 if (pvti && vclock_was_used(VDSO_CLOCKMODE_PVCLOCK)) 98 return vmf_insert_pfn_prot(vma, vmf->address, 99 __pa(pvti) >> PAGE_SHIFT, 100 pgprot_decrypted(vma->vm_page_prot)); 101 break; 102 } 103 #endif /* CONFIG_PARAVIRT_CLOCK */ 104 #ifdef CONFIG_HYPERV_TIMER 105 case VDSO_PAGE_HVCLOCK_OFFSET: 106 { 107 unsigned long pfn = hv_get_tsc_pfn(); 108 if (pfn && vclock_was_used(VDSO_CLOCKMODE_HVCLOCK)) 109 return vmf_insert_pfn(vma, vmf->address, pfn); 110 break; 111 } 112 #endif /* CONFIG_HYPERV_TIMER */ 113 } 114 115 return VM_FAULT_SIGBUS; 116 } 117 118 static const struct vm_special_mapping vdso_mapping = { 119 .name = "[vdso]", 120 .fault = vdso_fault, 121 .mremap = vdso_mremap, 122 }; 123 static const struct vm_special_mapping vvar_vclock_mapping = { 124 .name = "[vvar_vclock]", 125 .fault = vvar_vclock_fault, 126 }; 127 128 /* 129 * Add vdso and vvar mappings to current process. 130 * @image - blob to map 131 * @addr - request a specific address (zero to map at free addr) 132 */ 133 static int map_vdso(const struct vdso_image *image, unsigned long addr) 134 { 135 struct mm_struct *mm = current->mm; 136 struct vm_area_struct *vma; 137 unsigned long text_start; 138 int ret = 0; 139 140 if (mmap_write_lock_killable(mm)) 141 return -EINTR; 142 143 addr = get_unmapped_area(NULL, addr, 144 image->size + __VDSO_PAGES * PAGE_SIZE, 0, 0); 145 if (IS_ERR_VALUE(addr)) { 146 ret = addr; 147 goto up_fail; 148 } 149 150 text_start = addr + __VDSO_PAGES * PAGE_SIZE; 151 152 /* 153 * MAYWRITE to allow gdb to COW and set breakpoints 154 */ 155 vma = _install_special_mapping(mm, 156 text_start, 157 image->size, 158 VM_READ|VM_EXEC| 159 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC| 160 VM_SEALED_SYSMAP, 161 &vdso_mapping); 162 163 if (IS_ERR(vma)) { 164 ret = PTR_ERR(vma); 165 goto up_fail; 166 } 167 168 vma = vdso_install_vvar_mapping(mm, addr); 169 if (IS_ERR(vma)) { 170 ret = PTR_ERR(vma); 171 do_munmap(mm, text_start, image->size, NULL); 172 goto up_fail; 173 } 174 175 vma = _install_special_mapping(mm, 176 VDSO_VCLOCK_PAGES_START(addr), 177 VDSO_NR_VCLOCK_PAGES * PAGE_SIZE, 178 VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP| 179 VM_PFNMAP|VM_SEALED_SYSMAP, 180 &vvar_vclock_mapping); 181 182 if (IS_ERR(vma)) { 183 ret = PTR_ERR(vma); 184 do_munmap(mm, text_start, image->size, NULL); 185 do_munmap(mm, addr, image->size, NULL); 186 goto up_fail; 187 } 188 189 current->mm->context.vdso = (void __user *)text_start; 190 current->mm->context.vdso_image = image; 191 192 up_fail: 193 mmap_write_unlock(mm); 194 return ret; 195 } 196 197 int map_vdso_once(const struct vdso_image *image, unsigned long addr) 198 { 199 struct mm_struct *mm = current->mm; 200 struct vm_area_struct *vma; 201 VMA_ITERATOR(vmi, mm, 0); 202 203 mmap_write_lock(mm); 204 /* 205 * Check if we have already mapped vdso blob - fail to prevent 206 * abusing from userspace install_special_mapping, which may 207 * not do accounting and rlimit right. 208 * We could search vma near context.vdso, but it's a slowpath, 209 * so let's explicitly check all VMAs to be completely sure. 210 */ 211 for_each_vma(vmi, vma) { 212 if (vma_is_special_mapping(vma, &vdso_mapping) || 213 vma_is_special_mapping(vma, &vdso_vvar_mapping) || 214 vma_is_special_mapping(vma, &vvar_vclock_mapping)) { 215 mmap_write_unlock(mm); 216 return -EEXIST; 217 } 218 } 219 mmap_write_unlock(mm); 220 221 return map_vdso(image, addr); 222 } 223 224 static int load_vdso32(void) 225 { 226 if (vdso32_enabled != 1) /* Other values all mean "disabled" */ 227 return 0; 228 229 return map_vdso(&vdso32_image, 0); 230 } 231 232 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) 233 { 234 if (IS_ENABLED(CONFIG_X86_64)) { 235 if (!vdso64_enabled) 236 return 0; 237 238 return map_vdso(&vdso64_image, 0); 239 } 240 241 return load_vdso32(); 242 } 243 244 #ifdef CONFIG_COMPAT 245 int compat_arch_setup_additional_pages(struct linux_binprm *bprm, 246 int uses_interp, bool x32) 247 { 248 if (IS_ENABLED(CONFIG_X86_X32_ABI) && x32) { 249 if (!vdso64_enabled) 250 return 0; 251 return map_vdso(&vdsox32_image, 0); 252 } 253 254 if (IS_ENABLED(CONFIG_IA32_EMULATION)) 255 return load_vdso32(); 256 257 return 0; 258 } 259 #endif 260 261 bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs) 262 { 263 const struct vdso_image *image = current->mm->context.vdso_image; 264 unsigned long vdso = (unsigned long) current->mm->context.vdso; 265 266 if (in_ia32_syscall() && image == &vdso32_image) { 267 if (regs->ip == vdso + image->sym_vdso32_sigreturn_landing_pad || 268 regs->ip == vdso + image->sym_vdso32_rt_sigreturn_landing_pad) 269 return true; 270 } 271 return false; 272 } 273 274 #ifdef CONFIG_X86_64 275 static __init int vdso_setup(char *s) 276 { 277 vdso64_enabled = simple_strtoul(s, NULL, 0); 278 return 1; 279 } 280 __setup("vdso=", vdso_setup); 281 #endif /* CONFIG_X86_64 */ 282