2 * Copyright 2007 Andi Kleen, SUSE Labs.
3 * Subject to the GPL, v.2
5 * This contains most of the x86 vDSO kernel-side code.
9 #include <linux/sched.h>
10 #include <linux/slab.h>
11 #include <linux/init.h>
12 #include <linux/random.h>
13 #include <linux/elf.h>
14 #include <linux/cpu.h>
15 #include <linux/ptrace.h>
16 #include <asm/pvclock.h>
17 #include <asm/vgtod.h>
18 #include <asm/proto.h>
23 #include <asm/cpufeature.h>
25 #if defined(CONFIG_X86_64)
26 unsigned int __read_mostly vdso64_enabled = 1;
29 void __init init_vdso_image(const struct vdso_image *image)
31 BUG_ON(image->size % PAGE_SIZE != 0);
33 apply_alternatives((struct alt_instr *)(image->data + image->alt),
34 (struct alt_instr *)(image->data + image->alt +
40 static int vdso_fault(const struct vm_special_mapping *sm,
41 struct vm_area_struct *vma, struct vm_fault *vmf)
43 const struct vdso_image *image = vma->vm_mm->context.vdso_image;
45 if (!image || (vmf->pgoff << PAGE_SHIFT) >= image->size)
46 return VM_FAULT_SIGBUS;
48 vmf->page = virt_to_page(image->data + (vmf->pgoff << PAGE_SHIFT));
53 static void vdso_fix_landing(const struct vdso_image *image,
54 struct vm_area_struct *new_vma)
56 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
57 if (in_ia32_syscall() && image == &vdso_image_32) {
58 struct pt_regs *regs = current_pt_regs();
59 unsigned long vdso_land = image->sym_int80_landing_pad;
60 unsigned long old_land_addr = vdso_land +
61 (unsigned long)current->mm->context.vdso;
63 /* Fixing userspace landing - look at do_fast_syscall_32 */
64 if (regs->ip == old_land_addr)
65 regs->ip = new_vma->vm_start + vdso_land;
70 static int vdso_mremap(const struct vm_special_mapping *sm,
71 struct vm_area_struct *new_vma)
73 unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
74 const struct vdso_image *image = current->mm->context.vdso_image;
76 if (image->size != new_size)
79 if (WARN_ON_ONCE(current->mm != new_vma->vm_mm))
82 vdso_fix_landing(image, new_vma);
83 current->mm->context.vdso = (void __user *)new_vma->vm_start;
88 static int vvar_fault(const struct vm_special_mapping *sm,
89 struct vm_area_struct *vma, struct vm_fault *vmf)
91 const struct vdso_image *image = vma->vm_mm->context.vdso_image;
96 return VM_FAULT_SIGBUS;
98 sym_offset = (long)(vmf->pgoff << PAGE_SHIFT) +
99 image->sym_vvar_start;
102 * Sanity check: a symbol offset of zero means that the page
103 * does not exist for this vdso image, not that the page is at
104 * offset zero relative to the text mapping. This should be
105 * impossible here, because sym_offset should only be zero for
106 * the page past the end of the vvar mapping.
109 return VM_FAULT_SIGBUS;
111 if (sym_offset == image->sym_vvar_page) {
112 ret = vm_insert_pfn(vma, vmf->address,
113 __pa_symbol(&__vvar_page) >> PAGE_SHIFT);
114 } else if (sym_offset == image->sym_pvclock_page) {
115 struct pvclock_vsyscall_time_info *pvti =
116 pvclock_pvti_cpu0_va();
117 if (pvti && vclock_was_used(VCLOCK_PVCLOCK)) {
121 __pa(pvti) >> PAGE_SHIFT);
125 if (ret == 0 || ret == -EBUSY)
126 return VM_FAULT_NOPAGE;
128 return VM_FAULT_SIGBUS;
131 static const struct vm_special_mapping vdso_mapping = {
134 .mremap = vdso_mremap,
136 static const struct vm_special_mapping vvar_mapping = {
142 * Add vdso and vvar mappings to current process.
143 * @image - blob to map
144 * @addr - request a specific address (zero to map at free addr)
146 static int map_vdso(const struct vdso_image *image, unsigned long addr)
148 struct mm_struct *mm = current->mm;
149 struct vm_area_struct *vma;
150 unsigned long text_start;
153 if (down_write_killable(&mm->mmap_sem))
156 addr = get_unmapped_area(NULL, addr,
157 image->size - image->sym_vvar_start, 0, 0);
158 if (IS_ERR_VALUE(addr)) {
163 text_start = addr - image->sym_vvar_start;
166 * MAYWRITE to allow gdb to COW and set breakpoints
168 vma = _install_special_mapping(mm,
172 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
180 vma = _install_special_mapping(mm,
182 -image->sym_vvar_start,
183 VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP|
189 do_munmap(mm, text_start, image->size);
191 current->mm->context.vdso = (void __user *)text_start;
192 current->mm->context.vdso_image = image;
196 up_write(&mm->mmap_sem);
202 * Put the vdso above the (randomized) stack with another randomized
203 * offset. This way there is no hole in the middle of address space.
204 * To save memory make sure it is still in the same PTE as the stack
205 * top. This doesn't give that many random bits.
207 * Note that this algorithm is imperfect: the distribution of the vdso
208 * start address within a PMD is biased toward the end.
210 * Only used for the 64-bit and x32 vdsos.
212 static unsigned long vdso_addr(unsigned long start, unsigned len)
214 unsigned long addr, end;
218 * Round up the start address. It can start out unaligned as a result
219 * of stack start randomization.
221 start = PAGE_ALIGN(start);
223 /* Round the lowest possible end address up to a PMD boundary. */
224 end = (start + len + PMD_SIZE - 1) & PMD_MASK;
225 if (end >= TASK_SIZE_MAX)
230 offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
231 addr = start + (offset << PAGE_SHIFT);
237 * Forcibly align the final address in case we have a hardware
238 * issue that requires alignment for performance reasons.
240 addr = align_vdso_addr(addr);
245 static int map_vdso_randomized(const struct vdso_image *image)
247 unsigned long addr = vdso_addr(current->mm->start_stack, image->size-image->sym_vvar_start);
249 return map_vdso(image, addr);
253 int map_vdso_once(const struct vdso_image *image, unsigned long addr)
255 struct mm_struct *mm = current->mm;
256 struct vm_area_struct *vma;
258 down_write(&mm->mmap_sem);
260 * Check if we have already mapped vdso blob - fail to prevent
261 * abusing from userspace install_speciall_mapping, which may
262 * not do accounting and rlimit right.
263 * We could search vma near context.vdso, but it's a slowpath,
264 * so let's explicitely check all VMAs to be completely sure.
266 for (vma = mm->mmap; vma; vma = vma->vm_next) {
267 if (vma_is_special_mapping(vma, &vdso_mapping) ||
268 vma_is_special_mapping(vma, &vvar_mapping)) {
269 up_write(&mm->mmap_sem);
273 up_write(&mm->mmap_sem);
275 return map_vdso(image, addr);
278 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
279 static int load_vdso32(void)
281 if (vdso32_enabled != 1) /* Other values all mean "disabled" */
284 return map_vdso(&vdso_image_32, 0);
289 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
294 return map_vdso_randomized(&vdso_image_64);
298 int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
301 #ifdef CONFIG_X86_X32_ABI
302 if (test_thread_flag(TIF_X32)) {
305 return map_vdso_randomized(&vdso_image_x32);
308 #ifdef CONFIG_IA32_EMULATION
309 return load_vdso32();
316 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
318 return load_vdso32();
323 static __init int vdso_setup(char *s)
325 vdso64_enabled = simple_strtoul(s, NULL, 0);
328 __setup("vdso=", vdso_setup);
332 static void vgetcpu_cpu_init(void *arg)
334 int cpu = smp_processor_id();
335 struct desc_struct d = { };
336 unsigned long node = 0;
338 node = cpu_to_node(cpu);
340 if (static_cpu_has(X86_FEATURE_RDTSCP))
341 write_rdtscp_aux((node << 12) | cpu);
344 * Store cpu number in limit so that it can be loaded
345 * quickly in user space in vgetcpu. (12 bits for the CPU
346 * and 8 bits for the node)
348 d.limit0 = cpu | ((node & 0xf) << 12);
350 d.type = 5; /* RO data, expand down, accessed */
351 d.dpl = 3; /* Visible to user code */
352 d.s = 1; /* Not a system segment */
353 d.p = 1; /* Present */
354 d.d = 1; /* 32-bit */
356 write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S);
359 static int vgetcpu_online(unsigned int cpu)
361 return smp_call_function_single(cpu, vgetcpu_cpu_init, NULL, 1);
364 static int __init init_vdso(void)
366 init_vdso_image(&vdso_image_64);
368 #ifdef CONFIG_X86_X32_ABI
369 init_vdso_image(&vdso_image_x32);
372 /* notifier priority > KVM */
373 return cpuhp_setup_state(CPUHP_AP_X86_VDSO_VMA_ONLINE,
374 "AP_X86_VDSO_VMA_ONLINE", vgetcpu_online, NULL);
376 subsys_initcall(init_vdso);
377 #endif /* CONFIG_X86_64 */