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 <asm/vgtod.h>
16 #include <asm/proto.h>
23 #if defined(CONFIG_X86_64)
24 unsigned int __read_mostly vdso64_enabled = 1;
27 void __init init_vdso_image(const struct vdso_image *image)
30 int npages = (image->size) / PAGE_SIZE;
32 BUG_ON(image->size % PAGE_SIZE != 0);
33 for (i = 0; i < npages; i++)
34 image->text_mapping.pages[i] =
35 virt_to_page(image->data + i*PAGE_SIZE);
37 apply_alternatives((struct alt_instr *)(image->data + image->alt),
38 (struct alt_instr *)(image->data + image->alt +
45 * Put the vdso above the (randomized) stack with another randomized
46 * offset. This way there is no hole in the middle of address space.
47 * To save memory make sure it is still in the same PTE as the stack
48 * top. This doesn't give that many random bits.
50 * Note that this algorithm is imperfect: the distribution of the vdso
51 * start address within a PMD is biased toward the end.
53 * Only used for the 64-bit and x32 vdsos.
55 static unsigned long vdso_addr(unsigned long start, unsigned len)
60 unsigned long addr, end;
64 * Round up the start address. It can start out unaligned as a result
65 * of stack start randomization.
67 start = PAGE_ALIGN(start);
69 /* Round the lowest possible end address up to a PMD boundary. */
70 end = (start + len + PMD_SIZE - 1) & PMD_MASK;
71 if (end >= TASK_SIZE_MAX)
76 offset = get_random_int() % (((end - start) >> PAGE_SHIFT) + 1);
77 addr = start + (offset << PAGE_SHIFT);
83 * Forcibly align the final address in case we have a hardware
84 * issue that requires alignment for performance reasons.
86 addr = align_vdso_addr(addr);
92 static int map_vdso(const struct vdso_image *image, bool calculate_addr)
94 struct mm_struct *mm = current->mm;
95 struct vm_area_struct *vma;
96 unsigned long addr, text_start;
98 static struct page *no_pages[] = {NULL};
99 static struct vm_special_mapping vvar_mapping = {
104 if (calculate_addr) {
105 addr = vdso_addr(current->mm->start_stack,
106 image->size - image->sym_vvar_start);
111 down_write(&mm->mmap_sem);
113 addr = get_unmapped_area(NULL, addr,
114 image->size - image->sym_vvar_start, 0, 0);
115 if (IS_ERR_VALUE(addr)) {
120 text_start = addr - image->sym_vvar_start;
121 current->mm->context.vdso = (void __user *)text_start;
124 * MAYWRITE to allow gdb to COW and set breakpoints
126 vma = _install_special_mapping(mm,
130 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
131 &image->text_mapping);
138 vma = _install_special_mapping(mm,
140 -image->sym_vvar_start,
149 if (image->sym_vvar_page)
150 ret = remap_pfn_range(vma,
151 text_start + image->sym_vvar_page,
152 __pa_symbol(&__vvar_page) >> PAGE_SHIFT,
159 #ifdef CONFIG_HPET_TIMER
160 if (hpet_address && image->sym_hpet_page) {
161 ret = io_remap_pfn_range(vma,
162 text_start + image->sym_hpet_page,
163 hpet_address >> PAGE_SHIFT,
165 pgprot_noncached(PAGE_READONLY));
174 current->mm->context.vdso = NULL;
176 up_write(&mm->mmap_sem);
180 #if defined(CONFIG_X86_32) || defined(CONFIG_IA32_EMULATION)
181 static int load_vdso32(void)
185 if (vdso32_enabled != 1) /* Other values all mean "disabled" */
188 ret = map_vdso(selected_vdso32, false);
192 if (selected_vdso32->sym_VDSO32_SYSENTER_RETURN)
193 current_thread_info()->sysenter_return =
194 current->mm->context.vdso +
195 selected_vdso32->sym_VDSO32_SYSENTER_RETURN;
202 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
207 return map_vdso(&vdso_image_64, true);
211 int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
214 #ifdef CONFIG_X86_X32_ABI
215 if (test_thread_flag(TIF_X32)) {
219 return map_vdso(&vdso_image_x32, true);
222 #ifdef CONFIG_IA32_EMULATION
223 return load_vdso32();
230 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
232 return load_vdso32();
237 static __init int vdso_setup(char *s)
239 vdso64_enabled = simple_strtoul(s, NULL, 0);
242 __setup("vdso=", vdso_setup);
246 static void vgetcpu_cpu_init(void *arg)
248 int cpu = smp_processor_id();
249 struct desc_struct d = { };
250 unsigned long node = 0;
252 node = cpu_to_node(cpu);
254 if (cpu_has(&cpu_data(cpu), X86_FEATURE_RDTSCP))
255 write_rdtscp_aux((node << 12) | cpu);
258 * Store cpu number in limit so that it can be loaded
259 * quickly in user space in vgetcpu. (12 bits for the CPU
260 * and 8 bits for the node)
262 d.limit0 = cpu | ((node & 0xf) << 12);
264 d.type = 5; /* RO data, expand down, accessed */
265 d.dpl = 3; /* Visible to user code */
266 d.s = 1; /* Not a system segment */
267 d.p = 1; /* Present */
268 d.d = 1; /* 32-bit */
270 write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S);
274 vgetcpu_cpu_notifier(struct notifier_block *n, unsigned long action, void *arg)
276 long cpu = (long)arg;
278 if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN)
279 smp_call_function_single(cpu, vgetcpu_cpu_init, NULL, 1);
284 static int __init init_vdso(void)
286 init_vdso_image(&vdso_image_64);
288 #ifdef CONFIG_X86_X32_ABI
289 init_vdso_image(&vdso_image_x32);
292 cpu_notifier_register_begin();
294 on_each_cpu(vgetcpu_cpu_init, NULL, 1);
295 /* notifier priority > KVM */
296 __hotcpu_notifier(vgetcpu_cpu_notifier, 30);
298 cpu_notifier_register_done();
302 subsys_initcall(init_vdso);
303 #endif /* CONFIG_X86_64 */