1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright IBM Corp. 2008
6 * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
9 #include <linux/init.h>
10 #include <linux/errno.h>
11 #include <linux/sched.h>
12 #include <linux/kernel.h>
14 #include <linux/smp.h>
15 #include <linux/stddef.h>
16 #include <linux/unistd.h>
17 #include <linux/slab.h>
18 #include <linux/user.h>
19 #include <linux/elf.h>
20 #include <linux/security.h>
21 #include <linux/memblock.h>
22 #include <linux/compat.h>
23 #include <asm/asm-offsets.h>
24 #include <asm/pgtable.h>
25 #include <asm/processor.h>
27 #include <asm/mmu_context.h>
28 #include <asm/sections.h>
30 #include <asm/facility.h>
32 #ifdef CONFIG_COMPAT_VDSO
33 extern char vdso32_start, vdso32_end;
34 static void *vdso32_kbase = &vdso32_start;
35 static unsigned int vdso32_pages;
36 static struct page **vdso32_pagelist;
39 extern char vdso64_start, vdso64_end;
40 static void *vdso64_kbase = &vdso64_start;
41 static unsigned int vdso64_pages;
42 static struct page **vdso64_pagelist;
45 * Should the kernel map a VDSO page into processes and pass its
46 * address down to glibc upon exec()?
48 unsigned int __read_mostly vdso_enabled = 1;
50 static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
51 struct vm_area_struct *vma, struct vm_fault *vmf)
53 struct page **vdso_pagelist;
54 unsigned long vdso_pages;
56 vdso_pagelist = vdso64_pagelist;
57 vdso_pages = vdso64_pages;
58 #ifdef CONFIG_COMPAT_VDSO
59 if (vma->vm_mm->context.compat_mm) {
60 vdso_pagelist = vdso32_pagelist;
61 vdso_pages = vdso32_pages;
65 if (vmf->pgoff >= vdso_pages)
66 return VM_FAULT_SIGBUS;
68 vmf->page = vdso_pagelist[vmf->pgoff];
73 static int vdso_mremap(const struct vm_special_mapping *sm,
74 struct vm_area_struct *vma)
76 unsigned long vdso_pages;
78 vdso_pages = vdso64_pages;
79 #ifdef CONFIG_COMPAT_VDSO
80 if (vma->vm_mm->context.compat_mm)
81 vdso_pages = vdso32_pages;
84 if ((vdso_pages << PAGE_SHIFT) != vma->vm_end - vma->vm_start)
87 if (WARN_ON_ONCE(current->mm != vma->vm_mm))
90 current->mm->context.vdso_base = vma->vm_start;
94 static const struct vm_special_mapping vdso_mapping = {
97 .mremap = vdso_mremap,
100 static int __init vdso_setup(char *s)
106 if (strncmp(s, "on", 3) == 0)
108 else if (strncmp(s, "off", 4) == 0)
111 rc = kstrtoul(s, 0, &val);
112 vdso_enabled = rc ? 0 : !!val;
116 __setup("vdso=", vdso_setup);
122 struct vdso_data data;
124 } vdso_data_store __page_aligned_data;
125 struct vdso_data *vdso_data = &vdso_data_store.data;
128 * Setup vdso data page.
130 static void __init vdso_init_data(struct vdso_data *vd)
132 vd->ectg_available = test_facility(31);
136 * Allocate/free per cpu vdso data.
138 #define SEGMENT_ORDER 2
141 * The initial vdso_data structure for the boot CPU. Eventually
142 * it is replaced with a properly allocated structure in vdso_init.
143 * This is necessary because a valid S390_lowcore.vdso_per_cpu_data
144 * pointer is required to be able to return from an interrupt or
145 * program check. See the exit paths in entry.S.
147 struct vdso_data boot_vdso_data __initdata;
149 void __init vdso_alloc_boot_cpu(struct lowcore *lowcore)
151 lowcore->vdso_per_cpu_data = (unsigned long) &boot_vdso_data;
154 int vdso_alloc_per_cpu(struct lowcore *lowcore)
156 unsigned long segment_table, page_table, page_frame;
157 struct vdso_per_cpu_data *vd;
159 segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER);
160 page_table = get_zeroed_page(GFP_KERNEL);
161 page_frame = get_zeroed_page(GFP_KERNEL);
162 if (!segment_table || !page_table || !page_frame)
164 arch_set_page_dat(virt_to_page(segment_table), SEGMENT_ORDER);
165 arch_set_page_dat(virt_to_page(page_table), 0);
167 /* Initialize per-cpu vdso data page */
168 vd = (struct vdso_per_cpu_data *) page_frame;
169 vd->cpu_nr = lowcore->cpu_nr;
170 vd->node_id = cpu_to_node(vd->cpu_nr);
172 /* Set up page table for the vdso address space */
173 memset64((u64 *)segment_table, _SEGMENT_ENTRY_EMPTY, _CRST_ENTRIES);
174 memset64((u64 *)page_table, _PAGE_INVALID, PTRS_PER_PTE);
176 *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table;
177 *(unsigned long *) page_table = _PAGE_PROTECT + page_frame;
179 lowcore->vdso_asce = segment_table +
180 _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT;
181 lowcore->vdso_per_cpu_data = page_frame;
186 free_page(page_frame);
187 free_page(page_table);
188 free_pages(segment_table, SEGMENT_ORDER);
192 void vdso_free_per_cpu(struct lowcore *lowcore)
194 unsigned long segment_table, page_table, page_frame;
196 segment_table = lowcore->vdso_asce & PAGE_MASK;
197 page_table = *(unsigned long *) segment_table;
198 page_frame = *(unsigned long *) page_table;
200 free_page(page_frame);
201 free_page(page_table);
202 free_pages(segment_table, SEGMENT_ORDER);
206 * This is called from binfmt_elf, we create the special vma for the
207 * vDSO and insert it into the mm struct tree
209 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
211 struct mm_struct *mm = current->mm;
212 struct vm_area_struct *vma;
213 unsigned long vdso_pages;
214 unsigned long vdso_base;
220 * Only map the vdso for dynamically linked elf binaries.
225 vdso_pages = vdso64_pages;
226 #ifdef CONFIG_COMPAT_VDSO
227 mm->context.compat_mm = is_compat_task();
228 if (mm->context.compat_mm)
229 vdso_pages = vdso32_pages;
232 * vDSO has a problem and was disabled, just don't "enable" it for
239 * pick a base address for the vDSO in process space. We try to put
240 * it at vdso_base which is the "natural" base for it, but we might
241 * fail and end up putting it elsewhere.
243 if (down_write_killable(&mm->mmap_sem))
245 vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0);
246 if (IS_ERR_VALUE(vdso_base)) {
252 * our vma flags don't have VM_WRITE so by default, the process
253 * isn't allowed to write those pages.
254 * gdb can break that with ptrace interface, and thus trigger COW
255 * on those pages but it's then your responsibility to never do that
256 * on the "data" page of the vDSO or you'll stop getting kernel
257 * updates and your nice userland gettimeofday will be totally dead.
258 * It's fine to use that for setting breakpoints in the vDSO code
261 vma = _install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
263 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
270 current->mm->context.vdso_base = vdso_base;
274 up_write(&mm->mmap_sem);
278 static int __init vdso_init(void)
282 vdso_init_data(vdso_data);
283 #ifdef CONFIG_COMPAT_VDSO
284 /* Calculate the size of the 32 bit vDSO */
285 vdso32_pages = ((&vdso32_end - &vdso32_start
286 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
288 /* Make sure pages are in the correct state */
289 vdso32_pagelist = kcalloc(vdso32_pages + 1, sizeof(struct page *),
291 BUG_ON(vdso32_pagelist == NULL);
292 for (i = 0; i < vdso32_pages - 1; i++) {
293 struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
295 vdso32_pagelist[i] = pg;
297 vdso32_pagelist[vdso32_pages - 1] = virt_to_page(vdso_data);
298 vdso32_pagelist[vdso32_pages] = NULL;
301 /* Calculate the size of the 64 bit vDSO */
302 vdso64_pages = ((&vdso64_end - &vdso64_start
303 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
305 /* Make sure pages are in the correct state */
306 vdso64_pagelist = kcalloc(vdso64_pages + 1, sizeof(struct page *),
308 BUG_ON(vdso64_pagelist == NULL);
309 for (i = 0; i < vdso64_pages - 1; i++) {
310 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
312 vdso64_pagelist[i] = pg;
314 vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data);
315 vdso64_pagelist[vdso64_pages] = NULL;
316 if (vdso_alloc_per_cpu(&S390_lowcore))
319 get_page(virt_to_page(vdso_data));
323 early_initcall(vdso_init);