1 /*
2 * vdso setup for s390
3 *
4 * Copyright IBM Corp. 2008
5 * Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License (version 2 only)
9 * as published by the Free Software Foundation.
10 */
11
12 #include <linux/module.h>
13 #include <linux/errno.h>
14 #include <linux/sched.h>
15 #include <linux/kernel.h>
16 #include <linux/mm.h>
17 #include <linux/smp.h>
18 #include <linux/stddef.h>
19 #include <linux/unistd.h>
20 #include <linux/slab.h>
21 #include <linux/user.h>
22 #include <linux/elf.h>
23 #include <linux/security.h>
24 #include <linux/bootmem.h>
25 #include <linux/compat.h>
26 #include <asm/asm-offsets.h>
27 #include <asm/pgtable.h>
28 #include <asm/processor.h>
29 #include <asm/mmu.h>
30 #include <asm/mmu_context.h>
31 #include <asm/sections.h>
32 #include <asm/vdso.h>
33 #include <asm/facility.h>
34
35 #ifdef CONFIG_COMPAT
36 extern char vdso32_start, vdso32_end;
37 static void *vdso32_kbase = &vdso32_start;
38 static unsigned int vdso32_pages;
39 static struct page **vdso32_pagelist;
40 #endif
41
42 extern char vdso64_start, vdso64_end;
43 static void *vdso64_kbase = &vdso64_start;
44 static unsigned int vdso64_pages;
45 static struct page **vdso64_pagelist;
46
47 /*
48 * Should the kernel map a VDSO page into processes and pass its
49 * address down to glibc upon exec()?
50 */
51 unsigned int __read_mostly vdso_enabled = 1;
52
vdso_setup(char * s)53 static int __init vdso_setup(char *s)
54 {
55 unsigned long val;
56 int rc;
57
58 rc = 0;
59 if (strncmp(s, "on", 3) == 0)
60 vdso_enabled = 1;
61 else if (strncmp(s, "off", 4) == 0)
62 vdso_enabled = 0;
63 else {
64 rc = kstrtoul(s, 0, &val);
65 vdso_enabled = rc ? 0 : !!val;
66 }
67 return !rc;
68 }
69 __setup("vdso=", vdso_setup);
70
71 /*
72 * The vdso data page
73 */
74 static union {
75 struct vdso_data data;
76 u8 page[PAGE_SIZE];
77 } vdso_data_store __page_aligned_data;
78 struct vdso_data *vdso_data = &vdso_data_store.data;
79
80 /*
81 * Setup vdso data page.
82 */
vdso_init_data(struct vdso_data * vd)83 static void vdso_init_data(struct vdso_data *vd)
84 {
85 vd->ectg_available = test_facility(31);
86 }
87
88 /*
89 * Allocate/free per cpu vdso data.
90 */
91 #define SEGMENT_ORDER 2
92
vdso_alloc_per_cpu(struct _lowcore * lowcore)93 int vdso_alloc_per_cpu(struct _lowcore *lowcore)
94 {
95 unsigned long segment_table, page_table, page_frame;
96 u32 *psal, *aste;
97 int i;
98
99 lowcore->vdso_per_cpu_data = __LC_PASTE;
100
101 if (!vdso_enabled)
102 return 0;
103
104 segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER);
105 page_table = get_zeroed_page(GFP_KERNEL | GFP_DMA);
106 page_frame = get_zeroed_page(GFP_KERNEL);
107 if (!segment_table || !page_table || !page_frame)
108 goto out;
109
110 clear_table((unsigned long *) segment_table, _SEGMENT_ENTRY_EMPTY,
111 PAGE_SIZE << SEGMENT_ORDER);
112 clear_table((unsigned long *) page_table, _PAGE_INVALID,
113 256*sizeof(unsigned long));
114
115 *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table;
116 *(unsigned long *) page_table = _PAGE_PROTECT + page_frame;
117
118 psal = (u32 *) (page_table + 256*sizeof(unsigned long));
119 aste = psal + 32;
120
121 for (i = 4; i < 32; i += 4)
122 psal[i] = 0x80000000;
123
124 lowcore->paste[4] = (u32)(addr_t) psal;
125 psal[0] = 0x02000000;
126 psal[2] = (u32)(addr_t) aste;
127 *(unsigned long *) (aste + 2) = segment_table +
128 _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT;
129 aste[4] = (u32)(addr_t) psal;
130 lowcore->vdso_per_cpu_data = page_frame;
131
132 return 0;
133
134 out:
135 free_page(page_frame);
136 free_page(page_table);
137 free_pages(segment_table, SEGMENT_ORDER);
138 return -ENOMEM;
139 }
140
vdso_free_per_cpu(struct _lowcore * lowcore)141 void vdso_free_per_cpu(struct _lowcore *lowcore)
142 {
143 unsigned long segment_table, page_table, page_frame;
144 u32 *psal, *aste;
145
146 if (!vdso_enabled)
147 return;
148
149 psal = (u32 *)(addr_t) lowcore->paste[4];
150 aste = (u32 *)(addr_t) psal[2];
151 segment_table = *(unsigned long *)(aste + 2) & PAGE_MASK;
152 page_table = *(unsigned long *) segment_table;
153 page_frame = *(unsigned long *) page_table;
154
155 free_page(page_frame);
156 free_page(page_table);
157 free_pages(segment_table, SEGMENT_ORDER);
158 }
159
vdso_init_cr5(void)160 static void vdso_init_cr5(void)
161 {
162 unsigned long cr5;
163
164 if (!vdso_enabled)
165 return;
166 cr5 = offsetof(struct _lowcore, paste);
167 __ctl_load(cr5, 5, 5);
168 }
169
170 /*
171 * This is called from binfmt_elf, we create the special vma for the
172 * vDSO and insert it into the mm struct tree
173 */
arch_setup_additional_pages(struct linux_binprm * bprm,int uses_interp)174 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
175 {
176 struct mm_struct *mm = current->mm;
177 struct page **vdso_pagelist;
178 unsigned long vdso_pages;
179 unsigned long vdso_base;
180 int rc;
181
182 if (!vdso_enabled)
183 return 0;
184 /*
185 * Only map the vdso for dynamically linked elf binaries.
186 */
187 if (!uses_interp)
188 return 0;
189
190 vdso_pagelist = vdso64_pagelist;
191 vdso_pages = vdso64_pages;
192 #ifdef CONFIG_COMPAT
193 if (is_compat_task()) {
194 vdso_pagelist = vdso32_pagelist;
195 vdso_pages = vdso32_pages;
196 }
197 #endif
198 /*
199 * vDSO has a problem and was disabled, just don't "enable" it for
200 * the process
201 */
202 if (vdso_pages == 0)
203 return 0;
204
205 current->mm->context.vdso_base = 0;
206
207 /*
208 * pick a base address for the vDSO in process space. We try to put
209 * it at vdso_base which is the "natural" base for it, but we might
210 * fail and end up putting it elsewhere.
211 */
212 down_write(&mm->mmap_sem);
213 vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0);
214 if (IS_ERR_VALUE(vdso_base)) {
215 rc = vdso_base;
216 goto out_up;
217 }
218
219 /*
220 * Put vDSO base into mm struct. We need to do this before calling
221 * install_special_mapping or the perf counter mmap tracking code
222 * will fail to recognise it as a vDSO (since arch_vma_name fails).
223 */
224 current->mm->context.vdso_base = vdso_base;
225
226 /*
227 * our vma flags don't have VM_WRITE so by default, the process
228 * isn't allowed to write those pages.
229 * gdb can break that with ptrace interface, and thus trigger COW
230 * on those pages but it's then your responsibility to never do that
231 * on the "data" page of the vDSO or you'll stop getting kernel
232 * updates and your nice userland gettimeofday will be totally dead.
233 * It's fine to use that for setting breakpoints in the vDSO code
234 * pages though.
235 */
236 rc = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
237 VM_READ|VM_EXEC|
238 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
239 vdso_pagelist);
240 if (rc)
241 current->mm->context.vdso_base = 0;
242 out_up:
243 up_write(&mm->mmap_sem);
244 return rc;
245 }
246
arch_vma_name(struct vm_area_struct * vma)247 const char *arch_vma_name(struct vm_area_struct *vma)
248 {
249 if (vma->vm_mm && vma->vm_start == vma->vm_mm->context.vdso_base)
250 return "[vdso]";
251 return NULL;
252 }
253
vdso_init(void)254 static int __init vdso_init(void)
255 {
256 int i;
257
258 if (!vdso_enabled)
259 return 0;
260 vdso_init_data(vdso_data);
261 #ifdef CONFIG_COMPAT
262 /* Calculate the size of the 32 bit vDSO */
263 vdso32_pages = ((&vdso32_end - &vdso32_start
264 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
265
266 /* Make sure pages are in the correct state */
267 vdso32_pagelist = kzalloc(sizeof(struct page *) * (vdso32_pages + 1),
268 GFP_KERNEL);
269 BUG_ON(vdso32_pagelist == NULL);
270 for (i = 0; i < vdso32_pages - 1; i++) {
271 struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
272 ClearPageReserved(pg);
273 get_page(pg);
274 vdso32_pagelist[i] = pg;
275 }
276 vdso32_pagelist[vdso32_pages - 1] = virt_to_page(vdso_data);
277 vdso32_pagelist[vdso32_pages] = NULL;
278 #endif
279
280 /* Calculate the size of the 64 bit vDSO */
281 vdso64_pages = ((&vdso64_end - &vdso64_start
282 + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
283
284 /* Make sure pages are in the correct state */
285 vdso64_pagelist = kzalloc(sizeof(struct page *) * (vdso64_pages + 1),
286 GFP_KERNEL);
287 BUG_ON(vdso64_pagelist == NULL);
288 for (i = 0; i < vdso64_pages - 1; i++) {
289 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
290 ClearPageReserved(pg);
291 get_page(pg);
292 vdso64_pagelist[i] = pg;
293 }
294 vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data);
295 vdso64_pagelist[vdso64_pages] = NULL;
296 if (vdso_alloc_per_cpu(&S390_lowcore))
297 BUG();
298 vdso_init_cr5();
299
300 get_page(virt_to_page(vdso_data));
301
302 smp_mb();
303
304 return 0;
305 }
306 early_initcall(vdso_init);
307