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Linux/arch/s390/kernel/vdso.c

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  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 #if defined(CONFIG_32BIT) || defined(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 #ifdef CONFIG_64BIT
 43 extern char vdso64_start, vdso64_end;
 44 static void *vdso64_kbase = &vdso64_start;
 45 static unsigned int vdso64_pages;
 46 static struct page **vdso64_pagelist;
 47 #endif /* CONFIG_64BIT */
 48 
 49 /*
 50  * Should the kernel map a VDSO page into processes and pass its
 51  * address down to glibc upon exec()?
 52  */
 53 unsigned int __read_mostly vdso_enabled = 1;
 54 
 55 static int __init vdso_setup(char *s)
 56 {
 57         unsigned long val;
 58         int rc;
 59 
 60         rc = 0;
 61         if (strncmp(s, "on", 3) == 0)
 62                 vdso_enabled = 1;
 63         else if (strncmp(s, "off", 4) == 0)
 64                 vdso_enabled = 0;
 65         else {
 66                 rc = strict_strtoul(s, 0, &val);
 67                 vdso_enabled = rc ? 0 : !!val;
 68         }
 69         return !rc;
 70 }
 71 __setup("vdso=", vdso_setup);
 72 
 73 /*
 74  * The vdso data page
 75  */
 76 static union {
 77         struct vdso_data        data;
 78         u8                      page[PAGE_SIZE];
 79 } vdso_data_store __page_aligned_data;
 80 struct vdso_data *vdso_data = &vdso_data_store.data;
 81 
 82 /*
 83  * Setup vdso data page.
 84  */
 85 static void vdso_init_data(struct vdso_data *vd)
 86 {
 87         vd->ectg_available =
 88                 s390_user_mode != HOME_SPACE_MODE && test_facility(31);
 89 }
 90 
 91 #ifdef CONFIG_64BIT
 92 /*
 93  * Allocate/free per cpu vdso data.
 94  */
 95 #define SEGMENT_ORDER   2
 96 
 97 int vdso_alloc_per_cpu(struct _lowcore *lowcore)
 98 {
 99         unsigned long segment_table, page_table, page_frame;
100         u32 *psal, *aste;
101         int i;
102 
103         lowcore->vdso_per_cpu_data = __LC_PASTE;
104 
105         if (s390_user_mode == HOME_SPACE_MODE || !vdso_enabled)
106                 return 0;
107 
108         segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER);
109         page_table = get_zeroed_page(GFP_KERNEL | GFP_DMA);
110         page_frame = get_zeroed_page(GFP_KERNEL);
111         if (!segment_table || !page_table || !page_frame)
112                 goto out;
113 
114         clear_table((unsigned long *) segment_table, _SEGMENT_ENTRY_EMPTY,
115                     PAGE_SIZE << SEGMENT_ORDER);
116         clear_table((unsigned long *) page_table, _PAGE_TYPE_EMPTY,
117                     256*sizeof(unsigned long));
118 
119         *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table;
120         *(unsigned long *) page_table = _PAGE_RO + page_frame;
121 
122         psal = (u32 *) (page_table + 256*sizeof(unsigned long));
123         aste = psal + 32;
124 
125         for (i = 4; i < 32; i += 4)
126                 psal[i] = 0x80000000;
127 
128         lowcore->paste[4] = (u32)(addr_t) psal;
129         psal[0] = 0x20000000;
130         psal[2] = (u32)(addr_t) aste;
131         *(unsigned long *) (aste + 2) = segment_table +
132                 _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT;
133         aste[4] = (u32)(addr_t) psal;
134         lowcore->vdso_per_cpu_data = page_frame;
135 
136         return 0;
137 
138 out:
139         free_page(page_frame);
140         free_page(page_table);
141         free_pages(segment_table, SEGMENT_ORDER);
142         return -ENOMEM;
143 }
144 
145 void vdso_free_per_cpu(struct _lowcore *lowcore)
146 {
147         unsigned long segment_table, page_table, page_frame;
148         u32 *psal, *aste;
149 
150         if (s390_user_mode == HOME_SPACE_MODE || !vdso_enabled)
151                 return;
152 
153         psal = (u32 *)(addr_t) lowcore->paste[4];
154         aste = (u32 *)(addr_t) psal[2];
155         segment_table = *(unsigned long *)(aste + 2) & PAGE_MASK;
156         page_table = *(unsigned long *) segment_table;
157         page_frame = *(unsigned long *) page_table;
158 
159         free_page(page_frame);
160         free_page(page_table);
161         free_pages(segment_table, SEGMENT_ORDER);
162 }
163 
164 static void vdso_init_cr5(void)
165 {
166         unsigned long cr5;
167 
168         if (s390_user_mode == HOME_SPACE_MODE || !vdso_enabled)
169                 return;
170         cr5 = offsetof(struct _lowcore, paste);
171         __ctl_load(cr5, 5, 5);
172 }
173 #endif /* CONFIG_64BIT */
174 
175 /*
176  * This is called from binfmt_elf, we create the special vma for the
177  * vDSO and insert it into the mm struct tree
178  */
179 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
180 {
181         struct mm_struct *mm = current->mm;
182         struct page **vdso_pagelist;
183         unsigned long vdso_pages;
184         unsigned long vdso_base;
185         int rc;
186 
187         if (!vdso_enabled)
188                 return 0;
189         /*
190          * Only map the vdso for dynamically linked elf binaries.
191          */
192         if (!uses_interp)
193                 return 0;
194 
195 #ifdef CONFIG_64BIT
196         vdso_pagelist = vdso64_pagelist;
197         vdso_pages = vdso64_pages;
198 #ifdef CONFIG_COMPAT
199         if (is_compat_task()) {
200                 vdso_pagelist = vdso32_pagelist;
201                 vdso_pages = vdso32_pages;
202         }
203 #endif
204 #else
205         vdso_pagelist = vdso32_pagelist;
206         vdso_pages = vdso32_pages;
207 #endif
208 
209         /*
210          * vDSO has a problem and was disabled, just don't "enable" it for
211          * the process
212          */
213         if (vdso_pages == 0)
214                 return 0;
215 
216         current->mm->context.vdso_base = 0;
217 
218         /*
219          * pick a base address for the vDSO in process space. We try to put
220          * it at vdso_base which is the "natural" base for it, but we might
221          * fail and end up putting it elsewhere.
222          */
223         down_write(&mm->mmap_sem);
224         vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0);
225         if (IS_ERR_VALUE(vdso_base)) {
226                 rc = vdso_base;
227                 goto out_up;
228         }
229 
230         /*
231          * Put vDSO base into mm struct. We need to do this before calling
232          * install_special_mapping or the perf counter mmap tracking code
233          * will fail to recognise it as a vDSO (since arch_vma_name fails).
234          */
235         current->mm->context.vdso_base = vdso_base;
236 
237         /*
238          * our vma flags don't have VM_WRITE so by default, the process
239          * isn't allowed to write those pages.
240          * gdb can break that with ptrace interface, and thus trigger COW
241          * on those pages but it's then your responsibility to never do that
242          * on the "data" page of the vDSO or you'll stop getting kernel
243          * updates and your nice userland gettimeofday will be totally dead.
244          * It's fine to use that for setting breakpoints in the vDSO code
245          * pages though.
246          */
247         rc = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
248                                      VM_READ|VM_EXEC|
249                                      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
250                                      vdso_pagelist);
251         if (rc)
252                 current->mm->context.vdso_base = 0;
253 out_up:
254         up_write(&mm->mmap_sem);
255         return rc;
256 }
257 
258 const char *arch_vma_name(struct vm_area_struct *vma)
259 {
260         if (vma->vm_mm && vma->vm_start == vma->vm_mm->context.vdso_base)
261                 return "[vdso]";
262         return NULL;
263 }
264 
265 static int __init vdso_init(void)
266 {
267         int i;
268 
269         if (!vdso_enabled)
270                 return 0;
271         vdso_init_data(vdso_data);
272 #if defined(CONFIG_32BIT) || defined(CONFIG_COMPAT)
273         /* Calculate the size of the 32 bit vDSO */
274         vdso32_pages = ((&vdso32_end - &vdso32_start
275                          + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
276 
277         /* Make sure pages are in the correct state */
278         vdso32_pagelist = kzalloc(sizeof(struct page *) * (vdso32_pages + 1),
279                                   GFP_KERNEL);
280         BUG_ON(vdso32_pagelist == NULL);
281         for (i = 0; i < vdso32_pages - 1; i++) {
282                 struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
283                 ClearPageReserved(pg);
284                 get_page(pg);
285                 vdso32_pagelist[i] = pg;
286         }
287         vdso32_pagelist[vdso32_pages - 1] = virt_to_page(vdso_data);
288         vdso32_pagelist[vdso32_pages] = NULL;
289 #endif
290 
291 #ifdef CONFIG_64BIT
292         /* Calculate the size of the 64 bit vDSO */
293         vdso64_pages = ((&vdso64_end - &vdso64_start
294                          + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
295 
296         /* Make sure pages are in the correct state */
297         vdso64_pagelist = kzalloc(sizeof(struct page *) * (vdso64_pages + 1),
298                                   GFP_KERNEL);
299         BUG_ON(vdso64_pagelist == NULL);
300         for (i = 0; i < vdso64_pages - 1; i++) {
301                 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
302                 ClearPageReserved(pg);
303                 get_page(pg);
304                 vdso64_pagelist[i] = pg;
305         }
306         vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data);
307         vdso64_pagelist[vdso64_pages] = NULL;
308         if (vdso_alloc_per_cpu(&S390_lowcore))
309                 BUG();
310         vdso_init_cr5();
311 #endif /* CONFIG_64BIT */
312 
313         get_page(virt_to_page(vdso_data));
314 
315         smp_wmb();
316 
317         return 0;
318 }
319 early_initcall(vdso_init);
320 
321 int in_gate_area_no_mm(unsigned long addr)
322 {
323         return 0;
324 }
325 
326 int in_gate_area(struct mm_struct *mm, unsigned long addr)
327 {
328         return 0;
329 }
330 
331 struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
332 {
333         return NULL;
334 }
335 

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