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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 #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 
 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  */
 83 static void __init 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 
 93 int vdso_alloc_per_cpu(struct lowcore *lowcore)
 94 {
 95         unsigned long segment_table, page_table, page_frame;
 96         struct vdso_per_cpu_data *vd;
 97         u32 *psal, *aste;
 98         int i;
 99 
100         lowcore->vdso_per_cpu_data = __LC_PASTE;
101 
102         if (!vdso_enabled)
103                 return 0;
104 
105         segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER);
106         page_table = get_zeroed_page(GFP_KERNEL | GFP_DMA);
107         page_frame = get_zeroed_page(GFP_KERNEL);
108         if (!segment_table || !page_table || !page_frame)
109                 goto out;
110 
111         /* Initialize per-cpu vdso data page */
112         vd = (struct vdso_per_cpu_data *) page_frame;
113         vd->cpu_nr = lowcore->cpu_nr;
114         vd->node_id = cpu_to_node(vd->cpu_nr);
115 
116         /* Set up access register mode page table */
117         clear_table((unsigned long *) segment_table, _SEGMENT_ENTRY_EMPTY,
118                     PAGE_SIZE << SEGMENT_ORDER);
119         clear_table((unsigned long *) page_table, _PAGE_INVALID,
120                     256*sizeof(unsigned long));
121 
122         *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table;
123         *(unsigned long *) page_table = _PAGE_PROTECT + page_frame;
124 
125         psal = (u32 *) (page_table + 256*sizeof(unsigned long));
126         aste = psal + 32;
127 
128         for (i = 4; i < 32; i += 4)
129                 psal[i] = 0x80000000;
130 
131         lowcore->paste[4] = (u32)(addr_t) psal;
132         psal[0] = 0x02000000;
133         psal[2] = (u32)(addr_t) aste;
134         *(unsigned long *) (aste + 2) = segment_table +
135                 _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT;
136         aste[4] = (u32)(addr_t) psal;
137         lowcore->vdso_per_cpu_data = page_frame;
138 
139         return 0;
140 
141 out:
142         free_page(page_frame);
143         free_page(page_table);
144         free_pages(segment_table, SEGMENT_ORDER);
145         return -ENOMEM;
146 }
147 
148 void vdso_free_per_cpu(struct lowcore *lowcore)
149 {
150         unsigned long segment_table, page_table, page_frame;
151         u32 *psal, *aste;
152 
153         if (!vdso_enabled)
154                 return;
155 
156         psal = (u32 *)(addr_t) lowcore->paste[4];
157         aste = (u32 *)(addr_t) psal[2];
158         segment_table = *(unsigned long *)(aste + 2) & PAGE_MASK;
159         page_table = *(unsigned long *) segment_table;
160         page_frame = *(unsigned long *) page_table;
161 
162         free_page(page_frame);
163         free_page(page_table);
164         free_pages(segment_table, SEGMENT_ORDER);
165 }
166 
167 static void vdso_init_cr5(void)
168 {
169         unsigned long cr5;
170 
171         if (!vdso_enabled)
172                 return;
173         cr5 = offsetof(struct lowcore, paste);
174         __ctl_load(cr5, 5, 5);
175 }
176 
177 /*
178  * This is called from binfmt_elf, we create the special vma for the
179  * vDSO and insert it into the mm struct tree
180  */
181 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
182 {
183         struct mm_struct *mm = current->mm;
184         struct page **vdso_pagelist;
185         unsigned long vdso_pages;
186         unsigned long vdso_base;
187         int rc;
188 
189         if (!vdso_enabled)
190                 return 0;
191         /*
192          * Only map the vdso for dynamically linked elf binaries.
193          */
194         if (!uses_interp)
195                 return 0;
196 
197         vdso_pagelist = vdso64_pagelist;
198         vdso_pages = vdso64_pages;
199 #ifdef CONFIG_COMPAT
200         if (is_compat_task()) {
201                 vdso_pagelist = vdso32_pagelist;
202                 vdso_pages = vdso32_pages;
203         }
204 #endif
205         /*
206          * vDSO has a problem and was disabled, just don't "enable" it for
207          * the process
208          */
209         if (vdso_pages == 0)
210                 return 0;
211 
212         current->mm->context.vdso_base = 0;
213 
214         /*
215          * pick a base address for the vDSO in process space. We try to put
216          * it at vdso_base which is the "natural" base for it, but we might
217          * fail and end up putting it elsewhere.
218          */
219         if (down_write_killable(&mm->mmap_sem))
220                 return -EINTR;
221         vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0);
222         if (IS_ERR_VALUE(vdso_base)) {
223                 rc = vdso_base;
224                 goto out_up;
225         }
226 
227         /*
228          * Put vDSO base into mm struct. We need to do this before calling
229          * install_special_mapping or the perf counter mmap tracking code
230          * will fail to recognise it as a vDSO (since arch_vma_name fails).
231          */
232         current->mm->context.vdso_base = vdso_base;
233 
234         /*
235          * our vma flags don't have VM_WRITE so by default, the process
236          * isn't allowed to write those pages.
237          * gdb can break that with ptrace interface, and thus trigger COW
238          * on those pages but it's then your responsibility to never do that
239          * on the "data" page of the vDSO or you'll stop getting kernel
240          * updates and your nice userland gettimeofday will be totally dead.
241          * It's fine to use that for setting breakpoints in the vDSO code
242          * pages though.
243          */
244         rc = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
245                                      VM_READ|VM_EXEC|
246                                      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
247                                      vdso_pagelist);
248         if (rc)
249                 current->mm->context.vdso_base = 0;
250 out_up:
251         up_write(&mm->mmap_sem);
252         return rc;
253 }
254 
255 const char *arch_vma_name(struct vm_area_struct *vma)
256 {
257         if (vma->vm_mm && vma->vm_start == vma->vm_mm->context.vdso_base)
258                 return "[vdso]";
259         return NULL;
260 }
261 
262 static int __init vdso_init(void)
263 {
264         int i;
265 
266         if (!vdso_enabled)
267                 return 0;
268         vdso_init_data(vdso_data);
269 #ifdef CONFIG_COMPAT
270         /* Calculate the size of the 32 bit vDSO */
271         vdso32_pages = ((&vdso32_end - &vdso32_start
272                          + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
273 
274         /* Make sure pages are in the correct state */
275         vdso32_pagelist = kzalloc(sizeof(struct page *) * (vdso32_pages + 1),
276                                   GFP_KERNEL);
277         BUG_ON(vdso32_pagelist == NULL);
278         for (i = 0; i < vdso32_pages - 1; i++) {
279                 struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
280                 ClearPageReserved(pg);
281                 get_page(pg);
282                 vdso32_pagelist[i] = pg;
283         }
284         vdso32_pagelist[vdso32_pages - 1] = virt_to_page(vdso_data);
285         vdso32_pagelist[vdso32_pages] = NULL;
286 #endif
287 
288         /* Calculate the size of the 64 bit vDSO */
289         vdso64_pages = ((&vdso64_end - &vdso64_start
290                          + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
291 
292         /* Make sure pages are in the correct state */
293         vdso64_pagelist = kzalloc(sizeof(struct page *) * (vdso64_pages + 1),
294                                   GFP_KERNEL);
295         BUG_ON(vdso64_pagelist == NULL);
296         for (i = 0; i < vdso64_pages - 1; i++) {
297                 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
298                 ClearPageReserved(pg);
299                 get_page(pg);
300                 vdso64_pagelist[i] = pg;
301         }
302         vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data);
303         vdso64_pagelist[vdso64_pages] = NULL;
304         if (vdso_alloc_per_cpu(&S390_lowcore))
305                 BUG();
306         vdso_init_cr5();
307 
308         get_page(virt_to_page(vdso_data));
309 
310         return 0;
311 }
312 early_initcall(vdso_init);
313 

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