arch/s390/kernel/vdso.c

   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 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         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
 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
 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  */
 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
 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
 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         return 0;
 303 }
 304 early_initcall(vdso_init);