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/init.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 vdso_fault(const struct vm_special_mapping *sm,
  54                       struct vm_area_struct *vma, struct vm_fault *vmf)
  55 {
  56         struct page **vdso_pagelist;
  57         unsigned long vdso_pages;
  58
  59         vdso_pagelist = vdso64_pagelist;
  60         vdso_pages = vdso64_pages;
  61 #ifdef CONFIG_COMPAT
  62         if (is_compat_task()) {
  63                 vdso_pagelist = vdso32_pagelist;
  64                 vdso_pages = vdso32_pages;
  65         }
  66 #endif
  67
  68         if (vmf->pgoff >= vdso_pages)
  69                 return VM_FAULT_SIGBUS;
  70
  71         vmf->page = vdso_pagelist[vmf->pgoff];
  72         get_page(vmf->page);
  73         return 0;
  74 }
  75
  76 static int vdso_mremap(const struct vm_special_mapping *sm,
  77                        struct vm_area_struct *vma)
  78 {
  79         unsigned long vdso_pages;
  80
  81         vdso_pages = vdso64_pages;
  82 #ifdef CONFIG_COMPAT
  83         if (is_compat_task())
  84                 vdso_pages = vdso32_pages;
  85 #endif
  86
  87         if ((vdso_pages << PAGE_SHIFT) != vma->vm_end - vma->vm_start)
  88                 return -EINVAL;
  89
  90         if (WARN_ON_ONCE(current->mm != vma->vm_mm))
  91                 return -EFAULT;
  92
  93         current->mm->context.vdso_base = vma->vm_start;
  94         return 0;
  95 }
  96
  97 static const struct vm_special_mapping vdso_mapping = {
  98         .name = "[vdso]",
  99         .fault = vdso_fault,
 100         .mremap = vdso_mremap,
 101 };
 102
 103 static int __init vdso_setup(char *s)
 104 {
 105         unsigned long val;
 106         int rc;
 107
 108         rc = 0;
 109         if (strncmp(s, "on", 3) == 0)
 110                 vdso_enabled = 1;
 111         else if (strncmp(s, "off", 4) == 0)
 112                 vdso_enabled = 0;
 113         else {
 114                 rc = kstrtoul(s, 0, &val);
 115                 vdso_enabled = rc ? 0 : !!val;
 116         }
 117         return !rc;
 118 }
 119 __setup("vdso=", vdso_setup);
 120
 121 /*
 122  * The vdso data page
 123  */
 124 static union {
 125         struct vdso_data        data;
 126         u8                      page[PAGE_SIZE];
 127 } vdso_data_store __page_aligned_data;
 128 struct vdso_data *vdso_data = &vdso_data_store.data;
 129
 130 /*
 131  * Setup vdso data page.
 132  */
 133 static void __init vdso_init_data(struct vdso_data *vd)
 134 {
 135         vd->ectg_available = test_facility(31);
 136 }
 137
 138 /*
 139  * Allocate/free per cpu vdso data.
 140  */
 141 #define SEGMENT_ORDER   2
 142
 143 /*
 144  * The initial vdso_data structure for the boot CPU. Eventually
 145  * it is replaced with a properly allocated structure in vdso_init.
 146  * This is necessary because a valid S390_lowcore.vdso_per_cpu_data
 147  * pointer is required to be able to return from an interrupt or
 148  * program check. See the exit paths in entry.S.
 149  */
 150 struct vdso_data boot_vdso_data __initdata;
 151
 152 void __init vdso_alloc_boot_cpu(struct lowcore *lowcore)
 153 {
 154         lowcore->vdso_per_cpu_data = (unsigned long) &boot_vdso_data;
 155 }
 156
 157 int vdso_alloc_per_cpu(struct lowcore *lowcore)
 158 {
 159         unsigned long segment_table, page_table, page_frame;
 160         struct vdso_per_cpu_data *vd;
 161         u32 *psal, *aste;
 162         int i;
 163
 164         lowcore->vdso_per_cpu_data = __LC_PASTE;
 165
 166         if (!vdso_enabled)
 167                 return 0;
 168
 169         segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER);
 170         page_table = get_zeroed_page(GFP_KERNEL | GFP_DMA);
 171         page_frame = get_zeroed_page(GFP_KERNEL);
 172         if (!segment_table || !page_table || !page_frame)
 173                 goto out;
 174         arch_set_page_dat(virt_to_page(segment_table), SEGMENT_ORDER);
 175         arch_set_page_dat(virt_to_page(page_table), 0);
 176
 177         /* Initialize per-cpu vdso data page */
 178         vd = (struct vdso_per_cpu_data *) page_frame;
 179         vd->cpu_nr = lowcore->cpu_nr;
 180         vd->node_id = cpu_to_node(vd->cpu_nr);
 181
 182         /* Set up access register mode page table */
 183         memset64((u64 *)segment_table, _SEGMENT_ENTRY_EMPTY, _CRST_ENTRIES);
 184         memset64((u64 *)page_table, _PAGE_INVALID, PTRS_PER_PTE);
 185
 186         *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table;
 187         *(unsigned long *) page_table = _PAGE_PROTECT + page_frame;
 188
 189         psal = (u32 *) (page_table + 256*sizeof(unsigned long));
 190         aste = psal + 32;
 191
 192         for (i = 4; i < 32; i += 4)
 193                 psal[i] = 0x80000000;
 194
 195         lowcore->paste[4] = (u32)(addr_t) psal;
 196         psal[0] = 0x02000000;
 197         psal[2] = (u32)(addr_t) aste;
 198         *(unsigned long *) (aste + 2) = segment_table +
 199                 _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT;
 200         aste[4] = (u32)(addr_t) psal;
 201         lowcore->vdso_per_cpu_data = page_frame;
 202
 203         return 0;
 204
 205 out:
 206         free_page(page_frame);
 207         free_page(page_table);
 208         free_pages(segment_table, SEGMENT_ORDER);
 209         return -ENOMEM;
 210 }
 211
 212 void vdso_free_per_cpu(struct lowcore *lowcore)
 213 {
 214         unsigned long segment_table, page_table, page_frame;
 215         u32 *psal, *aste;
 216
 217         if (!vdso_enabled)
 218                 return;
 219
 220         psal = (u32 *)(addr_t) lowcore->paste[4];
 221         aste = (u32 *)(addr_t) psal[2];
 222         segment_table = *(unsigned long *)(aste + 2) & PAGE_MASK;
 223         page_table = *(unsigned long *) segment_table;
 224         page_frame = *(unsigned long *) page_table;
 225
 226         free_page(page_frame);
 227         free_page(page_table);
 228         free_pages(segment_table, SEGMENT_ORDER);
 229 }
 230
 231 static void vdso_init_cr5(void)
 232 {
 233         unsigned long cr5;
 234
 235         if (!vdso_enabled)
 236                 return;
 237         cr5 = offsetof(struct lowcore, paste);
 238         __ctl_load(cr5, 5, 5);
 239 }
 240
 241 /*
 242  * This is called from binfmt_elf, we create the special vma for the
 243  * vDSO and insert it into the mm struct tree
 244  */
 245 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 246 {
 247         struct mm_struct *mm = current->mm;
 248         struct vm_area_struct *vma;
 249         unsigned long vdso_pages;
 250         unsigned long vdso_base;
 251         int rc;
 252
 253         if (!vdso_enabled)
 254                 return 0;
 255         /*
 256          * Only map the vdso for dynamically linked elf binaries.
 257          */
 258         if (!uses_interp)
 259                 return 0;
 260
 261         vdso_pages = vdso64_pages;
 262 #ifdef CONFIG_COMPAT
 263         if (is_compat_task())
 264                 vdso_pages = vdso32_pages;
 265 #endif
 266         /*
 267          * vDSO has a problem and was disabled, just don't "enable" it for
 268          * the process
 269          */
 270         if (vdso_pages == 0)
 271                 return 0;
 272
 273         /*
 274          * pick a base address for the vDSO in process space. We try to put
 275          * it at vdso_base which is the "natural" base for it, but we might
 276          * fail and end up putting it elsewhere.
 277          */
 278         if (down_write_killable(&mm->mmap_sem))
 279                 return -EINTR;
 280         vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0);
 281         if (IS_ERR_VALUE(vdso_base)) {
 282                 rc = vdso_base;
 283                 goto out_up;
 284         }
 285
 286         /*
 287          * our vma flags don't have VM_WRITE so by default, the process
 288          * isn't allowed to write those pages.
 289          * gdb can break that with ptrace interface, and thus trigger COW
 290          * on those pages but it's then your responsibility to never do that
 291          * on the "data" page of the vDSO or you'll stop getting kernel
 292          * updates and your nice userland gettimeofday will be totally dead.
 293          * It's fine to use that for setting breakpoints in the vDSO code
 294          * pages though.
 295          */
 296         vma = _install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
 297                                        VM_READ|VM_EXEC|
 298                                        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 299                                        &vdso_mapping);
 300         if (IS_ERR(vma)) {
 301                 rc = PTR_ERR(vma);
 302                 goto out_up;
 303         }
 304
 305         current->mm->context.vdso_base = vdso_base;
 306         rc = 0;
 307
 308 out_up:
 309         up_write(&mm->mmap_sem);
 310         return rc;
 311 }
 312
 313 static int __init vdso_init(void)
 314 {
 315         int i;
 316
 317         if (!vdso_enabled)
 318                 return 0;
 319         vdso_init_data(vdso_data);
 320 #ifdef CONFIG_COMPAT
 321         /* Calculate the size of the 32 bit vDSO */
 322         vdso32_pages = ((&vdso32_end - &vdso32_start
 323                          + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
 324
 325         /* Make sure pages are in the correct state */
 326         vdso32_pagelist = kzalloc(sizeof(struct page *) * (vdso32_pages + 1),
 327                                   GFP_KERNEL);
 328         BUG_ON(vdso32_pagelist == NULL);
 329         for (i = 0; i < vdso32_pages - 1; i++) {
 330                 struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
 331                 ClearPageReserved(pg);
 332                 get_page(pg);
 333                 vdso32_pagelist[i] = pg;
 334         }
 335         vdso32_pagelist[vdso32_pages - 1] = virt_to_page(vdso_data);
 336         vdso32_pagelist[vdso32_pages] = NULL;
 337 #endif
 338
 339         /* Calculate the size of the 64 bit vDSO */
 340         vdso64_pages = ((&vdso64_end - &vdso64_start
 341                          + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
 342
 343         /* Make sure pages are in the correct state */
 344         vdso64_pagelist = kzalloc(sizeof(struct page *) * (vdso64_pages + 1),
 345                                   GFP_KERNEL);
 346         BUG_ON(vdso64_pagelist == NULL);
 347         for (i = 0; i < vdso64_pages - 1; i++) {
 348                 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
 349                 ClearPageReserved(pg);
 350                 get_page(pg);
 351                 vdso64_pagelist[i] = pg;
 352         }
 353         vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data);
 354         vdso64_pagelist[vdso64_pages] = NULL;
 355         if (vdso_alloc_per_cpu(&S390_lowcore))
 356                 BUG();
 357         vdso_init_cr5();
 358
 359         get_page(virt_to_page(vdso_data));
 360
 361         return 0;
 362 }
 363 early_initcall(vdso_init);