release/src-rt-6.x.4708/linux/linux-2.6.36/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/system.h>
  29 #include <asm/processor.h>
  30 #include <asm/mmu.h>
  31 #include <asm/mmu_context.h>
  32 #include <asm/sections.h>
  33 #include <asm/vdso.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         unsigned int facility_list;
  88
  89         facility_list = stfl();
  90         vd->ectg_available =
  91                 user_mode != HOME_SPACE_MODE && (facility_list & 1);
  92 }
  93
  94 #ifdef CONFIG_64BIT
  95 /*
  96  * Setup per cpu vdso data page.
  97  */
  98 static void vdso_init_per_cpu_data(int cpu, struct vdso_per_cpu_data *vpcd)
  99 {
 100 }
 101
 102 /*
 103  * Allocate/free per cpu vdso data.
 104  */
 105 #define SEGMENT_ORDER   2
 106
 107 int vdso_alloc_per_cpu(int cpu, struct _lowcore *lowcore)
 108 {
 109         unsigned long segment_table, page_table, page_frame;
 110         u32 *psal, *aste;
 111         int i;
 112
 113         lowcore->vdso_per_cpu_data = __LC_PASTE;
 114
 115         if (user_mode == HOME_SPACE_MODE || !vdso_enabled)
 116                 return 0;
 117
 118         segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER);
 119         page_table = get_zeroed_page(GFP_KERNEL | GFP_DMA);
 120         page_frame = get_zeroed_page(GFP_KERNEL);
 121         if (!segment_table || !page_table || !page_frame)
 122                 goto out;
 123
 124         clear_table((unsigned long *) segment_table, _SEGMENT_ENTRY_EMPTY,
 125                     PAGE_SIZE << SEGMENT_ORDER);
 126         clear_table((unsigned long *) page_table, _PAGE_TYPE_EMPTY,
 127                     256*sizeof(unsigned long));
 128
 129         *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table;
 130         *(unsigned long *) page_table = _PAGE_RO + page_frame;
 131
 132         psal = (u32 *) (page_table + 256*sizeof(unsigned long));
 133         aste = psal + 32;
 134
 135         for (i = 4; i < 32; i += 4)
 136                 psal[i] = 0x80000000;
 137
 138         lowcore->paste[4] = (u32)(addr_t) psal;
 139         psal[0] = 0x20000000;
 140         psal[2] = (u32)(addr_t) aste;
 141         *(unsigned long *) (aste + 2) = segment_table +
 142                 _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT;
 143         aste[4] = (u32)(addr_t) psal;
 144         lowcore->vdso_per_cpu_data = page_frame;
 145
 146         vdso_init_per_cpu_data(cpu, (struct vdso_per_cpu_data *) page_frame);
 147         return 0;
 148
 149 out:
 150         free_page(page_frame);
 151         free_page(page_table);
 152         free_pages(segment_table, SEGMENT_ORDER);
 153         return -ENOMEM;
 154 }
 155
 156 void vdso_free_per_cpu(int cpu, struct _lowcore *lowcore)
 157 {
 158         unsigned long segment_table, page_table, page_frame;
 159         u32 *psal, *aste;
 160
 161         if (user_mode == HOME_SPACE_MODE || !vdso_enabled)
 162                 return;
 163
 164         psal = (u32 *)(addr_t) lowcore->paste[4];
 165         aste = (u32 *)(addr_t) psal[2];
 166         segment_table = *(unsigned long *)(aste + 2) & PAGE_MASK;
 167         page_table = *(unsigned long *) segment_table;
 168         page_frame = *(unsigned long *) page_table;
 169
 170         free_page(page_frame);
 171         free_page(page_table);
 172         free_pages(segment_table, SEGMENT_ORDER);
 173 }
 174
 175 static void __vdso_init_cr5(void *dummy)
 176 {
 177         unsigned long cr5;
 178
 179         cr5 = offsetof(struct _lowcore, paste);
 180         __ctl_load(cr5, 5, 5);
 181 }
 182
 183 static void vdso_init_cr5(void)
 184 {
 185         if (user_mode != HOME_SPACE_MODE && vdso_enabled)
 186                 on_each_cpu(__vdso_init_cr5, NULL, 1);
 187 }
 188 #endif /* CONFIG_64BIT */
 189
 190 /*
 191  * This is called from binfmt_elf, we create the special vma for the
 192  * vDSO and insert it into the mm struct tree
 193  */
 194 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 195 {
 196         struct mm_struct *mm = current->mm;
 197         struct page **vdso_pagelist;
 198         unsigned long vdso_pages;
 199         unsigned long vdso_base;
 200         int rc;
 201
 202         if (!vdso_enabled)
 203                 return 0;
 204         /*
 205          * Only map the vdso for dynamically linked elf binaries.
 206          */
 207         if (!uses_interp)
 208                 return 0;
 209
 210         vdso_base = mm->mmap_base;
 211 #ifdef CONFIG_64BIT
 212         vdso_pagelist = vdso64_pagelist;
 213         vdso_pages = vdso64_pages;
 214 #ifdef CONFIG_COMPAT
 215         if (is_compat_task()) {
 216                 vdso_pagelist = vdso32_pagelist;
 217                 vdso_pages = vdso32_pages;
 218         }
 219 #endif
 220 #else
 221         vdso_pagelist = vdso32_pagelist;
 222         vdso_pages = vdso32_pages;
 223 #endif
 224
 225         /*
 226          * vDSO has a problem and was disabled, just don't "enable" it for
 227          * the process
 228          */
 229         if (vdso_pages == 0)
 230                 return 0;
 231
 232         current->mm->context.vdso_base = 0;
 233
 234         /*
 235          * pick a base address for the vDSO in process space. We try to put
 236          * it at vdso_base which is the "natural" base for it, but we might
 237          * fail and end up putting it elsewhere.
 238          */
 239         down_write(&mm->mmap_sem);
 240         vdso_base = get_unmapped_area(NULL, vdso_base,
 241                                       vdso_pages << PAGE_SHIFT, 0, 0);
 242         if (IS_ERR_VALUE(vdso_base)) {
 243                 rc = vdso_base;
 244                 goto out_up;
 245         }
 246
 247         /*
 248          * Put vDSO base into mm struct. We need to do this before calling
 249          * install_special_mapping or the perf counter mmap tracking code
 250          * will fail to recognise it as a vDSO (since arch_vma_name fails).
 251          */
 252         current->mm->context.vdso_base = vdso_base;
 253
 254         /*
 255          * our vma flags don't have VM_WRITE so by default, the process
 256          * isn't allowed to write those pages.
 257          * gdb can break that with ptrace interface, and thus trigger COW
 258          * on those pages but it's then your responsibility to never do that
 259          * on the "data" page of the vDSO or you'll stop getting kernel
 260          * updates and your nice userland gettimeofday will be totally dead.
 261          * It's fine to use that for setting breakpoints in the vDSO code
 262          * pages though
 263          *
 264          * Make sure the vDSO gets into every core dump.
 265          * Dumping its contents makes post-mortem fully interpretable later
 266          * without matching up the same kernel and hardware config to see
 267          * what PC values meant.
 268          */
 269         rc = install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
 270                                      VM_READ|VM_EXEC|
 271                                      VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
 272                                      VM_ALWAYSDUMP,
 273                                      vdso_pagelist);
 274         if (rc)
 275                 current->mm->context.vdso_base = 0;
 276 out_up:
 277         up_write(&mm->mmap_sem);
 278         return rc;
 279 }
 280
 281 const char *arch_vma_name(struct vm_area_struct *vma)
 282 {
 283         if (vma->vm_mm && vma->vm_start == vma->vm_mm->context.vdso_base)
 284                 return "[vdso]";
 285         return NULL;
 286 }
 287
 288 static int __init vdso_init(void)
 289 {
 290         int i;
 291
 292         if (!vdso_enabled)
 293                 return 0;
 294         vdso_init_data(vdso_data);
 295 #if defined(CONFIG_32BIT) || defined(CONFIG_COMPAT)
 296         /* Calculate the size of the 32 bit vDSO */
 297         vdso32_pages = ((&vdso32_end - &vdso32_start
 298                          + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
 299
 300         /* Make sure pages are in the correct state */
 301         vdso32_pagelist = kzalloc(sizeof(struct page *) * (vdso32_pages + 1),
 302                                   GFP_KERNEL);
 303         BUG_ON(vdso32_pagelist == NULL);
 304         for (i = 0; i < vdso32_pages - 1; i++) {
 305                 struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
 306                 ClearPageReserved(pg);
 307                 get_page(pg);
 308                 vdso32_pagelist[i] = pg;
 309         }
 310         vdso32_pagelist[vdso32_pages - 1] = virt_to_page(vdso_data);
 311         vdso32_pagelist[vdso32_pages] = NULL;
 312 #endif
 313
 314 #ifdef CONFIG_64BIT
 315         /* Calculate the size of the 64 bit vDSO */
 316         vdso64_pages = ((&vdso64_end - &vdso64_start
 317                          + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
 318
 319         /* Make sure pages are in the correct state */
 320         vdso64_pagelist = kzalloc(sizeof(struct page *) * (vdso64_pages + 1),
 321                                   GFP_KERNEL);
 322         BUG_ON(vdso64_pagelist == NULL);
 323         for (i = 0; i < vdso64_pages - 1; i++) {
 324                 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
 325                 ClearPageReserved(pg);
 326                 get_page(pg);
 327                 vdso64_pagelist[i] = pg;
 328         }
 329         vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data);
 330         vdso64_pagelist[vdso64_pages] = NULL;
 331 #ifndef CONFIG_SMP
 332         if (vdso_alloc_per_cpu(0, &S390_lowcore))
 333                 BUG();
 334 #endif
 335         vdso_init_cr5();
 336 #endif /* CONFIG_64BIT */
 337
 338         get_page(virt_to_page(vdso_data));
 339
 340         smp_wmb();
 341
 342         return 0;
 343 }
 344 arch_initcall(vdso_init);
 345
 346 int in_gate_area_no_task(unsigned long addr)
 347 {
 348         return 0;
 349 }
 350
 351 int in_gate_area(struct task_struct *task, unsigned long addr)
 352 {
 353         return 0;
 354 }
 355
 356 struct vm_area_struct *get_gate_vma(struct task_struct *tsk)
 357 {
 358         return NULL;
 359 }