arch/s390/kernel/vdso.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * vdso setup for s390
   4  *
   5  *  Copyright IBM Corp. 2008
   6  *  Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
   7  */
   8
   9 #include <linux/init.h>
  10 #include <linux/errno.h>
  11 #include <linux/sched.h>
  12 #include <linux/kernel.h>
  13 #include <linux/mm.h>
  14 #include <linux/smp.h>
  15 #include <linux/stddef.h>
  16 #include <linux/unistd.h>
  17 #include <linux/slab.h>
  18 #include <linux/user.h>
  19 #include <linux/elf.h>
  20 #include <linux/security.h>
  21 #include <linux/memblock.h>
  22 #include <linux/compat.h>
  23 #include <asm/asm-offsets.h>
  24 #include <asm/pgtable.h>
  25 #include <asm/processor.h>
  26 #include <asm/mmu.h>
  27 #include <asm/mmu_context.h>
  28 #include <asm/sections.h>
  29 #include <asm/vdso.h>
  30 #include <asm/facility.h>
  31
  32 #ifdef CONFIG_COMPAT
  33 extern char vdso32_start, vdso32_end;
  34 static void *vdso32_kbase = &vdso32_start;
  35 static unsigned int vdso32_pages;
  36 static struct page **vdso32_pagelist;
  37 #endif
  38
  39 extern char vdso64_start, vdso64_end;
  40 static void *vdso64_kbase = &vdso64_start;
  41 static unsigned int vdso64_pages;
  42 static struct page **vdso64_pagelist;
  43
  44 /*
  45  * Should the kernel map a VDSO page into processes and pass its
  46  * address down to glibc upon exec()?
  47  */
  48 unsigned int __read_mostly vdso_enabled = 1;
  49
  50 static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
  51                       struct vm_area_struct *vma, struct vm_fault *vmf)
  52 {
  53         struct page **vdso_pagelist;
  54         unsigned long vdso_pages;
  55
  56         vdso_pagelist = vdso64_pagelist;
  57         vdso_pages = vdso64_pages;
  58 #ifdef CONFIG_COMPAT
  59         if (vma->vm_mm->context.compat_mm) {
  60                 vdso_pagelist = vdso32_pagelist;
  61                 vdso_pages = vdso32_pages;
  62         }
  63 #endif
  64
  65         if (vmf->pgoff >= vdso_pages)
  66                 return VM_FAULT_SIGBUS;
  67
  68         vmf->page = vdso_pagelist[vmf->pgoff];
  69         get_page(vmf->page);
  70         return 0;
  71 }
  72
  73 static int vdso_mremap(const struct vm_special_mapping *sm,
  74                        struct vm_area_struct *vma)
  75 {
  76         unsigned long vdso_pages;
  77
  78         vdso_pages = vdso64_pages;
  79 #ifdef CONFIG_COMPAT
  80         if (vma->vm_mm->context.compat_mm)
  81                 vdso_pages = vdso32_pages;
  82 #endif
  83
  84         if ((vdso_pages << PAGE_SHIFT) != vma->vm_end - vma->vm_start)
  85                 return -EINVAL;
  86
  87         if (WARN_ON_ONCE(current->mm != vma->vm_mm))
  88                 return -EFAULT;
  89
  90         current->mm->context.vdso_base = vma->vm_start;
  91         return 0;
  92 }
  93
  94 static const struct vm_special_mapping vdso_mapping = {
  95         .name = "[vdso]",
  96         .fault = vdso_fault,
  97         .mremap = vdso_mremap,
  98 };
  99
 100 static int __init vdso_setup(char *s)
 101 {
 102         unsigned long val;
 103         int rc;
 104
 105         rc = 0;
 106         if (strncmp(s, "on", 3) == 0)
 107                 vdso_enabled = 1;
 108         else if (strncmp(s, "off", 4) == 0)
 109                 vdso_enabled = 0;
 110         else {
 111                 rc = kstrtoul(s, 0, &val);
 112                 vdso_enabled = rc ? 0 : !!val;
 113         }
 114         return !rc;
 115 }
 116 __setup("vdso=", vdso_setup);
 117
 118 /*
 119  * The vdso data page
 120  */
 121 static union {
 122         struct vdso_data        data;
 123         u8                      page[PAGE_SIZE];
 124 } vdso_data_store __page_aligned_data;
 125 struct vdso_data *vdso_data = &vdso_data_store.data;
 126
 127 /*
 128  * Setup vdso data page.
 129  */
 130 static void __init vdso_init_data(struct vdso_data *vd)
 131 {
 132         vd->ectg_available = test_facility(31);
 133 }
 134
 135 /*
 136  * Allocate/free per cpu vdso data.
 137  */
 138 #define SEGMENT_ORDER   2
 139
 140 /*
 141  * The initial vdso_data structure for the boot CPU. Eventually
 142  * it is replaced with a properly allocated structure in vdso_init.
 143  * This is necessary because a valid S390_lowcore.vdso_per_cpu_data
 144  * pointer is required to be able to return from an interrupt or
 145  * program check. See the exit paths in entry.S.
 146  */
 147 struct vdso_data boot_vdso_data __initdata;
 148
 149 void __init vdso_alloc_boot_cpu(struct lowcore *lowcore)
 150 {
 151         lowcore->vdso_per_cpu_data = (unsigned long) &boot_vdso_data;
 152 }
 153
 154 int vdso_alloc_per_cpu(struct lowcore *lowcore)
 155 {
 156         unsigned long segment_table, page_table, page_frame;
 157         struct vdso_per_cpu_data *vd;
 158
 159         segment_table = __get_free_pages(GFP_KERNEL, SEGMENT_ORDER);
 160         page_table = get_zeroed_page(GFP_KERNEL);
 161         page_frame = get_zeroed_page(GFP_KERNEL);
 162         if (!segment_table || !page_table || !page_frame)
 163                 goto out;
 164         arch_set_page_dat(virt_to_page(segment_table), SEGMENT_ORDER);
 165         arch_set_page_dat(virt_to_page(page_table), 0);
 166
 167         /* Initialize per-cpu vdso data page */
 168         vd = (struct vdso_per_cpu_data *) page_frame;
 169         vd->cpu_nr = lowcore->cpu_nr;
 170         vd->node_id = cpu_to_node(vd->cpu_nr);
 171
 172         /* Set up page table for the vdso address space */
 173         memset64((u64 *)segment_table, _SEGMENT_ENTRY_EMPTY, _CRST_ENTRIES);
 174         memset64((u64 *)page_table, _PAGE_INVALID, PTRS_PER_PTE);
 175
 176         *(unsigned long *) segment_table = _SEGMENT_ENTRY + page_table;
 177         *(unsigned long *) page_table = _PAGE_PROTECT + page_frame;
 178
 179         lowcore->vdso_asce = segment_table +
 180                 _ASCE_TABLE_LENGTH + _ASCE_USER_BITS + _ASCE_TYPE_SEGMENT;
 181         lowcore->vdso_per_cpu_data = page_frame;
 182
 183         return 0;
 184
 185 out:
 186         free_page(page_frame);
 187         free_page(page_table);
 188         free_pages(segment_table, SEGMENT_ORDER);
 189         return -ENOMEM;
 190 }
 191
 192 void vdso_free_per_cpu(struct lowcore *lowcore)
 193 {
 194         unsigned long segment_table, page_table, page_frame;
 195
 196         segment_table = lowcore->vdso_asce & PAGE_MASK;
 197         page_table = *(unsigned long *) segment_table;
 198         page_frame = *(unsigned long *) page_table;
 199
 200         free_page(page_frame);
 201         free_page(page_table);
 202         free_pages(segment_table, SEGMENT_ORDER);
 203 }
 204
 205 /*
 206  * This is called from binfmt_elf, we create the special vma for the
 207  * vDSO and insert it into the mm struct tree
 208  */
 209 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 210 {
 211         struct mm_struct *mm = current->mm;
 212         struct vm_area_struct *vma;
 213         unsigned long vdso_pages;
 214         unsigned long vdso_base;
 215         int rc;
 216
 217         if (!vdso_enabled)
 218                 return 0;
 219         /*
 220          * Only map the vdso for dynamically linked elf binaries.
 221          */
 222         if (!uses_interp)
 223                 return 0;
 224
 225         vdso_pages = vdso64_pages;
 226 #ifdef CONFIG_COMPAT
 227         mm->context.compat_mm = is_compat_task();
 228         if (mm->context.compat_mm)
 229                 vdso_pages = vdso32_pages;
 230 #endif
 231         /*
 232          * vDSO has a problem and was disabled, just don't "enable" it for
 233          * the process
 234          */
 235         if (vdso_pages == 0)
 236                 return 0;
 237
 238         /*
 239          * pick a base address for the vDSO in process space. We try to put
 240          * it at vdso_base which is the "natural" base for it, but we might
 241          * fail and end up putting it elsewhere.
 242          */
 243         if (down_write_killable(&mm->mmap_sem))
 244                 return -EINTR;
 245         vdso_base = get_unmapped_area(NULL, 0, vdso_pages << PAGE_SHIFT, 0, 0);
 246         if (IS_ERR_VALUE(vdso_base)) {
 247                 rc = vdso_base;
 248                 goto out_up;
 249         }
 250
 251         /*
 252          * our vma flags don't have VM_WRITE so by default, the process
 253          * isn't allowed to write those pages.
 254          * gdb can break that with ptrace interface, and thus trigger COW
 255          * on those pages but it's then your responsibility to never do that
 256          * on the "data" page of the vDSO or you'll stop getting kernel
 257          * updates and your nice userland gettimeofday will be totally dead.
 258          * It's fine to use that for setting breakpoints in the vDSO code
 259          * pages though.
 260          */
 261         vma = _install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
 262                                        VM_READ|VM_EXEC|
 263                                        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 264                                        &vdso_mapping);
 265         if (IS_ERR(vma)) {
 266                 rc = PTR_ERR(vma);
 267                 goto out_up;
 268         }
 269
 270         current->mm->context.vdso_base = vdso_base;
 271         rc = 0;
 272
 273 out_up:
 274         up_write(&mm->mmap_sem);
 275         return rc;
 276 }
 277
 278 static int __init vdso_init(void)
 279 {
 280         int i;
 281
 282         vdso_init_data(vdso_data);
 283 #ifdef CONFIG_COMPAT
 284         /* Calculate the size of the 32 bit vDSO */
 285         vdso32_pages = ((&vdso32_end - &vdso32_start
 286                          + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
 287
 288         /* Make sure pages are in the correct state */
 289         vdso32_pagelist = kcalloc(vdso32_pages + 1, sizeof(struct page *),
 290                                   GFP_KERNEL);
 291         BUG_ON(vdso32_pagelist == NULL);
 292         for (i = 0; i < vdso32_pages - 1; i++) {
 293                 struct page *pg = virt_to_page(vdso32_kbase + i*PAGE_SIZE);
 294                 ClearPageReserved(pg);
 295                 get_page(pg);
 296                 vdso32_pagelist[i] = pg;
 297         }
 298         vdso32_pagelist[vdso32_pages - 1] = virt_to_page(vdso_data);
 299         vdso32_pagelist[vdso32_pages] = NULL;
 300 #endif
 301
 302         /* Calculate the size of the 64 bit vDSO */
 303         vdso64_pages = ((&vdso64_end - &vdso64_start
 304                          + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
 305
 306         /* Make sure pages are in the correct state */
 307         vdso64_pagelist = kcalloc(vdso64_pages + 1, sizeof(struct page *),
 308                                   GFP_KERNEL);
 309         BUG_ON(vdso64_pagelist == NULL);
 310         for (i = 0; i < vdso64_pages - 1; i++) {
 311                 struct page *pg = virt_to_page(vdso64_kbase + i*PAGE_SIZE);
 312                 ClearPageReserved(pg);
 313                 get_page(pg);
 314                 vdso64_pagelist[i] = pg;
 315         }
 316         vdso64_pagelist[vdso64_pages - 1] = virt_to_page(vdso_data);
 317         vdso64_pagelist[vdso64_pages] = NULL;
 318         if (vdso_alloc_per_cpu(&S390_lowcore))
 319                 BUG();
 320
 321         get_page(virt_to_page(vdso_data));
 322
 323         return 0;
 324 }
 325 early_initcall(vdso_init);