arch/arm64/kernel/vdso.c

   1 /*
   2  * VDSO implementation for AArch64 and vector page setup for AArch32.
   3  *
   4  * Copyright (C) 2012 ARM Limited
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  *
  18  * Author: Will Deacon <will.deacon@arm.com>
  19  */
  20
  21 #include <linux/kernel.h>
  22 #include <linux/clocksource.h>
  23 #include <linux/elf.h>
  24 #include <linux/err.h>
  25 #include <linux/errno.h>
  26 #include <linux/gfp.h>
  27 #include <linux/mm.h>
  28 #include <linux/sched.h>
  29 #include <linux/signal.h>
  30 #include <linux/slab.h>
  31 #include <linux/timekeeper_internal.h>
  32 #include <linux/vmalloc.h>
  33
  34 #include <asm/cacheflush.h>
  35 #include <asm/signal32.h>
  36 #include <asm/vdso.h>
  37 #include <asm/vdso_datapage.h>
  38
  39 extern char vdso_start, vdso_end;
  40 static unsigned long vdso_pages;
  41 static struct page **vdso_pagelist;
  42
  43 /*
  44  * The vDSO data page.
  45  */
  46 static union {
  47         struct vdso_data        data;
  48         u8                      page[PAGE_SIZE];
  49 } vdso_data_store __page_aligned_data;
  50 struct vdso_data *vdso_data = &vdso_data_store.data;
  51
  52 #ifdef CONFIG_COMPAT
  53 /*
  54  * Create and map the vectors page for AArch32 tasks.
  55  */
  56 static struct page *vectors_page[1];
  57
  58 static int alloc_vectors_page(void)
  59 {
  60         extern char __kuser_helper_start[], __kuser_helper_end[];
  61         extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
  62
  63         int kuser_sz = __kuser_helper_end - __kuser_helper_start;
  64         int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
  65         unsigned long vpage;
  66
  67         vpage = get_zeroed_page(GFP_ATOMIC);
  68
  69         if (!vpage)
  70                 return -ENOMEM;
  71
  72         /* kuser helpers */
  73         memcpy((void *)vpage + 0x1000 - kuser_sz, __kuser_helper_start,
  74                 kuser_sz);
  75
  76         /* sigreturn code */
  77         memcpy((void *)vpage + AARCH32_KERN_SIGRET_CODE_OFFSET,
  78                __aarch32_sigret_code_start, sigret_sz);
  79
  80         flush_icache_range(vpage, vpage + PAGE_SIZE);
  81         vectors_page[0] = virt_to_page(vpage);
  82
  83         return 0;
  84 }
  85 arch_initcall(alloc_vectors_page);
  86
  87 int aarch32_setup_vectors_page(struct linux_binprm *bprm, int uses_interp)
  88 {
  89         struct mm_struct *mm = current->mm;
  90         unsigned long addr = AARCH32_VECTORS_BASE;
  91         int ret;
  92
  93         down_write(&mm->mmap_sem);
  94         current->mm->context.vdso = (void *)addr;
  95
  96         /* Map vectors page at the high address. */
  97         ret = install_special_mapping(mm, addr, PAGE_SIZE,
  98                                       VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC,
  99                                       vectors_page);
 100
 101         up_write(&mm->mmap_sem);
 102
 103         return ret;
 104 }
 105 #endif /* CONFIG_COMPAT */
 106
 107 static int __init vdso_init(void)
 108 {
 109         int i;
 110
 111         if (memcmp(&vdso_start, "\177ELF", 4)) {
 112                 pr_err("vDSO is not a valid ELF object!\n");
 113                 return -EINVAL;
 114         }
 115
 116         vdso_pages = (&vdso_end - &vdso_start) >> PAGE_SHIFT;
 117         pr_info("vdso: %ld pages (%ld code, %ld data) at base %p\n",
 118                 vdso_pages + 1, vdso_pages, 1L, &vdso_start);
 119
 120         /* Allocate the vDSO pagelist, plus a page for the data. */
 121         vdso_pagelist = kcalloc(vdso_pages + 1, sizeof(struct page *),
 122                                 GFP_KERNEL);
 123         if (vdso_pagelist == NULL)
 124                 return -ENOMEM;
 125
 126         /* Grab the vDSO code pages. */
 127         for (i = 0; i < vdso_pages; i++)
 128                 vdso_pagelist[i] = virt_to_page(&vdso_start + i * PAGE_SIZE);
 129
 130         /* Grab the vDSO data page. */
 131         vdso_pagelist[i] = virt_to_page(vdso_data);
 132
 133         return 0;
 134 }
 135 arch_initcall(vdso_init);
 136
 137 int arch_setup_additional_pages(struct linux_binprm *bprm,
 138                                 int uses_interp)
 139 {
 140         struct mm_struct *mm = current->mm;
 141         unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
 142         int ret;
 143
 144         vdso_text_len = vdso_pages << PAGE_SHIFT;
 145         /* Be sure to map the data page */
 146         vdso_mapping_len = vdso_text_len + PAGE_SIZE;
 147
 148         down_write(&mm->mmap_sem);
 149         vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
 150         if (IS_ERR_VALUE(vdso_base)) {
 151                 ret = vdso_base;
 152                 goto up_fail;
 153         }
 154         mm->context.vdso = (void *)vdso_base;
 155
 156         ret = install_special_mapping(mm, vdso_base, vdso_text_len,
 157                                       VM_READ|VM_EXEC|
 158                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 159                                       vdso_pagelist);
 160         if (ret)
 161                 goto up_fail;
 162
 163         vdso_base += vdso_text_len;
 164         ret = install_special_mapping(mm, vdso_base, PAGE_SIZE,
 165                                       VM_READ|VM_MAYREAD,
 166                                       vdso_pagelist + vdso_pages);
 167         if (ret)
 168                 goto up_fail;
 169
 170         up_write(&mm->mmap_sem);
 171         return 0;
 172
 173 up_fail:
 174         mm->context.vdso = NULL;
 175         up_write(&mm->mmap_sem);
 176         return ret;
 177 }
 178
 179 const char *arch_vma_name(struct vm_area_struct *vma)
 180 {
 181         unsigned long vdso_text;
 182
 183         if (!vma->vm_mm)
 184                 return NULL;
 185
 186         vdso_text = (unsigned long)vma->vm_mm->context.vdso;
 187
 188         /*
 189          * We can re-use the vdso pointer in mm_context_t for identifying
 190          * the vectors page for compat applications. The vDSO will always
 191          * sit above TASK_UNMAPPED_BASE and so we don't need to worry about
 192          * it conflicting with the vectors base.
 193          */
 194         if (vma->vm_start == vdso_text) {
 195 #ifdef CONFIG_COMPAT
 196                 if (vma->vm_start == AARCH32_VECTORS_BASE)
 197                         return "[vectors]";
 198 #endif
 199                 return "[vdso]";
 200         } else if (vma->vm_start == (vdso_text + (vdso_pages << PAGE_SHIFT))) {
 201                 return "[vvar]";
 202         }
 203
 204         return NULL;
 205 }
 206
 207 /*
 208  * We define AT_SYSINFO_EHDR, so we need these function stubs to keep
 209  * Linux happy.
 210  */
 211 int in_gate_area_no_mm(unsigned long addr)
 212 {
 213         return 0;
 214 }
 215
 216 int in_gate_area(struct mm_struct *mm, unsigned long addr)
 217 {
 218         return 0;
 219 }
 220
 221 struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
 222 {
 223         return NULL;
 224 }
 225
 226 /*
 227  * Update the vDSO data page to keep in sync with kernel timekeeping.
 228  */
 229 void update_vsyscall(struct timekeeper *tk)
 230 {
 231         struct timespec xtime_coarse;
 232         u32 use_syscall = strcmp(tk->clock->name, "arch_sys_counter");
 233
 234         ++vdso_data->tb_seq_count;
 235         smp_wmb();
 236
 237         xtime_coarse = __current_kernel_time();
 238         vdso_data->use_syscall                  = use_syscall;
 239         vdso_data->xtime_coarse_sec             = xtime_coarse.tv_sec;
 240         vdso_data->xtime_coarse_nsec            = xtime_coarse.tv_nsec;
 241         vdso_data->wtm_clock_sec                = tk->wall_to_monotonic.tv_sec;
 242         vdso_data->wtm_clock_nsec               = tk->wall_to_monotonic.tv_nsec;
 243
 244         if (!use_syscall) {
 245                 vdso_data->cs_cycle_last        = tk->clock->cycle_last;
 246                 vdso_data->xtime_clock_sec      = tk->xtime_sec;
 247                 vdso_data->xtime_clock_nsec     = tk->xtime_nsec;
 248                 vdso_data->cs_mult              = tk->mult;
 249                 vdso_data->cs_shift             = tk->shift;
 250         }
 251
 252         smp_wmb();
 253         ++vdso_data->tb_seq_count;
 254 }
 255
 256 void update_vsyscall_tz(void)
 257 {
 258         vdso_data->tz_minuteswest       = sys_tz.tz_minuteswest;
 259         vdso_data->tz_dsttime           = sys_tz.tz_dsttime;
 260 }