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         static struct vm_special_mapping spec = {
  92                 .name   = "[vectors]",
  93                 .pages  = vectors_page,
  94
  95         };
  96         void *ret;
  97
  98         down_write(&mm->mmap_sem);
  99         current->mm->context.vdso = (void *)addr;
 100
 101         /* Map vectors page at the high address. */
 102         ret = _install_special_mapping(mm, addr, PAGE_SIZE,
 103                                        VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC,
 104                                        &spec);
 105
 106         up_write(&mm->mmap_sem);
 107
 108         return PTR_ERR_OR_ZERO(ret);
 109 }
 110 #endif /* CONFIG_COMPAT */
 111
 112 static struct vm_special_mapping vdso_spec[2];
 113
 114 static int __init vdso_init(void)
 115 {
 116         int i;
 117
 118         if (memcmp(&vdso_start, "\177ELF", 4)) {
 119                 pr_err("vDSO is not a valid ELF object!\n");
 120                 return -EINVAL;
 121         }
 122
 123         vdso_pages = (&vdso_end - &vdso_start) >> PAGE_SHIFT;
 124         pr_info("vdso: %ld pages (%ld code @ %p, %ld data @ %p)\n",
 125                 vdso_pages + 1, vdso_pages, &vdso_start, 1L, vdso_data);
 126
 127         /* Allocate the vDSO pagelist, plus a page for the data. */
 128         vdso_pagelist = kcalloc(vdso_pages + 1, sizeof(struct page *),
 129                                 GFP_KERNEL);
 130         if (vdso_pagelist == NULL)
 131                 return -ENOMEM;
 132
 133         /* Grab the vDSO data page. */
 134         vdso_pagelist[0] = virt_to_page(vdso_data);
 135
 136         /* Grab the vDSO code pages. */
 137         for (i = 0; i < vdso_pages; i++)
 138                 vdso_pagelist[i + 1] = virt_to_page(&vdso_start + i * PAGE_SIZE);
 139
 140         /* Populate the special mapping structures */
 141         vdso_spec[0] = (struct vm_special_mapping) {
 142                 .name   = "[vvar]",
 143                 .pages  = vdso_pagelist,
 144         };
 145
 146         vdso_spec[1] = (struct vm_special_mapping) {
 147                 .name   = "[vdso]",
 148                 .pages  = &vdso_pagelist[1],
 149         };
 150
 151         return 0;
 152 }
 153 arch_initcall(vdso_init);
 154
 155 int arch_setup_additional_pages(struct linux_binprm *bprm,
 156                                 int uses_interp)
 157 {
 158         struct mm_struct *mm = current->mm;
 159         unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
 160         void *ret;
 161
 162         vdso_text_len = vdso_pages << PAGE_SHIFT;
 163         /* Be sure to map the data page */
 164         vdso_mapping_len = vdso_text_len + PAGE_SIZE;
 165
 166         down_write(&mm->mmap_sem);
 167         vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
 168         if (IS_ERR_VALUE(vdso_base)) {
 169                 ret = ERR_PTR(vdso_base);
 170                 goto up_fail;
 171         }
 172         ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE,
 173                                        VM_READ|VM_MAYREAD,
 174                                        &vdso_spec[0]);
 175         if (IS_ERR(ret))
 176                 goto up_fail;
 177
 178         vdso_base += PAGE_SIZE;
 179         mm->context.vdso = (void *)vdso_base;
 180         ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
 181                                        VM_READ|VM_EXEC|
 182                                        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 183                                        &vdso_spec[1]);
 184         if (IS_ERR(ret))
 185                 goto up_fail;
 186
 187
 188         up_write(&mm->mmap_sem);
 189         return 0;
 190
 191 up_fail:
 192         mm->context.vdso = NULL;
 193         up_write(&mm->mmap_sem);
 194         return PTR_ERR(ret);
 195 }
 196
 197 /*
 198  * Update the vDSO data page to keep in sync with kernel timekeeping.
 199  */
 200 void update_vsyscall(struct timekeeper *tk)
 201 {
 202         u32 use_syscall = strcmp(tk->tkr_mono.clock->name, "arch_sys_counter");
 203
 204         ++vdso_data->tb_seq_count;
 205         smp_wmb();
 206
 207         vdso_data->use_syscall                  = use_syscall;
 208         vdso_data->xtime_coarse_sec             = tk->xtime_sec;
 209         vdso_data->xtime_coarse_nsec            = tk->tkr_mono.xtime_nsec >>
 210                                                         tk->tkr_mono.shift;
 211         vdso_data->wtm_clock_sec                = tk->wall_to_monotonic.tv_sec;
 212         vdso_data->wtm_clock_nsec               = tk->wall_to_monotonic.tv_nsec;
 213
 214         if (!use_syscall) {
 215                 vdso_data->cs_cycle_last        = tk->tkr_mono.cycle_last;
 216                 vdso_data->xtime_clock_sec      = tk->xtime_sec;
 217                 vdso_data->xtime_clock_nsec     = tk->tkr_mono.xtime_nsec;
 218                 vdso_data->cs_mult              = tk->tkr_mono.mult;
 219                 vdso_data->cs_shift             = tk->tkr_mono.shift;
 220         }
 221
 222         smp_wmb();
 223         ++vdso_data->tb_seq_count;
 224 }
 225
 226 void update_vsyscall_tz(void)
 227 {
 228         vdso_data->tz_minuteswest       = sys_tz.tz_minuteswest;
 229         vdso_data->tz_dsttime           = sys_tz.tz_dsttime;
 230 }