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         int kuser_sz = __kuser_helper_end - __kuser_helper_start;
  62         unsigned long vpage;
  63
  64         vpage = get_zeroed_page(GFP_ATOMIC);
  65
  66         if (!vpage)
  67                 return -ENOMEM;
  68
  69         /* kuser helpers */
  70         memcpy((void *)vpage + 0x1000 - kuser_sz, __kuser_helper_start,
  71                 kuser_sz);
  72
  73         /* sigreturn code */
  74         memcpy((void *)vpage + AARCH32_KERN_SIGRET_CODE_OFFSET,
  75                 aarch32_sigret_code, sizeof(aarch32_sigret_code));
  76
  77         flush_icache_range(vpage, vpage + PAGE_SIZE);
  78         vectors_page[0] = virt_to_page(vpage);
  79
  80         return 0;
  81 }
  82 arch_initcall(alloc_vectors_page);
  83
  84 int aarch32_setup_vectors_page(struct linux_binprm *bprm, int uses_interp)
  85 {
  86         struct mm_struct *mm = current->mm;
  87         unsigned long addr = AARCH32_VECTORS_BASE;
  88         int ret;
  89
  90         down_write(&mm->mmap_sem);
  91         current->mm->context.vdso = (void *)addr;
  92
  93         /* Map vectors page at the high address. */
  94         ret = install_special_mapping(mm, addr, PAGE_SIZE,
  95                                       VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC,
  96                                       vectors_page);
  97
  98         up_write(&mm->mmap_sem);
  99
 100         return ret;
 101 }
 102 #endif /* CONFIG_COMPAT */
 103
 104 static int __init vdso_init(void)
 105 {
 106         int i;
 107
 108         if (memcmp(&vdso_start, "\177ELF", 4)) {
 109                 pr_err("vDSO is not a valid ELF object!\n");
 110                 return -EINVAL;
 111         }
 112
 113         vdso_pages = (&vdso_end - &vdso_start) >> PAGE_SHIFT;
 114         pr_info("vdso: %ld pages (%ld code, %ld data) at base %p\n",
 115                 vdso_pages + 1, vdso_pages, 1L, &vdso_start);
 116
 117         /* Allocate the vDSO pagelist, plus a page for the data. */
 118         vdso_pagelist = kcalloc(vdso_pages + 1, sizeof(struct page *),
 119                                 GFP_KERNEL);
 120         if (vdso_pagelist == NULL)
 121                 return -ENOMEM;
 122
 123         /* Grab the vDSO code pages. */
 124         for (i = 0; i < vdso_pages; i++)
 125                 vdso_pagelist[i] = virt_to_page(&vdso_start + i * PAGE_SIZE);
 126
 127         /* Grab the vDSO data page. */
 128         vdso_pagelist[i] = virt_to_page(vdso_data);
 129
 130         return 0;
 131 }
 132 arch_initcall(vdso_init);
 133
 134 int arch_setup_additional_pages(struct linux_binprm *bprm,
 135                                 int uses_interp)
 136 {
 137         struct mm_struct *mm = current->mm;
 138         unsigned long vdso_base, vdso_mapping_len;
 139         int ret;
 140
 141         /* Be sure to map the data page */
 142         vdso_mapping_len = (vdso_pages + 1) << PAGE_SHIFT;
 143
 144         down_write(&mm->mmap_sem);
 145         vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
 146         if (IS_ERR_VALUE(vdso_base)) {
 147                 ret = vdso_base;
 148                 goto up_fail;
 149         }
 150         mm->context.vdso = (void *)vdso_base;
 151
 152         ret = install_special_mapping(mm, vdso_base, vdso_mapping_len,
 153                                       VM_READ|VM_EXEC|
 154                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 155                                       vdso_pagelist);
 156         if (ret) {
 157                 mm->context.vdso = NULL;
 158                 goto up_fail;
 159         }
 160
 161 up_fail:
 162         up_write(&mm->mmap_sem);
 163
 164         return ret;
 165 }
 166
 167 const char *arch_vma_name(struct vm_area_struct *vma)
 168 {
 169         /*
 170          * We can re-use the vdso pointer in mm_context_t for identifying
 171          * the vectors page for compat applications. The vDSO will always
 172          * sit above TASK_UNMAPPED_BASE and so we don't need to worry about
 173          * it conflicting with the vectors base.
 174          */
 175         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso) {
 176 #ifdef CONFIG_COMPAT
 177                 if (vma->vm_start == AARCH32_VECTORS_BASE)
 178                         return "[vectors]";
 179 #endif
 180                 return "[vdso]";
 181         }
 182
 183         return NULL;
 184 }
 185
 186 /*
 187  * We define AT_SYSINFO_EHDR, so we need these function stubs to keep
 188  * Linux happy.
 189  */
 190 int in_gate_area_no_mm(unsigned long addr)
 191 {
 192         return 0;
 193 }
 194
 195 int in_gate_area(struct mm_struct *mm, unsigned long addr)
 196 {
 197         return 0;
 198 }
 199
 200 struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
 201 {
 202         return NULL;
 203 }
 204
 205 /*
 206  * Update the vDSO data page to keep in sync with kernel timekeeping.
 207  */
 208 void update_vsyscall(struct timekeeper *tk)
 209 {
 210         struct timespec xtime_coarse;
 211         u32 use_syscall = strcmp(tk->clock->name, "arch_sys_counter");
 212
 213         ++vdso_data->tb_seq_count;
 214         smp_wmb();
 215
 216         xtime_coarse = __current_kernel_time();
 217         vdso_data->use_syscall                  = use_syscall;
 218         vdso_data->xtime_coarse_sec             = xtime_coarse.tv_sec;
 219         vdso_data->xtime_coarse_nsec            = xtime_coarse.tv_nsec;
 220         vdso_data->wtm_clock_sec                = tk->wall_to_monotonic.tv_sec;
 221         vdso_data->wtm_clock_nsec               = tk->wall_to_monotonic.tv_nsec;
 222
 223         if (!use_syscall) {
 224                 vdso_data->cs_cycle_last        = tk->clock->cycle_last;
 225                 vdso_data->xtime_clock_sec      = tk->xtime_sec;
 226                 vdso_data->xtime_clock_nsec     = tk->xtime_nsec;
 227                 vdso_data->cs_mult              = tk->mult;
 228                 vdso_data->cs_shift             = tk->shift;
 229         }
 230
 231         smp_wmb();
 232         ++vdso_data->tb_seq_count;
 233 }
 234
 235 void update_vsyscall_tz(void)
 236 {
 237         vdso_data->tz_minuteswest       = sys_tz.tz_minuteswest;
 238         vdso_data->tz_dsttime           = sys_tz.tz_dsttime;
 239 }