arch/mips/kernel/vdso.c

   1 /*
   2  * Copyright (C) 2015 Imagination Technologies
   3  * Author: Alex Smith <alex.smith@imgtec.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License as published by the
   7  * Free Software Foundation;  either version 2 of the  License, or (at your
   8  * option) any later version.
   9  */
  10
  11 #include <linux/binfmts.h>
  12 #include <linux/elf.h>
  13 #include <linux/err.h>
  14 #include <linux/init.h>
  15 #include <linux/ioport.h>
  16 #include <linux/kernel.h>
  17 #include <linux/mm.h>
  18 #include <linux/random.h>
  19 #include <linux/sched.h>
  20 #include <linux/slab.h>
  21 #include <linux/timekeeper_internal.h>
  22
  23 #include <asm/abi.h>
  24 #include <asm/mips-cps.h>
  25 #include <asm/page.h>
  26 #include <asm/vdso.h>
  27
  28 /* Kernel-provided data used by the VDSO. */
  29 static union mips_vdso_data vdso_data __page_aligned_data;
  30
  31 /*
  32  * Mapping for the VDSO data/GIC pages. The real pages are mapped manually, as
  33  * what we map and where within the area they are mapped is determined at
  34  * runtime.
  35  */
  36 static struct page *no_pages[] = { NULL };
  37 static struct vm_special_mapping vdso_vvar_mapping = {
  38         .name = "[vvar]",
  39         .pages = no_pages,
  40 };
  41
  42 static void __init init_vdso_image(struct mips_vdso_image *image)
  43 {
  44         unsigned long num_pages, i;
  45         unsigned long data_pfn;
  46
  47         BUG_ON(!PAGE_ALIGNED(image->data));
  48         BUG_ON(!PAGE_ALIGNED(image->size));
  49
  50         num_pages = image->size / PAGE_SIZE;
  51
  52         data_pfn = __phys_to_pfn(__pa_symbol(image->data));
  53         for (i = 0; i < num_pages; i++)
  54                 image->mapping.pages[i] = pfn_to_page(data_pfn + i);
  55 }
  56
  57 static int __init init_vdso(void)
  58 {
  59         init_vdso_image(&vdso_image);
  60
  61 #ifdef CONFIG_MIPS32_O32
  62         init_vdso_image(&vdso_image_o32);
  63 #endif
  64
  65 #ifdef CONFIG_MIPS32_N32
  66         init_vdso_image(&vdso_image_n32);
  67 #endif
  68
  69         return 0;
  70 }
  71 subsys_initcall(init_vdso);
  72
  73 void update_vsyscall(struct timekeeper *tk)
  74 {
  75         vdso_data_write_begin(&vdso_data);
  76
  77         vdso_data.xtime_sec = tk->xtime_sec;
  78         vdso_data.xtime_nsec = tk->tkr_mono.xtime_nsec;
  79         vdso_data.wall_to_mono_sec = tk->wall_to_monotonic.tv_sec;
  80         vdso_data.wall_to_mono_nsec = tk->wall_to_monotonic.tv_nsec;
  81         vdso_data.cs_shift = tk->tkr_mono.shift;
  82
  83         vdso_data.clock_mode = tk->tkr_mono.clock->archdata.vdso_clock_mode;
  84         if (vdso_data.clock_mode != VDSO_CLOCK_NONE) {
  85                 vdso_data.cs_mult = tk->tkr_mono.mult;
  86                 vdso_data.cs_cycle_last = tk->tkr_mono.cycle_last;
  87                 vdso_data.cs_mask = tk->tkr_mono.mask;
  88         }
  89
  90         vdso_data_write_end(&vdso_data);
  91 }
  92
  93 void update_vsyscall_tz(void)
  94 {
  95         if (vdso_data.clock_mode != VDSO_CLOCK_NONE) {
  96                 vdso_data.tz_minuteswest = sys_tz.tz_minuteswest;
  97                 vdso_data.tz_dsttime = sys_tz.tz_dsttime;
  98         }
  99 }
 100
 101 static unsigned long vdso_base(void)
 102 {
 103         unsigned long base;
 104
 105         /* Skip the delay slot emulation page */
 106         base = STACK_TOP + PAGE_SIZE;
 107
 108         if (current->flags & PF_RANDOMIZE) {
 109                 base += get_random_int() & (VDSO_RANDOMIZE_SIZE - 1);
 110                 base = PAGE_ALIGN(base);
 111         }
 112
 113         return base;
 114 }
 115
 116 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 117 {
 118         struct mips_vdso_image *image = current->thread.abi->vdso;
 119         struct mm_struct *mm = current->mm;
 120         unsigned long gic_size, vvar_size, size, base, data_addr, vdso_addr, gic_pfn;
 121         struct vm_area_struct *vma;
 122         int ret;
 123
 124         if (down_write_killable(&mm->mmap_sem))
 125                 return -EINTR;
 126
 127         /* Map delay slot emulation page */
 128         base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
 129                            VM_READ|VM_WRITE|VM_EXEC|
 130                            VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 131                            0, NULL);
 132         if (IS_ERR_VALUE(base)) {
 133                 ret = base;
 134                 goto out;
 135         }
 136
 137         /*
 138          * Determine total area size. This includes the VDSO data itself, the
 139          * data page, and the GIC user page if present. Always create a mapping
 140          * for the GIC user area if the GIC is present regardless of whether it
 141          * is the current clocksource, in case it comes into use later on. We
 142          * only map a page even though the total area is 64K, as we only need
 143          * the counter registers at the start.
 144          */
 145         gic_size = mips_gic_present() ? PAGE_SIZE : 0;
 146         vvar_size = gic_size + PAGE_SIZE;
 147         size = vvar_size + image->size;
 148
 149         /*
 150          * Find a region that's large enough for us to perform the
 151          * colour-matching alignment below.
 152          */
 153         if (cpu_has_dc_aliases)
 154                 size += shm_align_mask + 1;
 155
 156         base = get_unmapped_area(NULL, vdso_base(), size, 0, 0);
 157         if (IS_ERR_VALUE(base)) {
 158                 ret = base;
 159                 goto out;
 160         }
 161
 162         /*
 163          * If we suffer from dcache aliasing, ensure that the VDSO data page
 164          * mapping is coloured the same as the kernel's mapping of that memory.
 165          * This ensures that when the kernel updates the VDSO data userland
 166          * will observe it without requiring cache invalidations.
 167          */
 168         if (cpu_has_dc_aliases) {
 169                 base = __ALIGN_MASK(base, shm_align_mask);
 170                 base += ((unsigned long)&vdso_data - gic_size) & shm_align_mask;
 171         }
 172
 173         data_addr = base + gic_size;
 174         vdso_addr = data_addr + PAGE_SIZE;
 175
 176         vma = _install_special_mapping(mm, base, vvar_size,
 177                                        VM_READ | VM_MAYREAD,
 178                                        &vdso_vvar_mapping);
 179         if (IS_ERR(vma)) {
 180                 ret = PTR_ERR(vma);
 181                 goto out;
 182         }
 183
 184         /* Map GIC user page. */
 185         if (gic_size) {
 186                 gic_pfn = virt_to_phys(mips_gic_base + MIPS_GIC_USER_OFS) >> PAGE_SHIFT;
 187
 188                 ret = io_remap_pfn_range(vma, base, gic_pfn, gic_size,
 189                                          pgprot_noncached(PAGE_READONLY));
 190                 if (ret)
 191                         goto out;
 192         }
 193
 194         /* Map data page. */
 195         ret = remap_pfn_range(vma, data_addr,
 196                               virt_to_phys(&vdso_data) >> PAGE_SHIFT,
 197                               PAGE_SIZE, PAGE_READONLY);
 198         if (ret)
 199                 goto out;
 200
 201         /* Map VDSO image. */
 202         vma = _install_special_mapping(mm, vdso_addr, image->size,
 203                                        VM_READ | VM_EXEC |
 204                                        VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
 205                                        &image->mapping);
 206         if (IS_ERR(vma)) {
 207                 ret = PTR_ERR(vma);
 208                 goto out;
 209         }
 210
 211         mm->context.vdso = (void *)vdso_addr;
 212         ret = 0;
 213
 214 out:
 215         up_write(&mm->mmap_sem);
 216         return ret;
 217 }