arch/mips/kernel/vdso.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2015 Imagination Technologies
   4  * Author: Alex Smith <alex.smith@imgtec.com>
   5  */
   6
   7 #include <linux/binfmts.h>
   8 #include <linux/elf.h>
   9 #include <linux/err.h>
  10 #include <linux/init.h>
  11 #include <linux/ioport.h>
  12 #include <linux/kernel.h>
  13 #include <linux/mm.h>
  14 #include <linux/random.h>
  15 #include <linux/sched.h>
  16 #include <linux/slab.h>
  17 #include <linux/timekeeper_internal.h>
  18
  19 #include <asm/abi.h>
  20 #include <asm/mips-cps.h>
  21 #include <asm/page.h>
  22 #include <asm/vdso.h>
  23
  24 /* Kernel-provided data used by the VDSO. */
  25 static union mips_vdso_data vdso_data __page_aligned_data;
  26
  27 /*
  28  * Mapping for the VDSO data/GIC pages. The real pages are mapped manually, as
  29  * what we map and where within the area they are mapped is determined at
  30  * runtime.
  31  */
  32 static struct page *no_pages[] = { NULL };
  33 static struct vm_special_mapping vdso_vvar_mapping = {
  34         .name = "[vvar]",
  35         .pages = no_pages,
  36 };
  37
  38 static void __init init_vdso_image(struct mips_vdso_image *image)
  39 {
  40         unsigned long num_pages, i;
  41         unsigned long data_pfn;
  42
  43         BUG_ON(!PAGE_ALIGNED(image->data));
  44         BUG_ON(!PAGE_ALIGNED(image->size));
  45
  46         num_pages = image->size / PAGE_SIZE;
  47
  48         data_pfn = __phys_to_pfn(__pa_symbol(image->data));
  49         for (i = 0; i < num_pages; i++)
  50                 image->mapping.pages[i] = pfn_to_page(data_pfn + i);
  51 }
  52
  53 static int __init init_vdso(void)
  54 {
  55         init_vdso_image(&vdso_image);
  56
  57 #ifdef CONFIG_MIPS32_O32
  58         init_vdso_image(&vdso_image_o32);
  59 #endif
  60
  61 #ifdef CONFIG_MIPS32_N32
  62         init_vdso_image(&vdso_image_n32);
  63 #endif
  64
  65         return 0;
  66 }
  67 subsys_initcall(init_vdso);
  68
  69 void update_vsyscall(struct timekeeper *tk)
  70 {
  71         vdso_data_write_begin(&vdso_data);
  72
  73         vdso_data.xtime_sec = tk->xtime_sec;
  74         vdso_data.xtime_nsec = tk->tkr_mono.xtime_nsec;
  75         vdso_data.wall_to_mono_sec = tk->wall_to_monotonic.tv_sec;
  76         vdso_data.wall_to_mono_nsec = tk->wall_to_monotonic.tv_nsec;
  77         vdso_data.cs_shift = tk->tkr_mono.shift;
  78
  79         vdso_data.clock_mode = tk->tkr_mono.clock->archdata.vdso_clock_mode;
  80         if (vdso_data.clock_mode != VDSO_CLOCK_NONE) {
  81                 vdso_data.cs_mult = tk->tkr_mono.mult;
  82                 vdso_data.cs_cycle_last = tk->tkr_mono.cycle_last;
  83                 vdso_data.cs_mask = tk->tkr_mono.mask;
  84         }
  85
  86         vdso_data_write_end(&vdso_data);
  87 }
  88
  89 void update_vsyscall_tz(void)
  90 {
  91         if (vdso_data.clock_mode != VDSO_CLOCK_NONE) {
  92                 vdso_data.tz_minuteswest = sys_tz.tz_minuteswest;
  93                 vdso_data.tz_dsttime = sys_tz.tz_dsttime;
  94         }
  95 }
  96
  97 static unsigned long vdso_base(void)
  98 {
  99         unsigned long base;
 100
 101         /* Skip the delay slot emulation page */
 102         base = STACK_TOP + PAGE_SIZE;
 103
 104         if (current->flags & PF_RANDOMIZE) {
 105                 base += get_random_int() & (VDSO_RANDOMIZE_SIZE - 1);
 106                 base = PAGE_ALIGN(base);
 107         }
 108
 109         return base;
 110 }
 111
 112 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 113 {
 114         struct mips_vdso_image *image = current->thread.abi->vdso;
 115         struct mm_struct *mm = current->mm;
 116         unsigned long gic_size, vvar_size, size, base, data_addr, vdso_addr, gic_pfn;
 117         struct vm_area_struct *vma;
 118         int ret;
 119
 120         if (down_write_killable(&mm->mmap_sem))
 121                 return -EINTR;
 122
 123         /* Map delay slot emulation page */
 124         base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
 125                            VM_READ | VM_EXEC |
 126                            VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
 127                            0, NULL);
 128         if (IS_ERR_VALUE(base)) {
 129                 ret = base;
 130                 goto out;
 131         }
 132
 133         /*
 134          * Determine total area size. This includes the VDSO data itself, the
 135          * data page, and the GIC user page if present. Always create a mapping
 136          * for the GIC user area if the GIC is present regardless of whether it
 137          * is the current clocksource, in case it comes into use later on. We
 138          * only map a page even though the total area is 64K, as we only need
 139          * the counter registers at the start.
 140          */
 141         gic_size = mips_gic_present() ? PAGE_SIZE : 0;
 142         vvar_size = gic_size + PAGE_SIZE;
 143         size = vvar_size + image->size;
 144
 145         /*
 146          * Find a region that's large enough for us to perform the
 147          * colour-matching alignment below.
 148          */
 149         if (cpu_has_dc_aliases)
 150                 size += shm_align_mask + 1;
 151
 152         base = get_unmapped_area(NULL, vdso_base(), size, 0, 0);
 153         if (IS_ERR_VALUE(base)) {
 154                 ret = base;
 155                 goto out;
 156         }
 157
 158         /*
 159          * If we suffer from dcache aliasing, ensure that the VDSO data page
 160          * mapping is coloured the same as the kernel's mapping of that memory.
 161          * This ensures that when the kernel updates the VDSO data userland
 162          * will observe it without requiring cache invalidations.
 163          */
 164         if (cpu_has_dc_aliases) {
 165                 base = __ALIGN_MASK(base, shm_align_mask);
 166                 base += ((unsigned long)&vdso_data - gic_size) & shm_align_mask;
 167         }
 168
 169         data_addr = base + gic_size;
 170         vdso_addr = data_addr + PAGE_SIZE;
 171
 172         vma = _install_special_mapping(mm, base, vvar_size,
 173                                        VM_READ | VM_MAYREAD,
 174                                        &vdso_vvar_mapping);
 175         if (IS_ERR(vma)) {
 176                 ret = PTR_ERR(vma);
 177                 goto out;
 178         }
 179
 180         /* Map GIC user page. */
 181         if (gic_size) {
 182                 gic_pfn = virt_to_phys(mips_gic_base + MIPS_GIC_USER_OFS) >> PAGE_SHIFT;
 183
 184                 ret = io_remap_pfn_range(vma, base, gic_pfn, gic_size,
 185                                          pgprot_noncached(PAGE_READONLY));
 186                 if (ret)
 187                         goto out;
 188         }
 189
 190         /* Map data page. */
 191         ret = remap_pfn_range(vma, data_addr,
 192                               virt_to_phys(&vdso_data) >> PAGE_SHIFT,
 193                               PAGE_SIZE, PAGE_READONLY);
 194         if (ret)
 195                 goto out;
 196
 197         /* Map VDSO image. */
 198         vma = _install_special_mapping(mm, vdso_addr, image->size,
 199                                        VM_READ | VM_EXEC |
 200                                        VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
 201                                        &image->mapping);
 202         if (IS_ERR(vma)) {
 203                 ret = PTR_ERR(vma);
 204                 goto out;
 205         }
 206
 207         mm->context.vdso = (void *)vdso_addr;
 208         ret = 0;
 209
 210 out:
 211         up_write(&mm->mmap_sem);
 212         return ret;
 213 }