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