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 #include <vdso/helpers.h>
  24 #include <vdso/vsyscall.h>
  25
  26 /* Kernel-provided data used by the VDSO. */
  27 static union mips_vdso_data mips_vdso_data __page_aligned_data;
  28 struct vdso_data *vdso_data = mips_vdso_data.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 static unsigned long vdso_base(void)
  73 {
  74         unsigned long base;
  75
  76         /* Skip the delay slot emulation page */
  77         base = STACK_TOP + PAGE_SIZE;
  78
  79         if (current->flags & PF_RANDOMIZE) {
  80                 base += get_random_int() & (VDSO_RANDOMIZE_SIZE - 1);
  81                 base = PAGE_ALIGN(base);
  82         }
  83
  84         return base;
  85 }
  86
  87 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  88 {
  89         struct mips_vdso_image *image = current->thread.abi->vdso;
  90         struct mm_struct *mm = current->mm;
  91         unsigned long gic_size, vvar_size, size, base, data_addr, vdso_addr, gic_pfn;
  92         struct vm_area_struct *vma;
  93         int ret;
  94
  95         if (down_write_killable(&mm->mmap_sem))
  96                 return -EINTR;
  97
  98         /* Map delay slot emulation page */
  99         base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
 100                            VM_READ | VM_EXEC |
 101                            VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
 102                            0, NULL);
 103         if (IS_ERR_VALUE(base)) {
 104                 ret = base;
 105                 goto out;
 106         }
 107
 108         /*
 109          * Determine total area size. This includes the VDSO data itself, the
 110          * data page, and the GIC user page if present. Always create a mapping
 111          * for the GIC user area if the GIC is present regardless of whether it
 112          * is the current clocksource, in case it comes into use later on. We
 113          * only map a page even though the total area is 64K, as we only need
 114          * the counter registers at the start.
 115          */
 116         gic_size = mips_gic_present() ? PAGE_SIZE : 0;
 117         vvar_size = gic_size + PAGE_SIZE;
 118         size = vvar_size + image->size;
 119
 120         /*
 121          * Find a region that's large enough for us to perform the
 122          * colour-matching alignment below.
 123          */
 124         if (cpu_has_dc_aliases)
 125                 size += shm_align_mask + 1;
 126
 127         base = get_unmapped_area(NULL, vdso_base(), size, 0, 0);
 128         if (IS_ERR_VALUE(base)) {
 129                 ret = base;
 130                 goto out;
 131         }
 132
 133         /*
 134          * If we suffer from dcache aliasing, ensure that the VDSO data page
 135          * mapping is coloured the same as the kernel's mapping of that memory.
 136          * This ensures that when the kernel updates the VDSO data userland
 137          * will observe it without requiring cache invalidations.
 138          */
 139         if (cpu_has_dc_aliases) {
 140                 base = __ALIGN_MASK(base, shm_align_mask);
 141                 base += ((unsigned long)vdso_data - gic_size) & shm_align_mask;
 142         }
 143
 144         data_addr = base + gic_size;
 145         vdso_addr = data_addr + PAGE_SIZE;
 146
 147         vma = _install_special_mapping(mm, base, vvar_size,
 148                                        VM_READ | VM_MAYREAD,
 149                                        &vdso_vvar_mapping);
 150         if (IS_ERR(vma)) {
 151                 ret = PTR_ERR(vma);
 152                 goto out;
 153         }
 154
 155         /* Map GIC user page. */
 156         if (gic_size) {
 157                 gic_pfn = virt_to_phys(mips_gic_base + MIPS_GIC_USER_OFS) >> PAGE_SHIFT;
 158
 159                 ret = io_remap_pfn_range(vma, base, gic_pfn, gic_size,
 160                                          pgprot_noncached(PAGE_READONLY));
 161                 if (ret)
 162                         goto out;
 163         }
 164
 165         /* Map data page. */
 166         ret = remap_pfn_range(vma, data_addr,
 167                               virt_to_phys(vdso_data) >> PAGE_SHIFT,
 168                               PAGE_SIZE, PAGE_READONLY);
 169         if (ret)
 170                 goto out;
 171
 172         /* Map VDSO image. */
 173         vma = _install_special_mapping(mm, vdso_addr, image->size,
 174                                        VM_READ | VM_EXEC |
 175                                        VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
 176                                        &image->mapping);
 177         if (IS_ERR(vma)) {
 178                 ret = PTR_ERR(vma);
 179                 goto out;
 180         }
 181
 182         mm->context.vdso = (void *)vdso_addr;
 183         ret = 0;
 184
 185 out:
 186         up_write(&mm->mmap_sem);
 187         return ret;
 188 }