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 = STACK_TOP;
  75
  76         if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
  77                 /* Skip the delay slot emulation page */
  78                 base += PAGE_SIZE;
  79         }
  80
  81         if (current->flags & PF_RANDOMIZE) {
  82                 base += prandom_u32_max(VDSO_RANDOMIZE_SIZE);
  83                 base = PAGE_ALIGN(base);
  84         }
  85
  86         return base;
  87 }
  88
  89 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  90 {
  91         struct mips_vdso_image *image = current->thread.abi->vdso;
  92         struct mm_struct *mm = current->mm;
  93         unsigned long gic_size, vvar_size, size, base, data_addr, vdso_addr, gic_pfn, gic_base;
  94         struct vm_area_struct *vma;
  95         int ret;
  96
  97         if (mmap_write_lock_killable(mm))
  98                 return -EINTR;
  99
 100         if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
 101                 /* Map delay slot emulation page */
 102                 base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
 103                                 VM_READ | VM_EXEC |
 104                                 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
 105                                 0, NULL);
 106                 if (IS_ERR_VALUE(base)) {
 107                         ret = base;
 108                         goto out;
 109                 }
 110         }
 111
 112         /*
 113          * Determine total area size. This includes the VDSO data itself, the
 114          * data page, and the GIC user page if present. Always create a mapping
 115          * for the GIC user area if the GIC is present regardless of whether it
 116          * is the current clocksource, in case it comes into use later on. We
 117          * only map a page even though the total area is 64K, as we only need
 118          * the counter registers at the start.
 119          */
 120         gic_size = mips_gic_present() ? PAGE_SIZE : 0;
 121         vvar_size = gic_size + PAGE_SIZE;
 122         size = vvar_size + image->size;
 123
 124         /*
 125          * Find a region that's large enough for us to perform the
 126          * colour-matching alignment below.
 127          */
 128         if (cpu_has_dc_aliases)
 129                 size += shm_align_mask + 1;
 130
 131         base = get_unmapped_area(NULL, vdso_base(), size, 0, 0);
 132         if (IS_ERR_VALUE(base)) {
 133                 ret = base;
 134                 goto out;
 135         }
 136
 137         /*
 138          * If we suffer from dcache aliasing, ensure that the VDSO data page
 139          * mapping is coloured the same as the kernel's mapping of that memory.
 140          * This ensures that when the kernel updates the VDSO data userland
 141          * will observe it without requiring cache invalidations.
 142          */
 143         if (cpu_has_dc_aliases) {
 144                 base = __ALIGN_MASK(base, shm_align_mask);
 145                 base += ((unsigned long)vdso_data - gic_size) & shm_align_mask;
 146         }
 147
 148         data_addr = base + gic_size;
 149         vdso_addr = data_addr + PAGE_SIZE;
 150
 151         vma = _install_special_mapping(mm, base, vvar_size,
 152                                        VM_READ | VM_MAYREAD,
 153                                        &vdso_vvar_mapping);
 154         if (IS_ERR(vma)) {
 155                 ret = PTR_ERR(vma);
 156                 goto out;
 157         }
 158
 159         /* Map GIC user page. */
 160         if (gic_size) {
 161                 gic_base = (unsigned long)mips_gic_base + MIPS_GIC_USER_OFS;
 162                 gic_pfn = PFN_DOWN(__pa(gic_base));
 163
 164                 ret = io_remap_pfn_range(vma, base, gic_pfn, gic_size,
 165                                          pgprot_noncached(vma->vm_page_prot));
 166                 if (ret)
 167                         goto out;
 168         }
 169
 170         /* Map data page. */
 171         ret = remap_pfn_range(vma, data_addr,
 172                               virt_to_phys(vdso_data) >> PAGE_SHIFT,
 173                               PAGE_SIZE, vma->vm_page_prot);
 174         if (ret)
 175                 goto out;
 176
 177         /* Map VDSO image. */
 178         vma = _install_special_mapping(mm, vdso_addr, image->size,
 179                                        VM_READ | VM_EXEC |
 180                                        VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
 181                                        &image->mapping);
 182         if (IS_ERR(vma)) {
 183                 ret = PTR_ERR(vma);
 184                 goto out;
 185         }
 186
 187         mm->context.vdso = (void *)vdso_addr;
 188         ret = 0;
 189
 190 out:
 191         mmap_write_unlock(mm);
 192         return ret;
 193 }