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
  18 #include <asm/abi.h>
  19 #include <asm/mips-cps.h>
  20 #include <asm/page.h>
  21 #include <asm/vdso.h>
  22 #include <vdso/helpers.h>
  23 #include <vdso/vsyscall.h>
  24
  25 /* Kernel-provided data used by the VDSO. */
  26 static union vdso_data_store mips_vdso_data __page_aligned_data;
  27 struct vdso_data *vdso_data = mips_vdso_data.data;
  28
  29 /*
  30  * Mapping for the VDSO data/GIC pages. The real pages are mapped manually, as
  31  * what we map and where within the area they are mapped is determined at
  32  * runtime.
  33  */
  34 static struct page *no_pages[] = { NULL };
  35 static struct vm_special_mapping vdso_vvar_mapping = {
  36         .name = "[vvar]",
  37         .pages = no_pages,
  38 };
  39
  40 static void __init init_vdso_image(struct mips_vdso_image *image)
  41 {
  42         unsigned long num_pages, i;
  43         unsigned long data_pfn;
  44
  45         BUG_ON(!PAGE_ALIGNED(image->data));
  46         BUG_ON(!PAGE_ALIGNED(image->size));
  47
  48         num_pages = image->size / PAGE_SIZE;
  49
  50         data_pfn = __phys_to_pfn(__pa_symbol(image->data));
  51         for (i = 0; i < num_pages; i++)
  52                 image->mapping.pages[i] = pfn_to_page(data_pfn + i);
  53 }
  54
  55 static int __init init_vdso(void)
  56 {
  57         init_vdso_image(&vdso_image);
  58
  59 #ifdef CONFIG_MIPS32_O32
  60         init_vdso_image(&vdso_image_o32);
  61 #endif
  62
  63 #ifdef CONFIG_MIPS32_N32
  64         init_vdso_image(&vdso_image_n32);
  65 #endif
  66
  67         return 0;
  68 }
  69 subsys_initcall(init_vdso);
  70
  71 static unsigned long vdso_base(void)
  72 {
  73         unsigned long base = STACK_TOP;
  74
  75         if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
  76                 /* Skip the delay slot emulation page */
  77                 base += PAGE_SIZE;
  78         }
  79
  80         if (current->flags & PF_RANDOMIZE) {
  81                 base += get_random_u32_below(VDSO_RANDOMIZE_SIZE);
  82                 base = PAGE_ALIGN(base);
  83         }
  84
  85         return base;
  86 }
  87
  88 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  89 {
  90         struct mips_vdso_image *image = current->thread.abi->vdso;
  91         struct mm_struct *mm = current->mm;
  92         unsigned long gic_size, vvar_size, size, base, data_addr, vdso_addr, gic_pfn, gic_base;
  93         struct vm_area_struct *vma;
  94         int ret;
  95
  96         if (mmap_write_lock_killable(mm))
  97                 return -EINTR;
  98
  99         if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
 100                 /* Map delay slot emulation page */
 101                 base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
 102                                 VM_READ | VM_EXEC |
 103                                 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
 104                                 0, NULL);
 105                 if (IS_ERR_VALUE(base)) {
 106                         ret = base;
 107                         goto out;
 108                 }
 109         }
 110
 111         /*
 112          * Determine total area size. This includes the VDSO data itself, the
 113          * data page, and the GIC user page if present. Always create a mapping
 114          * for the GIC user area if the GIC is present regardless of whether it
 115          * is the current clocksource, in case it comes into use later on. We
 116          * only map a page even though the total area is 64K, as we only need
 117          * the counter registers at the start.
 118          */
 119         gic_size = mips_gic_present() ? PAGE_SIZE : 0;
 120         vvar_size = gic_size + PAGE_SIZE;
 121         size = vvar_size + image->size;
 122
 123         /*
 124          * Find a region that's large enough for us to perform the
 125          * colour-matching alignment below.
 126          */
 127         if (cpu_has_dc_aliases)
 128                 size += shm_align_mask + 1;
 129
 130         base = get_unmapped_area(NULL, vdso_base(), size, 0, 0);
 131         if (IS_ERR_VALUE(base)) {
 132                 ret = base;
 133                 goto out;
 134         }
 135
 136         /*
 137          * If we suffer from dcache aliasing, ensure that the VDSO data page
 138          * mapping is coloured the same as the kernel's mapping of that memory.
 139          * This ensures that when the kernel updates the VDSO data userland
 140          * will observe it without requiring cache invalidations.
 141          */
 142         if (cpu_has_dc_aliases) {
 143                 base = __ALIGN_MASK(base, shm_align_mask);
 144                 base += ((unsigned long)vdso_data - gic_size) & shm_align_mask;
 145         }
 146
 147         data_addr = base + gic_size;
 148         vdso_addr = data_addr + PAGE_SIZE;
 149
 150         vma = _install_special_mapping(mm, base, vvar_size,
 151                                        VM_READ | VM_MAYREAD,
 152                                        &vdso_vvar_mapping);
 153         if (IS_ERR(vma)) {
 154                 ret = PTR_ERR(vma);
 155                 goto out;
 156         }
 157
 158         /* Map GIC user page. */
 159         if (gic_size) {
 160                 gic_base = (unsigned long)mips_gic_base + MIPS_GIC_USER_OFS;
 161                 gic_pfn = PFN_DOWN(__pa(gic_base));
 162
 163                 ret = io_remap_pfn_range(vma, base, gic_pfn, gic_size,
 164                                          pgprot_noncached(vma->vm_page_prot));
 165                 if (ret)
 166                         goto out;
 167         }
 168
 169         /* Map data page. */
 170         ret = remap_pfn_range(vma, data_addr,
 171                               virt_to_phys(vdso_data) >> PAGE_SHIFT,
 172                               PAGE_SIZE, vma->vm_page_prot);
 173         if (ret)
 174                 goto out;
 175
 176         /* Map VDSO image. */
 177         vma = _install_special_mapping(mm, vdso_addr, image->size,
 178                                        VM_READ | VM_EXEC |
 179                                        VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
 180                                        &image->mapping);
 181         if (IS_ERR(vma)) {
 182                 ret = PTR_ERR(vma);
 183                 goto out;
 184         }
 185
 186         mm->context.vdso = (void *)vdso_addr;
 187         ret = 0;
 188
 189 out:
 190         mmap_write_unlock(mm);
 191         return ret;
 192 }