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/mm.h>
  16 #include <linux/sched.h>
  17 #include <linux/slab.h>
  18
  19 #include <asm/abi.h>
  20 #include <asm/vdso.h>
  21
  22 /* Kernel-provided data used by the VDSO. */
  23 static union mips_vdso_data vdso_data __page_aligned_data;
  24
  25 /*
  26  * Mapping for the VDSO data pages. The real pages are mapped manually, as
  27  * what we map and where within the area they are mapped is determined at
  28  * runtime.
  29  */
  30 static struct page *no_pages[] = { NULL };
  31 static struct vm_special_mapping vdso_vvar_mapping = {
  32         .name = "[vvar]",
  33         .pages = no_pages,
  34 };
  35
  36 static void __init init_vdso_image(struct mips_vdso_image *image)
  37 {
  38         unsigned long num_pages, i;
  39
  40         BUG_ON(!PAGE_ALIGNED(image->data));
  41         BUG_ON(!PAGE_ALIGNED(image->size));
  42
  43         num_pages = image->size / PAGE_SIZE;
  44
  45         for (i = 0; i < num_pages; i++) {
  46                 image->mapping.pages[i] =
  47                         virt_to_page(image->data + (i * PAGE_SIZE));
  48         }
  49 }
  50
  51 static int __init init_vdso(void)
  52 {
  53         init_vdso_image(&vdso_image);
  54
  55 #ifdef CONFIG_MIPS32_O32
  56         init_vdso_image(&vdso_image_o32);
  57 #endif
  58
  59 #ifdef CONFIG_MIPS32_N32
  60         init_vdso_image(&vdso_image_n32);
  61 #endif
  62
  63         return 0;
  64 }
  65 subsys_initcall(init_vdso);
  66
  67 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  68 {
  69         struct mips_vdso_image *image = current->thread.abi->vdso;
  70         struct mm_struct *mm = current->mm;
  71         unsigned long base, vdso_addr;
  72         struct vm_area_struct *vma;
  73         int ret;
  74
  75         down_write(&mm->mmap_sem);
  76
  77         base = get_unmapped_area(NULL, 0, PAGE_SIZE + image->size, 0, 0);
  78         if (IS_ERR_VALUE(base)) {
  79                 ret = base;
  80                 goto out;
  81         }
  82
  83         vdso_addr = base + PAGE_SIZE;
  84
  85         vma = _install_special_mapping(mm, base, PAGE_SIZE,
  86                                        VM_READ | VM_MAYREAD,
  87                                        &vdso_vvar_mapping);
  88         if (IS_ERR(vma)) {
  89                 ret = PTR_ERR(vma);
  90                 goto out;
  91         }
  92
  93         /* Map data page. */
  94         ret = remap_pfn_range(vma, base,
  95                               virt_to_phys(&vdso_data) >> PAGE_SHIFT,
  96                               PAGE_SIZE, PAGE_READONLY);
  97         if (ret)
  98                 goto out;
  99
 100         /* Map VDSO image. */
 101         vma = _install_special_mapping(mm, vdso_addr, image->size,
 102                                        VM_READ | VM_EXEC |
 103                                        VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
 104                                        &image->mapping);
 105         if (IS_ERR(vma)) {
 106                 ret = PTR_ERR(vma);
 107                 goto out;
 108         }
 109
 110         mm->context.vdso = (void *)vdso_addr;
 111         ret = 0;
 112
 113 out:
 114         up_write(&mm->mmap_sem);
 115         return ret;
 116 }