arch/riscv/kernel/vdso.c

   1 /*
   2  * Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
   3  *                    <benh@kernel.crashing.org>
   4  * Copyright (C) 2012 ARM Limited
   5  * Copyright (C) 2015 Regents of the University of California
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <linux/mm.h>
  21 #include <linux/slab.h>
  22 #include <linux/binfmts.h>
  23 #include <linux/err.h>
  24
  25 #include <asm/vdso.h>
  26
  27 extern char vdso_start[], vdso_end[];
  28
  29 static unsigned int vdso_pages;
  30 static struct page **vdso_pagelist;
  31
  32 /*
  33  * The vDSO data page.
  34  */
  35 static union {
  36         struct vdso_data        data;
  37         u8                      page[PAGE_SIZE];
  38 } vdso_data_store __page_aligned_data;
  39 struct vdso_data *vdso_data = &vdso_data_store.data;
  40
  41 static int __init vdso_init(void)
  42 {
  43         unsigned int i;
  44
  45         vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
  46         vdso_pagelist =
  47                 kcalloc(vdso_pages + 1, sizeof(struct page *), GFP_KERNEL);
  48         if (unlikely(vdso_pagelist == NULL)) {
  49                 pr_err("vdso: pagelist allocation failed\n");
  50                 return -ENOMEM;
  51         }
  52
  53         for (i = 0; i < vdso_pages; i++) {
  54                 struct page *pg;
  55
  56                 pg = virt_to_page(vdso_start + (i << PAGE_SHIFT));
  57                 ClearPageReserved(pg);
  58                 vdso_pagelist[i] = pg;
  59         }
  60         vdso_pagelist[i] = virt_to_page(vdso_data);
  61
  62         return 0;
  63 }
  64 arch_initcall(vdso_init);
  65
  66 int arch_setup_additional_pages(struct linux_binprm *bprm,
  67         int uses_interp)
  68 {
  69         struct mm_struct *mm = current->mm;
  70         unsigned long vdso_base, vdso_len;
  71         int ret;
  72
  73         vdso_len = (vdso_pages + 1) << PAGE_SHIFT;
  74
  75         down_write(&mm->mmap_sem);
  76         vdso_base = get_unmapped_area(NULL, 0, vdso_len, 0, 0);
  77         if (IS_ERR_VALUE(vdso_base)) {
  78                 ret = vdso_base;
  79                 goto end;
  80         }
  81
  82         /*
  83          * Put vDSO base into mm struct. We need to do this before calling
  84          * install_special_mapping or the perf counter mmap tracking code
  85          * will fail to recognise it as a vDSO (since arch_vma_name fails).
  86          */
  87         mm->context.vdso = (void *)vdso_base;
  88
  89         ret = install_special_mapping(mm, vdso_base, vdso_len,
  90                 (VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
  91                 vdso_pagelist);
  92
  93         if (unlikely(ret))
  94                 mm->context.vdso = NULL;
  95
  96 end:
  97         up_write(&mm->mmap_sem);
  98         return ret;
  99 }
 100
 101 const char *arch_vma_name(struct vm_area_struct *vma)
 102 {
 103         if (vma->vm_mm && (vma->vm_start == (long)vma->vm_mm->context.vdso))
 104                 return "[vdso]";
 105         return NULL;
 106 }
 107
 108 /*
 109  * Function stubs to prevent linker errors when AT_SYSINFO_EHDR is defined
 110  */
 111
 112 int in_gate_area_no_mm(unsigned long addr)
 113 {
 114         return 0;
 115 }
 116
 117 int in_gate_area(struct mm_struct *mm, unsigned long addr)
 118 {
 119         return 0;
 120 }
 121
 122 struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
 123 {
 124         return NULL;
 125 }