arch/riscv/kernel/vdso.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2004 Benjamin Herrenschmidt, IBM Corp.
   4  *                    <benh@kernel.crashing.org>
   5  * Copyright (C) 2012 ARM Limited
   6  * Copyright (C) 2015 Regents of the University of California
   7  */
   8
   9 #include <linux/elf.h>
  10 #include <linux/mm.h>
  11 #include <linux/slab.h>
  12 #include <linux/binfmts.h>
  13 #include <linux/err.h>
  14 #include <asm/page.h>
  15 #ifdef GENERIC_TIME_VSYSCALL
  16 #include <vdso/datapage.h>
  17 #else
  18 #include <asm/vdso.h>
  19 #endif
  20
  21 extern char vdso_start[], vdso_end[];
  22
  23 static unsigned int vdso_pages;
  24 static struct page **vdso_pagelist;
  25
  26 /*
  27  * The vDSO data page.
  28  */
  29 static union {
  30         struct vdso_data        data;
  31         u8                      page[PAGE_SIZE];
  32 } vdso_data_store __page_aligned_data;
  33 struct vdso_data *vdso_data = &vdso_data_store.data;
  34
  35 static int __init vdso_init(void)
  36 {
  37         unsigned int i;
  38
  39         vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
  40         vdso_pagelist =
  41                 kcalloc(vdso_pages + 1, sizeof(struct page *), GFP_KERNEL);
  42         if (unlikely(vdso_pagelist == NULL)) {
  43                 pr_err("vdso: pagelist allocation failed\n");
  44                 return -ENOMEM;
  45         }
  46
  47         for (i = 0; i < vdso_pages; i++) {
  48                 struct page *pg;
  49
  50                 pg = virt_to_page(vdso_start + (i << PAGE_SHIFT));
  51                 vdso_pagelist[i] = pg;
  52         }
  53         vdso_pagelist[i] = virt_to_page(vdso_data);
  54
  55         return 0;
  56 }
  57 arch_initcall(vdso_init);
  58
  59 int arch_setup_additional_pages(struct linux_binprm *bprm,
  60         int uses_interp)
  61 {
  62         struct mm_struct *mm = current->mm;
  63         unsigned long vdso_base, vdso_len;
  64         int ret;
  65
  66         vdso_len = (vdso_pages + 1) << PAGE_SHIFT;
  67
  68         mmap_write_lock(mm);
  69         vdso_base = get_unmapped_area(NULL, 0, vdso_len, 0, 0);
  70         if (IS_ERR_VALUE(vdso_base)) {
  71                 ret = vdso_base;
  72                 goto end;
  73         }
  74
  75         /*
  76          * Put vDSO base into mm struct. We need to do this before calling
  77          * install_special_mapping or the perf counter mmap tracking code
  78          * will fail to recognise it as a vDSO (since arch_vma_name fails).
  79          */
  80         mm->context.vdso = (void *)vdso_base;
  81
  82         ret =
  83            install_special_mapping(mm, vdso_base, vdso_pages << PAGE_SHIFT,
  84                 (VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
  85                 vdso_pagelist);
  86
  87         if (unlikely(ret)) {
  88                 mm->context.vdso = NULL;
  89                 goto end;
  90         }
  91
  92         vdso_base += (vdso_pages << PAGE_SHIFT);
  93         ret = install_special_mapping(mm, vdso_base, PAGE_SIZE,
  94                 (VM_READ | VM_MAYREAD), &vdso_pagelist[vdso_pages]);
  95
  96         if (unlikely(ret))
  97                 mm->context.vdso = NULL;
  98 end:
  99         mmap_write_unlock(mm);
 100         return ret;
 101 }
 102
 103 const char *arch_vma_name(struct vm_area_struct *vma)
 104 {
 105         if (vma->vm_mm && (vma->vm_start == (long)vma->vm_mm->context.vdso))
 106                 return "[vdso]";
 107         if (vma->vm_mm && (vma->vm_start ==
 108                            (long)vma->vm_mm->context.vdso + PAGE_SIZE))
 109                 return "[vdso_data]";
 110         return NULL;
 111 }