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 #include <asm/vdso.h>
  16
  17 #ifdef CONFIG_GENERIC_TIME_VSYSCALL
  18 #include <vdso/datapage.h>
  19 #else
  20 struct vdso_data {
  21 };
  22 #endif
  23
  24 extern char vdso_start[], vdso_end[];
  25
  26 enum vvar_pages {
  27         VVAR_DATA_PAGE_OFFSET,
  28         VVAR_NR_PAGES,
  29 };
  30
  31 #define VVAR_SIZE  (VVAR_NR_PAGES << PAGE_SHIFT)
  32
  33 static unsigned int vdso_pages __ro_after_init;
  34 static struct page **vdso_pagelist __ro_after_init;
  35
  36 /*
  37  * The vDSO data page.
  38  */
  39 static union {
  40         struct vdso_data        data;
  41         u8                      page[PAGE_SIZE];
  42 } vdso_data_store __page_aligned_data;
  43 struct vdso_data *vdso_data = &vdso_data_store.data;
  44
  45 static int __init vdso_init(void)
  46 {
  47         unsigned int i;
  48
  49         vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
  50         vdso_pagelist =
  51                 kcalloc(vdso_pages + VVAR_NR_PAGES, sizeof(struct page *), GFP_KERNEL);
  52         if (unlikely(vdso_pagelist == NULL)) {
  53                 pr_err("vdso: pagelist allocation failed\n");
  54                 return -ENOMEM;
  55         }
  56
  57         for (i = 0; i < vdso_pages; i++) {
  58                 struct page *pg;
  59
  60                 pg = virt_to_page(vdso_start + (i << PAGE_SHIFT));
  61                 vdso_pagelist[i] = pg;
  62         }
  63         vdso_pagelist[i] = virt_to_page(vdso_data);
  64
  65         return 0;
  66 }
  67 arch_initcall(vdso_init);
  68
  69 int arch_setup_additional_pages(struct linux_binprm *bprm,
  70         int uses_interp)
  71 {
  72         struct mm_struct *mm = current->mm;
  73         unsigned long vdso_base, vdso_len;
  74         int ret;
  75
  76         BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
  77
  78         vdso_len = (vdso_pages + VVAR_NR_PAGES) << PAGE_SHIFT;
  79
  80         if (mmap_write_lock_killable(mm))
  81                 return -EINTR;
  82
  83         vdso_base = get_unmapped_area(NULL, 0, vdso_len, 0, 0);
  84         if (IS_ERR_VALUE(vdso_base)) {
  85                 ret = vdso_base;
  86                 goto end;
  87         }
  88
  89         mm->context.vdso = NULL;
  90         ret = install_special_mapping(mm, vdso_base, VVAR_SIZE,
  91                 (VM_READ | VM_MAYREAD), &vdso_pagelist[vdso_pages]);
  92         if (unlikely(ret))
  93                 goto end;
  94
  95         ret =
  96            install_special_mapping(mm, vdso_base + VVAR_SIZE,
  97                 vdso_pages << PAGE_SHIFT,
  98                 (VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
  99                 vdso_pagelist);
 100
 101         if (unlikely(ret))
 102                 goto end;
 103
 104         /*
 105          * Put vDSO base into mm struct. We need to do this before calling
 106          * install_special_mapping or the perf counter mmap tracking code
 107          * will fail to recognise it as a vDSO (since arch_vma_name fails).
 108          */
 109         mm->context.vdso = (void *)vdso_base + VVAR_SIZE;
 110
 111 end:
 112         mmap_write_unlock(mm);
 113         return ret;
 114 }
 115
 116 const char *arch_vma_name(struct vm_area_struct *vma)
 117 {
 118         if (vma->vm_mm && (vma->vm_start == (long)vma->vm_mm->context.vdso))
 119                 return "[vdso]";
 120         if (vma->vm_mm && (vma->vm_start ==
 121                            (long)vma->vm_mm->context.vdso - VVAR_SIZE))
 122                 return "[vdso_data]";
 123         return NULL;
 124 }