arch/x86/um/vdso/vma.c

   1 /*
   2  * Copyright (C) 2011 Richard Weinberger <richrd@nod.at>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/slab.h>
  10 #include <linux/sched.h>
  11 #include <linux/mm.h>
  12 #include <asm/page.h>
  13 #include <linux/init.h>
  14
  15 static unsigned int __read_mostly vdso_enabled = 1;
  16 unsigned long um_vdso_addr;
  17
  18 extern unsigned long task_size;
  19 extern char vdso_start[], vdso_end[];
  20
  21 static struct page **vdsop;
  22
  23 static int __init init_vdso(void)
  24 {
  25         struct page *um_vdso;
  26
  27         BUG_ON(vdso_end - vdso_start > PAGE_SIZE);
  28
  29         um_vdso_addr = task_size - PAGE_SIZE;
  30
  31         vdsop = kmalloc(sizeof(struct page *), GFP_KERNEL);
  32         if (!vdsop)
  33                 goto oom;
  34
  35         um_vdso = alloc_page(GFP_KERNEL);
  36         if (!um_vdso) {
  37                 kfree(vdsop);
  38
  39                 goto oom;
  40         }
  41
  42         copy_page(page_address(um_vdso), vdso_start);
  43         *vdsop = um_vdso;
  44
  45         return 0;
  46
  47 oom:
  48         printk(KERN_ERR "Cannot allocate vdso\n");
  49         vdso_enabled = 0;
  50
  51         return -ENOMEM;
  52 }
  53 subsys_initcall(init_vdso);
  54
  55 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  56 {
  57         int err;
  58         struct mm_struct *mm = current->mm;
  59
  60         if (!vdso_enabled)
  61                 return 0;
  62
  63         down_write(&mm->mmap_sem);
  64
  65         err = install_special_mapping(mm, um_vdso_addr, PAGE_SIZE,
  66                 VM_READ|VM_EXEC|
  67                 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
  68                 vdsop);
  69
  70         up_write(&mm->mmap_sem);
  71
  72         return err;
  73 }