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 <asm/elf.h>
  14 #include <linux/init.h>
  15
  16 static unsigned int __read_mostly vdso_enabled = 1;
  17 unsigned long um_vdso_addr;
  18
  19 extern unsigned long task_size;
  20 extern char vdso_start[], vdso_end[];
  21
  22 static struct page **vdsop;
  23
  24 static int __init init_vdso(void)
  25 {
  26         struct page *um_vdso;
  27
  28         BUG_ON(vdso_end - vdso_start > PAGE_SIZE);
  29
  30         um_vdso_addr = task_size - PAGE_SIZE;
  31
  32         vdsop = kmalloc(sizeof(struct page *), GFP_KERNEL);
  33         if (!vdsop)
  34                 goto oom;
  35
  36         um_vdso = alloc_page(GFP_KERNEL);
  37         if (!um_vdso) {
  38                 kfree(vdsop);
  39
  40                 goto oom;
  41         }
  42
  43         copy_page(page_address(um_vdso), vdso_start);
  44         *vdsop = um_vdso;
  45
  46         return 0;
  47
  48 oom:
  49         printk(KERN_ERR "Cannot allocate vdso\n");
  50         vdso_enabled = 0;
  51
  52         return -ENOMEM;
  53 }
  54 subsys_initcall(init_vdso);
  55
  56 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  57 {
  58         int err;
  59         struct mm_struct *mm = current->mm;
  60
  61         if (!vdso_enabled)
  62                 return 0;
  63
  64         if (down_write_killable(&mm->mmap_sem))
  65                 return -EINTR;
  66
  67         err = install_special_mapping(mm, um_vdso_addr, PAGE_SIZE,
  68                 VM_READ|VM_EXEC|
  69                 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
  70                 vdsop);
  71
  72         up_write(&mm->mmap_sem);
  73
  74         return err;
  75 }