arch/x86/um/vdso/vma.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2011 Richard Weinberger <richrd@nod.at>
   4  */
   5
   6 #include <linux/slab.h>
   7 #include <linux/sched.h>
   8 #include <linux/mm.h>
   9 #include <asm/page.h>
  10 #include <asm/elf.h>
  11 #include <linux/init.h>
  12
  13 static unsigned int __read_mostly vdso_enabled = 1;
  14 unsigned long um_vdso_addr;
  15
  16 extern unsigned long task_size;
  17 extern char vdso_start[], vdso_end[];
  18
  19 static struct page **vdsop;
  20
  21 static int __init init_vdso(void)
  22 {
  23         struct page *um_vdso;
  24
  25         BUG_ON(vdso_end - vdso_start > PAGE_SIZE);
  26
  27         um_vdso_addr = task_size - PAGE_SIZE;
  28
  29         vdsop = kmalloc(sizeof(struct page *), GFP_KERNEL);
  30         if (!vdsop)
  31                 goto oom;
  32
  33         um_vdso = alloc_page(GFP_KERNEL);
  34         if (!um_vdso) {
  35                 kfree(vdsop);
  36
  37                 goto oom;
  38         }
  39
  40         copy_page(page_address(um_vdso), vdso_start);
  41         *vdsop = um_vdso;
  42
  43         return 0;
  44
  45 oom:
  46         printk(KERN_ERR "Cannot allocate vdso\n");
  47         vdso_enabled = 0;
  48
  49         return -ENOMEM;
  50 }
  51 subsys_initcall(init_vdso);
  52
  53 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  54 {
  55         int err;
  56         struct mm_struct *mm = current->mm;
  57
  58         if (!vdso_enabled)
  59                 return 0;
  60
  61         if (down_write_killable(&mm->mmap_sem))
  62                 return -EINTR;
  63
  64         err = install_special_mapping(mm, um_vdso_addr, PAGE_SIZE,
  65                 VM_READ|VM_EXEC|
  66                 VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
  67                 vdsop);
  68
  69         up_write(&mm->mmap_sem);
  70
  71         return err;
  72 }