arch/hexagon/kernel/vdso.c

   1 /*
   2  * vDSO implementation for Hexagon
   3  *
   4  * Copyright (c) 2011, The Linux Foundation. All rights reserved.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 and
   8  * only version 2 as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  18  * 02110-1301, USA.
  19  */
  20
  21 #include <linux/err.h>
  22 #include <linux/mm.h>
  23 #include <linux/vmalloc.h>
  24 #include <linux/binfmts.h>
  25
  26 #include <asm/vdso.h>
  27
  28 static struct page *vdso_page;
  29
  30 /* Create a vDSO page holding the signal trampoline.
  31  * We want this for a non-executable stack.
  32  */
  33 static int __init vdso_init(void)
  34 {
  35         struct hexagon_vdso *vdso;
  36
  37         vdso_page = alloc_page(GFP_KERNEL);
  38         if (!vdso_page)
  39                 panic("Cannot allocate vdso");
  40
  41         vdso = vmap(&vdso_page, 1, 0, PAGE_KERNEL);
  42         if (!vdso)
  43                 panic("Cannot map vdso");
  44         clear_page(vdso);
  45
  46         /* Install the signal trampoline; currently looks like this:
  47          *      r6 = #__NR_rt_sigreturn;
  48          *      trap0(#1);
  49          */
  50         vdso->rt_signal_trampoline[0] = __rt_sigtramp_template[0];
  51         vdso->rt_signal_trampoline[1] = __rt_sigtramp_template[1];
  52
  53         vunmap(vdso);
  54
  55         return 0;
  56 }
  57 arch_initcall(vdso_init);
  58
  59 /*
  60  * Called from binfmt_elf.  Create a VMA for the vDSO page.
  61  */
  62 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  63 {
  64         int ret;
  65         unsigned long vdso_base;
  66         struct mm_struct *mm = current->mm;
  67
  68         down_write(&mm->mmap_sem);
  69
  70         /* Try to get it loaded right near ld.so/glibc. */
  71         vdso_base = STACK_TOP;
  72
  73         vdso_base = get_unmapped_area(NULL, vdso_base, PAGE_SIZE, 0, 0);
  74         if (IS_ERR_VALUE(vdso_base)) {
  75                 ret = vdso_base;
  76                 goto up_fail;
  77         }
  78
  79         /* MAYWRITE to allow gdb to COW and set breakpoints. */
  80         ret = install_special_mapping(mm, vdso_base, PAGE_SIZE,
  81                                       VM_READ|VM_EXEC|
  82                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
  83                                       &vdso_page);
  84
  85         if (ret)
  86                 goto up_fail;
  87
  88         mm->context.vdso = (void *)vdso_base;
  89
  90 up_fail:
  91         up_write(&mm->mmap_sem);
  92         return ret;
  93 }
  94
  95 const char *arch_vma_name(struct vm_area_struct *vma)
  96 {
  97         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
  98                 return "[vdso]";
  99         return NULL;
 100 }