arch/hexagon/kernel/vdso.c

   1 /*
   2  * vDSO implementation for Hexagon
   3  *
   4  * Copyright (c) 2011, Code Aurora Forum. 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
  25 #include <asm/vdso.h>
  26
  27 static struct page *vdso_page;
  28
  29 /* Create a vDSO page holding the signal trampoline.
  30  * We want this for a non-executable stack.
  31  */
  32 static int __init vdso_init(void)
  33 {
  34         struct hexagon_vdso *vdso;
  35
  36         vdso_page = alloc_page(GFP_KERNEL);
  37         if (!vdso_page)
  38                 panic("Cannot allocate vdso");
  39
  40         vdso = vmap(&vdso_page, 1, 0, PAGE_KERNEL);
  41         if (!vdso)
  42                 panic("Cannot map vdso");
  43         clear_page(vdso);
  44
  45         /* Install the signal trampoline; currently looks like this:
  46          *      r6 = #__NR_rt_sigreturn;
  47          *      trap0(#1);
  48          */
  49         vdso->rt_signal_trampoline[0] = __rt_sigtramp_template[0];
  50         vdso->rt_signal_trampoline[1] = __rt_sigtramp_template[1];
  51
  52         vunmap(vdso);
  53
  54         return 0;
  55 }
  56 arch_initcall(vdso_init);
  57
  58 /*
  59  * Called from binfmt_elf.  Create a VMA for the vDSO page.
  60  */
  61 int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
  62 {
  63         int ret;
  64         unsigned long vdso_base;
  65         struct mm_struct *mm = current->mm;
  66
  67         down_write(&mm->mmap_sem);
  68
  69         /* Try to get it loaded right near ld.so/glibc. */
  70         vdso_base = STACK_TOP;
  71
  72         vdso_base = get_unmapped_area(NULL, vdso_base, PAGE_SIZE, 0, 0);
  73         if (IS_ERR_VALUE(vdso_base)) {
  74                 ret = vdso_base;
  75                 goto up_fail;
  76         }
  77
  78         /* MAYWRITE to allow gdb to COW and set breakpoints. */
  79         ret = install_special_mapping(mm, vdso_base, PAGE_SIZE,
  80                                       VM_READ|VM_EXEC|
  81                                       VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC|
  82                                       VM_ALWAYSDUMP,
  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 }