LXR linux/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
  28static struct page *vdso_page;
  29
  30/* Create a vDSO page holding the signal trampoline.
  31 * We want this for a non-executable stack.
  32 */
  33static 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}
  57arch_initcall(vdso_init);
  58
  59/*
  60 * Called from binfmt_elf.  Create a VMA for the vDSO page.
  61 */
  62int 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
  90up_fail:
  91        up_write(&mm->mmap_sem);
  92        return ret;
  93}
  94
  95const 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}
 101