arch/sh/kernel/vsyscall/vsyscall.c

   1 /*
   2  * arch/sh/kernel/vsyscall/vsyscall.c
   3  *
   4  *  Copyright (C) 2006 Paul Mundt
   5  *
   6  * vDSO randomization
   7  * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
   8  *
   9  * This file is subject to the terms and conditions of the GNU General Public
  10  * License.  See the file "COPYING" in the main directory of this archive
  11  * for more details.
  12  */
  13 #include <linux/mm.h>
  14 #include <linux/slab.h>
  15 #include <linux/kernel.h>
  16 #include <linux/init.h>
  17 #include <linux/gfp.h>
  18 #include <linux/module.h>
  19 #include <linux/elf.h>
  20 #include <linux/sched.h>
  21 #include <linux/err.h>
  22
  23 /*
  24  * Should the kernel map a VDSO page into processes and pass its
  25  * address down to glibc upon exec()?
  26  */
  27 unsigned int __read_mostly vdso_enabled = 1;
  28 EXPORT_SYMBOL_GPL(vdso_enabled);
  29
  30 static int __init vdso_setup(char *s)
  31 {
  32         vdso_enabled = simple_strtoul(s, NULL, 0);
  33         return 1;
  34 }
  35 __setup("vdso=", vdso_setup);
  36
  37 /*
  38  * These symbols are defined by vsyscall.o to mark the bounds
  39  * of the ELF DSO images included therein.
  40  */
  41 extern const char vsyscall_trapa_start, vsyscall_trapa_end;
  42 static struct page *syscall_pages[1];
  43
  44 int __init vsyscall_init(void)
  45 {
  46         void *syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
  47         syscall_pages[0] = virt_to_page(syscall_page);
  48
  49         /*
  50          * XXX: Map this page to a fixmap entry if we get around
  51          * to adding the page to ELF core dumps
  52          */
  53
  54         memcpy(syscall_page,
  55                &vsyscall_trapa_start,
  56                &vsyscall_trapa_end - &vsyscall_trapa_start);
  57
  58         return 0;
  59 }
  60
  61 /* Setup a VMA at program startup for the vsyscall page */
  62 int arch_setup_additional_pages(struct linux_binprm *bprm,
  63                                 int executable_stack)
  64 {
  65         struct mm_struct *mm = current->mm;
  66         unsigned long addr;
  67         int ret;
  68
  69         down_write(&mm->mmap_sem);
  70         addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
  71         if (IS_ERR_VALUE(addr)) {
  72                 ret = addr;
  73                 goto up_fail;
  74         }
  75
  76         ret = install_special_mapping(mm, addr, PAGE_SIZE,
  77                                       VM_READ | VM_EXEC |
  78                                       VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC |
  79                                       VM_ALWAYSDUMP,
  80                                       syscall_pages);
  81         if (unlikely(ret))
  82                 goto up_fail;
  83
  84         current->mm->context.vdso = (void *)addr;
  85
  86 up_fail:
  87         up_write(&mm->mmap_sem);
  88         return ret;
  89 }
  90
  91 const char *arch_vma_name(struct vm_area_struct *vma)
  92 {
  93         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
  94                 return "[vdso]";
  95
  96         return NULL;
  97 }
  98
  99 struct vm_area_struct *get_gate_vma(struct task_struct *task)
 100 {
 101         return NULL;
 102 }
 103
 104 int in_gate_area(struct task_struct *task, unsigned long address)
 105 {
 106         return 0;
 107 }
 108
 109 int in_gate_area_no_task(unsigned long address)
 110 {
 111         return 0;
 112 }