arch/sh/kernel/vsyscall/vsyscall.c

   1 /*
   2  * arch/sh/kernel/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
  21 /*
  22  * Should the kernel map a VDSO page into processes and pass its
  23  * address down to glibc upon exec()?
  24  */
  25 unsigned int __read_mostly vdso_enabled = 1;
  26 EXPORT_SYMBOL_GPL(vdso_enabled);
  27
  28 static int __init vdso_setup(char *s)
  29 {
  30         vdso_enabled = simple_strtoul(s, NULL, 0);
  31         return 1;
  32 }
  33 __setup("vdso=", vdso_setup);
  34
  35 /*
  36  * These symbols are defined by vsyscall.o to mark the bounds
  37  * of the ELF DSO images included therein.
  38  */
  39 extern const char vsyscall_trapa_start, vsyscall_trapa_end;
  40 static void *syscall_page;
  41
  42 int __init vsyscall_init(void)
  43 {
  44         syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);
  45
  46         /*
  47          * XXX: Map this page to a fixmap entry if we get around
  48          * to adding the page to ELF core dumps
  49          */
  50
  51         memcpy(syscall_page,
  52                &vsyscall_trapa_start,
  53                &vsyscall_trapa_end - &vsyscall_trapa_start);
  54
  55         return 0;
  56 }
  57
  58 static struct page *syscall_vma_nopage(struct vm_area_struct *vma,
  59                                        unsigned long address, int *type)
  60 {
  61         unsigned long offset = address - vma->vm_start;
  62         struct page *page;
  63
  64         if (address < vma->vm_start || address > vma->vm_end)
  65                 return NOPAGE_SIGBUS;
  66
  67         page = virt_to_page(syscall_page + offset);
  68
  69         get_page(page);
  70
  71         return page;
  72 }
  73
  74 /* Prevent VMA merging */
  75 static void syscall_vma_close(struct vm_area_struct *vma)
  76 {
  77 }
  78
  79 static struct vm_operations_struct syscall_vm_ops = {
  80         .nopage = syscall_vma_nopage,
  81         .close  = syscall_vma_close,
  82 };
  83
  84 /* Setup a VMA at program startup for the vsyscall page */
  85 int arch_setup_additional_pages(struct linux_binprm *bprm,
  86                                 int executable_stack)
  87 {
  88         struct vm_area_struct *vma;
  89         struct mm_struct *mm = current->mm;
  90         unsigned long addr;
  91         int ret;
  92
  93         down_write(&mm->mmap_sem);
  94         addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
  95         if (IS_ERR_VALUE(addr)) {
  96                 ret = addr;
  97                 goto up_fail;
  98         }
  99
 100         vma = kmem_cache_zalloc(vm_area_cachep, SLAB_KERNEL);
 101         if (!vma) {
 102                 ret = -ENOMEM;
 103                 goto up_fail;
 104         }
 105
 106         vma->vm_start = addr;
 107         vma->vm_end = addr + PAGE_SIZE;
 108         /* MAYWRITE to allow gdb to COW and set breakpoints */
 109         vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYWRITE;
 110         vma->vm_flags |= mm->def_flags;
 111         vma->vm_page_prot = protection_map[vma->vm_flags & 7];
 112         vma->vm_ops = &syscall_vm_ops;
 113         vma->vm_mm = mm;
 114
 115         ret = insert_vm_struct(mm, vma);
 116         if (unlikely(ret)) {
 117                 kmem_cache_free(vm_area_cachep, vma);
 118                 goto up_fail;
 119         }
 120
 121         current->mm->context.vdso = (void *)addr;
 122
 123         mm->total_vm++;
 124 up_fail:
 125         up_write(&mm->mmap_sem);
 126         return ret;
 127 }
 128
 129 const char *arch_vma_name(struct vm_area_struct *vma)
 130 {
 131         if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
 132                 return "[vdso]";
 133
 134         return NULL;
 135 }
 136
 137 struct vm_area_struct *get_gate_vma(struct task_struct *task)
 138 {
 139         return NULL;
 140 }
 141
 142 int in_gate_area(struct task_struct *task, unsigned long address)
 143 {
 144         return 0;
 145 }
 146
 147 int in_gate_area_no_task(unsigned long address)
 148 {
 149         return 0;
 150 }