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