linux/arch/sh/kernel/vsyscall/vsyscall.c

/*
 * arch/sh/kernel/vsyscall.c
 *
 *  Copyright (C) 2006 Paul Mundt
 *
 * vDSO randomization
 * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 */
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/gfp.h>
#include <linux/module.h>
#include <linux/elf.h>

/*
 * Should the kernel map a VDSO page into processes and pass its
 * address down to glibc upon exec()?
 */
unsigned int __read_mostly vdso_enabled = 1;
EXPORT_SYMBOL_GPL(vdso_enabled);

static int __init vdso_setup(char *s)
{
	vdso_enabled = simple_strtoul(s, NULL, 0);
	return 1;
}
__setup("vdso=", vdso_setup);

/*
 * These symbols are defined by vsyscall.o to mark the bounds
 * of the ELF DSO images included therein.
 */
extern const char vsyscall_trapa_start, vsyscall_trapa_end;
static void *syscall_page;

int __init vsyscall_init(void)
{
	syscall_page = (void *)get_zeroed_page(GFP_ATOMIC);

	/*
	 * XXX: Map this page to a fixmap entry if we get around
	 * to adding the page to ELF core dumps
	 */

	memcpy(syscall_page,
	       &vsyscall_trapa_start,
	       &vsyscall_trapa_end - &vsyscall_trapa_start);

	return 0;
}

static struct page *syscall_vma_nopage(struct vm_area_struct *vma,
				       unsigned long address, int *type)
{
	unsigned long offset = address - vma->vm_start;
	struct page *page;

	if (address < vma->vm_start || address > vma->vm_end)
		return NOPAGE_SIGBUS;

	page = virt_to_page(syscall_page + offset);

	get_page(page);

	return page;
}

/* Prevent VMA merging */
static void syscall_vma_close(struct vm_area_struct *vma)
{
}

static struct vm_operations_struct syscall_vm_ops = {
	.nopage	= syscall_vma_nopage,
	.close	= syscall_vma_close,
};

/* Setup a VMA at program startup for the vsyscall page */
int arch_setup_additional_pages(struct linux_binprm *bprm,
				int executable_stack)
{
	struct vm_area_struct *vma;
	struct mm_struct *mm = current->mm;
	unsigned long addr;
	int ret;

	down_write(&mm->mmap_sem);
	addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
	if (IS_ERR_VALUE(addr)) {
		ret = addr;
		goto up_fail;
	}

	vma = kmem_cache_zalloc(vm_area_cachep, SLAB_KERNEL);
	if (!vma) {
		ret = -ENOMEM;
		goto up_fail;
	}

	vma->vm_start = addr;
	vma->vm_end = addr + PAGE_SIZE;
	/* MAYWRITE to allow gdb to COW and set breakpoints */
	vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYWRITE;
	vma->vm_flags |= mm->def_flags;
	vma->vm_page_prot = protection_map[vma->vm_flags & 7];
	vma->vm_ops = &syscall_vm_ops;
	vma->vm_mm = mm;

	ret = insert_vm_struct(mm, vma);
	if (unlikely(ret)) {
		kmem_cache_free(vm_area_cachep, vma);
		goto up_fail;
	}

	current->mm->context.vdso = (void *)addr;

	mm->total_vm++;
up_fail:
	up_write(&mm->mmap_sem);
	return ret;
}

const char *arch_vma_name(struct vm_area_struct *vma)
{
	if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
		return "[vdso]";

	return NULL;
}

struct vm_area_struct *get_gate_vma(struct task_struct *task)
{
	return NULL;
}

int in_gate_area(struct task_struct *task, unsigned long address)
{
	return 0;
}

int in_gate_area_no_task(unsigned long address)
{
	return 0;
}