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/*
* 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;
}
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