vma.c

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/*
 * Copyright (C) 2011 Richard Weinberger <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <asm/page.h>
#include <linux/init.h>

unsigned int __read_mostly vdso_enabled = 1;
unsigned long um_vdso_addr;

extern unsigned long task_size;
extern char vdso_start[], vdso_end[];

static struct page **vdsop;

static int __init init_vdso(void)
{
    struct page *um_vdso;

    BUG_ON(vdso_end - vdso_start > PAGE_SIZE);

    um_vdso_addr = task_size - PAGE_SIZE;

    vdsop = kmalloc(sizeof(struct page *), GFP_KERNEL);
    if (!vdsop)
        goto oom;

    um_vdso = alloc_page(GFP_KERNEL);
    if (!um_vdso) {
        kfree(vdsop);

        goto oom;
    }

    copy_page(page_address(um_vdso), vdso_start);
    *vdsop = um_vdso;

    return 0;

oom:
    printk(KERN_ERR "Cannot allocate vdso\n");
    vdso_enabled = 0;

    return -ENOMEM;
}
subsys_initcall(init_vdso);

int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
    int err;
    struct mm_struct *mm = current->mm;

    if (!vdso_enabled)
        return 0;

    down_write(&mm->mmap_sem);

    err = install_special_mapping(mm, um_vdso_addr, PAGE_SIZE,
        VM_READ|VM_EXEC|
        VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
        vdsop);

    up_write(&mm->mmap_sem);

    return err;
}