base.c

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/*
 *  linux/fs/proc/base.c
 *
 *  Copyright (C) 1991, 1992 Linus Torvalds
 *
 *  proc base directory handling functions
 *
 *  1999, Al Viro. Rewritten. Now it covers the whole per-process part.
 *  Instead of using magical inumbers to determine the kind of object
 *  we allocate and fill in-core inodes upon lookup. They don't even
 *  go into icache. We cache the reference to task_struct upon lookup too.
 *  Eventually it should become a filesystem in its own. We don't use the
 *  rest of procfs anymore.
 *
 *
 *  Changelog:
 *  17-Jan-2005
 *  Allan Bezerra
 *  Bruna Moreira <[email protected]>
 *  Edjard Mota <[email protected]>
 *  Ilias Biris <[email protected]>
 *  Mauricio Lin <[email protected]>
 *
 *  Embedded Linux Lab - 10LE Instituto Nokia de Tecnologia - INdT
 *
 *  A new process specific entry (smaps) included in /proc. It shows the
 *  size of rss for each memory area. The maps entry lacks information
 *  about physical memory size (rss) for each mapped file, i.e.,
 *  rss information for executables and library files.
 *  This additional information is useful for any tools that need to know
 *  about physical memory consumption for a process specific library.
 *
 *  Changelog:
 *  21-Feb-2005
 *  Embedded Linux Lab - 10LE Instituto Nokia de Tecnologia - INdT
 *  Pud inclusion in the page table walking.
 *
 *  ChangeLog:
 *  10-Mar-2005
 *  10LE Instituto Nokia de Tecnologia - INdT:
 *  A better way to walks through the page table as suggested by Hugh Dickins.
 *
 *  Simo Piiroinen <[email protected]>:
 *  Smaps information related to shared, private, clean and dirty pages.
 *
 *  Paul Mundt <[email protected]>:
 *  Overall revision about smaps.
 */

#include <asm/uaccess.h>

#include <linux/errno.h>
#include <linux/time.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/init.h>
#include <linux/capability.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/string.h>
#include <linux/seq_file.h>
#include <linux/namei.h>
#include <linux/mnt_namespace.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/rcupdate.h>
#include <linux/kallsyms.h>
#include <linux/stacktrace.h>
#include <linux/resource.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/ptrace.h>
#include <linux/tracehook.h>
#include <linux/cgroup.h>
#include <linux/cpuset.h>
#include <linux/audit.h>
#include <linux/poll.h>
#include <linux/nsproxy.h>
#include <linux/oom.h>
#include <linux/elf.h>
#include <linux/pid_namespace.h>
#include <linux/user_namespace.h>
#include <linux/fs_struct.h>
#include <linux/slab.h>
#include <linux/flex_array.h>
#ifdef CONFIG_HARDWALL
#include <asm/hardwall.h>
#endif
#include <trace/events/oom.h>
#include "internal.h"
#include "fd.h"

/* NOTE:
 *  Implementing inode permission operations in /proc is almost
 *  certainly an error.  Permission checks need to happen during
 *  each system call not at open time.  The reason is that most of
 *  what we wish to check for permissions in /proc varies at runtime.
 *
 *  The classic example of a problem is opening file descriptors
 *  in /proc for a task before it execs a suid executable.
 */

struct pid_entry {
    char *name;
    int len;
    umode_t mode;
    const struct inode_operations *iop;
    const struct file_operations *fop;
    union proc_op op;
};

#define NOD(NAME, MODE, IOP, FOP, OP) {         \
    .name = (NAME),                 \
    .len  = sizeof(NAME) - 1,           \
    .mode = MODE,                   \
    .iop  = IOP,                    \
    .fop  = FOP,                    \
    .op   = OP,                 \
}

#define DIR(NAME, MODE, iops, fops) \
    NOD(NAME, (S_IFDIR|(MODE)), &iops, &fops, {} )
#define LNK(NAME, get_link)                 \
    NOD(NAME, (S_IFLNK|S_IRWXUGO),              \
        &proc_pid_link_inode_operations, NULL,      \
        { .proc_get_link = get_link } )
#define REG(NAME, MODE, fops)               \
    NOD(NAME, (S_IFREG|(MODE)), NULL, &fops, {})
#define INF(NAME, MODE, read)               \
    NOD(NAME, (S_IFREG|(MODE)),             \
        NULL, &proc_info_file_operations,   \
        { .proc_read = read } )
#define ONE(NAME, MODE, show)               \
    NOD(NAME, (S_IFREG|(MODE)),             \
        NULL, &proc_single_file_operations, \
        { .proc_show = show } )

/*
 * Count the number of hardlinks for the pid_entry table, excluding the .
 * and .. links.
 */
static unsigned int pid_entry_count_dirs(const struct pid_entry *entries,
    unsigned int n)
{
    unsigned int i;
    unsigned int count;

    count = 0;
    for (i = 0; i < n; ++i) {
        if (S_ISDIR(entries[i].mode))
            ++count;
    }

    return count;
}

static int get_task_root(struct task_struct *task, struct path *root)
{
    int result = -ENOENT;

    task_lock(task);
    if (task->fs) {
        get_fs_root(task->fs, root);
        result = 0;
    }
    task_unlock(task);
    return result;
}

static int proc_cwd_link(struct dentry *dentry, struct path *path)
{
    struct task_struct *task = get_proc_task(dentry->d_inode);
    int result = -ENOENT;

    if (task) {
        task_lock(task);
        if (task->fs) {
            get_fs_pwd(task->fs, path);
            result = 0;
        }
        task_unlock(task);
        put_task_struct(task);
    }
    return result;
}

static int proc_root_link(struct dentry *dentry, struct path *path)
{
    struct task_struct *task = get_proc_task(dentry->d_inode);
    int result = -ENOENT;

    if (task) {
        result = get_task_root(task, path);
        put_task_struct(task);
    }
    return result;
}

static int proc_pid_cmdline(struct task_struct *task, char * buffer)
{
    int res = 0;
    unsigned int len;
    struct mm_struct *mm = get_task_mm(task);
    if (!mm)
        goto out;
    if (!mm->arg_end)
        goto out_mm;    /* Shh! No looking before we're done */

    len = mm->arg_end - mm->arg_start;
 
    if (len > PAGE_SIZE)
        len = PAGE_SIZE;
 
    res = access_process_vm(task, mm->arg_start, buffer, len, 0);

    // If the nul at the end of args has been overwritten, then
    // assume application is using setproctitle(3).
    if (res > 0 && buffer[res-1] != '\0' && len < PAGE_SIZE) {
        len = strnlen(buffer, res);
        if (len < res) {
            res = len;
        } else {
            len = mm->env_end - mm->env_start;
            if (len > PAGE_SIZE - res)
                len = PAGE_SIZE - res;
            res += access_process_vm(task, mm->env_start, buffer+res, len, 0);
            res = strnlen(buffer, res);
        }
    }
out_mm:
    mmput(mm);
out:
    return res;
}

static int proc_pid_auxv(struct task_struct *task, char *buffer)
{
    struct mm_struct *mm = mm_access(task, PTRACE_MODE_READ);
    int res = PTR_ERR(mm);
    if (mm && !IS_ERR(mm)) {
        unsigned int nwords = 0;
        do {
            nwords += 2;
        } while (mm->saved_auxv[nwords - 2] != 0); /* AT_NULL */
        res = nwords * sizeof(mm->saved_auxv[0]);
        if (res > PAGE_SIZE)
            res = PAGE_SIZE;
        memcpy(buffer, mm->saved_auxv, res);
        mmput(mm);
    }
    return res;
}


#ifdef CONFIG_KALLSYMS
/*
 * Provides a wchan file via kallsyms in a proper one-value-per-file format.
 * Returns the resolved symbol.  If that fails, simply return the address.
 */
static int proc_pid_wchan(struct task_struct *task, char *buffer)
{
    unsigned long wchan;
    char symname[KSYM_NAME_LEN];

    wchan = get_wchan(task);

    if (lookup_symbol_name(wchan, symname) < 0)
        if (!ptrace_may_access(task, PTRACE_MODE_READ))
            return 0;
        else
            return sprintf(buffer, "%lu", wchan);
    else
        return sprintf(buffer, "%s", symname);
}
#endif /* CONFIG_KALLSYMS */

static int lock_trace(struct task_struct *task)
{
    int err = mutex_lock_killable(&task->signal->cred_guard_mutex);
    if (err)
        return err;
    if (!ptrace_may_access(task, PTRACE_MODE_ATTACH)) {
        mutex_unlock(&task->signal->cred_guard_mutex);
        return -EPERM;
    }
    return 0;
}

static void unlock_trace(struct task_struct *task)
{
    mutex_unlock(&task->signal->cred_guard_mutex);
}

#ifdef CONFIG_STACKTRACE

#define MAX_STACK_TRACE_DEPTH   64

static int proc_pid_stack(struct seq_file *m, struct pid_namespace *ns,
              struct pid *pid, struct task_struct *task)
{
    struct stack_trace trace;
    unsigned long *entries;
    int err;
    int i;

    entries = kmalloc(MAX_STACK_TRACE_DEPTH * sizeof(*entries), GFP_KERNEL);
    if (!entries)
        return -ENOMEM;

    trace.nr_entries    = 0;
    trace.max_entries   = MAX_STACK_TRACE_DEPTH;
    trace.entries       = entries;
    trace.skip      = 0;

    err = lock_trace(task);
    if (!err) {
        save_stack_trace_tsk(task, &trace);

        for (i = 0; i < trace.nr_entries; i++) {
            seq_printf(m, "[<%pK>] %pS\n",
                   (void *)entries[i], (void *)entries[i]);
        }
        unlock_trace(task);
    }
    kfree(entries);

    return err;
}
#endif

#ifdef CONFIG_SCHEDSTATS
/*
 * Provides /proc/PID/schedstat
 */
static int proc_pid_schedstat(struct task_struct *task, char *buffer)
{
    return sprintf(buffer, "%llu %llu %lu\n",
            (unsigned long long)task->se.sum_exec_runtime,
            (unsigned long long)task->sched_info.run_delay,
            task->sched_info.pcount);
}
#endif

#ifdef CONFIG_LATENCYTOP
static int lstats_show_proc(struct seq_file *m, void *v)
{
    int i;
    struct inode *inode = m->private;
    struct task_struct *task = get_proc_task(inode);

    if (!task)
        return -ESRCH;
    seq_puts(m, "Latency Top version : v0.1\n");
    for (i = 0; i < 32; i++) {
        struct latency_record *lr = &task->latency_record[i];
        if (lr->backtrace[0]) {
            int q;
            seq_printf(m, "%i %li %li",
                   lr->count, lr->time, lr->max);
            for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
                unsigned long bt = lr->backtrace[q];
                if (!bt)
                    break;
                if (bt == ULONG_MAX)
                    break;
                seq_printf(m, " %ps", (void *)bt);
            }
            seq_putc(m, '\n');
        }

    }
    put_task_struct(task);
    return 0;
}

static int lstats_open(struct inode *inode, struct file *file)
{
    return single_open(file, lstats_show_proc, inode);
}

static ssize_t lstats_write(struct file *file, const char __user *buf,
                size_t count, loff_t *offs)
{
    struct task_struct *task = get_proc_task(file->f_dentry->d_inode);

    if (!task)
        return -ESRCH;
    clear_all_latency_tracing(task);
    put_task_struct(task);

    return count;
}

static const struct file_operations proc_lstats_operations = {
    .open       = lstats_open,
    .read       = seq_read,
    .write      = lstats_write,
    .llseek     = seq_lseek,
    .release    = single_release,
};

#endif

static int proc_oom_score(struct task_struct *task, char *buffer)
{
    unsigned long totalpages = totalram_pages + total_swap_pages;
    unsigned long points = 0;

    read_lock(&tasklist_lock);
    if (pid_alive(task))
        points = oom_badness(task, NULL, NULL, totalpages) *
                        1000 / totalpages;
    read_unlock(&tasklist_lock);
    return sprintf(buffer, "%lu\n", points);
}

struct limit_names {
    char *name;
    char *unit;
};

static const struct limit_names lnames[RLIM_NLIMITS] = {
    [RLIMIT_CPU] = {"Max cpu time", "seconds"},
    [RLIMIT_FSIZE] = {"Max file size", "bytes"},
    [RLIMIT_DATA] = {"Max data size", "bytes"},
    [RLIMIT_STACK] = {"Max stack size", "bytes"},
    [RLIMIT_CORE] = {"Max core file size", "bytes"},
    [RLIMIT_RSS] = {"Max resident set", "bytes"},
    [RLIMIT_NPROC] = {"Max processes", "processes"},
    [RLIMIT_NOFILE] = {"Max open files", "files"},
    [RLIMIT_MEMLOCK] = {"Max locked memory", "bytes"},
    [RLIMIT_AS] = {"Max address space", "bytes"},
    [RLIMIT_LOCKS] = {"Max file locks", "locks"},
    [RLIMIT_SIGPENDING] = {"Max pending signals", "signals"},
    [RLIMIT_MSGQUEUE] = {"Max msgqueue size", "bytes"},
    [RLIMIT_NICE] = {"Max nice priority", NULL},
    [RLIMIT_RTPRIO] = {"Max realtime priority", NULL},
    [RLIMIT_RTTIME] = {"Max realtime timeout", "us"},
};

/* Display limits for a process */
static int proc_pid_limits(struct task_struct *task, char *buffer)
{
    unsigned int i;
    int count = 0;
    unsigned long flags;
    char *bufptr = buffer;

    struct rlimit rlim[RLIM_NLIMITS];

    if (!lock_task_sighand(task, &flags))
        return 0;
    memcpy(rlim, task->signal->rlim, sizeof(struct rlimit) * RLIM_NLIMITS);
    unlock_task_sighand(task, &flags);

    /*
     * print the file header
     */
    count += sprintf(&bufptr[count], "%-25s %-20s %-20s %-10s\n",
            "Limit", "Soft Limit", "Hard Limit", "Units");

    for (i = 0; i < RLIM_NLIMITS; i++) {
        if (rlim[i].rlim_cur == RLIM_INFINITY)
            count += sprintf(&bufptr[count], "%-25s %-20s ",
                     lnames[i].name, "unlimited");
        else
            count += sprintf(&bufptr[count], "%-25s %-20lu ",
                     lnames[i].name, rlim[i].rlim_cur);

        if (rlim[i].rlim_max == RLIM_INFINITY)
            count += sprintf(&bufptr[count], "%-20s ", "unlimited");
        else
            count += sprintf(&bufptr[count], "%-20lu ",
                     rlim[i].rlim_max);

        if (lnames[i].unit)
            count += sprintf(&bufptr[count], "%-10s\n",
                     lnames[i].unit);
        else
            count += sprintf(&bufptr[count], "\n");
    }

    return count;
}

#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
static int proc_pid_syscall(struct task_struct *task, char *buffer)
{
    long nr;
    unsigned long args[6], sp, pc;
    int res = lock_trace(task);
    if (res)
        return res;

    if (task_current_syscall(task, &nr, args, 6, &sp, &pc))
        res = sprintf(buffer, "running\n");
    else if (nr < 0)
        res = sprintf(buffer, "%ld 0x%lx 0x%lx\n", nr, sp, pc);
    else
        res = sprintf(buffer,
               "%ld 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx\n",
               nr,
               args[0], args[1], args[2], args[3], args[4], args[5],
               sp, pc);
    unlock_trace(task);
    return res;
}
#endif /* CONFIG_HAVE_ARCH_TRACEHOOK */

/************************************************************************/
/*                       Here the fs part begins                        */
/************************************************************************/

/* permission checks */
static int proc_fd_access_allowed(struct inode *inode)
{
    struct task_struct *task;
    int allowed = 0;
    /* Allow access to a task's file descriptors if it is us or we
     * may use ptrace attach to the process and find out that
     * information.
     */
    task = get_proc_task(inode);
    if (task) {
        allowed = ptrace_may_access(task, PTRACE_MODE_READ);
        put_task_struct(task);
    }
    return allowed;
}

int proc_setattr(struct dentry *dentry, struct iattr *attr)
{
    int error;
    struct inode *inode = dentry->d_inode;

    if (attr->ia_valid & ATTR_MODE)
        return -EPERM;

    error = inode_change_ok(inode, attr);
    if (error)
        return error;

    if ((attr->ia_valid & ATTR_SIZE) &&
        attr->ia_size != i_size_read(inode)) {
        error = vmtruncate(inode, attr->ia_size);
        if (error)
            return error;
    }

    setattr_copy(inode, attr);
    mark_inode_dirty(inode);
    return 0;
}

/*
 * May current process learn task's sched/cmdline info (for hide_pid_min=1)
 * or euid/egid (for hide_pid_min=2)?
 */
static bool has_pid_permissions(struct pid_namespace *pid,
                 struct task_struct *task,
                 int hide_pid_min)
{
    if (pid->hide_pid < hide_pid_min)
        return true;
    if (in_group_p(pid->pid_gid))
        return true;
    return ptrace_may_access(task, PTRACE_MODE_READ);
}


static int proc_pid_permission(struct inode *inode, int mask)
{
    struct pid_namespace *pid = inode->i_sb->s_fs_info;
    struct task_struct *task;
    bool has_perms;

    task = get_proc_task(inode);
    if (!task)
        return -ESRCH;
    has_perms = has_pid_permissions(pid, task, 1);
    put_task_struct(task);

    if (!has_perms) {
        if (pid->hide_pid == 2) {
            /*
             * Let's make getdents(), stat(), and open()
             * consistent with each other.  If a process
             * may not stat() a file, it shouldn't be seen
             * in procfs at all.
             */
            return -ENOENT;
        }

        return -EPERM;
    }
    return generic_permission(inode, mask);
}



static const struct inode_operations proc_def_inode_operations = {
    .setattr    = proc_setattr,
};

#define PROC_BLOCK_SIZE (3*1024)        /* 4K page size but our output routines use some slack for overruns */

static ssize_t proc_info_read(struct file * file, char __user * buf,
              size_t count, loff_t *ppos)
{
    struct inode * inode = file->f_path.dentry->d_inode;
    unsigned long page;
    ssize_t length;
    struct task_struct *task = get_proc_task(inode);

    length = -ESRCH;
    if (!task)
        goto out_no_task;

    if (count > PROC_BLOCK_SIZE)
        count = PROC_BLOCK_SIZE;

    length = -ENOMEM;
    if (!(page = __get_free_page(GFP_TEMPORARY)))
        goto out;

    length = PROC_I(inode)->op.proc_read(task, (char*)page);

    if (length >= 0)
        length = simple_read_from_buffer(buf, count, ppos, (char *)page, length);
    free_page(page);
out:
    put_task_struct(task);
out_no_task:
    return length;
}

static const struct file_operations proc_info_file_operations = {
    .read       = proc_info_read,
    .llseek     = generic_file_llseek,
};

static int proc_single_show(struct seq_file *m, void *v)
{
    struct inode *inode = m->private;
    struct pid_namespace *ns;
    struct pid *pid;
    struct task_struct *task;
    int ret;

    ns = inode->i_sb->s_fs_info;
    pid = proc_pid(inode);
    task = get_pid_task(pid, PIDTYPE_PID);
    if (!task)
        return -ESRCH;

    ret = PROC_I(inode)->op.proc_show(m, ns, pid, task);

    put_task_struct(task);
    return ret;
}

static int proc_single_open(struct inode *inode, struct file *filp)
{
    return single_open(filp, proc_single_show, inode);
}

static const struct file_operations proc_single_file_operations = {
    .open       = proc_single_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = single_release,
};

static int __mem_open(struct inode *inode, struct file *file, unsigned int mode)
{
    struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
    struct mm_struct *mm;

    if (!task)
        return -ESRCH;

    mm = mm_access(task, mode);
    put_task_struct(task);

    if (IS_ERR(mm))
        return PTR_ERR(mm);

    if (mm) {
        /* ensure this mm_struct can't be freed */
        atomic_inc(&mm->mm_count);
        /* but do not pin its memory */
        mmput(mm);
    }

    file->private_data = mm;

    return 0;
}

static int mem_open(struct inode *inode, struct file *file)
{
    int ret = __mem_open(inode, file, PTRACE_MODE_ATTACH);

    /* OK to pass negative loff_t, we can catch out-of-range */
    file->f_mode |= FMODE_UNSIGNED_OFFSET;

    return ret;
}

static ssize_t mem_rw(struct file *file, char __user *buf,
            size_t count, loff_t *ppos, int write)
{
    struct mm_struct *mm = file->private_data;
    unsigned long addr = *ppos;
    ssize_t copied;
    char *page;

    if (!mm)
        return 0;

    page = (char *)__get_free_page(GFP_TEMPORARY);
    if (!page)
        return -ENOMEM;

    copied = 0;
    if (!atomic_inc_not_zero(&mm->mm_users))
        goto free;

    while (count > 0) {
        int this_len = min_t(int, count, PAGE_SIZE);

        if (write && copy_from_user(page, buf, this_len)) {
            copied = -EFAULT;
            break;
        }

        this_len = access_remote_vm(mm, addr, page, this_len, write);
        if (!this_len) {
            if (!copied)
                copied = -EIO;
            break;
        }

        if (!write && copy_to_user(buf, page, this_len)) {
            copied = -EFAULT;
            break;
        }

        buf += this_len;
        addr += this_len;
        copied += this_len;
        count -= this_len;
    }
    *ppos = addr;

    mmput(mm);
free:
    free_page((unsigned long) page);
    return copied;
}

static ssize_t mem_read(struct file *file, char __user *buf,
            size_t count, loff_t *ppos)
{
    return mem_rw(file, buf, count, ppos, 0);
}

static ssize_t mem_write(struct file *file, const char __user *buf,
             size_t count, loff_t *ppos)
{
    return mem_rw(file, (char __user*)buf, count, ppos, 1);
}

loff_t mem_lseek(struct file *file, loff_t offset, int orig)
{
    switch (orig) {
    case 0:
        file->f_pos = offset;
        break;
    case 1:
        file->f_pos += offset;
        break;
    default:
        return -EINVAL;
    }
    force_successful_syscall_return();
    return file->f_pos;
}

static int mem_release(struct inode *inode, struct file *file)
{
    struct mm_struct *mm = file->private_data;
    if (mm)
        mmdrop(mm);
    return 0;
}

static const struct file_operations proc_mem_operations = {
    .llseek     = mem_lseek,
    .read       = mem_read,
    .write      = mem_write,
    .open       = mem_open,
    .release    = mem_release,
};

static int environ_open(struct inode *inode, struct file *file)
{
    return __mem_open(inode, file, PTRACE_MODE_READ);
}

static ssize_t environ_read(struct file *file, char __user *buf,
            size_t count, loff_t *ppos)
{
    char *page;
    unsigned long src = *ppos;
    int ret = 0;
    struct mm_struct *mm = file->private_data;

    if (!mm)
        return 0;

    page = (char *)__get_free_page(GFP_TEMPORARY);
    if (!page)
        return -ENOMEM;

    ret = 0;
    if (!atomic_inc_not_zero(&mm->mm_users))
        goto free;
    while (count > 0) {
        size_t this_len, max_len;
        int retval;

        if (src >= (mm->env_end - mm->env_start))
            break;

        this_len = mm->env_end - (mm->env_start + src);

        max_len = min_t(size_t, PAGE_SIZE, count);
        this_len = min(max_len, this_len);

        retval = access_remote_vm(mm, (mm->env_start + src),
            page, this_len, 0);

        if (retval <= 0) {
            ret = retval;
            break;
        }

        if (copy_to_user(buf, page, retval)) {
            ret = -EFAULT;
            break;
        }

        ret += retval;
        src += retval;
        buf += retval;
        count -= retval;
    }
    *ppos = src;
    mmput(mm);

free:
    free_page((unsigned long) page);
    return ret;
}

static const struct file_operations proc_environ_operations = {
    .open       = environ_open,
    .read       = environ_read,
    .llseek     = generic_file_llseek,
    .release    = mem_release,
};

static ssize_t oom_adj_read(struct file *file, char __user *buf, size_t count,
                loff_t *ppos)
{
    struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
    char buffer[PROC_NUMBUF];
    int oom_adj = OOM_ADJUST_MIN;
    size_t len;
    unsigned long flags;

    if (!task)
        return -ESRCH;
    if (lock_task_sighand(task, &flags)) {
        if (task->signal->oom_score_adj == OOM_SCORE_ADJ_MAX)
            oom_adj = OOM_ADJUST_MAX;
        else
            oom_adj = (task->signal->oom_score_adj * -OOM_DISABLE) /
                  OOM_SCORE_ADJ_MAX;
        unlock_task_sighand(task, &flags);
    }
    put_task_struct(task);
    len = snprintf(buffer, sizeof(buffer), "%d\n", oom_adj);
    return simple_read_from_buffer(buf, count, ppos, buffer, len);
}

static ssize_t oom_adj_write(struct file *file, const char __user *buf,
                 size_t count, loff_t *ppos)
{
    struct task_struct *task;
    char buffer[PROC_NUMBUF];
    int oom_adj;
    unsigned long flags;
    int err;

    memset(buffer, 0, sizeof(buffer));
    if (count > sizeof(buffer) - 1)
        count = sizeof(buffer) - 1;
    if (copy_from_user(buffer, buf, count)) {
        err = -EFAULT;
        goto out;
    }

    err = kstrtoint(strstrip(buffer), 0, &oom_adj);
    if (err)
        goto out;
    if ((oom_adj < OOM_ADJUST_MIN || oom_adj > OOM_ADJUST_MAX) &&
         oom_adj != OOM_DISABLE) {
        err = -EINVAL;
        goto out;
    }

    task = get_proc_task(file->f_path.dentry->d_inode);
    if (!task) {
        err = -ESRCH;
        goto out;
    }

    task_lock(task);
    if (!task->mm) {
        err = -EINVAL;
        goto err_task_lock;
    }

    if (!lock_task_sighand(task, &flags)) {
        err = -ESRCH;
        goto err_task_lock;
    }

    /*
     * Scale /proc/pid/oom_score_adj appropriately ensuring that a maximum
     * value is always attainable.
     */
    if (oom_adj == OOM_ADJUST_MAX)
        oom_adj = OOM_SCORE_ADJ_MAX;
    else
        oom_adj = (oom_adj * OOM_SCORE_ADJ_MAX) / -OOM_DISABLE;

    if (oom_adj < task->signal->oom_score_adj &&
        !capable(CAP_SYS_RESOURCE)) {
        err = -EACCES;
        goto err_sighand;
    }

    /*
     * /proc/pid/oom_adj is provided for legacy purposes, ask users to use
     * /proc/pid/oom_score_adj instead.
     */
    printk_once(KERN_WARNING "%s (%d): /proc/%d/oom_adj is deprecated, please use /proc/%d/oom_score_adj instead.\n",
          current->comm, task_pid_nr(current), task_pid_nr(task),
          task_pid_nr(task));

    task->signal->oom_score_adj = oom_adj;
    trace_oom_score_adj_update(task);
err_sighand:
    unlock_task_sighand(task, &flags);
err_task_lock:
    task_unlock(task);
    put_task_struct(task);
out:
    return err < 0 ? err : count;
}

static const struct file_operations proc_oom_adj_operations = {
    .read       = oom_adj_read,
    .write      = oom_adj_write,
    .llseek     = generic_file_llseek,
};

static ssize_t oom_score_adj_read(struct file *file, char __user *buf,
                    size_t count, loff_t *ppos)
{
    struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
    char buffer[PROC_NUMBUF];
    int oom_score_adj = OOM_SCORE_ADJ_MIN;
    unsigned long flags;
    size_t len;

    if (!task)
        return -ESRCH;
    if (lock_task_sighand(task, &flags)) {
        oom_score_adj = task->signal->oom_score_adj;
        unlock_task_sighand(task, &flags);
    }
    put_task_struct(task);
    len = snprintf(buffer, sizeof(buffer), "%d\n", oom_score_adj);
    return simple_read_from_buffer(buf, count, ppos, buffer, len);
}

static ssize_t oom_score_adj_write(struct file *file, const char __user *buf,
                    size_t count, loff_t *ppos)
{
    struct task_struct *task;
    char buffer[PROC_NUMBUF];
    unsigned long flags;
    int oom_score_adj;
    int err;

    memset(buffer, 0, sizeof(buffer));
    if (count > sizeof(buffer) - 1)
        count = sizeof(buffer) - 1;
    if (copy_from_user(buffer, buf, count)) {
        err = -EFAULT;
        goto out;
    }

    err = kstrtoint(strstrip(buffer), 0, &oom_score_adj);
    if (err)
        goto out;
    if (oom_score_adj < OOM_SCORE_ADJ_MIN ||
            oom_score_adj > OOM_SCORE_ADJ_MAX) {
        err = -EINVAL;
        goto out;
    }

    task = get_proc_task(file->f_path.dentry->d_inode);
    if (!task) {
        err = -ESRCH;
        goto out;
    }

    task_lock(task);
    if (!task->mm) {
        err = -EINVAL;
        goto err_task_lock;
    }

    if (!lock_task_sighand(task, &flags)) {
        err = -ESRCH;
        goto err_task_lock;
    }

    if (oom_score_adj < task->signal->oom_score_adj_min &&
            !capable(CAP_SYS_RESOURCE)) {
        err = -EACCES;
        goto err_sighand;
    }

    task->signal->oom_score_adj = oom_score_adj;
    if (has_capability_noaudit(current, CAP_SYS_RESOURCE))
        task->signal->oom_score_adj_min = oom_score_adj;
    trace_oom_score_adj_update(task);

err_sighand:
    unlock_task_sighand(task, &flags);
err_task_lock:
    task_unlock(task);
    put_task_struct(task);
out:
    return err < 0 ? err : count;
}

static const struct file_operations proc_oom_score_adj_operations = {
    .read       = oom_score_adj_read,
    .write      = oom_score_adj_write,
    .llseek     = default_llseek,
};

#ifdef CONFIG_AUDITSYSCALL
#define TMPBUFLEN 21
static ssize_t proc_loginuid_read(struct file * file, char __user * buf,
                  size_t count, loff_t *ppos)
{
    struct inode * inode = file->f_path.dentry->d_inode;
    struct task_struct *task = get_proc_task(inode);
    ssize_t length;
    char tmpbuf[TMPBUFLEN];

    if (!task)
        return -ESRCH;
    length = scnprintf(tmpbuf, TMPBUFLEN, "%u",
               from_kuid(file->f_cred->user_ns,
                     audit_get_loginuid(task)));
    put_task_struct(task);
    return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
}

static ssize_t proc_loginuid_write(struct file * file, const char __user * buf,
                   size_t count, loff_t *ppos)
{
    struct inode * inode = file->f_path.dentry->d_inode;
    char *page, *tmp;
    ssize_t length;
    uid_t loginuid;
    kuid_t kloginuid;

    rcu_read_lock();
    if (current != pid_task(proc_pid(inode), PIDTYPE_PID)) {
        rcu_read_unlock();
        return -EPERM;
    }
    rcu_read_unlock();

    if (count >= PAGE_SIZE)
        count = PAGE_SIZE - 1;

    if (*ppos != 0) {
        /* No partial writes. */
        return -EINVAL;
    }
    page = (char*)__get_free_page(GFP_TEMPORARY);
    if (!page)
        return -ENOMEM;
    length = -EFAULT;
    if (copy_from_user(page, buf, count))
        goto out_free_page;

    page[count] = '\0';
    loginuid = simple_strtoul(page, &tmp, 10);
    if (tmp == page) {
        length = -EINVAL;
        goto out_free_page;

    }
    kloginuid = make_kuid(file->f_cred->user_ns, loginuid);
    if (!uid_valid(kloginuid)) {
        length = -EINVAL;
        goto out_free_page;
    }

    length = audit_set_loginuid(kloginuid);
    if (likely(length == 0))
        length = count;

out_free_page:
    free_page((unsigned long) page);
    return length;
}

static const struct file_operations proc_loginuid_operations = {
    .read       = proc_loginuid_read,
    .write      = proc_loginuid_write,
    .llseek     = generic_file_llseek,
};

static ssize_t proc_sessionid_read(struct file * file, char __user * buf,
                  size_t count, loff_t *ppos)
{
    struct inode * inode = file->f_path.dentry->d_inode;
    struct task_struct *task = get_proc_task(inode);
    ssize_t length;
    char tmpbuf[TMPBUFLEN];

    if (!task)
        return -ESRCH;
    length = scnprintf(tmpbuf, TMPBUFLEN, "%u",
                audit_get_sessionid(task));
    put_task_struct(task);
    return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
}

static const struct file_operations proc_sessionid_operations = {
    .read       = proc_sessionid_read,
    .llseek     = generic_file_llseek,
};
#endif

#ifdef CONFIG_FAULT_INJECTION
static ssize_t proc_fault_inject_read(struct file * file, char __user * buf,
                      size_t count, loff_t *ppos)
{
    struct task_struct *task = get_proc_task(file->f_dentry->d_inode);
    char buffer[PROC_NUMBUF];
    size_t len;
    int make_it_fail;

    if (!task)
        return -ESRCH;
    make_it_fail = task->make_it_fail;
    put_task_struct(task);

    len = snprintf(buffer, sizeof(buffer), "%i\n", make_it_fail);

    return simple_read_from_buffer(buf, count, ppos, buffer, len);
}

static ssize_t proc_fault_inject_write(struct file * file,
            const char __user * buf, size_t count, loff_t *ppos)
{
    struct task_struct *task;
    char buffer[PROC_NUMBUF], *end;
    int make_it_fail;

    if (!capable(CAP_SYS_RESOURCE))
        return -EPERM;
    memset(buffer, 0, sizeof(buffer));
    if (count > sizeof(buffer) - 1)
        count = sizeof(buffer) - 1;
    if (copy_from_user(buffer, buf, count))
        return -EFAULT;
    make_it_fail = simple_strtol(strstrip(buffer), &end, 0);
    if (*end)
        return -EINVAL;
    task = get_proc_task(file->f_dentry->d_inode);
    if (!task)
        return -ESRCH;
    task->make_it_fail = make_it_fail;
    put_task_struct(task);

    return count;
}

static const struct file_operations proc_fault_inject_operations = {
    .read       = proc_fault_inject_read,
    .write      = proc_fault_inject_write,
    .llseek     = generic_file_llseek,
};
#endif


#ifdef CONFIG_SCHED_DEBUG
/*
 * Print out various scheduling related per-task fields:
 */
static int sched_show(struct seq_file *m, void *v)
{
    struct inode *inode = m->private;
    struct task_struct *p;

    p = get_proc_task(inode);
    if (!p)
        return -ESRCH;
    proc_sched_show_task(p, m);

    put_task_struct(p);

    return 0;
}

static ssize_t
sched_write(struct file *file, const char __user *buf,
        size_t count, loff_t *offset)
{
    struct inode *inode = file->f_path.dentry->d_inode;
    struct task_struct *p;

    p = get_proc_task(inode);
    if (!p)
        return -ESRCH;
    proc_sched_set_task(p);

    put_task_struct(p);

    return count;
}

static int sched_open(struct inode *inode, struct file *filp)
{
    return single_open(filp, sched_show, inode);
}

static const struct file_operations proc_pid_sched_operations = {
    .open       = sched_open,
    .read       = seq_read,
    .write      = sched_write,
    .llseek     = seq_lseek,
    .release    = single_release,
};

#endif

#ifdef CONFIG_SCHED_AUTOGROUP
/*
 * Print out autogroup related information:
 */
static int sched_autogroup_show(struct seq_file *m, void *v)
{
    struct inode *inode = m->private;
    struct task_struct *p;

    p = get_proc_task(inode);
    if (!p)
        return -ESRCH;
    proc_sched_autogroup_show_task(p, m);

    put_task_struct(p);

    return 0;
}

static ssize_t
sched_autogroup_write(struct file *file, const char __user *buf,
        size_t count, loff_t *offset)
{
    struct inode *inode = file->f_path.dentry->d_inode;
    struct task_struct *p;
    char buffer[PROC_NUMBUF];
    int nice;
    int err;

    memset(buffer, 0, sizeof(buffer));
    if (count > sizeof(buffer) - 1)
        count = sizeof(buffer) - 1;
    if (copy_from_user(buffer, buf, count))
        return -EFAULT;

    err = kstrtoint(strstrip(buffer), 0, &nice);
    if (err < 0)
        return err;

    p = get_proc_task(inode);
    if (!p)
        return -ESRCH;

    err = proc_sched_autogroup_set_nice(p, nice);
    if (err)
        count = err;

    put_task_struct(p);

    return count;
}

static int sched_autogroup_open(struct inode *inode, struct file *filp)
{
    int ret;

    ret = single_open(filp, sched_autogroup_show, NULL);
    if (!ret) {
        struct seq_file *m = filp->private_data;

        m->private = inode;
    }
    return ret;
}

static const struct file_operations proc_pid_sched_autogroup_operations = {
    .open       = sched_autogroup_open,
    .read       = seq_read,
    .write      = sched_autogroup_write,
    .llseek     = seq_lseek,
    .release    = single_release,
};

#endif /* CONFIG_SCHED_AUTOGROUP */

static ssize_t comm_write(struct file *file, const char __user *buf,
                size_t count, loff_t *offset)
{
    struct inode *inode = file->f_path.dentry->d_inode;
    struct task_struct *p;
    char buffer[TASK_COMM_LEN];

    memset(buffer, 0, sizeof(buffer));
    if (count > sizeof(buffer) - 1)
        count = sizeof(buffer) - 1;
    if (copy_from_user(buffer, buf, count))
        return -EFAULT;

    p = get_proc_task(inode);
    if (!p)
        return -ESRCH;

    if (same_thread_group(current, p))
        set_task_comm(p, buffer);
    else
        count = -EINVAL;

    put_task_struct(p);

    return count;
}

static int comm_show(struct seq_file *m, void *v)
{
    struct inode *inode = m->private;
    struct task_struct *p;

    p = get_proc_task(inode);
    if (!p)
        return -ESRCH;

    task_lock(p);
    seq_printf(m, "%s\n", p->comm);
    task_unlock(p);

    put_task_struct(p);

    return 0;
}

static int comm_open(struct inode *inode, struct file *filp)
{
    return single_open(filp, comm_show, inode);
}

static const struct file_operations proc_pid_set_comm_operations = {
    .open       = comm_open,
    .read       = seq_read,
    .write      = comm_write,
    .llseek     = seq_lseek,
    .release    = single_release,
};

static int proc_exe_link(struct dentry *dentry, struct path *exe_path)
{
    struct task_struct *task;
    struct mm_struct *mm;
    struct file *exe_file;

    task = get_proc_task(dentry->d_inode);
    if (!task)
        return -ENOENT;
    mm = get_task_mm(task);
    put_task_struct(task);
    if (!mm)
        return -ENOENT;
    exe_file = get_mm_exe_file(mm);
    mmput(mm);
    if (exe_file) {
        *exe_path = exe_file->f_path;
        path_get(&exe_file->f_path);
        fput(exe_file);
        return 0;
    } else
        return -ENOENT;
}

static void *proc_pid_follow_link(struct dentry *dentry, struct nameidata *nd)
{
    struct inode *inode = dentry->d_inode;
    struct path path;
    int error = -EACCES;

    /* Are we allowed to snoop on the tasks file descriptors? */
    if (!proc_fd_access_allowed(inode))
        goto out;

    error = PROC_I(inode)->op.proc_get_link(dentry, &path);
    if (error)
        goto out;

    nd_jump_link(nd, &path);
    return NULL;
out:
    return ERR_PTR(error);
}

static int do_proc_readlink(struct path *path, char __user *buffer, int buflen)
{
    char *tmp = (char*)__get_free_page(GFP_TEMPORARY);
    char *pathname;
    int len;

    if (!tmp)
        return -ENOMEM;

    pathname = d_path(path, tmp, PAGE_SIZE);
    len = PTR_ERR(pathname);
    if (IS_ERR(pathname))
        goto out;
    len = tmp + PAGE_SIZE - 1 - pathname;

    if (len > buflen)
        len = buflen;
    if (copy_to_user(buffer, pathname, len))
        len = -EFAULT;
 out:
    free_page((unsigned long)tmp);
    return len;
}

static int proc_pid_readlink(struct dentry * dentry, char __user * buffer, int buflen)
{
    int error = -EACCES;
    struct inode *inode = dentry->d_inode;
    struct path path;

    /* Are we allowed to snoop on the tasks file descriptors? */
    if (!proc_fd_access_allowed(inode))
        goto out;

    error = PROC_I(inode)->op.proc_get_link(dentry, &path);
    if (error)
        goto out;

    error = do_proc_readlink(&path, buffer, buflen);
    path_put(&path);
out:
    return error;
}

const struct inode_operations proc_pid_link_inode_operations = {
    .readlink   = proc_pid_readlink,
    .follow_link    = proc_pid_follow_link,
    .setattr    = proc_setattr,
};


/* building an inode */

struct inode *proc_pid_make_inode(struct super_block * sb, struct task_struct *task)
{
    struct inode * inode;
    struct proc_inode *ei;
    const struct cred *cred;

    /* We need a new inode */

    inode = new_inode(sb);
    if (!inode)
        goto out;

    /* Common stuff */
    ei = PROC_I(inode);
    inode->i_ino = get_next_ino();
    inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
    inode->i_op = &proc_def_inode_operations;

    /*
     * grab the reference to task.
     */
    ei->pid = get_task_pid(task, PIDTYPE_PID);
    if (!ei->pid)
        goto out_unlock;

    if (task_dumpable(task)) {
        rcu_read_lock();
        cred = __task_cred(task);
        inode->i_uid = cred->euid;
        inode->i_gid = cred->egid;
        rcu_read_unlock();
    }
    security_task_to_inode(task, inode);

out:
    return inode;

out_unlock:
    iput(inode);
    return NULL;
}

int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
{
    struct inode *inode = dentry->d_inode;
    struct task_struct *task;
    const struct cred *cred;
    struct pid_namespace *pid = dentry->d_sb->s_fs_info;

    generic_fillattr(inode, stat);

    rcu_read_lock();
    stat->uid = GLOBAL_ROOT_UID;
    stat->gid = GLOBAL_ROOT_GID;
    task = pid_task(proc_pid(inode), PIDTYPE_PID);
    if (task) {
        if (!has_pid_permissions(pid, task, 2)) {
            rcu_read_unlock();
            /*
             * This doesn't prevent learning whether PID exists,
             * it only makes getattr() consistent with readdir().
             */
            return -ENOENT;
        }
        if ((inode->i_mode == (S_IFDIR|S_IRUGO|S_IXUGO)) ||
            task_dumpable(task)) {
            cred = __task_cred(task);
            stat->uid = cred->euid;
            stat->gid = cred->egid;
        }
    }
    rcu_read_unlock();
    return 0;
}

/* dentry stuff */

/*
 *  Exceptional case: normally we are not allowed to unhash a busy
 * directory. In this case, however, we can do it - no aliasing problems
 * due to the way we treat inodes.
 *
 * Rewrite the inode's ownerships here because the owning task may have
 * performed a setuid(), etc.
 *
 * Before the /proc/pid/status file was created the only way to read
 * the effective uid of a /process was to stat /proc/pid.  Reading
 * /proc/pid/status is slow enough that procps and other packages
 * kept stating /proc/pid.  To keep the rules in /proc simple I have
 * made this apply to all per process world readable and executable
 * directories.
 */
int pid_revalidate(struct dentry *dentry, unsigned int flags)
{
    struct inode *inode;
    struct task_struct *task;
    const struct cred *cred;

    if (flags & LOOKUP_RCU)
        return -ECHILD;

    inode = dentry->d_inode;
    task = get_proc_task(inode);

    if (task) {
        if ((inode->i_mode == (S_IFDIR|S_IRUGO|S_IXUGO)) ||
            task_dumpable(task)) {
            rcu_read_lock();
            cred = __task_cred(task);
            inode->i_uid = cred->euid;
            inode->i_gid = cred->egid;
            rcu_read_unlock();
        } else {
            inode->i_uid = GLOBAL_ROOT_UID;
            inode->i_gid = GLOBAL_ROOT_GID;
        }
        inode->i_mode &= ~(S_ISUID | S_ISGID);
        security_task_to_inode(task, inode);
        put_task_struct(task);
        return 1;
    }
    d_drop(dentry);
    return 0;
}

const struct dentry_operations pid_dentry_operations =
{
    .d_revalidate   = pid_revalidate,
    .d_delete   = pid_delete_dentry,
};

/* Lookups */

/*
 * Fill a directory entry.
 *
 * If possible create the dcache entry and derive our inode number and
 * file type from dcache entry.
 *
 * Since all of the proc inode numbers are dynamically generated, the inode
 * numbers do not exist until the inode is cache.  This means creating the
 * the dcache entry in readdir is necessary to keep the inode numbers
 * reported by readdir in sync with the inode numbers reported
 * by stat.
 */
int proc_fill_cache(struct file *filp, void *dirent, filldir_t filldir,
    const char *name, int len,
    instantiate_t instantiate, struct task_struct *task, const void *ptr)
{
    struct dentry *child, *dir = filp->f_path.dentry;
    struct inode *inode;
    struct qstr qname;
    ino_t ino = 0;
    unsigned type = DT_UNKNOWN;

    qname.name = name;
    qname.len  = len;
    qname.hash = full_name_hash(name, len);

    child = d_lookup(dir, &qname);
    if (!child) {
        struct dentry *new;
        new = d_alloc(dir, &qname);
        if (new) {
            child = instantiate(dir->d_inode, new, task, ptr);
            if (child)
                dput(new);
            else
                child = new;
        }
    }
    if (!child || IS_ERR(child) || !child->d_inode)
        goto end_instantiate;
    inode = child->d_inode;
    if (inode) {
        ino = inode->i_ino;
        type = inode->i_mode >> 12;
    }
    dput(child);
end_instantiate:
    if (!ino)
        ino = find_inode_number(dir, &qname);
    if (!ino)
        ino = 1;
    return filldir(dirent, name, len, filp->f_pos, ino, type);
}

#ifdef CONFIG_CHECKPOINT_RESTORE

/*
 * dname_to_vma_addr - maps a dentry name into two unsigned longs
 * which represent vma start and end addresses.
 */
static int dname_to_vma_addr(struct dentry *dentry,
                 unsigned long *start, unsigned long *end)
{
    if (sscanf(dentry->d_name.name, "%lx-%lx", start, end) != 2)
        return -EINVAL;

    return 0;
}

static int map_files_d_revalidate(struct dentry *dentry, unsigned int flags)
{
    unsigned long vm_start, vm_end;
    bool exact_vma_exists = false;
    struct mm_struct *mm = NULL;
    struct task_struct *task;
    const struct cred *cred;
    struct inode *inode;
    int status = 0;

    if (flags & LOOKUP_RCU)
        return -ECHILD;

    if (!capable(CAP_SYS_ADMIN)) {
        status = -EACCES;
        goto out_notask;
    }

    inode = dentry->d_inode;
    task = get_proc_task(inode);
    if (!task)
        goto out_notask;

    mm = mm_access(task, PTRACE_MODE_READ);
    if (IS_ERR_OR_NULL(mm))
        goto out;

    if (!dname_to_vma_addr(dentry, &vm_start, &vm_end)) {
        down_read(&mm->mmap_sem);
        exact_vma_exists = !!find_exact_vma(mm, vm_start, vm_end);
        up_read(&mm->mmap_sem);
    }

    mmput(mm);

    if (exact_vma_exists) {
        if (task_dumpable(task)) {
            rcu_read_lock();
            cred = __task_cred(task);
            inode->i_uid = cred->euid;
            inode->i_gid = cred->egid;
            rcu_read_unlock();
        } else {
            inode->i_uid = GLOBAL_ROOT_UID;
            inode->i_gid = GLOBAL_ROOT_GID;
        }
        security_task_to_inode(task, inode);
        status = 1;
    }

out:
    put_task_struct(task);

out_notask:
    if (status <= 0)
        d_drop(dentry);

    return status;
}

static const struct dentry_operations tid_map_files_dentry_operations = {
    .d_revalidate   = map_files_d_revalidate,
    .d_delete   = pid_delete_dentry,
};

static int proc_map_files_get_link(struct dentry *dentry, struct path *path)
{
    unsigned long vm_start, vm_end;
    struct vm_area_struct *vma;
    struct task_struct *task;
    struct mm_struct *mm;
    int rc;

    rc = -ENOENT;
    task = get_proc_task(dentry->d_inode);
    if (!task)
        goto out;

    mm = get_task_mm(task);
    put_task_struct(task);
    if (!mm)
        goto out;

    rc = dname_to_vma_addr(dentry, &vm_start, &vm_end);
    if (rc)
        goto out_mmput;

    down_read(&mm->mmap_sem);
    vma = find_exact_vma(mm, vm_start, vm_end);
    if (vma && vma->vm_file) {
        *path = vma->vm_file->f_path;
        path_get(path);
        rc = 0;
    }
    up_read(&mm->mmap_sem);

out_mmput:
    mmput(mm);
out:
    return rc;
}

struct map_files_info {
    fmode_t     mode;
    unsigned long   len;
    unsigned char   name[4*sizeof(long)+2]; /* max: %lx-%lx\0 */
};

static struct dentry *
proc_map_files_instantiate(struct inode *dir, struct dentry *dentry,
               struct task_struct *task, const void *ptr)
{
    fmode_t mode = (fmode_t)(unsigned long)ptr;
    struct proc_inode *ei;
    struct inode *inode;

    inode = proc_pid_make_inode(dir->i_sb, task);
    if (!inode)
        return ERR_PTR(-ENOENT);

    ei = PROC_I(inode);
    ei->op.proc_get_link = proc_map_files_get_link;

    inode->i_op = &proc_pid_link_inode_operations;
    inode->i_size = 64;
    inode->i_mode = S_IFLNK;

    if (mode & FMODE_READ)
        inode->i_mode |= S_IRUSR;
    if (mode & FMODE_WRITE)
        inode->i_mode |= S_IWUSR;

    d_set_d_op(dentry, &tid_map_files_dentry_operations);
    d_add(dentry, inode);

    return NULL;
}

static struct dentry *proc_map_files_lookup(struct inode *dir,
        struct dentry *dentry, unsigned int flags)
{
    unsigned long vm_start, vm_end;
    struct vm_area_struct *vma;
    struct task_struct *task;
    struct dentry *result;
    struct mm_struct *mm;

    result = ERR_PTR(-EACCES);
    if (!capable(CAP_SYS_ADMIN))
        goto out;

    result = ERR_PTR(-ENOENT);
    task = get_proc_task(dir);
    if (!task)
        goto out;

    result = ERR_PTR(-EACCES);
    if (!ptrace_may_access(task, PTRACE_MODE_READ))
        goto out_put_task;

    result = ERR_PTR(-ENOENT);
    if (dname_to_vma_addr(dentry, &vm_start, &vm_end))
        goto out_put_task;

    mm = get_task_mm(task);
    if (!mm)
        goto out_put_task;

    down_read(&mm->mmap_sem);
    vma = find_exact_vma(mm, vm_start, vm_end);
    if (!vma)
        goto out_no_vma;

    if (vma->vm_file)
        result = proc_map_files_instantiate(dir, dentry, task,
                (void *)(unsigned long)vma->vm_file->f_mode);

out_no_vma:
    up_read(&mm->mmap_sem);
    mmput(mm);
out_put_task:
    put_task_struct(task);
out:
    return result;
}

static const struct inode_operations proc_map_files_inode_operations = {
    .lookup     = proc_map_files_lookup,
    .permission = proc_fd_permission,
    .setattr    = proc_setattr,
};

static int
proc_map_files_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
    struct dentry *dentry = filp->f_path.dentry;
    struct inode *inode = dentry->d_inode;
    struct vm_area_struct *vma;
    struct task_struct *task;
    struct mm_struct *mm;
    ino_t ino;
    int ret;

    ret = -EACCES;
    if (!capable(CAP_SYS_ADMIN))
        goto out;

    ret = -ENOENT;
    task = get_proc_task(inode);
    if (!task)
        goto out;

    ret = -EACCES;
    if (!ptrace_may_access(task, PTRACE_MODE_READ))
        goto out_put_task;

    ret = 0;
    switch (filp->f_pos) {
    case 0:
        ino = inode->i_ino;
        if (filldir(dirent, ".", 1, 0, ino, DT_DIR) < 0)
            goto out_put_task;
        filp->f_pos++;
    case 1:
        ino = parent_ino(dentry);
        if (filldir(dirent, "..", 2, 1, ino, DT_DIR) < 0)
            goto out_put_task;
        filp->f_pos++;
    default:
    {
        unsigned long nr_files, pos, i;
        struct flex_array *fa = NULL;
        struct map_files_info info;
        struct map_files_info *p;

        mm = get_task_mm(task);
        if (!mm)
            goto out_put_task;
        down_read(&mm->mmap_sem);

        nr_files = 0;

        /*
         * We need two passes here:
         *
         *  1) Collect vmas of mapped files with mmap_sem taken
         *  2) Release mmap_sem and instantiate entries
         *
         * otherwise we get lockdep complained, since filldir()
         * routine might require mmap_sem taken in might_fault().
         */

        for (vma = mm->mmap, pos = 2; vma; vma = vma->vm_next) {
            if (vma->vm_file && ++pos > filp->f_pos)
                nr_files++;
        }

        if (nr_files) {
            fa = flex_array_alloc(sizeof(info), nr_files,
                        GFP_KERNEL);
            if (!fa || flex_array_prealloc(fa, 0, nr_files,
                            GFP_KERNEL)) {
                ret = -ENOMEM;
                if (fa)
                    flex_array_free(fa);
                up_read(&mm->mmap_sem);
                mmput(mm);
                goto out_put_task;
            }
            for (i = 0, vma = mm->mmap, pos = 2; vma;
                    vma = vma->vm_next) {
                if (!vma->vm_file)
                    continue;
                if (++pos <= filp->f_pos)
                    continue;

                info.mode = vma->vm_file->f_mode;
                info.len = snprintf(info.name,
                        sizeof(info.name), "%lx-%lx",
                        vma->vm_start, vma->vm_end);
                if (flex_array_put(fa, i++, &info, GFP_KERNEL))
                    BUG();
            }
        }
        up_read(&mm->mmap_sem);

        for (i = 0; i < nr_files; i++) {
            p = flex_array_get(fa, i);
            ret = proc_fill_cache(filp, dirent, filldir,
                          p->name, p->len,
                          proc_map_files_instantiate,
                          task,
                          (void *)(unsigned long)p->mode);
            if (ret)
                break;
            filp->f_pos++;
        }
        if (fa)
            flex_array_free(fa);
        mmput(mm);
    }
    }

out_put_task:
    put_task_struct(task);
out:
    return ret;
}

static const struct file_operations proc_map_files_operations = {
    .read       = generic_read_dir,
    .readdir    = proc_map_files_readdir,
    .llseek     = default_llseek,
};

#endif /* CONFIG_CHECKPOINT_RESTORE */

static struct dentry *proc_pident_instantiate(struct inode *dir,
    struct dentry *dentry, struct task_struct *task, const void *ptr)
{
    const struct pid_entry *p = ptr;
    struct inode *inode;
    struct proc_inode *ei;
    struct dentry *error = ERR_PTR(-ENOENT);

    inode = proc_pid_make_inode(dir->i_sb, task);
    if (!inode)
        goto out;

    ei = PROC_I(inode);
    inode->i_mode = p->mode;
    if (S_ISDIR(inode->i_mode))
        set_nlink(inode, 2);    /* Use getattr to fix if necessary */
    if (p->iop)
        inode->i_op = p->iop;
    if (p->fop)
        inode->i_fop = p->fop;
    ei->op = p->op;
    d_set_d_op(dentry, &pid_dentry_operations);
    d_add(dentry, inode);
    /* Close the race of the process dying before we return the dentry */
    if (pid_revalidate(dentry, 0))
        error = NULL;
out:
    return error;
}

static struct dentry *proc_pident_lookup(struct inode *dir, 
                     struct dentry *dentry,
                     const struct pid_entry *ents,
                     unsigned int nents)
{
    struct dentry *error;
    struct task_struct *task = get_proc_task(dir);
    const struct pid_entry *p, *last;

    error = ERR_PTR(-ENOENT);

    if (!task)
        goto out_no_task;

    /*
     * Yes, it does not scale. And it should not. Don't add
     * new entries into /proc/<tgid>/ without very good reasons.
     */
    last = &ents[nents - 1];
    for (p = ents; p <= last; p++) {
        if (p->len != dentry->d_name.len)
            continue;
        if (!memcmp(dentry->d_name.name, p->name, p->len))
            break;
    }
    if (p > last)
        goto out;

    error = proc_pident_instantiate(dir, dentry, task, p);
out:
    put_task_struct(task);
out_no_task:
    return error;
}

static int proc_pident_fill_cache(struct file *filp, void *dirent,
    filldir_t filldir, struct task_struct *task, const struct pid_entry *p)
{
    return proc_fill_cache(filp, dirent, filldir, p->name, p->len,
                proc_pident_instantiate, task, p);
}

static int proc_pident_readdir(struct file *filp,
        void *dirent, filldir_t filldir,
        const struct pid_entry *ents, unsigned int nents)
{
    int i;
    struct dentry *dentry = filp->f_path.dentry;
    struct inode *inode = dentry->d_inode;
    struct task_struct *task = get_proc_task(inode);
    const struct pid_entry *p, *last;
    ino_t ino;
    int ret;

    ret = -ENOENT;
    if (!task)
        goto out_no_task;

    ret = 0;
    i = filp->f_pos;
    switch (i) {
    case 0:
        ino = inode->i_ino;
        if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
            goto out;
        i++;
        filp->f_pos++;
        /* fall through */
    case 1:
        ino = parent_ino(dentry);
        if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
            goto out;
        i++;
        filp->f_pos++;
        /* fall through */
    default:
        i -= 2;
        if (i >= nents) {
            ret = 1;
            goto out;
        }
        p = ents + i;
        last = &ents[nents - 1];
        while (p <= last) {
            if (proc_pident_fill_cache(filp, dirent, filldir, task, p) < 0)
                goto out;
            filp->f_pos++;
            p++;
        }
    }

    ret = 1;
out:
    put_task_struct(task);
out_no_task:
    return ret;
}

#ifdef CONFIG_SECURITY
static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,
                  size_t count, loff_t *ppos)
{
    struct inode * inode = file->f_path.dentry->d_inode;
    char *p = NULL;
    ssize_t length;
    struct task_struct *task = get_proc_task(inode);

    if (!task)
        return -ESRCH;

    length = security_getprocattr(task,
                      (char*)file->f_path.dentry->d_name.name,
                      &p);
    put_task_struct(task);
    if (length > 0)
        length = simple_read_from_buffer(buf, count, ppos, p, length);
    kfree(p);
    return length;
}

static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
                   size_t count, loff_t *ppos)
{
    struct inode * inode = file->f_path.dentry->d_inode;
    char *page;
    ssize_t length;
    struct task_struct *task = get_proc_task(inode);

    length = -ESRCH;
    if (!task)
        goto out_no_task;
    if (count > PAGE_SIZE)
        count = PAGE_SIZE;

    /* No partial writes. */
    length = -EINVAL;
    if (*ppos != 0)
        goto out;

    length = -ENOMEM;
    page = (char*)__get_free_page(GFP_TEMPORARY);
    if (!page)
        goto out;

    length = -EFAULT;
    if (copy_from_user(page, buf, count))
        goto out_free;

    /* Guard against adverse ptrace interaction */
    length = mutex_lock_interruptible(&task->signal->cred_guard_mutex);
    if (length < 0)
        goto out_free;

    length = security_setprocattr(task,
                      (char*)file->f_path.dentry->d_name.name,
                      (void*)page, count);
    mutex_unlock(&task->signal->cred_guard_mutex);
out_free:
    free_page((unsigned long) page);
out:
    put_task_struct(task);
out_no_task:
    return length;
}

static const struct file_operations proc_pid_attr_operations = {
    .read       = proc_pid_attr_read,
    .write      = proc_pid_attr_write,
    .llseek     = generic_file_llseek,
};

static const struct pid_entry attr_dir_stuff[] = {
    REG("current",    S_IRUGO|S_IWUGO, proc_pid_attr_operations),
    REG("prev",       S_IRUGO,     proc_pid_attr_operations),
    REG("exec",       S_IRUGO|S_IWUGO, proc_pid_attr_operations),
    REG("fscreate",   S_IRUGO|S_IWUGO, proc_pid_attr_operations),
    REG("keycreate",  S_IRUGO|S_IWUGO, proc_pid_attr_operations),
    REG("sockcreate", S_IRUGO|S_IWUGO, proc_pid_attr_operations),
};

static int proc_attr_dir_readdir(struct file * filp,
                 void * dirent, filldir_t filldir)
{
    return proc_pident_readdir(filp,dirent,filldir,
                   attr_dir_stuff,ARRAY_SIZE(attr_dir_stuff));
}

static const struct file_operations proc_attr_dir_operations = {
    .read       = generic_read_dir,
    .readdir    = proc_attr_dir_readdir,
    .llseek     = default_llseek,
};

static struct dentry *proc_attr_dir_lookup(struct inode *dir,
                struct dentry *dentry, unsigned int flags)
{
    return proc_pident_lookup(dir, dentry,
                  attr_dir_stuff, ARRAY_SIZE(attr_dir_stuff));
}

static const struct inode_operations proc_attr_dir_inode_operations = {
    .lookup     = proc_attr_dir_lookup,
    .getattr    = pid_getattr,
    .setattr    = proc_setattr,
};

#endif

#ifdef CONFIG_ELF_CORE
static ssize_t proc_coredump_filter_read(struct file *file, char __user *buf,
                     size_t count, loff_t *ppos)
{
    struct task_struct *task = get_proc_task(file->f_dentry->d_inode);
    struct mm_struct *mm;
    char buffer[PROC_NUMBUF];
    size_t len;
    int ret;

    if (!task)
        return -ESRCH;

    ret = 0;
    mm = get_task_mm(task);
    if (mm) {
        len = snprintf(buffer, sizeof(buffer), "%08lx\n",
                   ((mm->flags & MMF_DUMP_FILTER_MASK) >>
                MMF_DUMP_FILTER_SHIFT));
        mmput(mm);
        ret = simple_read_from_buffer(buf, count, ppos, buffer, len);
    }

    put_task_struct(task);

    return ret;
}

static ssize_t proc_coredump_filter_write(struct file *file,
                      const char __user *buf,
                      size_t count,
                      loff_t *ppos)
{
    struct task_struct *task;
    struct mm_struct *mm;
    char buffer[PROC_NUMBUF], *end;
    unsigned int val;
    int ret;
    int i;
    unsigned long mask;

    ret = -EFAULT;
    memset(buffer, 0, sizeof(buffer));
    if (count > sizeof(buffer) - 1)
        count = sizeof(buffer) - 1;
    if (copy_from_user(buffer, buf, count))
        goto out_no_task;

    ret = -EINVAL;
    val = (unsigned int)simple_strtoul(buffer, &end, 0);
    if (*end == '\n')
        end++;
    if (end - buffer == 0)
        goto out_no_task;

    ret = -ESRCH;
    task = get_proc_task(file->f_dentry->d_inode);
    if (!task)
        goto out_no_task;

    ret = end - buffer;
    mm = get_task_mm(task);
    if (!mm)
        goto out_no_mm;

    for (i = 0, mask = 1; i < MMF_DUMP_FILTER_BITS; i++, mask <<= 1) {
        if (val & mask)
            set_bit(i + MMF_DUMP_FILTER_SHIFT, &mm->flags);
        else
            clear_bit(i + MMF_DUMP_FILTER_SHIFT, &mm->flags);
    }

    mmput(mm);
 out_no_mm:
    put_task_struct(task);
 out_no_task:
    return ret;
}

static const struct file_operations proc_coredump_filter_operations = {
    .read       = proc_coredump_filter_read,
    .write      = proc_coredump_filter_write,
    .llseek     = generic_file_llseek,
};
#endif

/*
 * /proc/self:
 */
static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
                  int buflen)
{
    struct pid_namespace *ns = dentry->d_sb->s_fs_info;
    pid_t tgid = task_tgid_nr_ns(current, ns);
    char tmp[PROC_NUMBUF];
    if (!tgid)
        return -ENOENT;
    sprintf(tmp, "%d", tgid);
    return vfs_readlink(dentry,buffer,buflen,tmp);
}

static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd)
{
    struct pid_namespace *ns = dentry->d_sb->s_fs_info;
    pid_t tgid = task_tgid_nr_ns(current, ns);
    char *name = ERR_PTR(-ENOENT);
    if (tgid) {
        /* 11 for max length of signed int in decimal + NULL term */
        name = kmalloc(12, GFP_KERNEL);
        if (!name)
            name = ERR_PTR(-ENOMEM);
        else
            sprintf(name, "%d", tgid);
    }
    nd_set_link(nd, name);
    return NULL;
}

static void proc_self_put_link(struct dentry *dentry, struct nameidata *nd,
                void *cookie)
{
    char *s = nd_get_link(nd);
    if (!IS_ERR(s))
        kfree(s);
}

static const struct inode_operations proc_self_inode_operations = {
    .readlink   = proc_self_readlink,
    .follow_link    = proc_self_follow_link,
    .put_link   = proc_self_put_link,
};

/*
 * proc base
 *
 * These are the directory entries in the root directory of /proc
 * that properly belong to the /proc filesystem, as they describe
 * describe something that is process related.
 */
static const struct pid_entry proc_base_stuff[] = {
    NOD("self", S_IFLNK|S_IRWXUGO,
        &proc_self_inode_operations, NULL, {}),
};

static struct dentry *proc_base_instantiate(struct inode *dir,
    struct dentry *dentry, struct task_struct *task, const void *ptr)
{
    const struct pid_entry *p = ptr;
    struct inode *inode;
    struct proc_inode *ei;
    struct dentry *error;

    /* Allocate the inode */
    error = ERR_PTR(-ENOMEM);
    inode = new_inode(dir->i_sb);
    if (!inode)
        goto out;

    /* Initialize the inode */
    ei = PROC_I(inode);
    inode->i_ino = get_next_ino();
    inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;

    /*
     * grab the reference to the task.
     */
    ei->pid = get_task_pid(task, PIDTYPE_PID);
    if (!ei->pid)
        goto out_iput;

    inode->i_mode = p->mode;
    if (S_ISDIR(inode->i_mode))
        set_nlink(inode, 2);
    if (S_ISLNK(inode->i_mode))
        inode->i_size = 64;
    if (p->iop)
        inode->i_op = p->iop;
    if (p->fop)
        inode->i_fop = p->fop;
    ei->op = p->op;
    d_add(dentry, inode);
    error = NULL;
out:
    return error;
out_iput:
    iput(inode);
    goto out;
}

static struct dentry *proc_base_lookup(struct inode *dir, struct dentry *dentry)
{
    struct dentry *error;
    struct task_struct *task = get_proc_task(dir);
    const struct pid_entry *p, *last;

    error = ERR_PTR(-ENOENT);

    if (!task)
        goto out_no_task;

    /* Lookup the directory entry */
    last = &proc_base_stuff[ARRAY_SIZE(proc_base_stuff) - 1];
    for (p = proc_base_stuff; p <= last; p++) {
        if (p->len != dentry->d_name.len)
            continue;
        if (!memcmp(dentry->d_name.name, p->name, p->len))
            break;
    }
    if (p > last)
        goto out;

    error = proc_base_instantiate(dir, dentry, task, p);

out:
    put_task_struct(task);
out_no_task:
    return error;
}

static int proc_base_fill_cache(struct file *filp, void *dirent,
    filldir_t filldir, struct task_struct *task, const struct pid_entry *p)
{
    return proc_fill_cache(filp, dirent, filldir, p->name, p->len,
                proc_base_instantiate, task, p);
}

#ifdef CONFIG_TASK_IO_ACCOUNTING
static int do_io_accounting(struct task_struct *task, char *buffer, int whole)
{
    struct task_io_accounting acct = task->ioac;
    unsigned long flags;
    int result;

    result = mutex_lock_killable(&task->signal->cred_guard_mutex);
    if (result)
        return result;

    if (!ptrace_may_access(task, PTRACE_MODE_READ)) {
        result = -EACCES;
        goto out_unlock;
    }

    if (whole && lock_task_sighand(task, &flags)) {
        struct task_struct *t = task;

        task_io_accounting_add(&acct, &task->signal->ioac);
        while_each_thread(task, t)
            task_io_accounting_add(&acct, &t->ioac);

        unlock_task_sighand(task, &flags);
    }
    result = sprintf(buffer,
            "rchar: %llu\n"
            "wchar: %llu\n"
            "syscr: %llu\n"
            "syscw: %llu\n"
            "read_bytes: %llu\n"
            "write_bytes: %llu\n"
            "cancelled_write_bytes: %llu\n",
            (unsigned long long)acct.rchar,
            (unsigned long long)acct.wchar,
            (unsigned long long)acct.syscr,
            (unsigned long long)acct.syscw,
            (unsigned long long)acct.read_bytes,
            (unsigned long long)acct.write_bytes,
            (unsigned long long)acct.cancelled_write_bytes);
out_unlock:
    mutex_unlock(&task->signal->cred_guard_mutex);
    return result;
}

static int proc_tid_io_accounting(struct task_struct *task, char *buffer)
{
    return do_io_accounting(task, buffer, 0);
}

static int proc_tgid_io_accounting(struct task_struct *task, char *buffer)
{
    return do_io_accounting(task, buffer, 1);
}
#endif /* CONFIG_TASK_IO_ACCOUNTING */

#ifdef CONFIG_USER_NS
static int proc_id_map_open(struct inode *inode, struct file *file,
    struct seq_operations *seq_ops)
{
    struct user_namespace *ns = NULL;
    struct task_struct *task;
    struct seq_file *seq;
    int ret = -EINVAL;

    task = get_proc_task(inode);
    if (task) {
        rcu_read_lock();
        ns = get_user_ns(task_cred_xxx(task, user_ns));
        rcu_read_unlock();
        put_task_struct(task);
    }
    if (!ns)
        goto err;

    ret = seq_open(file, seq_ops);
    if (ret)
        goto err_put_ns;

    seq = file->private_data;
    seq->private = ns;

    return 0;
err_put_ns:
    put_user_ns(ns);
err:
    return ret;
}

static int proc_id_map_release(struct inode *inode, struct file *file)
{
    struct seq_file *seq = file->private_data;
    struct user_namespace *ns = seq->private;
    put_user_ns(ns);
    return seq_release(inode, file);
}

static int proc_uid_map_open(struct inode *inode, struct file *file)
{
    return proc_id_map_open(inode, file, &proc_uid_seq_operations);
}

static int proc_gid_map_open(struct inode *inode, struct file *file)
{
    return proc_id_map_open(inode, file, &proc_gid_seq_operations);
}

static int proc_projid_map_open(struct inode *inode, struct file *file)
{
    return proc_id_map_open(inode, file, &proc_projid_seq_operations);
}

static const struct file_operations proc_uid_map_operations = {
    .open       = proc_uid_map_open,
    .write      = proc_uid_map_write,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = proc_id_map_release,
};

static const struct file_operations proc_gid_map_operations = {
    .open       = proc_gid_map_open,
    .write      = proc_gid_map_write,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = proc_id_map_release,
};

static const struct file_operations proc_projid_map_operations = {
    .open       = proc_projid_map_open,
    .write      = proc_projid_map_write,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = proc_id_map_release,
};
#endif /* CONFIG_USER_NS */

static int proc_pid_personality(struct seq_file *m, struct pid_namespace *ns,
                struct pid *pid, struct task_struct *task)
{
    int err = lock_trace(task);
    if (!err) {
        seq_printf(m, "%08x\n", task->personality);
        unlock_trace(task);
    }
    return err;
}

/*
 * Thread groups
 */
static const struct file_operations proc_task_operations;
static const struct inode_operations proc_task_inode_operations;

static const struct pid_entry tgid_base_stuff[] = {
    DIR("task",       S_IRUGO|S_IXUGO, proc_task_inode_operations, proc_task_operations),
    DIR("fd",         S_IRUSR|S_IXUSR, proc_fd_inode_operations, proc_fd_operations),
#ifdef CONFIG_CHECKPOINT_RESTORE
    DIR("map_files",  S_IRUSR|S_IXUSR, proc_map_files_inode_operations, proc_map_files_operations),
#endif
    DIR("fdinfo",     S_IRUSR|S_IXUSR, proc_fdinfo_inode_operations, proc_fdinfo_operations),
    DIR("ns",     S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_operations),
#ifdef CONFIG_NET
    DIR("net",        S_IRUGO|S_IXUGO, proc_net_inode_operations, proc_net_operations),
#endif
    REG("environ",    S_IRUSR, proc_environ_operations),
    INF("auxv",       S_IRUSR, proc_pid_auxv),
    ONE("status",     S_IRUGO, proc_pid_status),
    ONE("personality", S_IRUGO, proc_pid_personality),
    INF("limits",     S_IRUGO, proc_pid_limits),
#ifdef CONFIG_SCHED_DEBUG
    REG("sched",      S_IRUGO|S_IWUSR, proc_pid_sched_operations),
#endif
#ifdef CONFIG_SCHED_AUTOGROUP
    REG("autogroup",  S_IRUGO|S_IWUSR, proc_pid_sched_autogroup_operations),
#endif
    REG("comm",      S_IRUGO|S_IWUSR, proc_pid_set_comm_operations),
#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
    INF("syscall",    S_IRUGO, proc_pid_syscall),
#endif
    INF("cmdline",    S_IRUGO, proc_pid_cmdline),
    ONE("stat",       S_IRUGO, proc_tgid_stat),
    ONE("statm",      S_IRUGO, proc_pid_statm),
    REG("maps",       S_IRUGO, proc_pid_maps_operations),
#ifdef CONFIG_NUMA
    REG("numa_maps",  S_IRUGO, proc_pid_numa_maps_operations),
#endif
    REG("mem",        S_IRUSR|S_IWUSR, proc_mem_operations),
    LNK("cwd",        proc_cwd_link),
    LNK("root",       proc_root_link),
    LNK("exe",        proc_exe_link),
    REG("mounts",     S_IRUGO, proc_mounts_operations),
    REG("mountinfo",  S_IRUGO, proc_mountinfo_operations),
    REG("mountstats", S_IRUSR, proc_mountstats_operations),
#ifdef CONFIG_PROC_PAGE_MONITOR
    REG("clear_refs", S_IWUSR, proc_clear_refs_operations),
    REG("smaps",      S_IRUGO, proc_pid_smaps_operations),
    REG("pagemap",    S_IRUGO, proc_pagemap_operations),
#endif
#ifdef CONFIG_SECURITY
    DIR("attr",       S_IRUGO|S_IXUGO, proc_attr_dir_inode_operations, proc_attr_dir_operations),
#endif
#ifdef CONFIG_KALLSYMS
    INF("wchan",      S_IRUGO, proc_pid_wchan),
#endif
#ifdef CONFIG_STACKTRACE
    ONE("stack",      S_IRUGO, proc_pid_stack),
#endif
#ifdef CONFIG_SCHEDSTATS
    INF("schedstat",  S_IRUGO, proc_pid_schedstat),
#endif
#ifdef CONFIG_LATENCYTOP
    REG("latency",  S_IRUGO, proc_lstats_operations),
#endif
#ifdef CONFIG_PROC_PID_CPUSET
    REG("cpuset",     S_IRUGO, proc_cpuset_operations),
#endif
#ifdef CONFIG_CGROUPS
    REG("cgroup",  S_IRUGO, proc_cgroup_operations),
#endif
    INF("oom_score",  S_IRUGO, proc_oom_score),
    REG("oom_adj",    S_IRUGO|S_IWUSR, proc_oom_adj_operations),
    REG("oom_score_adj", S_IRUGO|S_IWUSR, proc_oom_score_adj_operations),
#ifdef CONFIG_AUDITSYSCALL
    REG("loginuid",   S_IWUSR|S_IRUGO, proc_loginuid_operations),
    REG("sessionid",  S_IRUGO, proc_sessionid_operations),
#endif
#ifdef CONFIG_FAULT_INJECTION
    REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
#endif
#ifdef CONFIG_ELF_CORE
    REG("coredump_filter", S_IRUGO|S_IWUSR, proc_coredump_filter_operations),
#endif
#ifdef CONFIG_TASK_IO_ACCOUNTING
    INF("io",   S_IRUSR, proc_tgid_io_accounting),
#endif
#ifdef CONFIG_HARDWALL
    INF("hardwall",   S_IRUGO, proc_pid_hardwall),
#endif
#ifdef CONFIG_USER_NS
    REG("uid_map",    S_IRUGO|S_IWUSR, proc_uid_map_operations),
    REG("gid_map",    S_IRUGO|S_IWUSR, proc_gid_map_operations),
    REG("projid_map", S_IRUGO|S_IWUSR, proc_projid_map_operations),
#endif
};

static int proc_tgid_base_readdir(struct file * filp,
                 void * dirent, filldir_t filldir)
{
    return proc_pident_readdir(filp,dirent,filldir,
                   tgid_base_stuff,ARRAY_SIZE(tgid_base_stuff));
}

static const struct file_operations proc_tgid_base_operations = {
    .read       = generic_read_dir,
    .readdir    = proc_tgid_base_readdir,
    .llseek     = default_llseek,
};

static struct dentry *proc_tgid_base_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
    return proc_pident_lookup(dir, dentry,
                  tgid_base_stuff, ARRAY_SIZE(tgid_base_stuff));
}

static const struct inode_operations proc_tgid_base_inode_operations = {
    .lookup     = proc_tgid_base_lookup,
    .getattr    = pid_getattr,
    .setattr    = proc_setattr,
    .permission = proc_pid_permission,
};

static void proc_flush_task_mnt(struct vfsmount *mnt, pid_t pid, pid_t tgid)
{
    struct dentry *dentry, *leader, *dir;
    char buf[PROC_NUMBUF];
    struct qstr name;

    name.name = buf;
    name.len = snprintf(buf, sizeof(buf), "%d", pid);
    dentry = d_hash_and_lookup(mnt->mnt_root, &name);
    if (dentry) {
        shrink_dcache_parent(dentry);
        d_drop(dentry);
        dput(dentry);
    }

    name.name = buf;
    name.len = snprintf(buf, sizeof(buf), "%d", tgid);
    leader = d_hash_and_lookup(mnt->mnt_root, &name);
    if (!leader)
        goto out;

    name.name = "task";
    name.len = strlen(name.name);
    dir = d_hash_and_lookup(leader, &name);
    if (!dir)
        goto out_put_leader;

    name.name = buf;
    name.len = snprintf(buf, sizeof(buf), "%d", pid);
    dentry = d_hash_and_lookup(dir, &name);
    if (dentry) {
        shrink_dcache_parent(dentry);
        d_drop(dentry);
        dput(dentry);
    }

    dput(dir);
out_put_leader:
    dput(leader);
out:
    return;
}

void proc_flush_task(struct task_struct *task)
{
    int i;
    struct pid *pid, *tgid;
    struct upid *upid;

    pid = task_pid(task);
    tgid = task_tgid(task);

    for (i = 0; i <= pid->level; i++) {
        upid = &pid->numbers[i];
        proc_flush_task_mnt(upid->ns->proc_mnt, upid->nr,
                    tgid->numbers[i].nr);
    }

    upid = &pid->numbers[pid->level];
    if (upid->nr == 1)
        pid_ns_release_proc(upid->ns);
}

static struct dentry *proc_pid_instantiate(struct inode *dir,
                       struct dentry * dentry,
                       struct task_struct *task, const void *ptr)
{
    struct dentry *error = ERR_PTR(-ENOENT);
    struct inode *inode;

    inode = proc_pid_make_inode(dir->i_sb, task);
    if (!inode)
        goto out;

    inode->i_mode = S_IFDIR|S_IRUGO|S_IXUGO;
    inode->i_op = &proc_tgid_base_inode_operations;
    inode->i_fop = &proc_tgid_base_operations;
    inode->i_flags|=S_IMMUTABLE;

    set_nlink(inode, 2 + pid_entry_count_dirs(tgid_base_stuff,
                          ARRAY_SIZE(tgid_base_stuff)));

    d_set_d_op(dentry, &pid_dentry_operations);

    d_add(dentry, inode);
    /* Close the race of the process dying before we return the dentry */
    if (pid_revalidate(dentry, 0))
        error = NULL;
out:
    return error;
}

struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags)
{
    struct dentry *result;
    struct task_struct *task;
    unsigned tgid;
    struct pid_namespace *ns;

    result = proc_base_lookup(dir, dentry);
    if (!IS_ERR(result) || PTR_ERR(result) != -ENOENT)
        goto out;

    tgid = name_to_int(dentry);
    if (tgid == ~0U)
        goto out;

    ns = dentry->d_sb->s_fs_info;
    rcu_read_lock();
    task = find_task_by_pid_ns(tgid, ns);
    if (task)
        get_task_struct(task);
    rcu_read_unlock();
    if (!task)
        goto out;

    result = proc_pid_instantiate(dir, dentry, task, NULL);
    put_task_struct(task);
out:
    return result;
}

/*
 * Find the first task with tgid >= tgid
 *
 */
struct tgid_iter {
    unsigned int tgid;
    struct task_struct *task;
};
static struct tgid_iter next_tgid(struct pid_namespace *ns, struct tgid_iter iter)
{
    struct pid *pid;

    if (iter.task)
        put_task_struct(iter.task);
    rcu_read_lock();
retry:
    iter.task = NULL;
    pid = find_ge_pid(iter.tgid, ns);
    if (pid) {
        iter.tgid = pid_nr_ns(pid, ns);
        iter.task = pid_task(pid, PIDTYPE_PID);
        /* What we to know is if the pid we have find is the
         * pid of a thread_group_leader.  Testing for task
         * being a thread_group_leader is the obvious thing
         * todo but there is a window when it fails, due to
         * the pid transfer logic in de_thread.
         *
         * So we perform the straight forward test of seeing
         * if the pid we have found is the pid of a thread
         * group leader, and don't worry if the task we have
         * found doesn't happen to be a thread group leader.
         * As we don't care in the case of readdir.
         */
        if (!iter.task || !has_group_leader_pid(iter.task)) {
            iter.tgid += 1;
            goto retry;
        }
        get_task_struct(iter.task);
    }
    rcu_read_unlock();
    return iter;
}

#define TGID_OFFSET (FIRST_PROCESS_ENTRY + ARRAY_SIZE(proc_base_stuff))

static int proc_pid_fill_cache(struct file *filp, void *dirent, filldir_t filldir,
    struct tgid_iter iter)
{
    char name[PROC_NUMBUF];
    int len = snprintf(name, sizeof(name), "%d", iter.tgid);
    return proc_fill_cache(filp, dirent, filldir, name, len,
                proc_pid_instantiate, iter.task, NULL);
}

static int fake_filldir(void *buf, const char *name, int namelen,
            loff_t offset, u64 ino, unsigned d_type)
{
    return 0;
}

/* for the /proc/ directory itself, after non-process stuff has been done */
int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
{
    unsigned int nr;
    struct task_struct *reaper;
    struct tgid_iter iter;
    struct pid_namespace *ns;
    filldir_t __filldir;

    if (filp->f_pos >= PID_MAX_LIMIT + TGID_OFFSET)
        goto out_no_task;
    nr = filp->f_pos - FIRST_PROCESS_ENTRY;

    reaper = get_proc_task(filp->f_path.dentry->d_inode);
    if (!reaper)
        goto out_no_task;

    for (; nr < ARRAY_SIZE(proc_base_stuff); filp->f_pos++, nr++) {
        const struct pid_entry *p = &proc_base_stuff[nr];
        if (proc_base_fill_cache(filp, dirent, filldir, reaper, p) < 0)
            goto out;
    }

    ns = filp->f_dentry->d_sb->s_fs_info;
    iter.task = NULL;
    iter.tgid = filp->f_pos - TGID_OFFSET;
    for (iter = next_tgid(ns, iter);
         iter.task;
         iter.tgid += 1, iter = next_tgid(ns, iter)) {
        if (has_pid_permissions(ns, iter.task, 2))
            __filldir = filldir;
        else
            __filldir = fake_filldir;

        filp->f_pos = iter.tgid + TGID_OFFSET;
        if (proc_pid_fill_cache(filp, dirent, __filldir, iter) < 0) {
            put_task_struct(iter.task);
            goto out;
        }
    }
    filp->f_pos = PID_MAX_LIMIT + TGID_OFFSET;
out:
    put_task_struct(reaper);
out_no_task:
    return 0;
}

/*
 * Tasks
 */
static const struct pid_entry tid_base_stuff[] = {
    DIR("fd",        S_IRUSR|S_IXUSR, proc_fd_inode_operations, proc_fd_operations),
    DIR("fdinfo",    S_IRUSR|S_IXUSR, proc_fdinfo_inode_operations, proc_fdinfo_operations),
    DIR("ns",    S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_operations),
    REG("environ",   S_IRUSR, proc_environ_operations),
    INF("auxv",      S_IRUSR, proc_pid_auxv),
    ONE("status",    S_IRUGO, proc_pid_status),
    ONE("personality", S_IRUGO, proc_pid_personality),
    INF("limits",    S_IRUGO, proc_pid_limits),
#ifdef CONFIG_SCHED_DEBUG
    REG("sched",     S_IRUGO|S_IWUSR, proc_pid_sched_operations),
#endif
    REG("comm",      S_IRUGO|S_IWUSR, proc_pid_set_comm_operations),
#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
    INF("syscall",   S_IRUGO, proc_pid_syscall),
#endif
    INF("cmdline",   S_IRUGO, proc_pid_cmdline),
    ONE("stat",      S_IRUGO, proc_tid_stat),
    ONE("statm",     S_IRUGO, proc_pid_statm),
    REG("maps",      S_IRUGO, proc_tid_maps_operations),
#ifdef CONFIG_CHECKPOINT_RESTORE
    REG("children",  S_IRUGO, proc_tid_children_operations),
#endif
#ifdef CONFIG_NUMA
    REG("numa_maps", S_IRUGO, proc_tid_numa_maps_operations),
#endif
    REG("mem",       S_IRUSR|S_IWUSR, proc_mem_operations),
    LNK("cwd",       proc_cwd_link),
    LNK("root",      proc_root_link),
    LNK("exe",       proc_exe_link),
    REG("mounts",    S_IRUGO, proc_mounts_operations),
    REG("mountinfo",  S_IRUGO, proc_mountinfo_operations),
#ifdef CONFIG_PROC_PAGE_MONITOR
    REG("clear_refs", S_IWUSR, proc_clear_refs_operations),
    REG("smaps",     S_IRUGO, proc_tid_smaps_operations),
    REG("pagemap",    S_IRUGO, proc_pagemap_operations),
#endif
#ifdef CONFIG_SECURITY
    DIR("attr",      S_IRUGO|S_IXUGO, proc_attr_dir_inode_operations, proc_attr_dir_operations),
#endif
#ifdef CONFIG_KALLSYMS
    INF("wchan",     S_IRUGO, proc_pid_wchan),
#endif
#ifdef CONFIG_STACKTRACE
    ONE("stack",      S_IRUGO, proc_pid_stack),
#endif
#ifdef CONFIG_SCHEDSTATS
    INF("schedstat", S_IRUGO, proc_pid_schedstat),
#endif
#ifdef CONFIG_LATENCYTOP
    REG("latency",  S_IRUGO, proc_lstats_operations),
#endif
#ifdef CONFIG_PROC_PID_CPUSET
    REG("cpuset",    S_IRUGO, proc_cpuset_operations),
#endif
#ifdef CONFIG_CGROUPS
    REG("cgroup",  S_IRUGO, proc_cgroup_operations),
#endif
    INF("oom_score", S_IRUGO, proc_oom_score),
    REG("oom_adj",   S_IRUGO|S_IWUSR, proc_oom_adj_operations),
    REG("oom_score_adj", S_IRUGO|S_IWUSR, proc_oom_score_adj_operations),
#ifdef CONFIG_AUDITSYSCALL
    REG("loginuid",  S_IWUSR|S_IRUGO, proc_loginuid_operations),
    REG("sessionid",  S_IRUGO, proc_sessionid_operations),
#endif
#ifdef CONFIG_FAULT_INJECTION
    REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
#endif
#ifdef CONFIG_TASK_IO_ACCOUNTING
    INF("io",   S_IRUSR, proc_tid_io_accounting),
#endif
#ifdef CONFIG_HARDWALL
    INF("hardwall",   S_IRUGO, proc_pid_hardwall),
#endif
#ifdef CONFIG_USER_NS
    REG("uid_map",    S_IRUGO|S_IWUSR, proc_uid_map_operations),
    REG("gid_map",    S_IRUGO|S_IWUSR, proc_gid_map_operations),
    REG("projid_map", S_IRUGO|S_IWUSR, proc_projid_map_operations),
#endif
};

static int proc_tid_base_readdir(struct file * filp,
                 void * dirent, filldir_t filldir)
{
    return proc_pident_readdir(filp,dirent,filldir,
                   tid_base_stuff,ARRAY_SIZE(tid_base_stuff));
}

static struct dentry *proc_tid_base_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
    return proc_pident_lookup(dir, dentry,
                  tid_base_stuff, ARRAY_SIZE(tid_base_stuff));
}

static const struct file_operations proc_tid_base_operations = {
    .read       = generic_read_dir,
    .readdir    = proc_tid_base_readdir,
    .llseek     = default_llseek,
};

static const struct inode_operations proc_tid_base_inode_operations = {
    .lookup     = proc_tid_base_lookup,
    .getattr    = pid_getattr,
    .setattr    = proc_setattr,
};

static struct dentry *proc_task_instantiate(struct inode *dir,
    struct dentry *dentry, struct task_struct *task, const void *ptr)
{
    struct dentry *error = ERR_PTR(-ENOENT);
    struct inode *inode;
    inode = proc_pid_make_inode(dir->i_sb, task);

    if (!inode)
        goto out;
    inode->i_mode = S_IFDIR|S_IRUGO|S_IXUGO;
    inode->i_op = &proc_tid_base_inode_operations;
    inode->i_fop = &proc_tid_base_operations;
    inode->i_flags|=S_IMMUTABLE;

    set_nlink(inode, 2 + pid_entry_count_dirs(tid_base_stuff,
                          ARRAY_SIZE(tid_base_stuff)));

    d_set_d_op(dentry, &pid_dentry_operations);

    d_add(dentry, inode);
    /* Close the race of the process dying before we return the dentry */
    if (pid_revalidate(dentry, 0))
        error = NULL;
out:
    return error;
}

static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags)
{
    struct dentry *result = ERR_PTR(-ENOENT);
    struct task_struct *task;
    struct task_struct *leader = get_proc_task(dir);
    unsigned tid;
    struct pid_namespace *ns;

    if (!leader)
        goto out_no_task;

    tid = name_to_int(dentry);
    if (tid == ~0U)
        goto out;

    ns = dentry->d_sb->s_fs_info;
    rcu_read_lock();
    task = find_task_by_pid_ns(tid, ns);
    if (task)
        get_task_struct(task);
    rcu_read_unlock();
    if (!task)
        goto out;
    if (!same_thread_group(leader, task))
        goto out_drop_task;

    result = proc_task_instantiate(dir, dentry, task, NULL);
out_drop_task:
    put_task_struct(task);
out:
    put_task_struct(leader);
out_no_task:
    return result;
}

/*
 * Find the first tid of a thread group to return to user space.
 *
 * Usually this is just the thread group leader, but if the users
 * buffer was too small or there was a seek into the middle of the
 * directory we have more work todo.
 *
 * In the case of a short read we start with find_task_by_pid.
 *
 * In the case of a seek we start with the leader and walk nr
 * threads past it.
 */
static struct task_struct *first_tid(struct task_struct *leader,
        int tid, int nr, struct pid_namespace *ns)
{
    struct task_struct *pos;

    rcu_read_lock();
    /* Attempt to start with the pid of a thread */
    if (tid && (nr > 0)) {
        pos = find_task_by_pid_ns(tid, ns);
        if (pos && (pos->group_leader == leader))
            goto found;
    }

    /* If nr exceeds the number of threads there is nothing todo */
    pos = NULL;
    if (nr && nr >= get_nr_threads(leader))
        goto out;

    /* If we haven't found our starting place yet start
     * with the leader and walk nr threads forward.
     */
    for (pos = leader; nr > 0; --nr) {
        pos = next_thread(pos);
        if (pos == leader) {
            pos = NULL;
            goto out;
        }
    }
found:
    get_task_struct(pos);
out:
    rcu_read_unlock();
    return pos;
}

/*
 * Find the next thread in the thread list.
 * Return NULL if there is an error or no next thread.
 *
 * The reference to the input task_struct is released.
 */
static struct task_struct *next_tid(struct task_struct *start)
{
    struct task_struct *pos = NULL;
    rcu_read_lock();
    if (pid_alive(start)) {
        pos = next_thread(start);
        if (thread_group_leader(pos))
            pos = NULL;
        else
            get_task_struct(pos);
    }
    rcu_read_unlock();
    put_task_struct(start);
    return pos;
}

static int proc_task_fill_cache(struct file *filp, void *dirent, filldir_t filldir,
    struct task_struct *task, int tid)
{
    char name[PROC_NUMBUF];
    int len = snprintf(name, sizeof(name), "%d", tid);
    return proc_fill_cache(filp, dirent, filldir, name, len,
                proc_task_instantiate, task, NULL);
}

/* for the /proc/TGID/task/ directories */
static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldir)
{
    struct dentry *dentry = filp->f_path.dentry;
    struct inode *inode = dentry->d_inode;
    struct task_struct *leader = NULL;
    struct task_struct *task;
    int retval = -ENOENT;
    ino_t ino;
    int tid;
    struct pid_namespace *ns;

    task = get_proc_task(inode);
    if (!task)
        goto out_no_task;
    rcu_read_lock();
    if (pid_alive(task)) {
        leader = task->group_leader;
        get_task_struct(leader);
    }
    rcu_read_unlock();
    put_task_struct(task);
    if (!leader)
        goto out_no_task;
    retval = 0;

    switch ((unsigned long)filp->f_pos) {
    case 0:
        ino = inode->i_ino;
        if (filldir(dirent, ".", 1, filp->f_pos, ino, DT_DIR) < 0)
            goto out;
        filp->f_pos++;
        /* fall through */
    case 1:
        ino = parent_ino(dentry);
        if (filldir(dirent, "..", 2, filp->f_pos, ino, DT_DIR) < 0)
            goto out;
        filp->f_pos++;
        /* fall through */
    }

    /* f_version caches the tgid value that the last readdir call couldn't
     * return. lseek aka telldir automagically resets f_version to 0.
     */
    ns = filp->f_dentry->d_sb->s_fs_info;
    tid = (int)filp->f_version;
    filp->f_version = 0;
    for (task = first_tid(leader, tid, filp->f_pos - 2, ns);
         task;
         task = next_tid(task), filp->f_pos++) {
        tid = task_pid_nr_ns(task, ns);
        if (proc_task_fill_cache(filp, dirent, filldir, task, tid) < 0) {
            /* returning this tgid failed, save it as the first
             * pid for the next readir call */
            filp->f_version = (u64)tid;
            put_task_struct(task);
            break;
        }
    }
out:
    put_task_struct(leader);
out_no_task:
    return retval;
}

static int proc_task_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
{
    struct inode *inode = dentry->d_inode;
    struct task_struct *p = get_proc_task(inode);
    generic_fillattr(inode, stat);

    if (p) {
        stat->nlink += get_nr_threads(p);
        put_task_struct(p);
    }

    return 0;
}

static const struct inode_operations proc_task_inode_operations = {
    .lookup     = proc_task_lookup,
    .getattr    = proc_task_getattr,
    .setattr    = proc_setattr,
    .permission = proc_pid_permission,
};

static const struct file_operations proc_task_operations = {
    .read       = generic_read_dir,
    .readdir    = proc_task_readdir,
    .llseek     = default_llseek,
};