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/*
* linux/fs/proc/link.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* /proc link-file handling code
*/
#include <asm/uaccess.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
static int proc_readlink(struct dentry *, char *, int);
static struct dentry * proc_follow_link(struct dentry *, struct dentry *);
/*
* links can't do much...
*/
static struct file_operations proc_fd_link_operations = {
NULL, /* lseek - default */
NULL, /* read - bad */
NULL, /* write - bad */
NULL, /* readdir - bad */
NULL, /* poll - default */
NULL, /* ioctl - default */
NULL, /* mmap */
NULL, /* very special open code */
NULL, /* flush */
NULL, /* no special release code */
NULL /* can't fsync */
};
struct inode_operations proc_link_inode_operations = {
&proc_fd_link_operations,/* file-operations */
NULL, /* create */
NULL, /* lookup */
NULL, /* link */
NULL, /* unlink */
NULL, /* symlink */
NULL, /* mkdir */
NULL, /* rmdir */
NULL, /* mknod */
NULL, /* rename */
proc_readlink, /* readlink */
proc_follow_link, /* follow_link */
NULL, /* readpage */
NULL, /* writepage */
NULL, /* bmap */
NULL, /* truncate */
proc_permission /* permission */
};
static struct dentry * proc_follow_link(struct dentry *dentry,
struct dentry *base)
{
struct inode *inode = dentry->d_inode;
struct task_struct *p;
struct dentry * result;
int ino, pid;
int error;
/* We don't need a base pointer in the /proc filesystem */
dput(base);
error = permission(inode, MAY_EXEC);
result = ERR_PTR(error);
if (error)
goto out;
ino = inode->i_ino;
pid = ino >> 16;
ino &= 0x0000ffff;
result = ERR_PTR(-ENOENT);
read_lock(&tasklist_lock);
p = find_task_by_pid(pid);
if (!p)
goto out_unlock;
switch (ino) {
case PROC_PID_CWD:
if (!p->fs || !p->fs->pwd)
goto out_unlock;
result = p->fs->pwd;
goto out_dget;
case PROC_PID_ROOT:
if (!p->fs || !p->fs->root)
goto out_unlock;
result = p->fs->root;
goto out_dget;
case PROC_PID_EXE: {
struct vm_area_struct * vma;
if (!p->mm)
goto out_unlock;
vma = p->mm->mmap;
while (vma) {
if ((vma->vm_flags & VM_EXECUTABLE) &&
vma->vm_file) {
result = vma->vm_file->f_dentry;
goto out_dget;
}
vma = vma->vm_next;
}
goto out_unlock;
}
default:
if (ino & PROC_PID_FD_DIR) {
struct file * file;
ino &= 0x7fff;
file = fcheck_task(p, ino);
if (!file || !file->f_dentry)
goto out_unlock;
result = file->f_dentry;
goto out_dget;
}
}
out_dget:
result = dget(result);
out_unlock:
read_unlock(&tasklist_lock);
out:
return result;
}
/*
* This pretty-prints the pathname of a dentry,
* clarifying sockets etc.
*/
static int do_proc_readlink(struct dentry *dentry, char * buffer, int buflen)
{
struct inode * inode;
char * tmp = (char*)__get_free_page(GFP_KERNEL), *path, *pattern;
int len;
/* Check for special dentries.. */
pattern = NULL;
inode = dentry->d_inode;
if (inode && dentry->d_parent == dentry) {
if (S_ISSOCK(inode->i_mode))
pattern = "socket:[%lu]";
if (S_ISFIFO(inode->i_mode))
pattern = "pipe:[%lu]";
}
if (pattern) {
len = sprintf(tmp, pattern, inode->i_ino);
path = tmp;
} else {
path = d_path(dentry, tmp, PAGE_SIZE);
len = tmp + PAGE_SIZE - path;
}
if (len < buflen)
buflen = len;
dput(dentry);
copy_to_user(buffer, path, buflen);
free_page((unsigned long)tmp);
return buflen;
}
static int proc_readlink(struct dentry * dentry, char * buffer, int buflen)
{
int error;
dentry = proc_follow_link(dentry, NULL);
error = PTR_ERR(dentry);
if (!IS_ERR(dentry)) {
error = -ENOENT;
if (dentry) {
error = do_proc_readlink(dentry, buffer, buflen);
}
}
return error;
}
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