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/*
* linux/fs/proc/link.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* /proc link-file handling code
*/
#include <asm/segment.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
static int proc_readlink(struct inode *, char *, int);
static int proc_follow_link(struct inode *, struct inode *, int, int,
struct inode **);
static int proc_fd_dupf(struct inode * inode, struct file * f);
#define PLAN9_SEMANTICS
/*
* 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, /* select - default */
NULL, /* ioctl - default */
NULL, /* mmap */
proc_fd_dupf, /* very special open code */
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, /* bmap */
NULL, /* truncate */
NULL /* permission */
};
/*
* This open routine is somewhat of a hack.... what we are doing is
* looking up the file structure of the newly opened proc fd file, and
* replacing it with the actual file structure of the process's file
* descriptor. This allows plan 9 semantics, so that the returned
* file descriptor is an dup of the target file descriptor.
*/
static int proc_fd_dupf(struct inode * inode, struct file * f)
{
unsigned int pid, ino;
int i, fd;
struct task_struct * p;
struct file *new_f;
for(fd=0 ; fd<NR_OPEN ; fd++)
if (current->files->fd[fd] == f)
break;
if (fd>=NR_OPEN)
return -ENOENT; /* should never happen */
ino = inode->i_ino;
pid = ino >> 16;
ino &= 0x0000ffff;
for (i = 0 ; i < NR_TASKS ; i++)
if ((p = task[i]) && p->pid == pid)
break;
if ((i >= NR_TASKS) ||
((ino >> 8) != 1) || !(new_f = p->files->fd[ino & 0x0ff]))
return -ENOENT;
if (new_f->f_mode && !f->f_mode && 3)
return -EPERM;
new_f->f_count++;
current->files->fd[fd] = new_f;
if (!--f->f_count)
iput(f->f_inode);
return 0;
}
static int proc_follow_link(struct inode * dir, struct inode * inode,
int flag, int mode, struct inode ** res_inode)
{
unsigned int pid, ino;
struct task_struct * p;
struct inode * new_inode;
int i;
*res_inode = NULL;
if (dir)
iput(dir);
if (!inode)
return -ENOENT;
if (!permission(inode, MAY_EXEC)) {
iput(inode);
return -EACCES;
}
ino = inode->i_ino;
pid = ino >> 16;
ino &= 0x0000ffff;
for (i = 0 ; i < NR_TASKS ; i++)
if ((p = task[i]) && p->pid == pid)
break;
if (i >= NR_TASKS) {
iput(inode);
return -ENOENT;
}
new_inode = NULL;
switch (ino) {
case PROC_PID_CWD:
new_inode = p->fs->pwd;
break;
case PROC_PID_ROOT:
new_inode = p->fs->root;
break;
case PROC_PID_EXE: {
struct vm_area_struct * vma = p->mm->mmap;
while (vma) {
if (vma->vm_flags & VM_EXECUTABLE) {
new_inode = vma->vm_inode;
break;
}
vma = vma->vm_next;
}
break;
}
default:
switch (ino >> 8) {
case PROC_PID_FD_DIR:
ino &= 0xff;
if (ino < NR_OPEN && p->files->fd[ino]) {
#ifdef PLAN9_SEMANTICS
if (dir) {
*res_inode = inode;
return 0;
}
#endif
new_inode = p->files->fd[ino]->f_inode;
}
break;
}
}
iput(inode);
if (!new_inode)
return -ENOENT;
*res_inode = new_inode;
new_inode->i_count++;
return 0;
}
static int proc_readlink(struct inode * inode, char * buffer, int buflen)
{
int i;
unsigned int dev,ino;
char buf[64];
if (!S_ISLNK(inode->i_mode)) {
iput(inode);
return -EINVAL;
}
i = proc_follow_link(NULL, inode, 0, 0, &inode);
if (i)
return i;
if (!inode)
return -EIO;
dev = inode->i_dev;
ino = inode->i_ino;
iput(inode);
i = sprintf(buf,"[%04x]:%u", dev, ino);
if (buflen > i)
buflen = i;
i = 0;
while (i < buflen)
put_fs_byte(buf[i++],buffer++);
return i;
}
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