1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
|
/*
* 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/fs.h>
#include <linux/mm.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
static int proc_readlink(struct inode *, char *, int);
static struct dentry * proc_follow_link(struct inode *, struct dentry *);
/*
* PLAN9_SEMANTICS won't work any more: it used an ugly hack that broke
* when the files[] array was updated only after the open code
*/
#undef 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, /* poll - default */
NULL, /* ioctl - default */
NULL, /* mmap */
NULL, /* 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, /* readpage */
NULL, /* writepage */
NULL, /* bmap */
NULL, /* truncate */
NULL /* permission */
};
static struct dentry * proc_follow_link(struct inode *inode, struct dentry *base)
{
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)
return result;
ino = inode->i_ino;
pid = ino >> 16;
ino &= 0x0000ffff;
p = find_task_by_pid(pid);
result = ERR_PTR(-ENOENT);
if (!p)
return result;
switch (ino) {
case PROC_PID_CWD:
if (!p->fs || !p->fs->pwd)
break;
result = dget(p->fs->pwd);
break;
case PROC_PID_ROOT:
if (!p->fs || !p->fs->root)
break;
result = dget(p->fs->root);
break;
case PROC_PID_EXE: {
struct vm_area_struct * vma;
if (!p->mm)
break;
vma = p->mm->mmap;
while (vma) {
if (vma->vm_flags & VM_EXECUTABLE)
return dget(vma->vm_dentry);
vma = vma->vm_next;
}
break;
}
default:
switch (ino >> 8) {
case PROC_PID_FD_DIR:
if (!p->files)
break;
ino &= 0xff;
if (ino >= NR_OPEN)
break;
if (!p->files->fd[ino])
break;
if (!p->files->fd[ino]->f_dentry)
break;
result = dget(p->files->fd[ino]->f_dentry);
break;
}
}
return result;
}
static int proc_readlink(struct inode * inode, char * buffer, int buflen)
{
int error;
struct dentry * dentry = proc_follow_link(inode, NULL);
error = PTR_ERR(dentry);
if (!IS_ERR(dentry)) {
error = -ENOENT;
if (dentry) {
char * tmp = (char*)__get_free_page(GFP_KERNEL), *path;
int len;
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);
error = buflen;
}
}
return error;
}
|
