linux-curproc.c revision 2eb90a757e9d953c9e2a8fce530422189992fb1b 
1/*
2 * GPL HEADER START
3 *
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 only,
8 * as published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13 * General Public License version 2 for more details (a copy is included
14 * in the LICENSE file that accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License
17 * version 2 along with this program; If not, see
18 * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
19 *
20 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
21 * CA 95054 USA or visit www.sun.com if you need additional information or
22 * have any questions.
23 *
24 * GPL HEADER END
25 */
26/*
27 * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
28 * Use is subject to license terms.
29 *
30 * Copyright (c) 2011, 2012, Intel Corporation.
31 */
32/*
33 * This file is part of Lustre, http://www.lustre.org/
34 * Lustre is a trademark of Sun Microsystems, Inc.
35 *
36 * libcfs/libcfs/linux/linux-curproc.c
37 *
38 * Lustre curproc API implementation for Linux kernel
39 *
40 * Author: Nikita Danilov <nikita@clusterfs.com>
41 */
42
43#include <linux/sched.h>
44#include <linux/fs_struct.h>
45
46#include <linux/compat.h>
47#include <linux/thread_info.h>
48
49#define DEBUG_SUBSYSTEM S_LNET
50
51#include <linux/libcfs/libcfs.h>
52
53/*
54 * Implementation of cfs_curproc API (see portals/include/libcfs/curproc.h)
55 * for Linux kernel.
56 */
57
58void cfs_cap_raise(cfs_cap_t cap)
59{
60	struct cred *cred;
61	if ((cred = prepare_creds())) {
62		cap_raise(cred->cap_effective, cap);
63		commit_creds(cred);
64	}
65}
66
67void cfs_cap_lower(cfs_cap_t cap)
68{
69	struct cred *cred;
70	if ((cred = prepare_creds())) {
71		cap_lower(cred->cap_effective, cap);
72		commit_creds(cred);
73	}
74}
75
76int cfs_cap_raised(cfs_cap_t cap)
77{
78	return cap_raised(current_cap(), cap);
79}
80
81void cfs_kernel_cap_pack(kernel_cap_t kcap, cfs_cap_t *cap)
82{
83	/* XXX lost high byte */
84	*cap = kcap.cap[0];
85}
86
87void cfs_kernel_cap_unpack(kernel_cap_t *kcap, cfs_cap_t cap)
88{
89	kcap->cap[0] = cap;
90}
91
92cfs_cap_t cfs_curproc_cap_pack(void)
93{
94	cfs_cap_t cap;
95	cfs_kernel_cap_pack(current_cap(), &cap);
96	return cap;
97}
98
99static int cfs_access_process_vm(struct task_struct *tsk, unsigned long addr,
100				 void *buf, int len, int write)
101{
102	/* Just copied from kernel for the kernels which doesn't
103	 * have access_process_vm() exported */
104	struct mm_struct *mm;
105	struct vm_area_struct *vma;
106	struct page *page;
107	void *old_buf = buf;
108
109	mm = get_task_mm(tsk);
110	if (!mm)
111		return 0;
112
113	down_read(&mm->mmap_sem);
114	/* ignore errors, just check how much was successfully transferred */
115	while (len) {
116		int bytes, rc, offset;
117		void *maddr;
118
119		rc = get_user_pages(tsk, mm, addr, 1,
120				     write, 1, &page, &vma);
121		if (rc <= 0)
122			break;
123
124		bytes = len;
125		offset = addr & (PAGE_SIZE-1);
126		if (bytes > PAGE_SIZE-offset)
127			bytes = PAGE_SIZE-offset;
128
129		maddr = kmap(page);
130		if (write) {
131			copy_to_user_page(vma, page, addr,
132					  maddr + offset, buf, bytes);
133			set_page_dirty_lock(page);
134		} else {
135			copy_from_user_page(vma, page, addr,
136					    buf, maddr + offset, bytes);
137		}
138		kunmap(page);
139		page_cache_release(page);
140		len -= bytes;
141		buf += bytes;
142		addr += bytes;
143	}
144	up_read(&mm->mmap_sem);
145	mmput(mm);
146
147	return buf - old_buf;
148}
149
150/* Read the environment variable of current process specified by @key. */
151int cfs_get_environ(const char *key, char *value, int *val_len)
152{
153	struct mm_struct *mm;
154	char *buffer, *tmp_buf = NULL;
155	int buf_len = PAGE_CACHE_SIZE;
156	int key_len = strlen(key);
157	unsigned long addr;
158	int rc;
159
160	buffer = kmalloc(buf_len, GFP_USER);
161	if (!buffer)
162		return -ENOMEM;
163
164	mm = get_task_mm(current);
165	if (!mm) {
166		kfree(buffer);
167		return -EINVAL;
168	}
169
170	/* Avoid deadlocks on mmap_sem if called from sys_mmap_pgoff(),
171	 * which is already holding mmap_sem for writes.  If some other
172	 * thread gets the write lock in the meantime, this thread will
173	 * block, but at least it won't deadlock on itself.  LU-1735 */
174	if (down_read_trylock(&mm->mmap_sem) == 0) {
175		kfree(buffer);
176		return -EDEADLK;
177	}
178	up_read(&mm->mmap_sem);
179
180	addr = mm->env_start;
181	while (addr < mm->env_end) {
182		int this_len, retval, scan_len;
183		char *env_start, *env_end;
184
185		memset(buffer, 0, buf_len);
186
187		this_len = min_t(int, mm->env_end - addr, buf_len);
188		retval = cfs_access_process_vm(current, addr, buffer,
189					       this_len, 0);
190		if (retval != this_len)
191			break;
192
193		addr += retval;
194
195		/* Parse the buffer to find out the specified key/value pair.
196		 * The "key=value" entries are separated by '\0'. */
197		env_start = buffer;
198		scan_len = this_len;
199		while (scan_len) {
200			char *entry;
201			int entry_len;
202
203			env_end = memscan(env_start, '\0', scan_len);
204			LASSERT(env_end >= env_start &&
205				env_end <= env_start + scan_len);
206
207			/* The last entry of this buffer cross the buffer
208			 * boundary, reread it in next cycle. */
209			if (unlikely(env_end - env_start == scan_len)) {
210				/* This entry is too large to fit in buffer */
211				if (unlikely(scan_len == this_len)) {
212					CERROR("Too long env variable.\n");
213					GOTO(out, rc = -EINVAL);
214				}
215				addr -= scan_len;
216				break;
217			}
218
219			entry = env_start;
220			entry_len = env_end - env_start;
221
222			/* Key length + length of '=' */
223			if (entry_len > key_len + 1 &&
224			    !memcmp(entry, key, key_len)) {
225				entry += key_len + 1;
226				entry_len -= key_len + 1;
227				/* The 'value' buffer passed in is too small.*/
228				if (entry_len >= *val_len)
229					GOTO(out, rc = -EOVERFLOW);
230
231				memcpy(value, entry, entry_len);
232				*val_len = entry_len;
233				GOTO(out, rc = 0);
234			}
235
236			scan_len -= (env_end - env_start + 1);
237			env_start = env_end + 1;
238		}
239	}
240	GOTO(out, rc = -ENOENT);
241
242out:
243	mmput(mm);
244	kfree((void *)buffer);
245	if (tmp_buf)
246		kfree((void *)tmp_buf);
247	return rc;
248}
249EXPORT_SYMBOL(cfs_get_environ);
250
251EXPORT_SYMBOL(cfs_cap_raise);
252EXPORT_SYMBOL(cfs_cap_lower);
253EXPORT_SYMBOL(cfs_cap_raised);
254EXPORT_SYMBOL(cfs_curproc_cap_pack);
255
256/*
257 * Local variables:
258 * c-indentation-style: "K&R"
259 * c-basic-offset: 8
260 * tab-width: 8
261 * fill-column: 80
262 * scroll-step: 1
263 * End:
264 */
265