1 /*
2 * linux/kernel/acct.c
3 *
4 * BSD Process Accounting for Linux
5 *
6 * Author: Marco van Wieringen <mvw@planets.elm.net>
7 *
8 * Some code based on ideas and code from:
9 * Thomas K. Dyas <tdyas@eden.rutgers.edu>
10 *
11 * This file implements BSD-style process accounting. Whenever any
12 * process exits, an accounting record of type "struct acct" is
13 * written to the file specified with the acct() system call. It is
14 * up to user-level programs to do useful things with the accounting
15 * log. The kernel just provides the raw accounting information.
16 *
17 * (C) Copyright 1995 - 1997 Marco van Wieringen - ELM Consultancy B.V.
18 *
19 * Plugged two leaks. 1) It didn't return acct_file into the free_filps if
20 * the file happened to be read-only. 2) If the accounting was suspended
21 * due to the lack of space it happily allowed to reopen it and completely
22 * lost the old acct_file. 3/10/98, Al Viro.
23 *
24 * Now we silently close acct_file on attempt to reopen. Cleaned sys_acct().
25 * XTerms and EMACS are manifestations of pure evil. 21/10/98, AV.
26 *
27 * Fixed a nasty interaction with with sys_umount(). If the accointing
28 * was suspeneded we failed to stop it on umount(). Messy.
29 * Another one: remount to readonly didn't stop accounting.
30 * Question: what should we do if we have CAP_SYS_ADMIN but not
31 * CAP_SYS_PACCT? Current code does the following: umount returns -EBUSY
32 * unless we are messing with the root. In that case we are getting a
33 * real mess with do_remount_sb(). 9/11/98, AV.
34 *
35 * Fixed a bunch of races (and pair of leaks). Probably not the best way,
36 * but this one obviously doesn't introduce deadlocks. Later. BTW, found
37 * one race (and leak) in BSD implementation.
38 * OK, that's better. ANOTHER race and leak in BSD variant. There always
39 * is one more bug... 10/11/98, AV.
40 *
41 * Oh, fsck... Oopsable SMP race in do_process_acct() - we must hold
42 * ->mmap_sem to walk the vma list of current->mm. Nasty, since it leaks
43 * a struct file opened for write. Fixed. 2/6/2000, AV.
44 */
45
46 #include <linux/config.h>
47 #include <linux/errno.h>
48 #include <linux/kernel.h>
49
50 #ifdef CONFIG_BSD_PROCESS_ACCT
51 #include <linux/mm.h>
52 #include <linux/slab.h>
53 #include <linux/acct.h>
54 #include <linux/smp_lock.h>
55 #include <linux/file.h>
56
57 #include <asm/uaccess.h>
58
59 /*
60 * These constants control the amount of freespace that suspend and
61 * resume the process accounting system, and the time delay between
62 * each check.
63 * Turned into sysctl-controllable parameters. AV, 12/11/98
64 */
65
66 int acct_parm[3] = {4, 2, 30};
67 #define RESUME (acct_parm[0]) /* >foo% free space - resume */
68 #define SUSPEND (acct_parm[1]) /* <foo% free space - suspend */
69 #define ACCT_TIMEOUT (acct_parm[2]) /* foo second timeout between checks */
70
71 /*
72 * External references and all of the globals.
73 */
74
75 static volatile int acct_active;
76 static volatile int acct_needcheck;
77 static struct file *acct_file;
78 static struct timer_list acct_timer;
79 static void do_acct_process(long, struct file *);
80
81 /*
82 * Called whenever the timer says to check the free space.
83 */
84 static void acct_timeout(unsigned long unused)
85 {
86 acct_needcheck = 1;
87 }
88
89 /*
90 * Check the amount of free space and suspend/resume accordingly.
91 */
92 static int check_free_space(struct file *file)
93 {
94 struct statfs sbuf;
95 int res;
96 int act;
97
98 lock_kernel();
99 res = acct_active;
100 if (!file || !acct_needcheck)
101 goto out;
102 unlock_kernel();
103
104 /* May block */
105 if (vfs_statfs(file->f_dentry->d_inode->i_sb, &sbuf))
106 return res;
107
108 if (sbuf.f_bavail <= SUSPEND * sbuf.f_blocks / 100)
109 act = -1;
110 else if (sbuf.f_bavail >= RESUME * sbuf.f_blocks / 100)
111 act = 1;
112 else
113 act = 0;
114
115 /*
116 * If some joker switched acct_file under us we'ld better be
117 * silent and _not_ touch anything.
118 */
119 lock_kernel();
120 if (file != acct_file) {
121 if (act)
122 res = act>0;
123 goto out;
124 }
125
126 if (acct_active) {
127 if (act < 0) {
128 acct_active = 0;
129 printk(KERN_INFO "Process accounting paused\n");
130 }
131 } else {
132 if (act > 0) {
133 acct_active = 1;
134 printk(KERN_INFO "Process accounting resumed\n");
135 }
136 }
137
138 del_timer(&acct_timer);
139 acct_needcheck = 0;
140 acct_timer.expires = jiffies + ACCT_TIMEOUT*HZ;
141 add_timer(&acct_timer);
142 res = acct_active;
143 out:
144 unlock_kernel();
145 return res;
146 }
147
148 /*
149 * sys_acct() is the only system call needed to implement process
150 * accounting. It takes the name of the file where accounting records
151 * should be written. If the filename is NULL, accounting will be
152 * shutdown.
153 */
154 asmlinkage long sys_acct(const char *name)
155 {
156 struct file *file = NULL, *old_acct = NULL;
157 char *tmp;
158 int error;
159
160 if (!capable(CAP_SYS_PACCT))
161 return -EPERM;
162
163 if (name) {
164 tmp = getname(name);
165 error = PTR_ERR(tmp);
166 if (IS_ERR(tmp))
167 goto out;
168 /* Difference from BSD - they don't do O_APPEND */
169 file = filp_open(tmp, O_WRONLY|O_APPEND, 0);
170 putname(tmp);
171 if (IS_ERR(file)) {
172 error = PTR_ERR(file);
173 goto out;
174 }
175 error = -EACCES;
176 if (!S_ISREG(file->f_dentry->d_inode->i_mode))
177 goto out_err;
178
179 error = -EIO;
180 if (!file->f_op->write)
181 goto out_err;
182 }
183
184 error = 0;
185 lock_kernel();
186 if (acct_file) {
187 old_acct = acct_file;
188 del_timer(&acct_timer);
189 acct_active = 0;
190 acct_needcheck = 0;
191 acct_file = NULL;
192 }
193 if (name) {
194 acct_file = file;
195 acct_needcheck = 0;
196 acct_active = 1;
197 /* It's been deleted if it was used before so this is safe */
198 init_timer(&acct_timer);
199 acct_timer.function = acct_timeout;
200 acct_timer.expires = jiffies + ACCT_TIMEOUT*HZ;
201 add_timer(&acct_timer);
202 }
203 unlock_kernel();
204 if (old_acct) {
205 do_acct_process(0,old_acct);
206 filp_close(old_acct, NULL);
207 }
208 out:
209 return error;
210 out_err:
211 filp_close(file, NULL);
212 goto out;
213 }
214
215 void acct_auto_close(kdev_t dev)
216 {
217 lock_kernel();
218 if (acct_file && acct_file->f_dentry->d_inode->i_dev == dev)
219 sys_acct(NULL);
220 unlock_kernel();
221 }
222
223 /*
224 * encode an unsigned long into a comp_t
225 *
226 * This routine has been adopted from the encode_comp_t() function in
227 * the kern_acct.c file of the FreeBSD operating system. The encoding
228 * is a 13-bit fraction with a 3-bit (base 8) exponent.
229 */
230
231 #define MANTSIZE 13 /* 13 bit mantissa. */
232 #define EXPSIZE 3 /* Base 8 (3 bit) exponent. */
233 #define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */
234
235 static comp_t encode_comp_t(unsigned long value)
236 {
237 int exp, rnd;
238
239 exp = rnd = 0;
240 while (value > MAXFRACT) {
241 rnd = value & (1 << (EXPSIZE - 1)); /* Round up? */
242 value >>= EXPSIZE; /* Base 8 exponent == 3 bit shift. */
243 exp++;
244 }
245
246 /*
247 * If we need to round up, do it (and handle overflow correctly).
248 */
249 if (rnd && (++value > MAXFRACT)) {
250 value >>= EXPSIZE;
251 exp++;
252 }
253
254 /*
255 * Clean it up and polish it off.
256 */
257 exp <<= MANTSIZE; /* Shift the exponent into place */
258 exp += value; /* and add on the mantissa. */
259 return exp;
260 }
261
262 /*
263 * Write an accounting entry for an exiting process
264 *
265 * The acct_process() call is the workhorse of the process
266 * accounting system. The struct acct is built here and then written
267 * into the accounting file. This function should only be called from
268 * do_exit().
269 */
270
271 /*
272 * do_acct_process does all actual work. Caller holds the reference to file.
273 */
274 static void do_acct_process(long exitcode, struct file *file)
275 {
276 struct acct ac;
277 mm_segment_t fs;
278 unsigned long vsize;
279
280 /*
281 * First check to see if there is enough free_space to continue
282 * the process accounting system.
283 */
284 if (!check_free_space(file))
285 return;
286
287 /*
288 * Fill the accounting struct with the needed info as recorded
289 * by the different kernel functions.
290 */
291 memset((caddr_t)&ac, 0, sizeof(struct acct));
292
293 strncpy(ac.ac_comm, current->comm, ACCT_COMM);
294 ac.ac_comm[ACCT_COMM - 1] = '\0';
295
296 ac.ac_btime = CT_TO_SECS(current->start_time) + (xtime.tv_sec - (jiffies / HZ));
297 ac.ac_etime = encode_comp_t(jiffies - current->start_time);
298 ac.ac_utime = encode_comp_t(current->times.tms_utime);
299 ac.ac_stime = encode_comp_t(current->times.tms_stime);
300 ac.ac_uid = current->uid;
301 ac.ac_gid = current->gid;
302 ac.ac_tty = (current->tty) ? kdev_t_to_nr(current->tty->device) : 0;
303
304 ac.ac_flag = 0;
305 if (current->flags & PF_FORKNOEXEC)
306 ac.ac_flag |= AFORK;
307 if (current->flags & PF_SUPERPRIV)
308 ac.ac_flag |= ASU;
309 if (current->flags & PF_DUMPCORE)
310 ac.ac_flag |= ACORE;
311 if (current->flags & PF_SIGNALED)
312 ac.ac_flag |= AXSIG;
313
314 vsize = 0;
315 if (current->mm) {
316 struct vm_area_struct *vma;
317 down(¤t->mm->mmap_sem);
318 vma = current->mm->mmap;
319 while (vma) {
320 vsize += vma->vm_end - vma->vm_start;
321 vma = vma->vm_next;
322 }
323 up(¤t->mm->mmap_sem);
324 }
325 vsize = vsize / 1024;
326 ac.ac_mem = encode_comp_t(vsize);
327 ac.ac_io = encode_comp_t(0 /* current->io_usage */); /* %% */
328 ac.ac_rw = encode_comp_t(ac.ac_io / 1024);
329 ac.ac_minflt = encode_comp_t(current->min_flt);
330 ac.ac_majflt = encode_comp_t(current->maj_flt);
331 ac.ac_swaps = encode_comp_t(current->nswap);
332 ac.ac_exitcode = exitcode;
333
334 /*
335 * Kernel segment override to datasegment and write it
336 * to the accounting file.
337 */
338 fs = get_fs();
339 set_fs(KERNEL_DS);
340 file->f_op->write(file, (char *)&ac,
341 sizeof(struct acct), &file->f_pos);
342 set_fs(fs);
343 }
344
345 /*
346 * acct_process - now just a wrapper around do_acct_process
347 */
348 int acct_process(long exitcode)
349 {
350 struct file *file = NULL;
351 lock_kernel();
352 if (acct_file) {
353 file = acct_file;
354 get_file(file);
355 unlock_kernel();
356 do_acct_process(exitcode, acct_file);
357 fput(file);
358 } else
359 unlock_kernel();
360 return 0;
361 }
362
363 #else
364 /*
365 * Dummy system call when BSD process accounting is not configured
366 * into the kernel.
367 */
368
369 asmlinkage long sys_acct(const char * filename)
370 {
371 return -ENOSYS;
372 }
373 #endif
374
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