1 | /* Copyright (C) 2008-2017 Free Software Foundation, Inc. |
2 | This file is part of the GNU C Library. |
3 | |
4 | The GNU C Library is free software; you can redistribute it and/or |
5 | modify it under the terms of the GNU Lesser General Public |
6 | License as published by the Free Software Foundation; either |
7 | version 2.1 of the License, or (at your option) any later version. |
8 | |
9 | The GNU C Library is distributed in the hope that it will be useful, |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
12 | Lesser General Public License for more details. |
13 | |
14 | You should have received a copy of the GNU Lesser General Public |
15 | License along with the GNU C Library; if not, see |
16 | <http://www.gnu.org/licenses/>. */ |
17 | |
18 | #include <errno.h> |
19 | #include <sys/times.h> |
20 | #include <sysdep.h> |
21 | |
22 | |
23 | clock_t |
24 | __times (struct tms *buf) |
25 | { |
26 | INTERNAL_SYSCALL_DECL (err); |
27 | clock_t ret = INTERNAL_SYSCALL (times, err, 1, buf); |
28 | if (INTERNAL_SYSCALL_ERROR_P (ret, err) |
29 | && __builtin_expect (INTERNAL_SYSCALL_ERRNO (ret, err) == EFAULT, 0) |
30 | && buf) |
31 | { |
32 | /* This might be an error or not. For architectures which have no |
33 | separate return value and error indicators we cannot |
34 | distinguish a return value of e.g. (clock_t) -14 from -EFAULT. |
35 | Therefore the only course of action is to dereference the user |
36 | -supplied structure on a return of (clock_t) -14. This will crash |
37 | applications which pass in an invalid non-NULL BUF pointer. |
38 | Note that Linux allows BUF to be NULL in which case we skip this. */ |
39 | #define touch(v) \ |
40 | do { \ |
41 | clock_t temp = v; \ |
42 | asm volatile ("" : "+r" (temp)); \ |
43 | v = temp; \ |
44 | } while (0) |
45 | touch (buf->tms_utime); |
46 | touch (buf->tms_stime); |
47 | touch (buf->tms_cutime); |
48 | touch (buf->tms_cstime); |
49 | |
50 | /* If we come here the memory is valid and the kernel did not |
51 | return an EFAULT error, but rather e.g. (clock_t) -14. |
52 | Return the value given by the kernel. */ |
53 | } |
54 | |
55 | /* On Linux this function never fails except with EFAULT. |
56 | POSIX says that returning a value (clock_t) -1 indicates an error, |
57 | but on Linux this is simply one of the valid clock values after |
58 | clock_t wraps. Therefore when we would return (clock_t) -1, we |
59 | instead return (clock_t) 0, and loose a tick of accuracy (having |
60 | returned 0 for two consecutive calls even though the clock |
61 | advanced). */ |
62 | if (ret == (clock_t) -1) |
63 | return (clock_t) 0; |
64 | |
65 | return ret; |
66 | } |
67 | weak_alias (__times, times) |
68 | |