1/* Copyright (C) 2008-2019 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
23clock_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}
67weak_alias (__times, times)
68