1/* Copyright (C) 2008-2020 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 <https://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 clock_t ret = INTERNAL_SYSCALL_CALL (times, buf);
27 if (INTERNAL_SYSCALL_ERROR_P (ret)
28 && __glibc_unlikely (INTERNAL_SYSCALL_ERRNO (ret) == EFAULT)
29 && buf)
30 {
31 /* This might be an error or not. For architectures which have no
32 separate return value and error indicators we cannot
33 distinguish a return value of e.g. (clock_t) -14 from -EFAULT.
34 Therefore the only course of action is to dereference the user
35 -supplied structure on a return of (clock_t) -14. This will crash
36 applications which pass in an invalid non-NULL BUF pointer.
37 Note that Linux allows BUF to be NULL in which case we skip this. */
38#define touch(v) \
39 do { \
40 clock_t temp = v; \
41 asm volatile ("" : "+r" (temp)); \
42 v = temp; \
43 } while (0)
44 touch (buf->tms_utime);
45 touch (buf->tms_stime);
46 touch (buf->tms_cutime);
47 touch (buf->tms_cstime);
48
49 /* If we come here the memory is valid and the kernel did not
50 return an EFAULT error, but rather e.g. (clock_t) -14.
51 Return the value given by the kernel. */
52 }
53
54 /* On Linux this function never fails except with EFAULT.
55 POSIX says that returning a value (clock_t) -1 indicates an error,
56 but on Linux this is simply one of the valid clock values after
57 clock_t wraps. Therefore when we would return (clock_t) -1, we
58 instead return (clock_t) 0, and loose a tick of accuracy (having
59 returned 0 for two consecutive calls even though the clock
60 advanced). */
61 if (ret == (clock_t) -1)
62 return (clock_t) 0;
63
64 return ret;
65}
66weak_alias (__times, times)
67