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68 lines
2.5 KiB
C
68 lines
2.5 KiB
C
/* Copyright (C) 2008-2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <sys/times.h>
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#include <sysdep.h>
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clock_t
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__times (struct tms *buf)
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{
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INTERNAL_SYSCALL_DECL (err);
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clock_t ret = INTERNAL_SYSCALL (times, err, 1, buf);
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if (INTERNAL_SYSCALL_ERROR_P (ret, err)
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&& __builtin_expect (INTERNAL_SYSCALL_ERRNO (ret, err) == EFAULT, 0)
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&& buf)
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{
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/* This might be an error or not. For architectures which have no
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separate return value and error indicators we cannot
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distinguish a return value of e.g. (clock_t) -14 from -EFAULT.
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Therefore the only course of action is to dereference the user
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-supplied structure on a return of (clock_t) -14. This will crash
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applications which pass in an invalid non-NULL BUF pointer.
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Note that Linux allows BUF to be NULL in which case we skip this. */
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#define touch(v) \
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do { \
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clock_t temp = v; \
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asm volatile ("" : "+r" (temp)); \
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v = temp; \
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} while (0)
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touch (buf->tms_utime);
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touch (buf->tms_stime);
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touch (buf->tms_cutime);
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touch (buf->tms_cstime);
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/* If we come here the memory is valid and the kernel did not
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return an EFAULT error, but rather e.g. (clock_t) -14.
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Return the value given by the kernel. */
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}
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/* On Linux this function never fails except with EFAULT.
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POSIX says that returning a value (clock_t) -1 indicates an error,
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but on Linux this is simply one of the valid clock values after
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clock_t wraps. Therefore when we would return (clock_t) -1, we
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instead return (clock_t) 0, and loose a tick of accuracy (having
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returned 0 for two consecutive calls even though the clock
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advanced). */
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if (ret == (clock_t) -1)
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return (clock_t) 0;
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return ret;
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}
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weak_alias (__times, times)
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