/usr/src/lttng-modules-2.5.1/probes/lttng-probe-user.c is in lttng-modules-dkms 2.5.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 | /*
* lttng-probe-user.c
*
* Copyright (C) 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; only
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <linux/uaccess.h>
#include "lttng-probe-user.h"
/*
* Calculate string length. Include final null terminating character if there is
* one, or ends at first fault. Disabling page faults ensures that we can safely
* call this from pretty much any context, including those where the caller
* holds mmap_sem, or any lock which nests in mmap_sem.
*/
long lttng_strlen_user_inatomic(const char *addr)
{
long count = 0;
mm_segment_t old_fs = get_fs();
set_fs(KERNEL_DS);
pagefault_disable();
for (;;) {
char v;
unsigned long ret;
ret = __copy_from_user_inatomic(&v,
(__force const char __user *)(addr),
sizeof(v));
if (unlikely(ret > 0))
break;
count++;
if (unlikely(!v))
break;
addr++;
}
pagefault_enable();
set_fs(old_fs);
return count;
}
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