[lttng-modules.git] / probes / lttng-probe-user.c

/*
 * 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 <linux/module.h>
#include <probes/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;

	if (!addr)
		return 0;

	old_fs = get_fs();
	set_fs(KERNEL_DS);
	pagefault_disable();
	for (;;) {
		char v;
		unsigned long ret;

		if (unlikely(!access_ok(VERIFY_READ,
				(__force const char __user *) addr,
				sizeof(v))))
			break;
		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;
}
EXPORT_SYMBOL_GPL(lttng_strlen_user_inatomic);
Commit	Line	Data
7b8ea3a5 MD	1	/*
	2	* lttng-probe-user.c
	3	*
	4	* Copyright (C) 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	5	*
	6	* This library is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU Lesser General Public
	8	* License as published by the Free Software Foundation; only
	9	* version 2.1 of the License.
	10	*
	11	* This library is distributed in the hope that it will be useful,
	12	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	14	* Lesser General Public License for more details.
	15	*
	16	* You should have received a copy of the GNU Lesser General Public
	17	* License along with this library; if not, write to the Free Software
	18	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	19	*/
	20
	21	#include <linux/uaccess.h>
8d90c035	22	#include <linux/module.h>
156a3977	23	#include <probes/lttng-probe-user.h>
7b8ea3a5 MD	24
	25	/*
	26	* Calculate string length. Include final null terminating character if there is
	27	* one, or ends at first fault. Disabling page faults ensures that we can safely
	28	* call this from pretty much any context, including those where the caller
	29	* holds mmap_sem, or any lock which nests in mmap_sem.
	30	*/
	31	long lttng_strlen_user_inatomic(const char *addr)
	32	{
	33	long count = 0;
a824008c	34	mm_segment_t old_fs;
7b8ea3a5	35
a824008c MD	36	if (!addr)
	37	return 0;
	38
	39	old_fs = get_fs();
7b8ea3a5 MD	40	set_fs(KERNEL_DS);
	41	pagefault_disable();
	42	for (;;) {
	43	char v;
2a8b83a1	44	unsigned long ret;
7b8ea3a5	45
f127e61e MD	46	if (unlikely(!access_ok(VERIFY_READ,
	47	(__force const char __user *) addr,
	48	sizeof(v))))
	49	break;
7b8ea3a5 MD	50	ret = __copy_from_user_inatomic(&v,
	51	(__force const char __user *)(addr),
	52	sizeof(v));
2a8b83a1	53	if (unlikely(ret > 0))
7b8ea3a5 MD	54	break;
	55	count++;
	56	if (unlikely(!v))
	57	break;
	58	addr++;
	59	}
	60	pagefault_enable();
	61	set_fs(old_fs);
	62	return count;
	63	}
f127e61e	64	EXPORT_SYMBOL_GPL(lttng_strlen_user_inatomic);