syscall-intercept 0.1.0

Userspace syscall intercepting library.
Documentation 
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/*
 * Copyright 2017, Intel Corporation
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in
 *       the documentation and/or other materials provided with the
 *       distribution.
 *
 *     * Neither the name of the copyright holder nor the names of its
 *       contributors may be used to endorse or promote products derived
 *       from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * magic_syscalls.h - internal interface used to send messages
 *  to libsyscall_intercept from testing code. Using this dirty trick
 *  avoids adding additional symbols to the public interface just
 *  for testing.
 *
 * If the need arises, this can be disabled by defining the
 * SYSCALL_INTERCEPT_WITHOUT_MAGIC_SYSCALLS macro during compilation.
 *
 * At the moment there are only two 'magic' syscalls which trigger
 * this feature:
 *
 * write(123, start_log_message, sizeof(start_log_message))
 * write(123, stop_log_message, sizeof(stop_log_message))
 *
 * These two syscalls are not handled as regular syscalls i.e.:
 * they are not forwarded to the kernel, neither to a hook routine.
 *
 * Notice: the arguments of the syscall must match exactly. Thus, if
 * for example a file with 123 is open, this feature does not interfere with
 * actual file operations on that file. A syscall such as:
 * write(123, "data", 4)
 * is handled as expected -- forwarded to kernel, or to hook routine.
 */

#ifndef INTERCEPT_MAGIC_SYSCALLS_H
#define INTERCEPT_MAGIC_SYSCALLS_H

#ifndef SYSCALL_INTERCEPT_WITHOUT_MAGIC_SYSCALLS


#include <syscall.h>
#include <unistd.h>

struct syscall_desc;

enum { SYSCALL_INT_MAGIC_WRITE_FD = 123 };

static const char start_log_message[] = "SYSCALL_INTERCEPT_TEST_START_LOG";
static const char stop_log_message[] = "SYSCALL_INTERCEPT_TEST_STOP_LOG";

static inline void
magic_syscall_start_log(const char *path, const char *trunc)
{
	syscall(SYS_write, SYSCALL_INT_MAGIC_WRITE_FD,
	    start_log_message, sizeof(start_log_message),
	    path, trunc);
}

static inline void
magic_syscall_stop_log(void)
{
	syscall(SYS_write, SYSCALL_INT_MAGIC_WRITE_FD,
	    stop_log_message, sizeof(stop_log_message));
}

int handle_magic_syscalls(struct syscall_desc *desc, long *result);


#else /* SYSCALL_INTERCEPT_WITHOUT_MAGIC_SYSCALLS */


static inline void
magic_syscall_start_log(const char *path)
{
	(void) path;
}

static inline void
magic_syscall_stop_log(void)
{
}

static inline int
handle_magic_syscalls(struct syscall_desc *desc, long *result);
{
	(void) result;
	(void) desc;

	return -1;
}


#endif /* SYSCALL_INTERCEPT_WITHOUT_MAGIC_SYSCALLS */

#endif