tests: compile some tools/tests as C++
[lttng-tools.git] / tests / utils / testapp / gen-syscall-events / gen-syscall-events.cpp
1 /*
2 * Copyright (C) 2017 Francis Deslauriers <francis.deslauriers@efficios.com>
3 *
4 * SPDX-License-Identifier: LGPL-2.1-only
5 *
6 */
7
8 #include <fcntl.h>
9 #include <stdio.h>
10 #include <sys/syscall.h>
11 #include <unistd.h>
12 #include <common/error.h>
13 #include <common/align.h>
14
15 #include "utils.h"
16
17 #define MAX_LEN 16
18
19 /*
20 * The LTTng system call tracing facilities can't handle page faults at the
21 * moment. If a fault would occur while reading a syscall argument, the
22 * tracer will report an empty string (""). Since the proper execution of the
23 * tests which use this generator depends on some syscall string arguments being
24 * present, this util allows us to mitigate the page-fault risk.
25 *
26 * This isn't a proper fix; it is simply the best we can do for now.
27 * See bug #1261 for more context.
28 */
29 static
30 void prefault_string(const char *p)
31 {
32 const char * const end = p + strlen(p) + 1;
33
34 while (p < end) {
35 /*
36 * Trigger a read attempt on *p, faulting-in the pages
37 * for reading.
38 */
39 asm volatile("" : : "m"(*p));
40 p += sysconf(_SC_PAGE_SIZE);
41 }
42 }
43
44 static
45 int open_read_close(const char *path)
46 {
47 int fd, ret;
48 char buf[MAX_LEN];
49
50 /*
51 * Start generating syscalls. We use syscall(2) to prevent libc from
52 * changing the underlying syscall (e.g. calling openat(2) instead of
53 * open(2)).
54 */
55 prefault_string(path);
56 fd = syscall(SYS_openat, AT_FDCWD, path, O_RDONLY);
57 if (fd < 0) {
58 PERROR_NO_LOGGER("Failed to open file with openat(): path = '%s'", path);
59 ret = -1;
60 goto error;
61 }
62
63 ret = syscall(SYS_read, fd, buf, MAX_LEN);
64 if (ret < 0) {
65 PERROR_NO_LOGGER("Failed to read file: path = '%s', fd = %d, length = %d",
66 path, fd, MAX_LEN);
67 ret = -1;
68 goto error;
69 }
70
71 ret = syscall(SYS_close, fd);
72 if (ret == -1) {
73 PERROR_NO_LOGGER("Failed to close file: path = '%s', fd = %d", path, fd);
74 ret = -1;
75 goto error;
76 }
77
78 error:
79 return ret;
80 }
81
82 /*
83 * The process waits for the creation of a file passed as argument from an
84 * external processes to execute a syscall and exiting. This is useful for tests
85 * in combinaison with LTTng's PID tracker feature where we can trace the kernel
86 * events generated by our test process only.
87 */
88 int main(int argc, char **argv)
89 {
90 int ret;
91 const char *start_file, *path1, *path2;
92
93 if (argc != 4) {
94 fprintf(stderr, "Error: Missing argument\n");
95 fprintf(stderr, "USAGE: %s PATH_WAIT_FILE PATH1_TO_OPEN PATH2_TO_OPEN\n", argv[0]);
96 ret = -1;
97 goto error;
98 }
99
100 start_file = argv[1];
101 path1 = argv[2];
102 path2 = argv[3];
103
104 /*
105 * Wait for the start_file to be created by an external process
106 * (typically the test script) before executing the syscalls.
107 */
108 ret = wait_on_file(start_file);
109 if (ret != 0) {
110 goto error;
111 }
112
113 /*
114 * Start generating syscalls. We use syscall(2) to prevent libc to change
115 * the underlying syscall. e.g. calling openat(2) instead of open(2).
116 */
117 ret = open_read_close(path1);
118 if (ret == -1) {
119 ret = -1;
120 goto error;
121 }
122
123 ret = open_read_close(path2);
124 if (ret == -1) {
125 ret = -1;
126 goto error;
127 }
128
129 error:
130 return ret;
131 }
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