/*
- * Copyright (C) - 2017 Francis Deslauriers <francis.deslauriers@efficios.com>
+ * Copyright (C) 2017 Francis Deslauriers <francis.deslauriers@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; version 2.1 of the License.
+ * SPDX-License-Identifier: LGPL-2.1-only
*
- * 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
*/
-#define _LGPL_SOURCE
-
#include <fcntl.h>
#include <stdio.h>
#include <sys/syscall.h>
#include <unistd.h>
+#include <common/error.h>
+#include <common/align.h>
#include "utils.h"
#define MAX_LEN 16
+
+/*
+ * The LTTng system call tracing facilities can't handle page faults at the
+ * moment. If a fault would occur while reading a syscall argument, the
+ * tracer will report an empty string (""). Since the proper execution of the
+ * tests which use this generator depends on some syscall string arguments being
+ * present, this util allows us to mitigate the page-fault risk.
+ *
+ * This isn't a proper fix; it is simply the best we can do for now.
+ * See bug #1261 for more context.
+ */
+static
+void prefault_string(const char *p)
+{
+ const char * const end = p + strlen(p) + 1;
+
+ while (p < end) {
+ /*
+ * Trigger a read attempt on *p, faulting-in the pages
+ * for reading.
+ */
+ asm volatile("" : : "m"(*p));
+ p += PAGE_SIZE;
+ }
+}
+
+static
+int open_read_close(const char *path)
+{
+ int fd, ret;
+ char buf[MAX_LEN];
+
+ /*
+ * Start generating syscalls. We use syscall(2) to prevent libc from
+ * changing the underlying syscall (e.g. calling openat(2) instead of
+ * open(2)).
+ */
+ prefault_string(path);
+ fd = syscall(SYS_openat, AT_FDCWD, path, O_RDONLY);
+ if (fd < 0) {
+ PERROR_NO_LOGGER("Failed to open file with openat(): path = '%s'", path);
+ ret = -1;
+ goto error;
+ }
+
+ ret = syscall(SYS_read, fd, buf, MAX_LEN);
+ if (ret < 0) {
+ PERROR_NO_LOGGER("Failed to read file: path = '%s', fd = %d, length = %d",
+ path, fd, MAX_LEN);
+ ret = -1;
+ goto error;
+ }
+
+ ret = syscall(SYS_close, fd);
+ if (ret == -1) {
+ PERROR_NO_LOGGER("Failed to close file: path = '%s', fd = %d", path, fd);
+ ret = -1;
+ goto error;
+ }
+
+error:
+ return ret;
+}
+
/*
* The process waits for the creation of a file passed as argument from an
* external processes to execute a syscall and exiting. This is useful for tests
*/
int main(int argc, char **argv)
{
- int fd, ret;
- char buf[MAX_LEN];
- char *start_file;
+ int ret;
+ const char *start_file, *path1, *path2;
- if (argc != 2) {
+ if (argc != 4) {
fprintf(stderr, "Error: Missing argument\n");
+ fprintf(stderr, "USAGE: %s PATH_WAIT_FILE PATH1_TO_OPEN PATH2_TO_OPEN\n", argv[0]);
fprintf(stderr, "USAGE: %s PATH_WAIT_FILE\n", argv[0]);
ret = -1;
goto error;
}
start_file = argv[1];
+ path1 = argv[2];
+ path2 = argv[3];
/*
* Wait for the start_file to be created by an external process
* Start generating syscalls. We use syscall(2) to prevent libc to change
* the underlying syscall. e.g. calling openat(2) instead of open(2).
*/
- fd = syscall(SYS_open, "/proc/cpuinfo", O_RDONLY);
- if (fd < 0) {
- perror("open");
- ret = -1;
- goto error;
- }
-
- ret = syscall(SYS_read, fd, buf, MAX_LEN);
- if (ret < 0) {
- perror("read");
+ ret = open_read_close(path1);
+ if (ret == -1) {
ret = -1;
goto error;
}
- ret = syscall(SYS_close, fd);
+ ret = open_read_close(path2);
if (ret == -1) {
- perror("close");
ret = -1;
goto error;
}