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/*
* SPDX-FileCopyrightText: 2017 Francis Deslauriers <francis.deslauriers@efficios.com>
*
* SPDX-License-Identifier: LGPL-2.1-only
*
*/
#include "utils.h"
#include <common/align.hpp>
#include <common/error.hpp>
#include <fcntl.h>
#include <stdio.h>
#include <sys/syscall.h>
#include <unistd.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 += sysconf(_SC_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
* in combinaison with LTTng's PID tracker feature where we can trace the kernel
* events generated by our test process only.
*/
int main(int argc, char **argv)
{
int ret;
const char *start_file, *path1, *path2;
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]);
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
* (typically the test script) before executing the syscalls.
*/
ret = wait_on_file(start_file);
if (ret != 0) {
goto error;
}
/*
* Start generating syscalls. We use syscall(2) to prevent libc to change
* the underlying syscall. e.g. calling openat(2) instead of open(2).
*/
ret = open_read_close(path1);
if (ret == -1) {
ret = -1;
goto error;
}
ret = open_read_close(path2);
if (ret == -1) {
ret = -1;
goto error;
}
error:
return ret;
}
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