docs: Add supported versions and fix-backport policy

[lttng-tools.git] / tests / utils / testapp / gen-syscall-events-callstack / gen-syscall-events-callstack.c

/*
 * Copyright (C) 2017 Francis Deslauriers <francis.deslauriers@efficios.com>
 *
 * SPDX-License-Identifier: LGPL-2.1-only
 *
 */

#include "utils.h"

#include <fcntl.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>

/**
 * 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.
 */

#if defined(__clang__)
#define nooptimization __attribute__((noinline)) __attribute__((optnone))
#else
#define nooptimization __attribute__((noinline)) __attribute__((optimize(0)))
#endif

volatile int val = 0;

long nooptimization my_gettid(void);
long nooptimization my_gettid(void)
{
	long ret;
#ifdef __x86_64
	asm volatile("syscall" : "=a"(ret) : "0"(__NR_gettid) : "cc", "rcx", "r11", "memory");
#elif defined(__i386)
	asm volatile("int $0x80" : "=a"(ret) : "0"(__NR_gettid) : "cc", "edi", "esi", "memory");
#else
#error "Userspace callstack test not supported for this architecture."
#endif
	return ret;
}

int nooptimization fct_c(void);
int nooptimization fct_c(void)
{
	return my_gettid();
}

int nooptimization fct_b(void);
int nooptimization fct_b(void)
{
	val += fct_c();
	return val;
}

int nooptimization fct_a(void);
int nooptimization fct_a(void)
{
	val += fct_b();
	return val;
}

int main(int argc, char **argv)
{
	int ret = 0;
	char *start_file;

	if (argc != 2) {
		fprintf(stderr, "Error: Missing argument\n");
		fprintf(stderr, "USAGE: %s PATH_WAIT_FILE\n", argv[0]);
		ret = -1;
		goto error;
	}

	start_file = argv[1];

	/*
	 * Wait for the start_file to be created by an external process
	 * (typically the test script) before executing the syscall
	 */
	ret = wait_on_file(start_file);
	if (ret != 0) {
		goto error;
	}

	/* Start the callchain to the syscall */
	ret = fct_a();

	/* Return success */
	if (ret >= 0) {
		ret = 0;
	}

error:
	return ret;
}