linux/tools/testing/selftests/powerpc/ptrace/child.h

// SPDX-License-Identifier: GPL-2.0+
/*
 * Helper functions to sync execution between parent and child processes.
 *
 * Copyright 2018, Thiago Jung Bauermann, IBM Corporation.
 */
#include <stdio.h>
#include <stdbool.h>
#include <semaphore.h>

/*
 * Information in a shared memory location for synchronization between child and
 * parent.
 */
struct child_sync {
	/* The parent waits on this semaphore. */
	sem_t sem_parent;

	/* If true, the child should give up as well. */
	bool parent_gave_up;

	/* The child waits on this semaphore. */
	sem_t sem_child;

	/* If true, the parent should give up as well. */
	bool child_gave_up;
};

#define CHILD_FAIL_IF(x, sync)						\
	do {								\
		if (x) {						\
			fprintf(stderr,					\
				"[FAIL] Test FAILED on line %d\n", __LINE__); \
			(sync)->child_gave_up = true;			\
			prod_parent(sync);				\
			return 1;					\
		}							\
	} while (0)

#define PARENT_FAIL_IF(x, sync)						\
	do {								\
		if (x) {						\
			fprintf(stderr,					\
				"[FAIL] Test FAILED on line %d\n", __LINE__); \
			(sync)->parent_gave_up = true;			\
			prod_child(sync);				\
			return 1;					\
		}							\
	} while (0)

#define PARENT_SKIP_IF_UNSUPPORTED(x, sync)				\
	do {								\
		if ((x) == -1 && (errno == ENODEV || errno == EINVAL)) { \
			(sync)->parent_gave_up = true;			\
			prod_child(sync);				\
			SKIP_IF(1);					\
		}							\
	} while (0)

int init_child_sync(struct child_sync *sync)
{
	int ret;

	ret = sem_init(&sync->sem_parent, 1, 0);
	if (ret) {
		perror("Semaphore initialization failed");
		return 1;
	}

	ret = sem_init(&sync->sem_child, 1, 0);
	if (ret) {
		perror("Semaphore initialization failed");
		return 1;
	}

	return 0;
}

void destroy_child_sync(struct child_sync *sync)
{
	sem_destroy(&sync->sem_parent);
	sem_destroy(&sync->sem_child);
}

int wait_child(struct child_sync *sync)
{
	int ret;

	/* Wait until the child prods us. */
	ret = sem_wait(&sync->sem_parent);
	if (ret) {
		perror("Error waiting for child");
		return 1;
	}

	return sync->child_gave_up;
}

int prod_child(struct child_sync *sync)
{
	int ret;

	/* Unblock the child now. */
	ret = sem_post(&sync->sem_child);
	if (ret) {
		perror("Error prodding child");
		return 1;
	}

	return 0;
}

int wait_parent(struct child_sync *sync)
{
	int ret;

	/* Wait until the parent prods us. */
	ret = sem_wait(&sync->sem_child);
	if (ret) {
		perror("Error waiting for parent");
		return 1;
	}

	return sync->parent_gave_up;
}

int prod_parent(struct child_sync *sync)
{
	int ret;

	/* Unblock the parent now. */
	ret = sem_post(&sync->sem_parent);
	if (ret) {
		perror("Error prodding parent");
		return 1;
	}

	return 0;
}