// https://syzkaller.appspot.com/bug?id=f43578b0440a3cd6f39af2bc30e5e4458f209025
// Copyright 2026 syzkaller project authors. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.

// IMPORTANT: Do not copy the macros or definitions below directly into your reproducer.
// Instead, add the following line to your reproducer:
// #include "race_toolkit.h"

// --- Race Condition Toolkit ---
// Macros and snippets for CPU pinning, memory barriers, and userfaultfd.

#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <linux/futex.h>
#include <linux/userfaultfd.h>
#include <poll.h>
#include <pthread.h>
#include <sched.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <time.h>
#include <unistd.h>

// Unbuffered I/O: Ensure logs are written immediately.
#define SETUP_UNBUFFERED_IO() setvbuf(stdout, NULL, _IONBF, 0)

// CPU Pinning: Pin the current thread to a specific CPU core.
#define PIN_TO_CPU(cpu)                                                \
	do {                                                           \
		cpu_set_t mask;                                        \
		CPU_ZERO(&mask);                                       \
		CPU_SET(cpu, &mask);                                   \
		if (sched_setaffinity(0, sizeof(mask), &mask) == -1) { \
			perror("sched_setaffinity");                   \
		}                                                      \
	} while (0)

// Memory Barrier: Ensure memory ordering.
#define MB() __atomic_thread_fence(__ATOMIC_SEQ_CST)

// Spin-wait Barrier: Wait until a memory location has a specific value.
// Best for tight race windows (low latency, no context switches).
#define WAIT_ON(addr, val)                                               \
	do {                                                             \
		while (__atomic_load_n(addr, __ATOMIC_ACQUIRE) != (val)) \
			;                                                \
	} while (0)

// Signal: Set a memory location to a specific value to release a WAIT_ON.
#define SIGNAL(addr, val) __atomic_store_n(addr, val, __ATOMIC_RELEASE)

// --- Timing Primitives ---
// Robust timing loops in VM environments (using CLOCK_MONOTONIC to avoid time(NULL) jumps).

static inline double timer_elapsed_sec(struct timespec* start)
{
	struct timespec now;
	if (clock_gettime(CLOCK_MONOTONIC, &now) == -1) {
		perror("clock_gettime(CLOCK_MONOTONIC) elapsed");
		exit(1);
	}
	return (double)(now.tv_sec - start->tv_sec) + (double)(now.tv_nsec - start->tv_nsec) / 1e9;
}

// Initialize a monotonic timer variable.
#define TIMER_START(t)                                          \
	struct timespec t;                                      \
	if (clock_gettime(CLOCK_MONOTONIC, &t) == -1) {         \
		perror("clock_gettime(CLOCK_MONOTONIC) start"); \
		exit(1);                                        \
	}

// Check if the elapsed time since 't' is less than 'sec' seconds.
#define TIMER_NOT_EXPIRED(t, sec) (timer_elapsed_sec(&(t)) < (double)(sec))

// Futex-based Event: Shared with syzkaller executor.
// Best for general synchronization or longer waits to save CPU.
typedef struct {
	int state;
} event_t;

static void event_init(event_t* ev)
{
	ev->state = 0;
}
static void event_reset(event_t* ev)
{
	ev->state = 0;
}

static void event_set(event_t* ev)
{
	if (__atomic_load_n(&ev->state, __ATOMIC_ACQUIRE)) {
		fprintf(stderr, "event already set\n");
		exit(1);
	}
	__atomic_store_n(&ev->state, 1, __ATOMIC_RELEASE);
	syscall(SYS_futex, &ev->state, FUTEX_WAKE | FUTEX_PRIVATE_FLAG, 1000000);
}

static void event_wait(event_t* ev)
{
	while (!__atomic_load_n(&ev->state, __ATOMIC_ACQUIRE))
		syscall(SYS_futex, &ev->state, FUTEX_WAIT | FUTEX_PRIVATE_FLAG, 0, 0);
}

// userfaultfd setup: Register a memory range for page fault handling.
static int setup_uffd(void* addr, size_t len)
{
	int uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
	if (uffd == -1)
		return -1;
	struct uffdio_api api = {.api = UFFD_API, .features = 0};
	if (ioctl(uffd, UFFDIO_API, &api) == -1) {
		close(uffd);
		return -1;
	}
	struct uffdio_register reg = {
	    .range = {.start = (uintptr_t)addr, .len = len},
	    .mode = UFFDIO_REGISTER_MODE_MISSING};
	if (ioctl(uffd, UFFDIO_REGISTER, &reg) == -1) {
		close(uffd);
		return -1;
	}
	return uffd;
}

// --- Guidance on Usage ---
// 1. Use WAIT_ON/SIGNAL for tight race conditions to avoid scheduling overhead.
// 2. Use event_t (futexes) for general coordination or when waiting for longer periods.
// 3. Always use PIN_TO_CPU to increase race probability on multi-core systems.
// 4. Use setup_uffd to register a memory range for page fault handling. This allows you to
//    pause a thread accessing that memory until you handle the fault, creating a reliable
//    and controllable race window.
// 5. Call SETUP_UNBUFFERED_IO() at the start of main() to ensure that logs are printed
//    immediately. This is essential for understanding the exact interleaving of events
//    when debugging race conditions.
// 6. For timing-based loops (e.g., running a race for 10 seconds), do NOT use time(NULL)
//    or loops relying on real-time clocks, as VM clocks are highly unreliable and can fail or drift.
//    Instead, use the robust monotonic timing primitives TIMER_START and TIMER_NOT_EXPIRED:
//        TIMER_START(start);
//        while (TIMER_NOT_EXPIRED(start, 10.0)) {
//            // Your race logic here
//        }

#include <glob.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <pthread.h>
#include <errno.h>

#define MAX_PATHS 2048

char *pci_power_paths[MAX_PATHS];
int num_pci_paths = 0;

char *acpi_status_paths[MAX_PATHS];
int num_acpi_paths = 0;

void collect_paths(const char *pattern, char **paths, int *count)
{
	glob_t globbuf;
	if (glob(pattern, 0, NULL, &globbuf) == 0) {
		for (size_t i = 0; i < globbuf.gl_pathc && *count < MAX_PATHS; i++) {
			paths[(*count)++] = strdup(globbuf.gl_pathv[i]);
		}
	}
	globfree(&globbuf);
}

void *pci_worker(void *arg)
{
	int cpu = (int)(intptr_t)arg;
	PIN_TO_CPU(cpu);

	unsigned int seed = cpu;

	TIMER_START(start);
	while (TIMER_NOT_EXPIRED(start, 5.0)) {
		if (num_pci_paths == 0)
			break;
		
		int idx = rand_r(&seed) % num_pci_paths;
		int fd = open(pci_power_paths[idx], O_WRONLY);
		if (fd >= 0) {
			if (rand_r(&seed) % 2) {
				if (write(fd, "auto\n", 5) < 0) {}
			} else {
				if (write(fd, "on\n", 3) < 0) {}
			}
			close(fd);
		}
	}
	return NULL;
}

void *acpi_worker(void *arg)
{
	int cpu = (int)(intptr_t)arg;
	PIN_TO_CPU(cpu);

	char buf[256];
	unsigned int seed = cpu;

	TIMER_START(start);
	while (TIMER_NOT_EXPIRED(start, 5.0)) {
		if (num_acpi_paths == 0)
			break;
		
		int idx = rand_r(&seed) % num_acpi_paths;
		int fd = open(acpi_status_paths[idx], O_RDONLY);
		if (fd >= 0) {
			ssize_t ret = read(fd, buf, sizeof(buf));
			(void)ret;
			close(fd);
		}
	}
	return NULL;
}

int main(void)
{
	SETUP_UNBUFFERED_IO();

	collect_paths("/sys/bus/pci/devices/*/power/control", pci_power_paths, &num_pci_paths);
	
	collect_paths("/sys/bus/acpi/devices/*/status", acpi_status_paths, &num_acpi_paths);
	collect_paths("/sys/bus/acpi/devices/*/path", acpi_status_paths, &num_acpi_paths);
	collect_paths("/sys/bus/acpi/devices/*/real_power_state", acpi_status_paths, &num_acpi_paths);

	if (num_pci_paths == 0 && num_acpi_paths == 0) {
		fprintf(stderr, "[-] No PCI power or ACPI sysfs paths found. Cannot reproduce.\n");
		return 1;
	}

	printf("[+] Found %d PCI power paths and %d ACPI status paths.\n", 
	       num_pci_paths, num_acpi_paths);

	pthread_t t1, t2, t3, t4;
	
	pthread_create(&t1, NULL, pci_worker, (void *)(intptr_t)0);
	pthread_create(&t2, NULL, pci_worker, (void *)(intptr_t)1);
	pthread_create(&t3, NULL, acpi_worker, (void *)(intptr_t)0);
	pthread_create(&t4, NULL, acpi_worker, (void *)(intptr_t)1);

	pthread_join(t1, NULL);
	pthread_join(t2, NULL);
	pthread_join(t3, NULL);
	pthread_join(t4, NULL);

	for (int i = 0; i < num_pci_paths; i++) {
		free(pci_power_paths[i]);
	}
	for (int i = 0; i < num_acpi_paths; i++) {
		free(acpi_status_paths[i]);
	}

	sleep(1);
	printf("[+] Done.\n");
	return 0;
}