asterinas/test/apps/signal_c/signal_test.c

// SPDX-License-Identifier: MPL-2.0

// This test file is from occlum signal test.

#define _GNU_SOURCE
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <unistd.h>
#include <ucontext.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <spawn.h>
#include <assert.h>
#include <fcntl.h>
#include <signal.h>
#include <pthread.h>
#include <errno.h>
#include <time.h>

// ============================================================================
// Helper functions
// ============================================================================

#define THROW_ERROR(fmt, ...)                                                   \
	do {                                                                    \
		printf("\t\tERROR:" fmt                                         \
		       " in func %s at line %d of file %s with errno %d: %s\n", \
		       ##__VA_ARGS__, __func__, __LINE__, __FILE__, errno,      \
		       strerror(errno));                                        \
		return -1;                                                      \
	} while (0)

// ============================================================================
// Test sigprocmask
// ============================================================================

#define sigcmpset(a, b) memcmp((a), (b), 8)

int test_sigprocmask()
{
	int ret;
	sigset_t new, old;
	sigset_t expected_old;

	// Check sigmask == []
	if ((ret = sigprocmask(0, NULL, &old)) < 0) {
		THROW_ERROR("sigprocmask failed unexpectedly");
	}
	sigemptyset(&expected_old);
	if (sigcmpset(&old, &expected_old) != 0) {
		THROW_ERROR("unexpected old sigset");
	}

	// SIG_BLOCK: [] --> [SIGSEGV]
	sigemptyset(&new);
	sigaddset(&new, SIGSEGV);
	if ((ret = sigprocmask(SIG_BLOCK, &new, &old)) < 0) {
		THROW_ERROR("sigprocmask failed unexpectedly");
	}
	sigemptyset(&expected_old);
	if (sigcmpset(&old, &expected_old) != 0) {
		THROW_ERROR("unexpected old sigset");
	}

	// SIG_SETMASK: [SIGSEGV] --> [SIGIO]
	sigemptyset(&new);
	sigaddset(&new, SIGIO);
	if ((ret = sigprocmask(SIG_SETMASK, &new, &old)) < 0) {
		THROW_ERROR("sigprocmask failed unexpectedly");
	}
	sigemptyset(&expected_old);
	sigaddset(&expected_old, SIGSEGV);
	if (sigcmpset(&old, &expected_old) != 0) {
		THROW_ERROR("unexpected old sigset");
	}

	// SIG_UNBLOCK: [SIGIO] -> []
	if ((ret = sigprocmask(SIG_UNBLOCK, &new, &old)) < 0) {
		THROW_ERROR("sigprocmask failed unexpectedly");
	}
	sigemptyset(&expected_old);
	sigaddset(&expected_old, SIGIO);
	if (sigcmpset(&old, &expected_old) != 0) {
		THROW_ERROR("unexpected old sigset");
	}

	// Check sigmask == []
	if ((ret = sigprocmask(0, NULL, &old)) < 0) {
		THROW_ERROR("sigprocmask failed unexpectedly");
	}
	sigemptyset(&expected_old);
	if (sigcmpset(&old, &expected_old) != 0) {
		THROW_ERROR("unexpected old sigset");
	}

	return 0;
}

// ============================================================================
// Test raise syscall and user-registered signal handlers
// ============================================================================

#define MAX_RECURSION_LEVEL 3

static void handle_sigio(int num, siginfo_t *info, void *context)
{
	static volatile int recursion_level = 0;
	printf("Hello from SIGIO signal handler (recursion_level = %d)!\n",
	       recursion_level);
	fflush(stdout);

	recursion_level++;
	if (recursion_level <= MAX_RECURSION_LEVEL) {
		raise(SIGIO);
	}
	recursion_level--;
}

int test_raise()
{
	struct sigaction new_action, old_action;
	memset(&new_action, 0, sizeof(struct sigaction));
	memset(&old_action, 0, sizeof(struct sigaction));
	new_action.sa_sigaction = handle_sigio;
	new_action.sa_flags = SA_SIGINFO | SA_NODEFER;
	if (sigaction(SIGIO, &new_action, &old_action) < 0) {
		THROW_ERROR("registering new signal handler failed");
	}
	if (old_action.sa_handler != SIG_DFL) {
		THROW_ERROR("unexpected old sig handler");
	}

	raise(SIGIO);

	if (sigaction(SIGIO, &old_action, NULL) < 0) {
		THROW_ERROR("restoring old signal handler failed");
	}
	return 0;
}

// ============================================================================
// Test catching and handling hardware exception
// ============================================================================

static void handle_sigfpe(int num, siginfo_t *info, void *_context)
{
	printf("SIGFPE Caught\n");
	fflush(stdout);
	assert(num == SIGFPE);
	assert(info->si_signo == SIGFPE);
	ucontext_t *ucontext = _context;
	mcontext_t *mcontext = &ucontext->uc_mcontext;
	// The faulty instruction should be `idiv %esi` (f7 fe)
	mcontext->gregs[REG_RIP] += 2;
	return;
}

// Note: this function is fragile in the sense that compiler may not always
// emit the instruction pattern that triggers divide-by-zero as we expect.
// TODO: rewrite this in assembly
int div_maybe_zero(int x, int y)
{
	return x / y;
}

#define fxsave(addr) __asm __volatile("fxsave %0" : "=m"(*(addr)))

int test_handle_sigfpe()
{
	// Set up a signal handler that handles divide-by-zero exception
	struct sigaction new_action, old_action;
	memset(&new_action, 0, sizeof(struct sigaction));
	memset(&old_action, 0, sizeof(struct sigaction));
	new_action.sa_sigaction = handle_sigfpe;
	new_action.sa_flags = SA_SIGINFO;
	if (sigaction(SIGFPE, &new_action, &old_action) < 0) {
		THROW_ERROR("registering new signal handler failed");
	}
	if (old_action.sa_handler != SIG_DFL) {
		THROW_ERROR("unexpected old sig handler");
	}

	char x[512] __attribute__((aligned(16))) = {};
	char y[512] __attribute__((aligned(16))) = {};

	// Trigger divide-by-zero exception
	int a = 1;
	int b = 0;
	// Use volatile to prevent compiler optimization
	volatile int c;
	fxsave(x);
	c = div_maybe_zero(a, b);
	(void)c;
	fxsave(y);

	// Asterinas does not save and restore fpregs now, so we emit this check.
	// if (memcmp(x, y, 512) != 0) {
	//     THROW_ERROR("floating point registers are modified");
	// }

	printf("Signal handler successfully jumped over the divide-by-zero instruction\n");
	fflush(stdout);

	if (sigaction(SIGFPE, &old_action, NULL) < 0) {
		THROW_ERROR("restoring old signal handler failed");
	}
	return 0;
}

// TODO: rewrite this in assembly
int read_maybe_null(int *p)
{
	return *p;
}

static void handle_sigsegv(int num, siginfo_t *info, void *_context)
{
	printf("SIGSEGV Caught\n");
	fflush(stdout);

	assert(num == SIGSEGV);
	assert(info->si_signo == SIGSEGV);

	ucontext_t *ucontext = _context;
	mcontext_t *mcontext = &ucontext->uc_mcontext;
	// TODO: how long is the instruction?
	// The faulty instruction should be `idiv %esi` (f7 fe)
	mcontext->gregs[REG_RIP] += 2;

	return;
}

int test_handle_sigsegv()
{
	// Set up a signal handler that handles divide-by-zero exception
	struct sigaction new_action, old_action;
	memset(&new_action, 0, sizeof(struct sigaction));
	memset(&old_action, 0, sizeof(struct sigaction));
	new_action.sa_sigaction = handle_sigsegv;
	new_action.sa_flags = SA_SIGINFO;
	if (sigaction(SIGSEGV, &new_action, &old_action) < 0) {
		THROW_ERROR("registering new signal handler failed");
	}
	if (old_action.sa_handler != SIG_DFL) {
		THROW_ERROR("unexpected old sig handler");
	}

	int *addr = NULL;
	volatile int val = read_maybe_null(addr);
	(void)val; // to suppress "unused variables" warning

	printf("Signal handler successfully jumped over a null-dereferencing instruction\n");
	fflush(stdout);

	if (sigaction(SIGSEGV, &old_action, NULL) < 0) {
		THROW_ERROR("restoring old signal handler failed");
	}
	return 0;
}

// ============================================================================
// Test SIGCHLD signal
// ============================================================================
int sigchld = 0;

void proc_exit()
{
	sigchld = 1;
}

int test_sigchld()
{
	signal(SIGCHLD, proc_exit);
	printf("Run a parent process has pid = %d\n", getpid());
	fflush(stdout);
	int pid = fork();
	if (pid == 0) {
		// child process
		printf("create a new proces successfully (pid = %d)\n",
		       getpid());
		fflush(stdout);
		exit(0);
	} else {
		// parent process
		wait(NULL);
		printf("sigchld = %d\n", sigchld);
		fflush(stdout);
	}
	return 0;
}

// ============================================================================
// Test handle signal on alternate signal stack
// ============================================================================

#define MAX_ALTSTACK_RECURSION_LEVEL 2

stack_t g_old_ss;

static void handle_sigpipe(int num, siginfo_t *info, void *context)
{
	static volatile int recursion_level = 0;
	printf("Hello from SIGPIPE signal handler on the alternate signal stack (recursion_level = %d)\n",
	       recursion_level);

	// save old_ss to check if we are on stack
	stack_t old_ss;
	sigaltstack(NULL, &old_ss);
	g_old_ss = old_ss;

	recursion_level++;
	if (recursion_level <= MAX_ALTSTACK_RECURSION_LEVEL) {
		raise(SIGPIPE);
	}
	recursion_level--;
}

#define SIGSTACKSIZE (4 * 4096)

int test_sigaltstack()
{
	static char stack[SIGSTACKSIZE];
	stack_t expected_ss = {
		.ss_size = SIGSTACKSIZE,
		.ss_sp = stack,
		.ss_flags = 0,
	};
	if (sigaltstack(&expected_ss, NULL) < 0) {
		THROW_ERROR("failed to call sigaltstack");
	}
	stack_t actual_ss;
	if (sigaltstack(NULL, &actual_ss) < 0) {
		THROW_ERROR("failed to call sigaltstack");
	}
	if (actual_ss.ss_size != expected_ss.ss_size ||
	    actual_ss.ss_sp != expected_ss.ss_sp ||
	    actual_ss.ss_flags != expected_ss.ss_flags) {
		THROW_ERROR("failed to check the signal stack after set");
	}

	struct sigaction new_action, old_action;
	memset(&new_action, 0, sizeof(struct sigaction));
	memset(&old_action, 0, sizeof(struct sigaction));
	new_action.sa_sigaction = handle_sigpipe;
	new_action.sa_flags = SA_SIGINFO | SA_NODEFER | SA_ONSTACK;
	if (sigaction(SIGPIPE, &new_action, &old_action) < 0) {
		THROW_ERROR("registering new signal handler failed");
	}
	if (old_action.sa_handler != SIG_DFL) {
		THROW_ERROR("unexpected old sig handler");
	}

	raise(SIGPIPE);
	if (g_old_ss.ss_flags != SS_ONSTACK) {
		THROW_ERROR("check stack flags failed");
	}

	if (sigaction(SIGPIPE, &old_action, NULL) < 0) {
		THROW_ERROR("restoring old signal handler failed");
	}
	return 0;
}

// ============================================================================
// Test sigpending
// ============================================================================
int test_sigpending()
{
	int ret;

	// Set up  signal handler for SIGSEGV and SIGIO
	struct sigaction new_action, old_sigsegv_action, old_sigio_action;
	memset(&new_action, 0, sizeof(struct sigaction));
	memset(&old_sigsegv_action, 0, sizeof(struct sigaction));
	new_action.sa_sigaction = handle_sigsegv;
	new_action.sa_flags = SA_SIGINFO;
	if (sigaction(SIGSEGV, &new_action, &old_sigsegv_action) < 0) {
		THROW_ERROR("registering new signal handler failed");
	}
	if (old_sigsegv_action.sa_handler != SIG_DFL) {
		THROW_ERROR("unexpected old sig handler");
	}

	memset(&new_action, 0, sizeof(struct sigaction));
	memset(&old_sigio_action, 0, sizeof(struct sigaction));
	new_action.sa_sigaction = handle_sigio;
	new_action.sa_flags = SA_SIGINFO | SA_NODEFER;
	if (sigaction(SIGIO, &new_action, &old_sigio_action) < 0) {
		THROW_ERROR("registering new signal handler failed");
	}
	if (old_sigio_action.sa_handler != SIG_DFL) {
		THROW_ERROR("unexpected old sig handler");
	}

	// Block SIGSEGV and SIGIO
	sigset_t new_set, old_set, pending_set;
	sigfillset(&new_set);
	sigaddset(&new_set, SIGSEGV);
	sigaddset(&new_set, SIGIO);
	if ((ret = sigprocmask(SIG_BLOCK, &new_set, &old_set)) < 0) {
		THROW_ERROR("sigprocmask failed unexpectedly");
	}

	// Send SIGSEGV and SIGIO signals to the current process twice
	kill(getpid(), SIGSEGV);
	kill(getpid(), SIGSEGV); // Repeat
	kill(getpid(), SIGIO);
	kill(getpid(), SIGIO); // Repeat

	// Check for pending signals
	if (sigpending(&pending_set) < 0) {
		THROW_ERROR("sigpending failed unexpectedly");
	}

	if (!sigismember(&pending_set, SIGSEGV)) {
		THROW_ERROR("SIGSEGV is not pending");
	}

	if (!sigismember(&pending_set, SIGIO)) {
		THROW_ERROR("SIGIO (real-time signal) is not pending");
	}

	// Unblock all signals and check if pending signals are cleared
	if (sigprocmask(SIG_SETMASK, &old_set, NULL) < 0) {
		THROW_ERROR(
			"sigprocmask failed unexpectedly, failed to restore signal mask");
	}

	// Fetch and check pending signals after unblocking
	if (sigpending(&pending_set) < 0) {
		THROW_ERROR("sigpending failed unexpectedly");
	}

	if (sigismember(&pending_set, SIGSEGV)) {
		THROW_ERROR("SIGSEGV is pending");
	}

	if (sigismember(&pending_set, SIGIO)) {
		THROW_ERROR("SIGIO (real-time signal) is  pending");
	}

	// Restore old sigaction
	if (sigaction(SIGSEGV, &old_sigsegv_action, NULL) < 0) {
		THROW_ERROR("restoring old signal handler failed");
	}
	if (sigaction(SIGIO, &old_sigio_action, NULL) < 0) {
		THROW_ERROR("restoring old signal handler failed");
	}

	return 0;
}

int main()
{
	test_sigprocmask();
	test_raise();
	test_handle_sigfpe();
	test_handle_sigsegv();
	test_sigchld();
	test_sigaltstack();
	test_sigpending();
	return 0;
}