toaruos/kernel/sys/signal.c

/* vim: tabstop=4 shiftwidth=4 noexpandtab
 * This file is part of ToaruOS and is released under the terms
 * of the NCSA / University of Illinois License - see LICENSE.md
 * Copyright (C) 2012-2018 K. Lange
 *
 * Signal Handling
 */

#include <kernel/system.h>
#include <kernel/signal.h>
#include <kernel/logging.h>

void enter_signal_handler(uintptr_t location, int signum, uintptr_t stack) {
	IRQ_OFF;
	asm volatile(
			"mov %2, %%esp\n"
			"pushl %1\n"           /*          argument count   */
			"pushl $" STRSTR(SIGNAL_RETURN) "\n"
			"mov $0x23, %%ax\n"    /* Segment selector */
			"mov %%ax, %%ds\n"
			"mov %%ax, %%es\n"
			"mov %%ax, %%fs\n"
			"mov %%ax, %%gs\n"
			"mov %%esp, %%eax\n"   /* Stack -> EAX */
			"pushl $0x23\n"        /* Segment selector again */
			"pushl %%eax\n"
			"pushf\n"              /* Push flags */
			"popl %%eax\n"         /* Fix the Interrupt flag */
			"orl  $0x200, %%eax\n"
			"pushl %%eax\n"
			"pushl $0x1B\n"
			"pushl %0\n"           /* Push the entry point */
			"iret\n"
			: : "m"(location), "m"(signum), "r"(stack) : "%ax", "%esp", "%eax");

	debug_print(CRITICAL, "Failed to jump to signal handler!");
}

static spin_lock_t sig_lock;
static spin_lock_t sig_lock_b;

char isdeadly[] = {
	0, /* 0? */
	1, /* SIGHUP     */
	1, /* SIGINT     */
	2, /* SIGQUIT    */
	2, /* SIGILL     */
	2, /* SIGTRAP    */
	2, /* SIGABRT    */
	2, /* SIGEMT     */
	2, /* SIGFPE     */
	1, /* SIGKILL    */
	2, /* SIGBUS     */
	2, /* SIGSEGV    */
	2, /* SIGSYS     */
	1, /* SIGPIPE    */
	1, /* SIGALRM    */
	1, /* SIGTERM    */
	1, /* SIGUSR1    */
	1, /* SIGUSR2    */
	0, /* SIGCHLD    */
	0, /* SIGPWR     */
	0, /* SIGWINCH   */
	0, /* SIGURG     */
	0, /* SIGPOLL    */
	3, /* SIGSTOP    */
	3, /* SIGTSTP    */
	0, /* SIGCONT    */
	3, /* SIGTTIN    */
	3, /* SIGTTOUT   */
	1, /* SIGVTALRM  */
	1, /* SIGPROF    */
	2, /* SIGXCPU    */
	2, /* SIGXFSZ    */
	0, /* SIGWAITING */
	1, /* SIGDIAF    */
	0, /* SIGHATE    */
	0, /* SIGWINEVENT*/
	0, /* SIGCAT     */
};

void handle_signal(process_t * proc, signal_t * sig) {
	uintptr_t handler = sig->handler;
	uintptr_t signum  = sig->signum;
	free(sig);

	if (proc->finished) {
		return;
	}

	if (signum == 0 || signum >= NUMSIGNALS) {
		/* Ignore */
		return;
	}

	if (!handler) {
		char dowhat = isdeadly[signum];
		if (dowhat == 1 || dowhat == 2) {
			debug_print(WARNING, "Process %d killed by unhandled signal (%d)", proc->id, signum);
			kexit(((128 + signum) << 8) | signum);
			__builtin_unreachable();
		} else {
			debug_print(WARNING, "Ignoring signal %d by default in pid %d", signum, proc->id);
		}
		/* XXX dowhat == 2: should dump core */
		/* XXX dowhat == 3: stop */
		return;
	}

	if (handler == 1) /* Ignore */ {
		return;
	}

	debug_print(NOTICE, "handling signal in process %d (%d) (0x%x)", proc->id, signum, handler);

	uintptr_t stack = 0xFFFF0000;
	if (proc->syscall_registers->useresp < 0x10000100) {
		stack = proc->image.user_stack;
	} else {
		stack = proc->syscall_registers->useresp;
	}

	/* Not marked as ignored, must call signal */
	enter_signal_handler(handler, signum, stack);

}

list_t * rets_from_sig;

void return_from_signal_handler(void) {
#if 0
	debug_print(ERROR, "Return From Signal for process %d", current_process->id);
#endif

	if (__builtin_expect(!rets_from_sig, 0)) {
		rets_from_sig = list_create();
	}

	spin_lock(sig_lock);
	list_insert(rets_from_sig, (process_t *)current_process);
	spin_unlock(sig_lock);

	switch_next();
}

void fix_signal_stacks(void) {
	uint8_t redo_me = 0;
	if (rets_from_sig) {
		spin_lock(sig_lock_b);
		while (rets_from_sig->head) {
			spin_lock(sig_lock);
			node_t * n = list_dequeue(rets_from_sig);
			spin_unlock(sig_lock);
			if (!n) {
				continue;
			}
			process_t * p = n->value;
			free(n);
			if (p == current_process) {
				redo_me = 1;
				continue;
			}
			p->thread.esp = p->signal_state.esp;
			p->thread.eip = p->signal_state.eip;
			p->thread.ebp = p->signal_state.ebp;
			if (!p->signal_kstack) {
				debug_print(ERROR, "Cannot restore signal stack for pid=%d - unset?", p->id);
			} else {
				debug_print(ERROR, "Restoring signal stack for pid=%d", p->id);
				memcpy((void *)(p->image.stack - KERNEL_STACK_SIZE), p->signal_kstack, KERNEL_STACK_SIZE);
				free(p->signal_kstack);
				p->signal_kstack = NULL;
			}
			make_process_ready(p);
		}
		spin_unlock(sig_lock_b);
	}
	if (redo_me) {
		spin_lock(sig_lock);
		list_insert(rets_from_sig, (process_t *)current_process);
		spin_unlock(sig_lock);
		switch_next();
	}
}

int send_signal(pid_t process, uint32_t signal, int force_root) {
	process_t * receiver = process_from_pid(process);

	if (!receiver) {
		/* Invalid pid */
		return 1;
	}

	if (!force_root && receiver->user != current_process->user && current_process->user != USER_ROOT_UID) {
		/* No way in hell. */
		return 1;
	}

	if (signal > NUMSIGNALS) {
		/* Invalid signal */
		return 1;
	}

	if (receiver->finished) {
		/* Can't send signals to finished processes */
		return 1;
	}

	if (!receiver->signals.functions[signal] && !isdeadly[signal]) {
		/* If we're blocking a signal and it's not going to kill us, don't deliver it */
		return 1;
	}

	/* Append signal to list */
	signal_t * sig = malloc(sizeof(signal_t));
	sig->handler = (uintptr_t)receiver->signals.functions[signal];
	sig->signum  = signal;
	memset(&sig->registers_before, 0x00, sizeof(regs_t));

	if (receiver->node_waits) {
		process_awaken_from_fswait(receiver, -1);
	}
	if (!process_is_ready(receiver)) {
		make_process_ready(receiver);
	}

	list_insert(receiver->signal_queue, sig);

	if (receiver == current_process) {
		/* Forces us to be rescheduled and enter signal handler */
		switch_next();
	}

	return 0;
}