SIGNALS

kernel/include/process.h

@@ -42,6 +42,7 @@ typedef struct image {
 	uintptr_t heap_actual; /* Actual heap location */
 	uintptr_t stack;       /* Process kernel stack */
 	uintptr_t user_stack;  /* User stack */
+	uintptr_t start;
 } image_t;
 
 /* Resizable descriptor table */
@@ -56,7 +57,7 @@ typedef struct descriptor_table {
 
 /* Signal Table */
 typedef struct signal_table {
-	uintptr_t *   functions[NUMSIGNALS];
+	uintptr_t functions[NUMSIGNALS];
 } sig_table_t;
 
 /* Portable process struct */
@@ -78,6 +79,9 @@ typedef struct process {
 	struct regs * syscall_registers; /* Registers at interrupt */
 	list_t *      wait_queue;
 	list_t *      shm_mappings;      /* Shared memory chunk mappings */
+	list_t *      signal_queue;      /* Queued signals */
+	thread_t      signal_state;
+	char *        signal_kstack;
 } process_t;
 
 void initialize_process_tree();
@@ -95,6 +99,7 @@ uint32_t process_append_fd(process_t * proc, fs_node_t * node);
 process_t * process_from_pid(pid_t pid);
 void delete_process(process_t * proc);
 uint32_t process_move_fd(process_t * proc, int src, int dest);
+int XXX_slow_process_is_queued(process_t * proc);
 
 volatile process_t * current_process;
 

kernel/include/system.h

@@ -107,6 +107,8 @@ struct regs {
 	unsigned int eip, cs, eflags, useresp, ss;
 };
 
+typedef struct regs regs_t;
+
 typedef void (*irq_handler_t) (struct regs *);
 
 /* Panic */
@@ -357,4 +359,10 @@ typedef struct {
 int wakeup_queue(list_t * queue);
 int sleep_on(list_t * queue);
 
+typedef struct {
+	uint32_t  signum;
+	uintptr_t handler;
+	regs_t registers_before;
+} signal_t;
+
 #endif

kernel/mem/mem.c

@@ -7,6 +7,7 @@
 #include <system.h>
 #include <process.h>
 #include <logging.h>
+#include <signal.h>
 
 #define KERNEL_HEAP_END 0x02000000
 
@@ -305,6 +306,11 @@ page_fault(
 	uint32_t faulting_address;
 	asm volatile("mov %%cr2, %0" : "=r"(faulting_address));
 
+	if (r->eip == 0xFFFFFFFF) {
+		return_from_signal_handler();
+	}
+
+#if 1
 	int present  = !(r->err_code & 0x1);
 	int rw       = r->err_code & 0x2;
 	int user     = r->err_code & 0x4;
@@ -313,8 +319,14 @@ page_fault(
 
 	kprintf("\033[1;37;41m");
 	kprintf("Segmentation fault. (p:%d,rw:%d,user:%d,res:%d,id:%d) at 0x%x eip:0x%x pid=%d\n", present, rw, user, reserved, id, faulting_address, r->eip, getpid());
-
 	HALT_AND_CATCH_FIRE("Segmentation fault", r);
+#else
+	signal_t * sig = malloc(sizeof(signal_t));
+	sig->handler = current_process->signals.functions[SIGSEGV];
+	sig->signum  = SIGSEGV;
+	handle_signal(current_process, sig);
+#endif
+
 }
 
 /*

kernel/misc/elf.c

@@ -98,7 +98,7 @@ exec(
 	free(header);
 	close_fs(file);
 
-	for (uintptr_t stack_pointer = 0x10000000; stack_pointer < 0x100F0000; stack_pointer += 0x1000) {
+	for (uintptr_t stack_pointer = 0x10000000; stack_pointer < 0x10100000; stack_pointer += 0x1000) {
 		alloc_frame(get_page(stack_pointer, 1, current_directory), 0, 1);
 	}
 
@@ -120,6 +120,8 @@ exec(
 		process_append_fd((process_t *)current_process, NULL);
 	}
 
+	current_process->image.start = entry;
+
 	/* Go go go */
 	enter_user_jmp(entry, argc, argv_, 0x100EFFFF);
 
@@ -150,6 +152,7 @@ system(
 		 * not all that much we can do right now. */
 		while (child_task->finished == 0) {
 			if (child_task->finished != 0) break;
+			switch_task(1);
 		}
 		/* Grab the child's return value */
 		int ret = child_task->status;

kernel/sys/process.c

@@ -176,6 +176,7 @@ process_t * spawn_init() {
 	init->finished = 0;
 	init->wait_queue = list_create();
 	init->shm_mappings = NULL;
+	init->signal_queue = list_create();
 
 	/* What the hey, let's also set the description on this one */
 	init->description = "[init]";
@@ -261,8 +262,10 @@ process_t * spawn_process(volatile process_t * parent) {
 	/* Zero out the process status */
 	proc->status = 0;
 	proc->finished = 0;
+	memset(proc->signals.functions, 0x00, sizeof(uintptr_t) * NUMSIGNALS);
 	proc->wait_queue = list_create();
 	proc->shm_mappings = list_create();
+	proc->signal_queue = list_create();
 
 	/* Insert the process into the process tree as a child
 	 * of the parent process. */
@@ -402,7 +405,9 @@ int wakeup_queue(list_t * queue) {
 	int awoken_processes = 0;
 	while (queue->length > 0) {
 		node_t * node = list_pop(queue);
-		make_process_ready(node->value);
+		if (!((process_t *)node->value)->finished) {
+			make_process_ready(node->value);
+		}
 		free(node);
 		awoken_processes++;
 	}
@@ -414,3 +419,12 @@ int sleep_on(list_t * queue) {
 	switch_task(0);
 	return 0;
 }
+
+int XXX_slow_process_is_queued(process_t * proc) {
+	foreach(node, process_queue) {
+		if (node->value == proc)
+			return 1;
+	}
+	return 0;
+}
+

kernel/sys/signal.c

@@ -0,0 +1,84 @@
+/* vim: tabstop=4 shiftwidth=4 noexpandtab
+ *
+ * Signal Handling
+ */
+
+#include <system.h>
+#include <signal.h>
+
+void enter_signal_handler(uintptr_t location, int signum, uintptr_t stack) {
+	kprintf("[debug] Jumping to 0x%x with %d pushed and a stack at 0x%x\n", location, signum, stack);
+	asm volatile(
+			"mov %2, %%esp\n"
+			"pushl %1\n"           /*          argument count   */
+			"pushl $0xFFFFFFFF\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");
+	kprintf("Yep, definitely an iret issue.\n");
+}
+
+void handle_signal(process_t * proc, signal_t * sig) {
+	kprintf("[signal] Need to process signal %d for process %d\n", sig->signum, proc->id);
+
+	if (!sig->handler) {
+		kprintf("[debug] Process %d killed by unhandled signal.\n", proc->id);
+		kprintf("Current process = %d\n", current_process->id);
+		kexit(127 + sig);
+		kprintf("Still here.\n");
+		return;
+	}
+
+	if (sig->handler == 1) /* Ignore */ {
+		return;
+	}
+
+	uintptr_t stack = 0x100EFFFF;
+
+	/* Not marked as ignored, must call signal */
+	enter_signal_handler(sig->handler, sig->signum, stack);
+
+}
+
+list_t * rets_from_sig;
+
+void return_from_signal_handler() {
+	kprintf("[debug] Return From Signal for process %d\n", current_process->id);
+
+	if (__builtin_expect(!rets_from_sig, 0)) {
+		rets_from_sig = list_create();
+	}
+
+	list_insert(rets_from_sig, current_process);
+
+	switch_next();
+}
+
+void fix_signal_stacks() {
+	if (rets_from_sig) {
+		while (rets_from_sig->head) {
+			node_t * n = list_dequeue(rets_from_sig);
+			process_t * p = n->value;
+			p->thread.esp = p->signal_state.esp;
+			p->thread.eip = p->signal_state.eip;
+			p->thread.ebp = p->signal_state.ebp;
+			memcpy(p->image.stack - KERNEL_STACK_SIZE, p->signal_kstack, KERNEL_STACK_SIZE);
+			free(p->signal_kstack);
+			make_process_ready(p);
+			free(n);
+		}
+	}
+}

kernel/sys/syscall.c

@@ -110,7 +110,6 @@ static int wait(int child) {
 		kprintf("Tried to wait for non-existent process\n");
 	}
 	while (child_task->finished == 0) {
-		if (child_task->finished != 0) break;
 		/* Add us to the wait queue for this child */
 		sleep_on(child_task->wait_queue);
 	}
@@ -313,6 +312,55 @@ static int kernel_name_XXX(char * buffer) {
 			__kernel_arch);
 }
 
+static int send_signal(pid_t process, uint32_t signal) {
+	process_t * receiver = process_from_pid(process);
+
+	if (!receiver) {
+		/* Invalid pid */
+		return 1;
+	}
+
+	if (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;
+	}
+
+	/* 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 (!XXX_slow_process_is_queued(receiver)) {
+		make_process_ready(receiver);
+	}
+
+	kprintf("[signal] Sending signal %d to PID %d from PID %d\n", signal, process, current_process->id);
+
+	list_insert(receiver->signal_queue, sig);
+
+	return 0;
+}
+
+static uintptr_t sys_signal(uint32_t signum, uintptr_t handler) {
+	if (signum >= NUMSIGNALS) {
+		return -1;
+	}
+	uintptr_t old = current_process->signals.functions[signum];
+	current_process->signals.functions[signum] = handler;
+	return old;
+}
+
 /*
 static void inspect_memory (uintptr_t vaddr) {
 	// Please use this scary hack of a function as infrequently as possible.
@@ -322,10 +370,10 @@ static void inspect_memory (uintptr_t vaddr) {
 
 static int reboot() {
 	kprintf("[kernel] Reboot requested from process %d by user #%d\n", current_process->id, current_process->user);
-	kprintf("[kernel] Good bye!\n");
-	if (current_process->user != 0) {
+	if (current_process->user != USER_ROOT_UID) {
 		return -1;
 	} else {
+		kprintf("[kernel] Good bye!\n");
 		/* Goodbye, cruel world */
 		uint8_t out = 0x02;
 		while ((out & 0x02) != 0) {
@@ -435,7 +483,9 @@ static uintptr_t syscalls[] = {
 	(uintptr_t)&mousedevice,
 	(uintptr_t)&sys_mkdir,
 	(uintptr_t)&shm_obtain,
-	(uintptr_t)&shm_release,			/* 36 */
+	(uintptr_t)&shm_release,		/* 36 */
+	(uintptr_t)&send_signal,
+	(uintptr_t)&sys_signal,
 	0
 };
 uint32_t num_syscalls;

kernel/sys/task.c

@@ -76,11 +76,14 @@ void free_directory(page_directory_t * dir) {
 void reap_process(process_t * proc) {
 	list_free(proc->wait_queue);
 	free(proc->wait_queue);
+	list_free(proc->signal_queue);
+	free(proc->signal_queue);
 	free((void *)(proc->image.stack - KERNEL_STACK_SIZE));
 	free_directory(proc->thread.page_directory);
 	free((void *)(proc->fds.entries));
+
 	shm_release_all(proc);
-	kprintf("reaping %s\n", proc->name);
+	kprintf("[kernel] reaping %s\n", proc->name);
 }
 
 /*
@@ -322,6 +325,17 @@ switch_task(uint8_t reschedule) {
 				reap_process(proc);
 			}
 		}
+		fix_signal_stacks();
+		/* XXX: Signals */
+		if (!current_process->finished) {
+			if (current_process->signal_queue->length > 0) {
+				node_t * node = list_dequeue(current_process->signal_queue);
+				signal_t * sig = node->value;
+				free(node);
+				handle_signal(current_process, sig);
+			}
+		}
+
 		return;
 	}
 
@@ -357,6 +371,16 @@ switch_next() {
 	/* Validate */
 	assert((eip > (uintptr_t)&code) && (eip < (uintptr_t)&end) && "Task switch return point is not within Kernel!");
 
+	if (!current_process->finished) {
+		if (current_process->signal_queue->length > 0) {
+			current_process->signal_kstack  = malloc(KERNEL_STACK_SIZE);
+			current_process->signal_state.esp = current_process->thread.esp;
+			current_process->signal_state.eip = current_process->thread.eip;
+			current_process->signal_state.ebp = current_process->thread.ebp;
+			memcpy(current_process->signal_kstack, current_process->image.stack - KERNEL_STACK_SIZE, KERNEL_STACK_SIZE);
+		}
+	}
+
 	/* Set the page directory */
 	current_directory = current_process->thread.page_directory;
 	/* Set the kernel stack in the TSS */

userspace/esh.c

@@ -18,6 +18,9 @@ DEFN_SYSCALL1(chdir, 28, char *);
 DEFN_SYSCALL0(getuid, 23);
 DEFN_SYSCALL0(gethostname, 32);
 
+DEFN_SYSCALL2(signal, 38, uint32_t, void *);
+DEFN_SYSCALL2(send_signal, 37, uint32_t, uint32_t)
+
 #define LINE_LEN 4096
 
 char cwd[1024] = {'/',0};
@@ -79,12 +82,24 @@ void draw_prompt(int ret) {
 	fflush(stdout);
 }
 
+uint32_t child = 0;
+
+void sig_int(int sig) {
+	if (child) {
+		syscall_send_signal(child, sig);
+	} else {
+		printf("stop that!\n");
+	}
+}
+
 int main(int argc, char ** argv) {
 	int  pid = getpid();
 	int  nowait = 0;
 	int  free_cmd = 0;
 	int  last_ret = 0;
 
+	syscall_signal(9, sig_int);
+
 	getusername();
 	gethostname();
 
@@ -168,6 +183,7 @@ int main(int argc, char ** argv) {
 			return i;
 		} else {
 			if (!nowait) {
+				child = f;
 				last_ret = syscall_wait(f);
 			}
 			free(cmd);

userspace/login.c

@@ -18,6 +18,25 @@ DEFN_SYSCALL1(setuid, 24, unsigned int);
 DEFN_SYSCALL1(kernel_string_XXX, 25, char *);
 DEFN_SYSCALL0(gethostname, 32);
 
+DEFN_SYSCALL2(signal, 38, uint32_t, void *);
+DEFN_SYSCALL2(send_signal, 37, uint32_t, uint32_t)
+
+uint32_t child = 0;
+
+void sig_int(int sig) {
+	/* Pass onto the shell */
+	if (child) {
+		syscall_send_signal(child, sig);
+	}
+	/* Else, ignore */
+}
+
+void sig_segv(int sig) {
+	printf("Segmentation fault.\n");
+	exit(127 + sig);
+	/* no return */
+}
+
 int checkUserPass(char * user, char * pass) {
 
 	/* Generate SHA512 */
@@ -62,6 +81,9 @@ int main(int argc, char ** argv) {
 
 	fprintf(stdout, "\n%s\n\n", _uname);
 
+	syscall_signal(9, sig_int);
+	syscall_signal(11, sig_segv);
+
 	while (1) {
 		char * username = malloc(sizeof(char) * 1024);
 		char * password = malloc(sizeof(char) * 1024);
@@ -100,8 +122,10 @@ int main(int argc, char ** argv) {
 			syscall_setuid(uid);
 			int i = execve(args[0], args, NULL);
 		} else {
+			child = f;
 			syscall_wait(f);
 		}
+		child = 0;
 		free(username);
 		free(password);
 	}

userspace/terminal.c

@@ -1,4 +1,5 @@
-/*
+/* vim: tabstop=4 shiftwidth=4 noexpandtab
+ *
  * Terminal Emulator
  */
 
@@ -2822,6 +2823,10 @@ void clear_input() {
 	input_collected = 0;
 }
 
+uint32_t child_pid = 0;
+
+DEFN_SYSCALL2(send_signal, 37, uint32_t, uint32_t)
+
 int buffer_put(char c) {
 	if (c == 8) {
 		/* Backspace */
@@ -2834,6 +2839,10 @@ int buffer_put(char c) {
 		}
 		return 0;
 	}
+	if (c == 3) {
+		syscall_send_signal(child_pid, 9);
+		return 0;
+	}
 	if (c < 10 || (c > 10 && c < 32) || c > 126) {
 		return 0;
 	}
@@ -2978,6 +2987,10 @@ int main(int argc, char ** argv) {
 		int i = execve(tokens[0], tokens, NULL);
 		return 0;
 	} else {
+
+		child_pid = f;
+		printf("[terminal] child is %d\n", child_pid);
+
 		char buf[1024];
 		while (1) {
 			struct stat _stat;