[sys] Fix fork syscall return values

kernel/include/syscall.h

@@ -67,7 +67,7 @@ DECL_SYSCALL0(getpid);
 DECL_SYSCALL3(execve, char *, char **, char **);
 DECL_SYSCALL0(fork);
 DECL_SYSCALL2(kill, int, int);
-DECL_SYSCALL1(wait, unsigned int);
+DECL_SYSCALL1(wait, int);
 
 /* Memory management */
 DECL_SYSCALL1(sbrk, int);

kernel/start.s

@@ -207,8 +207,8 @@ irq_common_stub:
 
 global read_eip
 read_eip: ; Clever girl
-    pop eax
+	pop eax
-    jmp eax
+	jmp eax
 
 global copy_page_physical
 copy_page_physical:

kernel/sys/syscall.c

@@ -85,7 +85,11 @@ static int write(int fd, char * ptr, int len) {
 	return out;
 }
 
-static int wait(unsigned int child) {
+static int wait(int child) {
+	if (child < 1) {
+		kprintf("lol nope\n");
+		return 0;
+	}
 	process_t * volatile child_task = process_from_pid(child);
 	/* If the child task doesn't exist, bail */
 	if (!child_task) return -1;
@@ -248,6 +252,9 @@ syscall_handler(
 	}
 	uintptr_t location = syscalls[r->eax];
 
+	/* In case of a fork, we need to return the PID to the correct place */
+	volatile uintptr_t stack = current_process->image.stack - KERNEL_STACK_SIZE;
+
 	uint32_t ret;
 	asm volatile (
 			"push %1\n"
@@ -262,5 +269,10 @@ syscall_handler(
 			"pop %%ebx\n"
 			"pop %%ebx\n"
 			: "=a" (ret) : "r" (r->edi), "r" (r->esi), "r" (r->edx), "r" (r->ecx), "r" (r->ebx), "r" (location));
+	volatile uintptr_t n_stack = current_process->image.stack - KERNEL_STACK_SIZE;
+	if (n_stack != stack) {
+		uintptr_t temp = ((uintptr_t)r - stack);
+		r = (struct regs *)(n_stack + temp);
+	}
 	r->eax = ret;
 }

kernel/sys/task.c

@@ -116,6 +116,9 @@ fork() {
 	/* Disable interrupts */
 	IRQ_OFF;
 
+	unsigned int magic = 0xDEADBEEF;
+	uintptr_t esp, ebp, eip;
+
 	/* Make a pointer to the parent process (us) on the stack */
 	process_t * parent = (process_t *)current_process;
 	/* Clone the current process' page directory */
@@ -124,14 +127,13 @@ fork() {
 	process_t * new_proc = spawn_process(current_process);
 	/* Set the new process' page directory to clone */
 	set_process_environment(new_proc, directory);
-
 	/* Read the instruction pointer */
-	uintptr_t eip = read_eip();
+	eip = read_eip();
 
 	if (current_process == parent) {
 		/* Returned as the parent */
-		uintptr_t esp;
+		/* Verify magic */
-		uintptr_t ebp;
+		assert(magic == 0xDEADBEEF && "Bad process fork magic (parent)!");
 		/* Collect the stack and base pointers */
 		asm volatile ("mov %%esp, %0" : "=r" (esp));
 		asm volatile ("mov %%ebp, %0" : "=r" (ebp));
@@ -145,15 +147,19 @@ fork() {
 		}
 		/* Copy the kernel stack from this process to new process */
 		memcpy((void *)(new_proc->image.stack - KERNEL_STACK_SIZE), (void *)(current_process->image.stack - KERNEL_STACK_SIZE), KERNEL_STACK_SIZE);
+
 		/* Set the new process instruction pointer (to the return from read_eip) */
 		new_proc->thread.eip = eip;
 		/* Add the new process to the ready queue */
 		make_process_ready(new_proc);
+
 		/* Reenable interrupts */
 		IRQ_ON;
+
 		/* Return the child PID */
 		return new_proc->id;
 	} else {
+		assert(magic == 0xDEADBEEF && "Bad process fork magic (child)!");
 		/* Child fork is complete, return */
 		return 0;
 	}

loader/syscall.c

@@ -12,4 +12,4 @@ DEFN_SYSCALL0(fork, 8)
 DEFN_SYSCALL0(getpid, 9)
 DEFN_SYSCALL1(sbrk, 10, int)
 
-DEFN_SYSCALL1(wait, 16, unsigned int)
+DEFN_SYSCALL1(wait, 17, int)