scheduler: handle userland thread exit

kernel-src/arch/x86-64/context.asm

@@ -1,6 +1,9 @@
 section .text
 global arch_context_switch
 arch_context_switch:
+	extern sched_userspacecheck
+	call sched_userspacecheck ; compiled with no_caller_saved_registers
+
 	; rdi is the pointer to the context struct
 	mov rsp, rdi
 

kernel-src/arch/x86-64/syscall.asm

@@ -195,6 +195,11 @@ arch_syscall_entry:
 	extern arch_syscall_log_return
 	call arch_syscall_log_return ; compiled with __attribute__((no_caller_saved_registers)) 
 
+	mov rdi, rsp
+	add rdi, 8 ; context pointer is after r9 argument
+	extern sched_userspacecheck
+	call sched_userspacecheck ; compiled with __attribute__((no_caller_saved_registers))
+
 	; restore context
 	add rsp, 32 ; r9 argument, cr2, gs, and fs are not popped.
 	pop rbx

kernel-src/include/x86-64/arch/context.h

@@ -98,5 +98,6 @@ void arch_context_saveandcall(void (*fn)(context_t *context), void *stack);
 	asm("ldmxcsr (%%rax)" : : "a"(&(t)->extracontext.mxcsr));
 
 #define ARCH_CONTEXT_INTSTATUS(x) ((x)->rflags & 0x200 ? true : false)
+#define ARCH_CONTEXT_ISUSER(x) ((x)->cs == 0x23)
 
 #endif

kernel-src/sys/scheduler.c

@@ -229,6 +229,47 @@ __attribute__((noreturn)) void sched_stopcurrentthread() {
 	switchthread(next);
 }
 
+void sched_procexit() {
+	proc_t *proc = _cpu()->thread->proc;
+
+	// close fds
+	for (int fd = 0; fd < proc->fdcount; ++fd)
+		fd_close(fd);
+
+	// zombify the proc
+	spinlock_acquire(&proc->lock);
+
+	VOP_RELEASE(proc->root);
+	VOP_RELEASE(proc->cwd);
+
+	proc->state = SCHED_PROC_STATE_ZOMBIE;
+	proc_t *lastchild = proc->child;
+
+	spinlock_acquire(&sched_initproc->lock);
+
+	bool haszombie = false;
+
+	while (lastchild && lastchild->sibling) {
+		if (lastchild->state == SCHED_PROC_STATE_ZOMBIE)
+			haszombie = true;
+
+		lastchild->parent = sched_initproc;
+		lastchild = lastchild->sibling;
+	}
+
+	if (lastchild) {
+		lastchild->sibling = sched_initproc->child;
+		sched_initproc->child = proc->child;
+	}
+
+	spinlock_release(&sched_initproc->lock);
+	spinlock_release(&proc->lock);
+
+	semaphore_signal(&proc->parent->waitsem);
+	if (haszombie)
+		semaphore_signal(&sched_initproc->waitsem);
+}
+
 __attribute__((noreturn)) void sched_threadexit() {
 	thread_t *thread = _cpu()->thread;
 	proc_t *proc = thread->proc;
@@ -239,8 +280,13 @@ __attribute__((noreturn)) void sched_threadexit() {
 	if (proc) {
 		__atomic_fetch_sub(&proc->runningthreadcount, 1, __ATOMIC_SEQ_CST);
 		__assert(oldctx != &vmm_kernelctx);
-		if (proc->runningthreadcount == 0)
+		if (proc->runningthreadcount == 0) {
+			if (thread->shouldexit)
+				proc->status = -1;
+
+			sched_procexit();
 			vmm_destroycontext(oldctx);
+		}
 	}
 
 	interrupt_set(false);
@@ -253,6 +299,18 @@ __attribute__((noreturn)) void sched_threadexit() {
 	sched_stopcurrentthread();
 }
 
+// called right before going back to userspace in places like the syscall handler or arch_context_switch
+__attribute__((no_caller_saved_registers)) void sched_userspacecheck(context_t *context) {
+	thread_t *thread = _cpu()->thread;
+	if (thread == NULL || ARCH_CONTEXT_ISUSER(context) == false)
+		return;
+
+	if (thread->shouldexit) {
+		interrupt_set(true);
+		sched_threadexit();
+	}
+}
+
 void sched_stopotherthreads() {
 	thread_t *thread = _cpu()->thread;
 	proc_t *proc = thread->proc;

kernel-src/sys/syscalls/exit.c

@@ -13,43 +13,7 @@ __attribute__((noreturn)) void syscall_exit(context_t *context, int status) {
 
 	sched_stopotherthreads();
 
-	// close fds
-	for (int fd = 0; fd < proc->fdcount; ++fd)
-		fd_close(fd);
-
-	// zombify the proc
-	spinlock_acquire(&proc->lock);
-
-	VOP_RELEASE(proc->root);
-	VOP_RELEASE(proc->cwd);
-
 	proc->status = status;
-	proc->state = SCHED_PROC_STATE_ZOMBIE;
-	proc_t *lastchild = proc->child;
-
-	spinlock_acquire(&sched_initproc->lock);
-
-	bool haszombie = false;
-
-	while (lastchild && lastchild->sibling) {
-		if (lastchild->state == SCHED_PROC_STATE_ZOMBIE)
-			haszombie = true;
-
-		lastchild->parent = sched_initproc;
-		lastchild = lastchild->sibling;
-	}
-
-	if (lastchild) {
-		lastchild->sibling = sched_initproc->child;
-		sched_initproc->child = proc->child;
-	}
-
-	spinlock_release(&sched_initproc->lock);
-	spinlock_release(&proc->lock);
-
-	semaphore_signal(&proc->parent->waitsem);
-	if (haszombie)
-		semaphore_signal(&sched_initproc->waitsem);
 
 	sched_threadexit();
 }