kernel: expose threads to userspace (newthread and threadexit syscalls)

kernel-src/sys/syscalls/execve.c

@@ -115,7 +115,7 @@ syscallret_t syscall_execve(context_t *context, char *upath, char *uargv[], char
 
 	ret.ret = 0;
 
-	// close CLOEXEC fds
+	// TODO close CLOEXEC fds
 
 	sched_stopotherthreads();
 

kernel-src/sys/syscalls/newthread.c

@@ -0,0 +1,63 @@
+#include <kernel/syscalls.h>
+#include <kernel/scheduler.h>
+#include <kernel/cmdline.h>
+#include <kernel/alloc.h>
+
+syscallret_t syscall_newthread(context_t *, void *entry, void *stack) {
+	syscallret_t ret = {
+		.ret = -1
+	};
+
+	// if the kernel was specified to have no user threading in the cmdline
+	if (cmdline_get("nomultithread")) {
+		ret.errno = ENOSYS;
+		return ret;
+	}
+
+	proc_t *proc = _cpu()->thread->proc;
+
+	spinlock_acquire(&proc->lock);
+
+	// if we currently don't want any more threads to start
+	if (proc->nomorethreads == true) {
+		spinlock_release(&proc->lock);
+		ret.errno = EAGAIN;
+		return ret;
+	}
+
+	int i;
+	for (i = 0; i < proc->threadtablesize; ++i) {
+		thread_t *thread = proc->threads[i];
+		if (thread == NULL || (thread->flags & SCHED_THREAD_FLAGS_DEAD) == 0)
+			continue;
+
+		// reuse the slot in the threads table
+		sched_destroythread(thread);
+		break;
+	}
+
+	if (i == proc->threadtablesize) {
+		// resize it
+		void *tmp = realloc(proc->threads, (proc->threadtablesize + 1) * sizeof(thread_t *));
+		if (tmp == NULL) {
+			ret.errno = ENOMEM;
+			goto cleanup;
+		}
+
+		proc->threads = tmp;
+	}
+
+	proc->threads[i] = sched_newthread(entry, 16 * PAGE_SIZE, 1, _cpu()->thread->proc, stack);
+	if (proc->threads[i] == NULL) {
+		ret.errno = ENOMEM;
+		goto cleanup;
+	}
+
+	proc->threads[i]->vmmctx = _cpu()->thread->vmmctx;
+
+	sched_queue(proc->threads[i]);
+
+	cleanup:
+	spinlock_release(&proc->lock);
+	return ret;
+}

kernel-src/sys/syscalls/threadexit.c

@@ -0,0 +1,6 @@
+#include <kernel/syscalls.h>
+#include <kernel/scheduler.h>
+
+syscallret_t syscall_threadexit(context_t *) {
+	sched_threadexit();
+}