user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/sysdeps/menix/generic/thread.cpp

@@ -0,0 +1,80 @@
+#include <errno.h>
+#include <menix/syscall.hpp>
+#include <mlibc/ansi-sysdeps.hpp>
+#include <mlibc/arch-defs.hpp>
+#include <mlibc/tcb.hpp>
+#include <sys/mman.h>
+
+extern "C" void __mlibc_enter_thread(void *entry, void *user_arg, Tcb *tcb) {
+	while (__atomic_load_n(&tcb->tid, __ATOMIC_RELAXED) == 0) {
+		mlibc::sys_futex_wait(&tcb->tid, 0, nullptr);
+	}
+
+	tcb->invokeThreadFunc(entry, user_arg);
+
+	__atomic_store_n(&tcb->didExit, 1, __ATOMIC_RELEASE);
+	mlibc::sys_futex_wake(&tcb->didExit);
+
+	mlibc::sys_thread_exit();
+}
+
+// Defined in <arch>/thread.S
+extern "C" void __mlibc_start_thread();
+
+#define DEFAULT_STACK 0x200000
+
+namespace mlibc {
+
+int sys_clone(void *tcb, pid_t *pid_out, void *stack) {
+	(void)tcb;
+	auto r = menix_syscall(SYSCALL_THREAD_CREATE, (size_t)__mlibc_start_thread, (size_t)stack);
+	if (r.error)
+		return r.error;
+	*pid_out = (pid_t)r.value;
+	return 0;
+}
+
+int sys_prepare_stack(
+    void **stack,
+    void *entry,
+    void *arg,
+    void *tcb,
+    size_t *stack_size,
+    size_t *guard_size,
+    void **stack_base
+) {
+	*guard_size = mlibc::page_size;
+
+	*stack_size = *stack_size ? *stack_size : DEFAULT_STACK;
+
+	if (!*stack) {
+		*stack_base = mmap(
+		    NULL,
+		    *stack_size + mlibc::page_size,
+		    PROT_READ | PROT_WRITE,
+		    MAP_ANONYMOUS | MAP_PRIVATE,
+		    -1,
+		    0
+		);
+		if (*stack_base == MAP_FAILED) {
+			return errno;
+		}
+		munmap((char *)*stack_base + *stack_size, mlibc::page_size);
+	} else {
+		*stack_base = *stack;
+	}
+
+	*stack = (void *)((char *)*stack_base + *stack_size);
+
+	void **stack_it = (void **)*stack;
+
+	*--stack_it = tcb;   // a2
+	*--stack_it = arg;   // a1
+	*--stack_it = entry; // a0
+
+	*stack = (void *)stack_it;
+
+	return 0;
+}
+
+} // namespace mlibc