user: implement mlibc as the libc, finally.

It's finally done..

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

user/include/mlibc/options/internal/m68k-include/mlibc/arch-defs.hpp

@@ -0,0 +1,13 @@
+#ifndef MLIBC_ARCH_DEFS_HPP
+#define MLIBC_ARCH_DEFS_HPP
+
+#include <stddef.h>
+
+namespace mlibc {
+
+// not strictly true, can be 4 or 8k on 68040/68060, and many more on others
+inline constexpr size_t page_size = 0x1000;
+
+} // namespace mlibc
+
+#endif // MLIBC_ARCH_DEFS_HPP

user/include/mlibc/options/internal/m68k-include/mlibc/thread.hpp

@@ -0,0 +1,24 @@
+#pragma once
+
+#include <stdint.h>
+#include <mlibc/internal-sysdeps.hpp>
+#include <mlibc/tcb.hpp>
+#include <bits/ensure.h>
+
+namespace mlibc {
+
+extern "C" void *__m68k_read_tp();
+
+inline Tcb *get_current_tcb() {
+	// On m68k, the end of the TCB is 0x7000 below the thread pointer.
+	void *ptr = __m68k_read_tp();
+	return reinterpret_cast<Tcb *>((uintptr_t)ptr - 0x7000 - sizeof(Tcb));
+}
+
+inline uintptr_t get_sp() {
+	uintptr_t sp;
+	asm volatile ("move.l %%sp, %0" : "=r"(sp));
+	return sp;
+}
+
+} // namespace mlibc