options/posix: implement pthread_self

meson.build

@@ -135,6 +135,7 @@ internal_sources = [
 	'options/internal/gcc/initfini.cpp',
 	'options/internal/gcc-extra/cxxabi.cpp',
 	'options/internal/x86_64/setjmp.S',
+	'options/internal/x86_64/thread.cpp',
 ]
 
 if not static

options/internal/include/mlibc/thread.hpp

@@ -0,0 +1,10 @@
+#ifndef MLIBC_THREAD_HPP
+#define MLIBC_THREAD_HPP
+
+namespace mlibc {
+
+void *get_current_tcb();
+
+}
+
+#endif // MLIBC_THREAD_HPP

options/internal/x86_64/thread.cpp

@@ -0,0 +1,13 @@
+#include <mlibc/thread.hpp>
+
+#include <stdint.h>
+
+namespace mlibc {
+
+void *get_current_tcb() {
+	uintptr_t ptr;
+	asm ("movq %%fs:0, %0" : "=r"(ptr));
+	return reinterpret_cast<void *>(ptr);
+}
+
+}

options/posix/generic/pthread-stubs.cpp

@@ -10,6 +10,7 @@
 #include <mlibc/allocator.hpp>
 #include <mlibc/debug.hpp>
 #include <mlibc/sysdeps.hpp>
+#include <mlibc/thread.hpp>
 
 static bool enableTrace = false;
 
@@ -100,10 +101,11 @@ int pthread_create(pthread_t *__restrict, const pthread_attr_t *__restrict,
 	__ensure(!"Not implemented");
 	__builtin_unreachable();
 }
+
 pthread_t pthread_self(void) {
-	__ensure(!"Not implemented");
-	__builtin_unreachable();
+	return reinterpret_cast<pthread_t>(mlibc::get_current_tcb());
 }
+
 int pthread_equal(pthread_t, pthread_t) {
 	__ensure(!"Not implemented");
 	__builtin_unreachable();