lib: c: pthread: implement pthread_self

lib/libc/pthread/sys/x86_64/pthread_self.S

@@ -1,9 +1,9 @@
 .code64
 
-.global pthread_self
+.global __pthread_self
-.type pthread_self, @function
+.type __pthread_self, @function
 
-pthread_self:
+__pthread_self:
 	push %rbp
 	mov %rsp, %rbp
 

lib/libc/pthread/thread/pthread.h

@@ -16,6 +16,7 @@ struct __pthread {
 	void *thr_result;
 };
 
+extern struct __pthread *__pthread_self(void);
 extern void __pthread_unmap_exit(
 	kern_handle_t address_space,
 	void *unmap_base,

lib/libc/pthread/thread/pthread_self.c

@@ -0,0 +1,36 @@
+#include "pthread.h"
+
+#include <mango/task.h>
+#include <mango/types.h>
+#include <string.h>
+#include <sys/mman.h>
+
+static struct __pthread main_thread = {0};
+
+struct __pthread *pthread_self(void)
+{
+	static int init = 0;
+	if (!init) {
+		kern_handle_t self_handle = KERN_HANDLE_INVALID;
+		kern_status_t status = thread_self(&self_handle);
+		if (status != KERN_OK) {
+			/* TODO set an errno value in a way that doesn't result
+			 * in a recursive call to pthread_self */
+			return NULL;
+		}
+		struct __pthread *self = &main_thread;
+		self->thr_self = self;
+		self->thr_handle = self_handle;
+		self->thr_map_base = self;
+		self->thr_map_size = sizeof *self;
+		thread_config_set(
+			self_handle,
+			THREAD_CFG_GSBASE,
+			&self,
+			sizeof(void *));
+		init = 1;
+		return self;
+	}
+
+	return __pthread_self();
+}