From f366a7723c403552bfe8428761ca78164182c889 Mon Sep 17 00:00:00 2001
From: Ludovic 'Archivist' Lagouardette <ludovic@nekoit.xyz>
Date: Thu, 22 Oct 2020 15:40:54 +0200
Subject: [PATCH] scaffolding of a system for async

---
 include/gp/vfs/platforms/gcc-x86_64.hpp | 51 ++++++++++++++++++++++++-
 include/gp/vfs/process_data.hpp         |  2 -
 include/gp/vfs/scheduler.hpp            | 13 +++++++
 3 files changed, 63 insertions(+), 3 deletions(-)

diff --git a/include/gp/vfs/platforms/gcc-x86_64.hpp b/include/gp/vfs/platforms/gcc-x86_64.hpp
index 0c1103e..366c4cb 100644
--- a/include/gp/vfs/platforms/gcc-x86_64.hpp
+++ b/include/gp/vfs/platforms/gcc-x86_64.hpp
@@ -1,9 +1,58 @@
 #pragma once
 
+#include <cstdint>
+
+#define no_inline_decl(a) [[gnu::noinline]] a
+
 namespace gp{
 	namespace specifics {
 		struct platform_data {
-			
+			uint64_t rbx, r12, r13, r14, r15;
+
+			void* stack_ptr;
+			void* base_ptr;
+
+			void pull() __attribute__((always_inline))
+			{
+				__asm__ __volatile__(
+				"movq %%rsp, %0\n"
+				"movq %%rbp, %1\n" 
+				"movq %%rbx, %2\n" 
+				"movq %%r12, %3\n" 
+				"movq %%r13, %4\n" 
+				"movq %%r14, %5\n" 
+				"movq %%r15, %6\n" 
+				: "=m"(stack_ptr)
+				, "=m"(base_ptr)
+				, "=m"(rbx)
+				, "=m"(r12)
+				, "=m"(r13)
+				, "=m"(r14)
+				, "=m"(r15));
+			}
+
+			void* push(void* location)  __attribute__((always_inline))
+			{
+				void* tmp = static_cast<char*>(stack_ptr) - sizeof(void*);
+				*static_cast<void**>(tmp) = location;
+				__asm__ __volatile__(
+				"movq %1, %%rsp\n"
+				"movq %2, %%rbp\n"
+				"movq %3, %%r12\n"
+				"movq %4, %%r13\n"
+				"movq %5, %%r14\n"
+				"movq %6, %%r15\n"
+				"popq %0\n" 
+				: "+r"(location) 
+				: "m"(tmp)
+				, "m"(base_ptr) 
+				, "m"(r12) 
+				, "m"(r13) 
+				, "m"(r14) 
+				, "m"(r15) 
+				: "memory");
+				return location;
+			}
 		};
 	}
 }
\ No newline at end of file
diff --git a/include/gp/vfs/process_data.hpp b/include/gp/vfs/process_data.hpp
index 2d04fb3..6db010c 100644
--- a/include/gp/vfs/process_data.hpp
+++ b/include/gp/vfs/process_data.hpp
@@ -19,8 +19,6 @@ namespace gp {
 	struct process_data{
 		[[no_unique_address]] gp::specifics::platform_data specifics;
 
-		void* stack_ptr;
-		void* base_ptr;
 		gp::function<void()> fn;
 		gp::indexed_array<gp::file_description*, gp_config::limits::max_fd_per_process> fds;
 	};
diff --git a/include/gp/vfs/scheduler.hpp b/include/gp/vfs/scheduler.hpp
index 79b53fe..3cbe276 100644
--- a/include/gp/vfs/scheduler.hpp
+++ b/include/gp/vfs/scheduler.hpp
@@ -7,8 +7,21 @@ namespace gp{
 
 class scheduler {
 	gp::indexed_array<gp::process_data*, gp_config::limits::max_processes> processes;
+	gp::specifics::platform_data root;
+	size_t current;
+	
+	no_inline_decl(
+		void yield_impl(bool terminate)
+	) {
+		
+	}
+
 public:
 	[[noreturn]] void run();
+	
+	void yield(){
+		yield_impl(false);
+	}
 };
 
 }
\ No newline at end of file