Get super basic ring3 task switching working

* It looks like UEFI enables SSE, so we need to tell clang -mno-sse for
  now to not use XMM* until we're ready to save them.
* SYSCALL is working from ring3 tasks, calling console printf!

src/kernel/interrupts.cpp

@@ -113,7 +113,6 @@ print_stacktrace(int skip = 0)
 addr_t
 isr_handler(addr_t return_rsp, cpu_state regs)
 {
-	log::debug(logs::task, "Starting RSP %016lx", return_rsp);
 	console *cons = console::get();
 
 	switch (static_cast<isr>(regs.interrupt & 0xff)) {
@@ -284,10 +283,8 @@ isr_handler(addr_t return_rsp, cpu_state regs)
 		print_stacktrace(2);
 		while(1) asm("hlt");
 	}
-
 	*reinterpret_cast<uint32_t *>(0xffffff80fee000b0) = 0;
 
-	log::debug(logs::task, "Returning RSP %016lx", return_rsp);
 	return return_rsp;
 }
 

src/kernel/interrupts.s

@@ -80,19 +80,10 @@ gdt_load:
 	pop rax
 %endmacro
 
-%macro load_kernel_segments 0
-	mov ax, 0x10	; load the kernel data segment
-	mov ds, ax
-	mov es, ax
-	mov fs, ax
-	mov gs, ax
-%endmacro
-
 extern isr_handler
 global isr_handler_prelude
 isr_handler_prelude:
 	push_all_and_segments
-	;load_kernel_segments
 
 	mov rdi, rsp
 	call isr_handler
@@ -108,7 +99,6 @@ extern irq_handler
 global irq_handler_prelude
 irq_handler_prelude:
 	push_all_and_segments
-	load_kernel_segments
 
 	call irq_handler
 
@@ -205,45 +195,18 @@ global taskA
 taskA:
 	push rbp
 	mov rbp, rsp
-	push 0x123456789abcdef0
-	push 0x0fedcba987654321
+	mov rax, 0xaaaaaaaaaaaaaaaa
+
+.loop:
+	syscall
+	jmp .loop
+
+global taskB
+taskB:
+	push rbp
+	mov rbp, rsp
+	mov rax, 0xbbbbbbbbbbbbbbbb
 
 .loop:
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
 	syscall
-	nop
-	nop
-	nop
-	nop
-	nop
-	nop
 	jmp .loop

src/kernel/scheduler.cpp

@@ -18,11 +18,7 @@ char taskBstack3[stack_size];
 uint64_t taskAcount = 0;
 
 extern "C" void taskA();
-
-void taskB()
-{
-	while (1);
-}
+extern "C" void taskB();
 
 
 scheduler::scheduler(lapic *apic) :
@@ -68,6 +64,8 @@ create_process(uint16_t pid, void *stack0, void *stack3, void (*rip)())
 void
 scheduler::start()
 {
+	log::info(logs::task, "Starting scheduler.");
+
 	m_apic->enable_timer(isr::isrTimer, 128, quantum, false);
 
 	m_processes.append({0, 0}); // The kernel idle task

src/kernel/wscript

@@ -29,7 +29,11 @@ def build(bld):
             return node.path_from(node.ctx.launch_node())
         def run(self):
             from subprocess import check_output
-            args = self.env.objdump + ["--source", "-D", self.inputs[0].abspath()]
+            args = self.env.objdump + [
+                    "--source",
+                    "-D",
+                    "-M", "intel",
+                    self.inputs[0].abspath()]
             with file(self.outputs[0].abspath(), 'w') as output:
                 output.write(check_output(args))