diff --git a/src/kernel/interrupts.cpp b/src/kernel/interrupts.cpp
index 9c2f50b..dc54281 100644
--- a/src/kernel/interrupts.cpp
+++ b/src/kernel/interrupts.cpp
@@ -18,8 +18,8 @@ static const uint16_t PIC2 = 0xa0;
 extern "C" {
 	void _halt();
 
-	uintptr_t isr_handler(uintptr_t, cpu_state);
-	uintptr_t irq_handler(uintptr_t, cpu_state);
+	uintptr_t isr_handler(uintptr_t, cpu_state*);
+	uintptr_t irq_handler(uintptr_t, cpu_state*);
 	uintptr_t syscall_handler(uintptr_t, cpu_state);
 
 #define ISR(i, name)     extern void name ();
@@ -105,23 +105,23 @@ interrupts_init()
 }
 
 uintptr_t
-isr_handler(uintptr_t return_rsp, cpu_state regs)
+isr_handler(uintptr_t return_rsp, cpu_state *regs)
 {
 	console *cons = console::get();
 
-	switch (static_cast<isr>(regs.interrupt & 0xff)) {
+	switch (static_cast<isr>(regs->interrupt & 0xff)) {
 
 	case isr::isrGPFault: {
 			cons->set_color(9);
 			cons->puts("\nGeneral Protection Fault:\n");
 			cons->set_color();
 
-			cons->printf("   errorcode: %lx", regs.errorcode);
-			if (regs.errorcode & 0x01) cons->puts(" external");
+			cons->printf("   errorcode: %lx", regs->errorcode);
+			if (regs->errorcode & 0x01) cons->puts(" external");
 
-			int index = (regs.errorcode & 0xffff) >> 4;
+			int index = (regs->errorcode & 0xffff) >> 4;
 			if (index) {
-				switch ((regs.errorcode & 0x07) >> 1) {
+				switch ((regs->errorcode & 0x07) >> 1) {
 				case 0:
 					cons->printf(" GDT[%x]\n", index);
 					gdt_dump();
@@ -140,10 +140,10 @@ isr_handler(uintptr_t return_rsp, cpu_state regs)
 			} else {
 				cons->putc('\n');
 			}
-			print_regs(regs);
+			print_regs(*regs);
 			/*
 			print_stacktrace(2);
-			print_stack(regs);
+			print_stack(*regs);
 			*/
 
 		}
@@ -156,19 +156,19 @@ isr_handler(uintptr_t return_rsp, cpu_state regs)
 			cons->set_color();
 
 			cons->puts("       flags:");
-			if (regs.errorcode & 0x01) cons->puts(" present");
-			if (regs.errorcode & 0x02) cons->puts(" write");
-			if (regs.errorcode & 0x04) cons->puts(" user");
-			if (regs.errorcode & 0x08) cons->puts(" reserved");
-			if (regs.errorcode & 0x10) cons->puts(" ip");
+			if (regs->errorcode & 0x01) cons->puts(" present");
+			if (regs->errorcode & 0x02) cons->puts(" write");
+			if (regs->errorcode & 0x04) cons->puts(" user");
+			if (regs->errorcode & 0x08) cons->puts(" reserved");
+			if (regs->errorcode & 0x10) cons->puts(" ip");
 			cons->puts("\n");
 
 			uint64_t cr2 = 0;
 			__asm__ __volatile__ ("mov %%cr2, %0" : "=r"(cr2));
 			print_reg("cr2", cr2);
 
-			print_reg("rsp", regs.user_rsp);
-			print_reg("rip", regs.rip);
+			print_reg("rsp", regs->user_rsp);
+			print_reg("rip", regs->rip);
 
 			cons->puts("\n");
 			print_stacktrace(2);
@@ -192,14 +192,14 @@ isr_handler(uintptr_t return_rsp, cpu_state regs)
 
 	case isr::isrAssert: {
 			cons->set_color();
-			print_regs(regs);
+			print_regs(*regs);
 			print_stacktrace(2);
 		}
 		_halt();
 		break;
 
 	case isr::isrSyscall: {
-			return_rsp = syscall_dispatch(return_rsp, regs);
+			return_rsp = syscall_dispatch(return_rsp, *regs);
 		}
 		break;
 
@@ -215,7 +215,7 @@ isr_handler(uintptr_t return_rsp, cpu_state regs)
 	case isr::isrIgnore5:
 	case isr::isrIgnore6:
 	case isr::isrIgnore7:
-		//cons->printf("\nIGNORED: %02x\n", regs.interrupt);
+		//cons->printf("\nIGNORED: %02x\n", regs->interrupt);
 		outb(PIC1, 0x20);
 		break;
 
@@ -227,7 +227,7 @@ isr_handler(uintptr_t return_rsp, cpu_state regs)
 	case isr::isrIgnoreD:
 	case isr::isrIgnoreE:
 	case isr::isrIgnoreF:
-		//cons->printf("\nIGNORED: %02x\n", regs.interrupt);
+		//cons->printf("\nIGNORED: %02x\n", regs->interrupt);
 		outb(PIC1, 0x20);
 		outb(PIC2, 0x20);
 		break;
@@ -235,13 +235,13 @@ isr_handler(uintptr_t return_rsp, cpu_state regs)
 	default:
 		cons->set_color(9);
 		cons->printf("\nReceived %02x interrupt:\n",
-				(static_cast<isr>(regs.interrupt)));
+				(static_cast<isr>(regs->interrupt)));
 
 		cons->set_color();
 		cons->printf("         ISR: %02lx  ERR: %lx\n\n",
-				regs.interrupt, regs.errorcode);
+				regs->interrupt, regs->errorcode);
 
-		print_regs(regs);
+		print_regs(*regs);
 		//print_stacktrace(2);
 		_halt();
 	}
@@ -251,16 +251,16 @@ isr_handler(uintptr_t return_rsp, cpu_state regs)
 }
 
 uintptr_t
-irq_handler(uintptr_t return_rsp, cpu_state regs)
+irq_handler(uintptr_t return_rsp, cpu_state *regs)
 {
 	console *cons = console::get();
-	uint8_t irq = get_irq(regs.interrupt);
+	uint8_t irq = get_irq(regs->interrupt);
 	if (! device_manager::get().dispatch_irq(irq)) {
 		cons->set_color(11);
 		cons->printf("\nReceived unknown IRQ: %d (vec %d)\n",
-				irq, regs.interrupt);
+				irq, regs->interrupt);
 		cons->set_color();
-		print_regs(regs);
+		print_regs(*regs);
 		_halt();
 	}
 
diff --git a/src/kernel/interrupts.s b/src/kernel/interrupts.s
index f7fb0dc..9013898 100644
--- a/src/kernel/interrupts.s
+++ b/src/kernel/interrupts.s
@@ -6,6 +6,7 @@ isr_handler_prelude:
 	push_all_and_segments
 
 	mov rdi, rsp
+	mov rsi, rsp
 	call isr_handler
 	mov rsp, rax
 
@@ -21,6 +22,7 @@ irq_handler_prelude:
 	push_all_and_segments
 
 	mov rdi, rsp
+	mov rsi, rsp
 	call irq_handler
 	mov rsp, rax
 
@@ -56,8 +58,8 @@ irq_handler_prelude:
 		jmp irq_handler_prelude
 %endmacro
 
-%define EISR(i, name)     EMIT_EISR name, i
-%define UISR(i, name)     EMIT_ISR name, i
+%define EISR(i, name)     EMIT_EISR name, i   ; ISR with error code
+%define UISR(i, name)     EMIT_ISR name, i    ; ISR callable from user space
 %define  ISR(i, name)     EMIT_ISR name, i
 %define  IRQ(i, q, name)  EMIT_IRQ name, i
 
diff --git a/src/kernel/scheduler.h b/src/kernel/scheduler.h
index f67a89e..2253473 100644
--- a/src/kernel/scheduler.h
+++ b/src/kernel/scheduler.h
@@ -10,7 +10,7 @@ class lapic;
 struct page_table;
 struct cpu_state;
 
-extern "C" uintptr_t isr_handler(uintptr_t, cpu_state);
+extern "C" uintptr_t isr_handler(uintptr_t, cpu_state*);
 
 
 /// The task scheduler
@@ -59,8 +59,8 @@ public:
 	static scheduler & get() { return s_instance; }
 
 private:
-	friend uintptr_t syscall_dispatch(uintptr_t, const cpu_state &);
-	friend uintptr_t isr_handler(uintptr_t, cpu_state);
+	friend uintptr_t syscall_dispatch(uintptr_t, cpu_state &);
+	friend uintptr_t isr_handler(uintptr_t, cpu_state*);
 
 	/// Handle a timer tick
 	/// \arg rsp0  The stack pointer of the current interrupt handler
diff --git a/src/kernel/syscall.cpp b/src/kernel/syscall.cpp
index 50f35bf..bdd65e2 100644
--- a/src/kernel/syscall.cpp
+++ b/src/kernel/syscall.cpp
@@ -35,7 +35,7 @@ syscall_enable()
 }
 
 uintptr_t
-syscall_dispatch(uintptr_t return_rsp, const cpu_state &regs)
+syscall_dispatch(uintptr_t return_rsp, cpu_state &regs)
 {
 	console *cons = console::get();
 	syscall call = static_cast<syscall>(regs.rax);
@@ -65,7 +65,7 @@ syscall_dispatch(uintptr_t return_rsp, const cpu_state &regs)
 			auto *p = s.current();
 			p->wait_on_signal(-1ull);
 			cons->printf("\nReceived PAUSE syscall\n");
-			return_rsp = s.tick(return_rsp);
+			return_rsp = s.schedule(return_rsp);
 			cons->set_color();
 		}
 		break;
@@ -78,7 +78,7 @@ syscall_dispatch(uintptr_t return_rsp, const cpu_state &regs)
 			auto *p = s.current();
 			p->wait_on_time(regs.rbx);
 			cons->printf("\nReceived SLEEP syscall\n");
-			return_rsp = s.tick(return_rsp);
+			return_rsp = s.schedule(return_rsp);
 			cons->set_color();
 		}
 		break;
diff --git a/src/kernel/syscall.h b/src/kernel/syscall.h
index 3aad6ae..12df735 100644
--- a/src/kernel/syscall.h
+++ b/src/kernel/syscall.h
@@ -16,5 +16,5 @@ enum class syscall : uint64_t
 };
 
 void syscall_enable();
-uintptr_t syscall_dispatch(uintptr_t, const cpu_state &);
+uintptr_t syscall_dispatch(uintptr_t, cpu_state &);