Kernel: optimize yielding

Doing a yield no longer raises a software interrupt. Instead it just
saves all the callee saved registers, ip, sp and return value. Because
yield is only called in the kernel, it can just restore registers and
jump to the target address. There is never a need to use iret :)

kernel/kernel/Processor.cpp

@@ -36,6 +36,7 @@ namespace Kernel
 	static BAN::Array<ProcessorID, 0xFF> s_processor_ids { PROCESSOR_NONE };
 
 	extern "C" void asm_syscall_handler();
+	extern "C" void asm_yield_trampoline(uintptr_t);
 
 	ProcessorID Processor::read_processor_id()
 	{
@@ -556,33 +557,7 @@ namespace Kernel
 		if (!scheduler().is_idle())
 			Thread::current().set_cpu_time_stop();
 
-#if ARCH(x86_64)
-		asm volatile(
-			"movq %%rsp, %%rcx;"
-			"movq %[load_sp], %%rsp;"
-			"int %[yield];"
-			"movq %%rcx, %%rsp;"
-			// NOTE: This is offset by 2 pointers since interrupt without PL change
-			//       does not push SP and SS. This allows accessing "whole" interrupt stack.
-			:: [load_sp]"r"(Processor::current_stack_top() - 2 * sizeof(uintptr_t)),
-			   [yield]"i"(static_cast<int>(IRQ_YIELD)) // WTF GCC 15
-			:  "memory", "rcx"
-		);
-#elif ARCH(i686)
-		asm volatile(
-			"movl %%esp, %%ecx;"
-			"movl %[load_sp], %%esp;"
-			"int %[yield];"
-			"movl %%ecx, %%esp;"
-			// NOTE: This is offset by 2 pointers since interrupt without PL change
-			//       does not push SP and SS. This allows accessing "whole" interrupt stack.
-			:: [load_sp]"r"(Processor::current_stack_top() - 2 * sizeof(uintptr_t)),
-			   [yield]"i"(static_cast<int>(IRQ_YIELD)) // WTF GCC 15
-			:  "memory", "ecx"
-		);
-#else
-		#error
-#endif
+		asm_yield_trampoline(Processor::current_stack_top());
 
 		processor_info.m_start_ns = SystemTimer::get().ns_since_boot();