Kernel: Fix multiprocessor for i686

i686 is now actually ran with multiple processors.

kernel/arch/i686/Syscall.S

@@ -1,3 +1,57 @@
+// arguments in EAX, EBX, ECX, EDX, ESI, EDI
+.global asm_syscall_handler
+asm_syscall_handler:
+	# save segment registers
+	pushw %ds
+	pushw %es
+	pushw %fs
+	pushw %gs
+
+	# save general purpose registers
+	pushl %ebx
+	pushl %ecx
+	pushl %edx
+	pushl %edi
+	pushl %esi
+	pushl %ebp
+
+	# align stack and push arguments
+	pushl %esp
+	addl $32, (%esp)
+	pushl %edi
+	pushl %esi
+	pushl %edx
+	pushl %ecx
+	pushl %ebx
+	pushl %eax
+
+	# load kernel segments
+	movw $0x10, %ax
+	movw %ax, %ds
+	movw %ax, %es
+	movw %ax, %fs
+	movw $0x28, %ax
+	movw %ax, %gs
+
+	call cpp_syscall_handler
+	addl $28, %esp
+
+	# restore general purpose registers
+	popl %ebp
+	popl %esi
+	popl %edi
+	popl %edx
+	popl %ecx
+	popl %ebx
+
+	# restore segment registers
+	popw %gs
+	popw %fs
+	popw %es
+	popw %ds
+
+	iret
+
 .global sys_fork_trampoline
 sys_fork_trampoline:
 	pushl %ebp

kernel/arch/i686/interrupts.S

@@ -24,22 +24,6 @@
 	popw %gs
 .endm
 
-.macro pop_userspace_skip_eax
-	popl %edi
-	popl %esi
-	popl %ebp
-	addl $4, %esp
-	popl %ebx
-	popl %edx
-	popl %ecx
-	addl $4, %esp
-
-	popw %ds
-	popw %es
-	popw %fs
-	popw %gs
-.endm
-
 isr_stub:
 	push_userspace
 	load_kernel_segments
@@ -81,46 +65,21 @@ irq_stub:
 	addl $8, %esp
 	iret
 
-.global asm_reschedule_handler
-asm_reschedule_handler:
-	push_userspace
-	load_kernel_segments
+.global asm_yield_handler
+asm_yield_handler:
+	# This can only be called from kernel, so no segment saving is needed
+	pushal
 
 	movl %esp,     %eax # interrupt registers ptr
-	leal 40(%esp), %ebx # interrupt stack ptr
+	leal 32(%esp), %ebx # interrupt stack ptr
 
-	subl $12, %esp
+	subl $4, %esp
 	pushl %eax
 	pushl %ebx
-	call cpp_reschedule_handler
-	addl $20, %esp
+	call cpp_yield_handler
+	addl $12, %esp
 
-	pop_userspace
-	iret
-
-// arguments in EAX, EBX, ECX, EDX, ESI, EDI
-.global syscall_asm
-syscall_asm:
-	push_userspace
-
-	subl $8, %esp
-
-	pushl %esp
-	addl $48, (%esp)
-
-	pushl %edi
-	pushl %esi
-	pushl %edx
-	pushl %ecx
-	pushl %ebx
-	pushl %eax
-
-	load_kernel_segments
-
-	call cpp_syscall_handler
-	addl $36, %esp
-
-	pop_userspace_skip_eax
+	popal
 	iret
 
 .macro isr n
@@ -211,3 +170,4 @@ irq 28
 irq 29
 irq 30
 irq 31
+irq 32

kernel/arch/x86_64/Syscall.S

@@ -1,3 +1,49 @@
+// arguments in RAX, RBX, RCX, RDX, RSI, RDI
+// System V ABI: RDI, RSI, RDX, RCX, R8, R9
+.global asm_syscall_handler
+asm_syscall_handler:
+	pushq %rbx
+	pushq %rcx
+	pushq %rdx
+	pushq %rdi
+	pushq %rsi
+	pushq %rbp
+	pushq %r8
+	pushq %r9
+	pushq %r10
+	pushq %r11
+	pushq %r12
+	pushq %r13
+	pushq %r14
+	pushq %r15
+
+	movq %rsi, %r8
+	movq %rdi, %r9
+	movq %rax, %rdi
+	movq %rbx, %rsi
+	xchgq %rcx, %rdx
+	leaq 112(%rsp), %rbx
+	pushq %rbx
+	call cpp_syscall_handler
+	addq $8, %rsp
+
+	popq %r15
+	popq %r14
+	popq %r13
+	popq %r12
+	popq %r11
+	popq %r10
+	popq %r9
+	popq %r8
+	popq %rbp
+	popq %rsi
+	popq %rdi
+	popq %rdx
+	popq %rcx
+	popq %rbx
+	iretq
+
+
 .global sys_fork_trampoline
 sys_fork_trampoline:
 	pushq %rbx

kernel/arch/x86_64/interrupts.S

@@ -34,23 +34,6 @@
 	popq %rax
 .endm
 
-.macro popaq_no_rax
-	popq %r15
-	popq %r14
-	popq %r13
-	popq %r12
-	popq %r11
-	popq %r10
-	popq %r9
-	popq %r8
-	popq %rdi
-	popq %rsi
-	popq %rbp
-	popq %rbx
-	popq %rdx
-	popq %rcx
-.endm
-
 isr_stub:
 	pushaq
 
@@ -78,6 +61,15 @@ irq_stub:
 	addq $16, %rsp
 	iretq
 
+.global asm_yield_handler
+asm_yield_handler:
+	pushaq
+	leaq 120(%rsp), %rdi # interrupt stack ptr
+	movq     %rsp,  %rsi # interrupt register ptr
+	call cpp_yield_handler
+	popaq
+	iretq
+
 .macro isr n
 	.global isr\n
 	isr\n:
@@ -166,31 +158,4 @@ irq 28
 irq 29
 irq 30
 irq 31
-
-.global asm_reschedule_handler
-asm_reschedule_handler:
-	pushaq
-	leaq 120(%rsp), %rdi # interrupt stack ptr
-	movq     %rsp,  %rsi # interrupt register ptr
-	call cpp_reschedule_handler
-	popaq
-	iretq
-
-// arguments in RAX, RBX, RCX, RDX, RSI, RDI
-// System V ABI: RDI, RSI, RDX, RCX, R8, R9
-.global syscall_asm
-syscall_asm:
-	pushaq
-	movq %rsi, %r8
-	movq %rdi, %r9
-	movq %rax, %rdi
-	movq %rbx, %rsi
-	xchgq %rcx, %rdx
-	movq %rsp, %rbx
-	addq $120, %rbx
-	pushq %rbx
-	call cpp_syscall_handler
-	addq $8, %rsp
-	popaq_no_rax
-	addq $8, %rsp
-	iretq
+irq 32

kernel/include/kernel/IDT.h

@@ -8,7 +8,8 @@
 #include <stdint.h>
 
 constexpr uint8_t IRQ_VECTOR_BASE = 0x20;
-constexpr uint8_t IRQ_IPI = 32;
+constexpr uint8_t IRQ_IPI	= 32;
+constexpr uint8_t IRQ_YIELD	= 33;
 
 namespace Kernel
 {

kernel/include/kernel/Scheduler.h

@@ -12,7 +12,6 @@ namespace Kernel
 	public:
 		static BAN::ErrorOr<void> initialize();
 		static Scheduler& get();
-		static bool is_started();
 
 		[[noreturn]] void start();
 

kernel/kernel/IDT.cpp

@@ -10,7 +10,7 @@
 #include <kernel/Timer/PIT.h>
 
 #define ISR_LIST_X X(0) X(1) X(2) X(3) X(4) X(5) X(6) X(7) X(8) X(9) X(10) X(11) X(12) X(13) X(14) X(15) X(16) X(17) X(18) X(19) X(20) X(21) X(22) X(23) X(24) X(25) X(26) X(27) X(28) X(29) X(30) X(31)
-#define IRQ_LIST_X X(0) X(1) X(2) X(3) X(4) X(5) X(6) X(7) X(8) X(9) X(10) X(11) X(12) X(13) X(14) X(15) X(16) X(17) X(18) X(19) X(20) X(21) X(22) X(23) X(24) X(25) X(26) X(27) X(28) X(29) X(30) X(31)
+#define IRQ_LIST_X X(0) X(1) X(2) X(3) X(4) X(5) X(6) X(7) X(8) X(9) X(10) X(11) X(12) X(13) X(14) X(15) X(16) X(17) X(18) X(19) X(20) X(21) X(22) X(23) X(24) X(25) X(26) X(27) X(28) X(29) X(30) X(31) X(32)
 
 namespace Kernel
 {
@@ -329,8 +329,11 @@ done:
 		return;
 	}
 
-	extern "C" void cpp_reschedule_handler(InterruptStack* interrupt_stack, InterruptRegisters* interrupt_registers)
+	extern "C" void cpp_yield_handler(InterruptStack* interrupt_stack, InterruptRegisters* interrupt_registers)
 	{
+		ASSERT(!InterruptController::get().is_in_service(IRQ_YIELD));
+		ASSERT(!GDT::is_user_segment(interrupt_stack->cs));
+
 		Processor::enter_interrupt(interrupt_stack, interrupt_registers);
 		Scheduler::get().irq_reschedule();
 		Processor::leave_interrupt();
@@ -346,8 +349,6 @@ done:
 			asm volatile("cli; 1: hlt; jmp 1b");
 		}
 
-		ASSERT(irq != IRQ_IPI);
-
 		if (!InterruptController::get().is_in_service(irq))
 			dprintln("spurious irq 0x{2H}", irq);
 		else
@@ -355,6 +356,8 @@ done:
 			InterruptController::get().eoi(irq);
 			if (auto* handler = s_interruptables[irq])
 				handler->handle_irq();
+			else if (irq == IRQ_IPI)
+				Scheduler::get().yield();
 			else
 				dprintln("no handler for irq 0x{2H}", irq);
 		}
@@ -400,8 +403,8 @@ done:
 	IRQ_LIST_X
 #undef X
 
-	extern "C" void asm_reschedule_handler();
-	extern "C" void syscall_asm();
+	extern "C" void asm_yield_handler();
+	extern "C" void asm_syscall_handler();
 
 	IDT* IDT::create()
 	{
@@ -418,9 +421,9 @@ done:
 		IRQ_LIST_X
 #undef X
 
-		idt->register_interrupt_handler(IRQ_VECTOR_BASE + IRQ_IPI, asm_reschedule_handler);
+		idt->register_interrupt_handler(IRQ_VECTOR_BASE + IRQ_YIELD, asm_yield_handler);
 
-		idt->register_syscall_handler(0x80, syscall_asm);
+		idt->register_syscall_handler(0x80, asm_syscall_handler);
 
 		return idt;
 	}

kernel/kernel/Scheduler.cpp

@@ -12,7 +12,6 @@ namespace Kernel
 {
 
 	static Scheduler* s_instance = nullptr;
-	static BAN::Atomic<bool> s_started { false };
 
 	BAN::ErrorOr<void> Scheduler::initialize()
 	{
@@ -33,13 +32,12 @@ namespace Kernel
 	{
 		ASSERT(Processor::get_interrupt_state() == InterruptState::Disabled);
 		ASSERT(!m_active_threads.empty());
-		yield();
-		ASSERT_NOT_REACHED();
-	}
 
-	bool Scheduler::is_started()
-	{
-		return s_started;
+		// broadcast ipi (yield) for each processor
+		InterruptController::get().broadcast_ipi();
+		yield();
+
+		ASSERT_NOT_REACHED();
 	}
 
 	Thread& Scheduler::current_thread()
@@ -122,20 +120,21 @@ namespace Kernel
 
 	void Scheduler::timer_reschedule()
 	{
-		// Broadcast IPI to all other processors for them
-		// to perform reschedule
-		InterruptController::get().broadcast_ipi();
-
 		{
 			SpinLockGuard _(m_lock);
 			m_blocking_threads.remove_with_wake_time(m_active_threads, SystemTimer::get().ms_since_boot());
 		}
 
+		// Broadcast IPI to all other processors for them
+		// to perform reschedule
+		InterruptController::get().broadcast_ipi();
 		yield();
 	}
 
 	void Scheduler::yield()
 	{
+		ASSERT(!m_lock.current_processor_has_lock());
+
 		auto state = Processor::get_interrupt_state();
 		Processor::set_interrupt_state(InterruptState::Disabled);
 
@@ -143,24 +142,24 @@ namespace Kernel
 		asm volatile(
 			"movq %%rsp, %%rcx;"
 			"movq %[load_sp], %%rsp;"
-			"int %[ipi];"
+			"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)),
-			   [ipi]"i"(IRQ_VECTOR_BASE + IRQ_IPI)
+			   [yield]"i"(IRQ_VECTOR_BASE + IRQ_YIELD)
 			:  "memory", "rcx"
 		);
 #elif ARCH(i686)
 		asm volatile(
 			"movl %%esp, %%ecx;"
 			"movl %[load_sp], %%esp;"
-			"int %[ipi];"
+			"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)),
-			   [ipi]"i"(IRQ_VECTOR_BASE + IRQ_IPI)
+			   [yield]"i"(IRQ_VECTOR_BASE + IRQ_YIELD)
 			:  "memory", "ecx"
 		);
 #else

kernel/kernel/Thread.cpp

@@ -265,7 +265,7 @@ namespace Kernel
 
 		m_interrupt_stack.ip = reinterpret_cast<vaddr_t>(start_kernel_thread);
 		m_interrupt_stack.cs = 0x08;
-		m_interrupt_stack.flags = 0x202;
+		m_interrupt_stack.flags = 0x002;
 		m_interrupt_stack.sp = kernel_stack_top() - 4 * sizeof(uintptr_t);
 		m_interrupt_stack.ss = 0x10;
 

kernel/kernel/kernel.cpp

@@ -218,7 +218,9 @@ extern "C" void ap_main()
 
 	dprintln("ap{} initialized", Processor::current_id());
 
-	while (!Scheduler::is_started())
-		__builtin_ia32_pause();
-	Scheduler::get().start();
+	// wait until scheduler is started and we get irq for reschedule
+	Processor::set_interrupt_state(InterruptState::Enabled);
+	while (true)
+		asm volatile("hlt");
+	ASSERT_NOT_REACHED();
 }