Kernel: Use syscall/sysret for syscalls in x86_64

kernel/include/kernel/API/Syscall.h

@@ -0,0 +1,44 @@
+#pragma once
+
+#include <kernel/Attributes.h>
+#include <kernel/IDT.h>
+#include <stdint.h>
+#include <sys/syscall.h>
+
+namespace Kernel
+{
+
+	ALWAYS_INLINE long syscall(int syscall, uintptr_t arg1 = 0, uintptr_t arg2 = 0, uintptr_t arg3 = 0, uintptr_t arg4 = 0, uintptr_t arg5 = 0)
+	{
+		long ret;
+#if ARCH(x86_64)
+		register uintptr_t r10 asm("r10") = arg3;
+		register uintptr_t r8  asm( "r8") = arg4;
+		register uintptr_t r9  asm( "r9") = arg5;
+		asm volatile(
+			"syscall"
+			: "=a"(ret)
+			, "+D"(syscall)
+			, "+S"(arg1)
+			, "+d"(arg2)
+			, "+r"(r10)
+			, "+r"(r8)
+			, "+r"(r9)
+			:: "rcx", "r11", "memory");
+#elif ARCH(i686)
+		asm volatile(
+			"int %[irq]"
+			: "=a"(ret)
+			: [irq]"i"(static_cast<int>(IRQ_SYSCALL)) // WTF GCC 15
+			, "a"(syscall)
+			, "b"(arg1)
+			, "c"(arg2)
+			, "d"(arg3)
+			, "S"(arg4)
+			, "D"(arg5)
+			: "memory");
+#endif
+		return ret;
+	}
+
+}

kernel/include/kernel/GDT.h

@@ -151,8 +151,8 @@ namespace Kernel
 
 	private:
 #if ARCH(x86_64)
-		BAN::Array<SegmentDescriptor, 7> m_gdt; // null, kernel code, kernel data, user code, user data, tss low, tss high
-		static constexpr uint16_t m_tss_offset = 0x28;
+		BAN::Array<SegmentDescriptor, 8> m_gdt; // null, kernel code, kernel data, user code (32 bit), user data, user code (64 bit), tss low, tss high
+		static constexpr uint16_t m_tss_offset = 0x30;
 #elif ARCH(i686)
 		BAN::Array<SegmentDescriptor, 9> m_gdt; // null, kernel code, kernel data, user code, user data, processor data, fsbase, gsbase, tss
 		static constexpr uint16_t m_tss_offset = 0x40;

kernel/include/kernel/IDT.h

@@ -18,7 +18,10 @@ namespace Kernel
 
 	constexpr uint8_t IRQ_VECTOR_BASE   = 0x20;
 	constexpr uint8_t IRQ_MSI_BASE      = 0x80;
+	constexpr uint8_t IRQ_MSI_END       = 0xF0;
+#if ARCH(i686)
 	constexpr uint8_t IRQ_SYSCALL       = 0xF0;
+#endif
 	constexpr uint8_t IRQ_YIELD         = 0xF1;
 	constexpr uint8_t IRQ_IPI           = 0xF2;
 	constexpr uint8_t IRQ_TIMER         = 0xF3;

kernel/include/kernel/PCI.h

@@ -187,7 +187,7 @@ namespace Kernel::PCI
 		void initialize_impl();
 
 	private:
-		static constexpr uint8_t m_msi_count = IRQ_SYSCALL - IRQ_MSI_BASE;
+		static constexpr uint8_t m_msi_count = IRQ_MSI_END - IRQ_MSI_BASE;
 		using PCIBus = BAN::Array<BAN::Array<Device, 8>, 32>;
 		BAN::Array<PCIBus, 256>  m_buses;
 		BAN::Array<paddr_t, 256> m_bus_pcie_paddr;

kernel/include/kernel/Processor.h

@@ -102,6 +102,8 @@ namespace Kernel
 		uintptr_t stack_bottom() const	{ return reinterpret_cast<uintptr_t>(m_stack); }
 		uintptr_t stack_top() const		{ return stack_bottom() + s_stack_size; }
 
+		static void set_thread_syscall_stack(vaddr_t vaddr) { write_gs_sized<vaddr_t>(offsetof(Processor, m_thread_syscall_stack), vaddr); }
+
 		static GDT& gdt() { return *read_gs_sized<GDT*>(offsetof(Processor, m_gdt)); }
 		static IDT& idt() { return *read_gs_sized<IDT*>(offsetof(Processor, m_idt)); }
 
@@ -137,6 +139,13 @@ namespace Kernel
 		static void initialize_smp();
 		static void initialize_shared_page();
 
+		static void dummy()
+		{
+#if ARCH(x86_64)
+			static_assert(offsetof(Processor, m_thread_syscall_stack) == 8, "This is hardcoded in Syscall.S");
+#endif
+		}
+
 		template<typename T>
 		static T read_gs_sized(uintptr_t offset) requires(sizeof(T) <= 8)
 		{
@@ -180,6 +189,8 @@ namespace Kernel
 		ProcessorID m_id { 0 };
 		uint8_t m_index { 0xFF };
 
+		vaddr_t m_thread_syscall_stack;
+
 		static constexpr size_t s_stack_size { 4096 };
 		void* m_stack { nullptr };
 

kernel/include/kernel/Syscall.h

@@ -1,27 +0,0 @@
-#pragma once
-
-#include <kernel/Attributes.h>
-#include <kernel/IDT.h>
-#include <stdint.h>
-#include <sys/syscall.h>
-
-namespace Kernel
-{
-
-	ALWAYS_INLINE long syscall(int syscall, uintptr_t arg1 = 0, uintptr_t arg2 = 0, uintptr_t arg3 = 0, uintptr_t arg4 = 0, uintptr_t arg5 = 0)
-	{
-		long ret;
-		asm volatile("int %[irq]"
-			: "=a"(ret)
-			: [irq]"i"(static_cast<int>(IRQ_SYSCALL)) // WTF GCC 15
-			, "a"(syscall)
-			, "b"((uintptr_t)arg1)
-			, "c"((uintptr_t)arg2)
-			, "d"((uintptr_t)arg3)
-			, "S"((uintptr_t)arg4)
-			, "D"((uintptr_t)arg5)
-			: "memory");
-		return ret;
-	}
-
-}