Kernel/LibC: Rework userspace syscall interface

Kernel syscall API no longer zeros all unused argument registers and
libc now uses inlined syscall macro internally. This significantly
cleans up generated code for basic syscall wrapper functions.

kernel/include/kernel/API/Syscall.h

@@ -1,44 +1,34 @@
 #pragma once
 
-#include <kernel/Attributes.h>
-#include <kernel/IDT.h>
-#include <stdint.h>
-#include <sys/syscall.h>
+#include <BAN/MacroUtils.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");
+#if defined(__x86_64__)
+	#define _kas_instruction "syscall"
+	#define _kas_result rax
+	#define _kas_arguments rdi, rsi, rdx, r10, r8, r9
+	#define _kas_globbers rcx, rdx, rdi, rsi, r8, r9, r10, r11
+#elif defined(__i686__)
+	#define _kas_instruction "int $0xF0"
+	#define _kas_result eax
+	#define _kas_arguments eax, ebx, ecx, edx, esi, edi
+	#define _kas_globbers
 #endif
-		return ret;
-	}
 
-}
+#define _kas_argument_var(index, value) register long _kas_a##index asm(_ban_stringify(_ban_get(index, _kas_arguments))) = (long)value;
+#define _kas_dummy_var(index, value) register long _kas_d##index asm(#value);
+#define _kas_input(index, _) "r"(_kas_a##index)
+#define _kas_output(index, _) , "=r"(_kas_d##index)
+#define _kas_globber(_, value) #value
+
+#define _kas_syscall(...) ({ \
+		register long _kas_ret asm(_ban_stringify(_kas_result)); \
+		_ban_for_each(_kas_argument_var, __VA_ARGS__) \
+		_ban_for_each(_kas_dummy_var, _kas_globbers) \
+		asm volatile( \
+			_kas_instruction \
+			: "=r"(_kas_ret) _ban_for_each(_kas_output, _kas_globbers) \
+			: _ban_for_each_comma(_kas_input, __VA_ARGS__) \
+			: "cc", "memory"); \
+		(void)_kas_a0; /* require 1 argument */ \
+		_kas_ret; \
+	})

kernel/include/kernel/IDT.h

@@ -20,7 +20,7 @@ namespace Kernel
 	constexpr uint8_t IRQ_MSI_BASE      = 0x80;
 	constexpr uint8_t IRQ_MSI_END       = 0xF0;
 #if ARCH(i686)
-	constexpr uint8_t IRQ_SYSCALL       = 0xF0;
+	constexpr uint8_t IRQ_SYSCALL       = 0xF0; // hard coded in kernel/API/Syscall.h
 #endif
 	constexpr uint8_t IRQ_IPI           = 0xF1;
 	constexpr uint8_t IRQ_TIMER         = 0xF2;