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.

userspace/libraries/LibC/CMakeLists.txt

@@ -74,7 +74,7 @@ set(LIBC_SOURCES
 )
 
 add_library(objlibc OBJECT ${LIBC_SOURCES})
-target_compile_definitions(objlibc PRIVATE __arch=${BANAN_ARCH})
+target_compile_definitions(objlibc PRIVATE __arch=${BANAN_ARCH} __is_libc)
 
 target_compile_options(objlibc PRIVATE -O2 -g -Wstack-usage=512 -fno-exceptions -fno-rtti -fpic)
 target_compile_options(objlibc PUBLIC -Wall -Wextra -Werror -Wno-error=stack-usage=)

userspace/libraries/LibC/include/unistd.h

@@ -608,6 +608,22 @@ char*				getpass(const char* prompt);
 
 long syscall(long syscall, ...);
 
+#ifdef __is_libc
+#include <kernel/API/Syscall.h>
+#include <errno.h>
+#define _syscall(...) ({ \
+		long _ret = -ERESTART; \
+		while (_ret == -ERESTART) \
+			_ret = _kas_syscall(__VA_ARGS__); \
+		if (_ret < 0) { \
+			errno = -_ret; \
+			_ret = -1; \
+		} \
+		_ret; \
+	})
+#define syscall _syscall
+#endif
+
 extern char** environ;
 
 __END_DECLS

userspace/libraries/LibC/unistd.cpp

@@ -254,32 +254,21 @@ void _exit(int status)
 	ASSERT_NOT_REACHED();
 }
 
+#undef syscall
 long syscall(long syscall, ...)
 {
 	va_list args;
 	va_start(args, syscall);
-
 	uintptr_t arg1 = va_arg(args, uintptr_t);
 	uintptr_t arg2 = va_arg(args, uintptr_t);
 	uintptr_t arg3 = va_arg(args, uintptr_t);
 	uintptr_t arg4 = va_arg(args, uintptr_t);
 	uintptr_t arg5 = va_arg(args, uintptr_t);
-
 	va_end(args);
 
-	long ret;
-	do
-		ret = Kernel::syscall(syscall, arg1, arg2, arg3, arg4, arg5);
-	while (ret == -ERESTART);
-
-	if (ret < 0)
-	{
-		errno = -ret;
-		return -1;
-	}
-
-	return ret;
+	return _syscall(syscall, arg1, arg2, arg3, arg4, arg5);
 }
+#define syscall _syscall
 
 int close(int fd)
 {