riscv64: add syscall helpers

Use syscall helpers to optimized io_uring_enter(2) calls, eliminating
the need for libc functions. These wrappers are adapted from liburing.

Signed-off-by: michalbiesek <michalbiesek@gmail.com>

arch/arch-riscv64.h

@@ -29,4 +29,90 @@ static inline int arch_init(char *envp[])
 	return 0;
 }
 
+#define __do_syscallM(...) ({						\
+	__asm__ volatile (						\
+		"ecall"							\
+		: "=r"(a0)						\
+		: __VA_ARGS__						\
+		: "memory", "a1");					\
+	(long) a0;							\
+})
+
+#define __do_syscallN(...) ({						\
+	__asm__ volatile (						\
+		"ecall"							\
+		: "=r"(a0)						\
+		: __VA_ARGS__						\
+		: "memory");					\
+	(long) a0;							\
+})
+
+#define __do_syscall0(__n) ({						\
+	register long a7 __asm__("a7") = __n;				\
+	register long a0 __asm__("a0");					\
+									\
+	__do_syscallM("r" (a7));					\
+})
+
+#define __do_syscall1(__n, __a) ({					\
+	register long a7 __asm__("a7") = __n;				\
+	register __typeof__(__a) a0 __asm__("a0") = __a;		\
+									\
+	__do_syscallM("r" (a7), "0" (a0));				\
+})
+
+#define __do_syscall2(__n, __a, __b) ({					\
+	register long a7 __asm__("a7") = __n;				\
+	register __typeof__(__a) a0 __asm__("a0") = __a;		\
+	register __typeof__(__b) a1 __asm__("a1") = __b;		\
+									\
+	__do_syscallN("r" (a7), "0" (a0), "r" (a1));			\
+})
+
+#define __do_syscall3(__n, __a, __b, __c) ({				\
+	register long a7 __asm__("a7") = __n;				\
+	register __typeof__(__a) a0 __asm__("a0") = __a;		\
+	register __typeof__(__b) a1 __asm__("a1") = __b;		\
+	register __typeof__(__c) a2 __asm__("a2") = __c;		\
+									\
+	__do_syscallN("r" (a7), "0" (a0), "r" (a1), "r" (a2));		\
+})
+
+#define __do_syscall4(__n, __a, __b, __c, __d) ({			\
+	register long a7 __asm__("a7") = __n;				\
+	register __typeof__(__a) a0 __asm__("a0") = __a;		\
+	register __typeof__(__b) a1 __asm__("a1") = __b;		\
+	register __typeof__(__c) a2 __asm__("a2") = __c;		\
+	register __typeof__(__d) a3 __asm__("a3") = __d;		\
+									\
+	__do_syscallN("r" (a7), "0" (a0), "r" (a1), "r" (a2), "r" (a3));\
+})
+
+#define __do_syscall5(__n, __a, __b, __c, __d, __e) ({			\
+	register long a7 __asm__("a7") = __n;				\
+	register __typeof__(__a) a0 __asm__("a0") = __a;		\
+	register __typeof__(__b) a1 __asm__("a1") = __b;		\
+	register __typeof__(__c) a2 __asm__("a2") = __c;		\
+	register __typeof__(__d) a3 __asm__("a3") = __d;		\
+	register __typeof__(__e) a4 __asm__("a4") = __e;		\
+									\
+	__do_syscallN("r" (a7), "0" (a0), "r" (a1), "r" (a2), "r" (a3),	\
+			"r"(a4));					\
+})
+
+#define __do_syscall6(__n, __a, __b, __c, __d, __e, __f) ({		\
+	register long a7 __asm__("a7") = __n;				\
+	register __typeof__(__a) a0 __asm__("a0") = __a;		\
+	register __typeof__(__b) a1 __asm__("a1") = __b;		\
+	register __typeof__(__c) a2 __asm__("a2") = __c;		\
+	register __typeof__(__d) a3 __asm__("a3") = __d;		\
+	register __typeof__(__e) a4 __asm__("a4") = __e;		\
+	register __typeof__(__f) a5 __asm__("a5") = __f;		\
+									\
+	__do_syscallN("r" (a7), "0" (a0), "r" (a1), "r" (a2), "r" (a3),	\
+			"r" (a4), "r"(a5));				\
+})
+
+#define FIO_ARCH_HAS_SYSCALL
+
 #endif