use syscall_arg_t and __scc macro for arguments to __alt_socketcall

otherwise, pointer arguments are sign-extended on x32, resulting in
EFAULT.

src/internal/syscall.h

@@ -58,7 +58,7 @@ hidden long __syscall_ret(unsigned long),
 #define __syscall_cp(...) __SYSCALL_DISP(__syscall_cp,__VA_ARGS__)
 #define syscall_cp(...) __syscall_ret(__syscall_cp(__VA_ARGS__))
 
-static inline long __alt_socketcall(int sys, int sock, int cp, long a, long b, long c, long d, long e, long f)
+static inline long __alt_socketcall(int sys, int sock, int cp, syscall_arg_t a, syscall_arg_t b, syscall_arg_t c, syscall_arg_t d, syscall_arg_t e, syscall_arg_t f)
 {
 	long r;
 	if (cp) r = __syscall_cp(sys, a, b, c, d, e, f);
@@ -71,9 +71,9 @@ static inline long __alt_socketcall(int sys, int sock, int cp, long a, long b, l
 	return r;
 }
 #define __socketcall(nm, a, b, c, d, e, f) __alt_socketcall(SYS_##nm, __SC_##nm, 0, \
-	(long)(a), (long)(b), (long)(c), (long)(d), (long)(e), (long)(f))
+	__scc(a), __scc(b), __scc(c), __scc(d), __scc(e), __scc(f))
 #define __socketcall_cp(nm, a, b, c, d, e, f) __alt_socketcall(SYS_##nm, __SC_##nm, 1, \
-	(long)(a), (long)(b), (long)(c), (long)(d), (long)(e), (long)(f))
+	__scc(a), __scc(b), __scc(c), __scc(d), __scc(e), __scc(f))
 
 /* fixup legacy 16-bit junk */