[UNIKRAFT PATCH] lib/syscall_shim: Avoid warning about unused system call arguments

[Simon Kuenzer <simon.kuenzer@xxxxxxxxx>]

Some system call implementations may not use all arguments which causes
a compiler warning. This commit adds the `__maybe_unused` attribute to
the arguments when one of the following macros is used for a system call
implementation: `UK_SYSCALL_DEFINE()`, `UK_LLSYSCALL_DEFINE()`,
`UK_SYSCALL_R_DEFINE()`, and `UK_LLSYSCALL_R_DEFINE()`.

Signed-off-by: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>
---
 lib/syscall_shim/include/uk/syscall.h | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/lib/syscall_shim/include/uk/syscall.h 
b/lib/syscall_shim/include/uk/syscall.h
index ffa9f1ee4..37d7f5f0e 100644
--- a/lib/syscall_shim/include/uk/syscall.h
+++ b/lib/syscall_shim/include/uk/syscall.h
@@ -105,6 +105,8 @@ typedef long uk_syscall_arg_t;
 
 #define UK_S_ARG_LONG(type, arg)   long arg
 #define UK_S_ARG_ACTUAL(type, arg) type arg
+#define UK_S_ARG_LONG_MAYBE_UNUSED(type, arg)   long arg __maybe_unused
+#define UK_S_ARG_ACTUAL_MAYBE_UNUSED(type, arg) type arg __maybe_unused
 #define UK_S_ARG_CAST_LONG(type, arg)   (long) arg
 #define UK_S_ARG_CAST_ACTUAL(type, arg) (type) arg
 
@@ -139,7 +141,8 @@ typedef long uk_syscall_arg_t;
                        UK_ARG_MAPx(x, UK_S_ARG_CAST_ACTUAL, __VA_ARGS__)); \
        }                                                               \
        static inline rtype __##ename(UK_ARG_MAPx(x,                    \
-                                                 UK_S_ARG_ACTUAL, __VA_ARGS__))
+                                                 UK_S_ARG_ACTUAL_MAYBE_UNUSED,\
+                                                 __VA_ARGS__))
 #define _UK_LLSYSCALL_DEFINE(...) __UK_LLSYSCALL_DEFINE(__VA_ARGS__)
 #define UK_LLSYSCALL_DEFINE(rtype, name, ...)                          \
        _UK_LLSYSCALL_DEFINE(__UK_SYSCALL_DEF_NARGS(__VA_ARGS__),       \
@@ -208,8 +211,9 @@ typedef long uk_syscall_arg_t;
                return (long) __##rname(                                \
                        UK_ARG_MAPx(x, UK_S_ARG_CAST_ACTUAL, __VA_ARGS__)); \
        }                                                               \
-       static inline rtype __##rname(UK_ARG_MAPx(x, UK_S_ARG_ACTUAL,   \
-                                                __VA_ARGS__))
+       static inline rtype __##rname(UK_ARG_MAPx(x,                    \
+                                                 UK_S_ARG_ACTUAL_MAYBE_UNUSED,\
+                                                 __VA_ARGS__))
 #define _UK_LLSYSCALL_R_DEFINE(...) __UK_LLSYSCALL_R_DEFINE(__VA_ARGS__)
 #define UK_LLSYSCALL_R_DEFINE(rtype, name, ...)                                
\
        _UK_LLSYSCALL_R_DEFINE(__UK_SYSCALL_DEF_NARGS(__VA_ARGS__),     \
-- 
2.20.1