missing_syscall: require a bunch of syscalls below baseline

pidfd-related ones are left out and will be dealt with later.

src/basic/missing_syscall.h

@@ -137,12 +137,7 @@ static inline int missing_name_to_handle_at(int fd, const char *name, struct fil
 
 #if !HAVE_SETNS
 static inline int missing_setns(int fd, int nstype) {
-#  ifdef __NR_setns
         return syscall(__NR_setns, fd, nstype);
-#  else
-        errno = ENOSYS;
-        return -1;
-#  endif
 }
 
 #  define setns missing_setns
@@ -162,12 +157,7 @@ static inline pid_t raw_getpid(void) {
 
 #if !HAVE_RENAMEAT2
 static inline int missing_renameat2(int oldfd, const char *oldname, int newfd, const char *newname, unsigned flags) {
-#  ifdef __NR_renameat2
         return syscall(__NR_renameat2, oldfd, oldname, newfd, newname, flags);
-#  else
-        errno = ENOSYS;
-        return -1;
-#  endif
 }
 
 #  define renameat2 missing_renameat2
@@ -177,12 +167,7 @@ static inline int missing_renameat2(int oldfd, const char *oldname, int newfd, c
 
 #if !HAVE_KCMP
 static inline int missing_kcmp(pid_t pid1, pid_t pid2, int type, unsigned long idx1, unsigned long idx2) {
-#  if defined __NR_kcmp && __NR_kcmp >= 0
         return syscall(__NR_kcmp, pid1, pid2, type, idx1, idx2);
-#  else
-        errno = ENOSYS;
-        return -1;
-#  endif
 }
 
 #  define kcmp missing_kcmp
@@ -192,34 +177,19 @@ static inline int missing_kcmp(pid_t pid1, pid_t pid2, int type, unsigned long i
 
 #if !HAVE_KEYCTL
 static inline long missing_keyctl(int cmd, unsigned long arg2, unsigned long arg3, unsigned long arg4, unsigned long arg5) {
-#  if defined __NR_keyctl && __NR_keyctl >= 0
         return syscall(__NR_keyctl, cmd, arg2, arg3, arg4, arg5);
-#  else
-        errno = ENOSYS;
-        return -1;
-#  endif
 
 #  define keyctl missing_keyctl
 }
 
 static inline key_serial_t missing_add_key(const char *type, const char *description, const void *payload, size_t plen, key_serial_t ringid) {
-#  if defined __NR_add_key && __NR_add_key >= 0
         return syscall(__NR_add_key, type, description, payload, plen, ringid);
-#  else
-        errno = ENOSYS;
-        return -1;
-#  endif
 
 #  define add_key missing_add_key
 }
 
 static inline key_serial_t missing_request_key(const char *type, const char *description, const char * callout_info, key_serial_t destringid) {
-#  if defined __NR_request_key && __NR_request_key >= 0
         return syscall(__NR_request_key, type, description, callout_info, destringid);
-#  else
-        errno = ENOSYS;
-        return -1;
-#  endif
 
 #  define request_key missing_request_key
 }
@@ -661,12 +631,7 @@ static inline ssize_t missing_getdents64(int fd, void *buffer, size_t length) {
 #if !HAVE_SCHED_SETATTR
 
 static inline ssize_t missing_sched_setattr(pid_t pid, struct sched_attr *attr, unsigned int flags) {
-#  if defined __NR_sched_setattr
         return syscall(__NR_sched_setattr, pid, attr, flags);
-#  else
-        errno = ENOSYS;
-        return -1;
-#  endif
 }
 
 #  define sched_setattr missing_sched_setattr