It has been removed from linux since

  61a47c1ad3a4 ("sysctl: Remove the sysctl system call")

It's a good news because it was not really supported by qemu.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200930003033.554124-5-laurent@vivier.eu>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 linux-user/syscall.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index cd520ae42e6d..f0df6aecef80 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -10529,12 +10529,6 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
 #if defined(TARGET_NR_fdatasync) /* Not on alpha (osf_datasync ?) */
     case TARGET_NR_fdatasync:
         return get_errno(fdatasync(arg1));
-#endif
-#ifdef TARGET_NR__sysctl
-    case TARGET_NR__sysctl:
-        /* We don't implement this, but ENOTDIR is always a safe
-           return value. */
-        return -TARGET_ENOTDIR;
 #endif
     case TARGET_NR_sched_getaffinity:
         {
-- 
2.26.2