net: add missing syscall for gethostname()

We need all the socket APIs to work from user mode.
tests/net/socket/misc now runs in userspace.

Fixes: #15227

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>

include/net/socket.h

@@ -382,7 +382,7 @@ int zsock_setsockopt(int sock, int level, int optname,
  * if :option:`CONFIG_NET_SOCKETS_POSIX_NAMES` is defined.
  * @endrststar
  */
-int zsock_gethostname(char *buf, size_t len);
+__syscall int zsock_gethostname(char *buf, size_t len);
 
 /**
  * @brief Convert network address from internal to numeric ASCII form

subsys/net/lib/sockets/sockets_misc.c

@@ -6,8 +6,9 @@
 
 #include <errno.h>
 #include <net/socket.h>
+#include <syscall_handler.h>
 
-int zsock_gethostname(char *buf, size_t len)
+int z_impl_zsock_gethostname(char *buf, size_t len)
 {
 	const char *p = net_hostname_get();
 
@@ -15,3 +16,11 @@ int zsock_gethostname(char *buf, size_t len)
 
 	return 0;
 }
+
+#ifdef CONFIG_USERSPACE
+Z_SYSCALL_HANDLER(zsock_gethostname, buf, len)
+{
+	Z_OOPS(Z_SYSCALL_MEMORY_WRITE(buf, len));
+	return z_impl_zsock_gethostname((char *)buf, len);
+}
+#endif

tests/net/socket/misc/prj.conf

@@ -23,7 +23,6 @@ CONFIG_NET_CONFIG_MY_IPV6_ADDR="2001:db8::1"
 
 CONFIG_MAIN_STACK_SIZE=2048
 CONFIG_ZTEST=y
-CONFIG_TEST_USERSPACE=n
 
 # User mode requirements
 CONFIG_HEAP_MEM_POOL_SIZE=128

tests/net/socket/misc/src/main.c

@@ -16,7 +16,7 @@ LOG_MODULE_REGISTER(net_test, CONFIG_NET_SOCKETS_LOG_LEVEL);
 
 void test_gethostname(void)
 {
-	static char buf[80];
+	static ZTEST_BMEM char buf[80];
 	int res;
 
 	res = gethostname(buf, sizeof(buf));