smb: client: Add tracepoint for krb5 auth

Add tracepoint to help debugging krb5 auth failures.

Example:

$ trace-cmd record -e smb3_kerberos_auth
$ mount.cifs ...
$ trace-cmd report
mount.cifs-1667 [003] ..... 5810.668549: smb3_kerberos_auth: vers=2
host=w22-dc1.zelda.test ip=192.168.124.30:445 sec=krb5 uid=0 cruid=0
user=root pid=1667 upcall_target=app err=-126

Signed-off-by: Paulo Alcantara (Red Hat) <[e-mail]>
Reviewed-by: David Howells <[e-mail]>
Cc: Pierguido Lambri <[e-mail]>
Cc: [e-mail]
Signed-off-by: Steve French <[e-mail]>

fs/smb/client/cifs_spnego.c

···
 	cifs_dbg(FYI, "key description = %s\n", description);
 	scoped_with_creds(spnego_cred)
 		spnego_key = request_key(&cifs_spnego_key_type, description, "");
+	trace_smb3_kerberos_auth(server, sesInfo, PTR_ERR_OR_ZERO(spnego_key));
 
 #ifdef CONFIG_CIFS_DEBUG2
 	if (cifsFYI && !IS_ERR(spnego_key)) {

fs/smb/client/smb2pdu.c

···
 	spnego_key = cifs_get_spnego_key(ses, server);
 	if (IS_ERR(spnego_key)) {
 		rc = PTR_ERR(spnego_key);
-		if (rc == -ENOKEY)
-			cifs_dbg(VFS, "Verify user has a krb5 ticket and keyutils is installed\n");
 		spnego_key = NULL;
 		goto out;
 	}

fs/smb/client/trace.c

···
  *   Author(s): Steve French <[e-mail]>
  */
 #include "cifsglob.h"
+#include "cifs_spnego.h"
 #define CREATE_TRACE_POINTS
 #include "trace.h"

fs/smb/client/trace.h

···
 DEFINE_SMB3_CREDIT_EVENT(overflow_credits);
 DEFINE_SMB3_CREDIT_EVENT(set_credits);
 
+TRACE_EVENT(smb3_kerberos_auth,
+		TP_PROTO(struct TCP_Server_Info *server,
+			 struct cifs_ses *ses,
+			 int rc),
+		TP_ARGS(server, ses, rc),
+		TP_STRUCT__entry(
+			__field(pid_t, pid)
+			__field(uid_t, uid)
+			__field(uid_t, cruid)
+			__string(host, server->hostname)
+			__string(user, ses->user_name)
+			__array(__u8, addr, sizeof(struct sockaddr_storage))
+			__array(char, sec, sizeof("ntlmsspi"))
+			__array(char, upcall_target, sizeof("mount"))
+			__field(int, rc)
+		),
+		TP_fast_assign(
+			__entry->pid = current->pid;
+			__entry->uid = from_kuid_munged(&init_user_ns, ses->linux_uid);
+			__entry->cruid = from_kuid_munged(&init_user_ns, ses->cred_uid);
+			__assign_str(host);
+			__assign_str(user);
+			memcpy(__entry->addr, &server->dstaddr, sizeof(__entry->addr));
+
+			if (server->sec_kerberos)
+				memcpy(__entry->sec, "krb5", sizeof("krb5"));
+			else if (server->sec_mskerberos)
+				memcpy(__entry->sec, "mskrb5", sizeof("mskrb5"));
+			else if (server->sec_iakerb)
+				memcpy(__entry->sec, "iakerb", sizeof("iakerb"));
+			else
+				memcpy(__entry->sec, "krb5", sizeof("krb5"));
+
+			if (ses->upcall_target == UPTARGET_MOUNT)
+				memcpy(__entry->upcall_target, "mount", sizeof("mount"));
+			else
+				memcpy(__entry->upcall_target, "app", sizeof("app"));
+			__entry->rc = rc;
+		),
+		TP_printk("vers=%d host=%s ip=%pISpsfc sec=%s uid=%d cruid=%d user=%s pid=%d upcall_target=%s err=%d",
+			  CIFS_SPNEGO_UPCALL_VERSION, __get_str(host), __entry->addr,
+			  __entry->sec, __entry->uid, __entry->cruid, __get_str(user),
+			  __entry->pid, __entry->upcall_target, __entry->rc))
 
 TRACE_EVENT(smb3_tcon_ref,
 	    TP_PROTO(unsigned int tcon_debug_id, int ref,