1 files changed, 27 insertions, 13 deletions

diff --git a/arch/um/drivers/mconsole_kern.c b/arch/um/drivers/mconsole_kern.c
index 96f0189327af..832d5c766ca8 100644
--- a/arch/um/drivers/mconsole_kern.c
+++ b/arch/um/drivers/mconsole_kern.c
@@ -371,14 +371,16 @@ static unsigned long long unplugged_pages_count = 0;
 static struct list_head unplugged_pages = LIST_HEAD_INIT(unplugged_pages);
 static int unplug_index = UNPLUGGED_PER_PAGE;
 
-static int mem_config(char *str)
+static int mem_config(char *str, char **error_out)
 {
 	unsigned long long diff;
 	int err = -EINVAL, i, add;
 	char *ret;
 
-	if(str[0] != '=')
+	if(str[0] != '='){
+		*error_out = "Expected '=' after 'mem'";
 		goto out;
+	}
 
 	str++;
 	if(str[0] == '-')
@@ -386,12 +388,17 @@ static int mem_config(char *str)
 	else if(str[0] == '+'){
 		add = 1;
 	}
-	else goto out;
+	else {
+		*error_out = "Expected increment to start with '-' or '+'";
+		goto out;
+	}
 
 	str++;
 	diff = memparse(str, &ret);
-	if(*ret != '\0')
+	if(*ret != '\0'){
+		*error_out = "Failed to parse memory increment";
 		goto out;
+	}
 
 	diff /= PAGE_SIZE;
 
@@ -435,11 +442,14 @@ static int mem_config(char *str)
 				unplugged = list_entry(entry,
 						       struct unplugged_pages,
 						       list);
-				unplugged->pages[unplug_index++] = addr;
 				err = os_drop_memory(addr, PAGE_SIZE);
-				if(err)
+				if(err){
 					printk("Failed to release memory - "
 					       "errno = %d\n", err);
+					*error_out = "Failed to release memory";
+					goto out;
+				}
+				unplugged->pages[unplug_index++] = addr;
 			}
 
 			unplugged_pages_count++;
@@ -470,8 +480,9 @@ static int mem_id(char **str, int *start_out, int *end_out)
 	return 0;
 }
 
-static int mem_remove(int n)
+static int mem_remove(int n, char **error_out)
 {
+	*error_out = "Memory doesn't support the remove operation";
 	return -EBUSY;
 }
 
@@ -542,7 +553,7 @@ static void mconsole_get_config(int (*get_config)(char *, char *, int,
 void mconsole_config(struct mc_request *req)
 {
 	struct mc_device *dev;
-	char *ptr = req->request.data, *name;
+	char *ptr = req->request.data, *name, *error_string = "";
 	int err;
 
 	ptr += strlen("config");
@@ -559,8 +570,8 @@ void mconsole_config(struct mc_request *req)
 		ptr++;
 
 	if(*ptr == '='){
-		err = (*dev->config)(name);
-		mconsole_reply(req, "", err, 0);
+		err = (*dev->config)(name, &error_string);
+		mconsole_reply(req, error_string, err, 0);
 	}
 	else mconsole_get_config(dev->get_config, req, name);
 }
@@ -595,13 +606,16 @@ void mconsole_remove(struct mc_request *req)
 		goto out;
 	}
 
-	err = (*dev->remove)(n);
+	err_msg = NULL;
+	err = (*dev->remove)(n, &err_msg);
 	switch(err){
 	case -ENODEV:
-		err_msg = "Device doesn't exist";
+		if(err_msg == NULL)
+			err_msg = "Device doesn't exist";
 		break;
 	case -EBUSY:
-		err_msg = "Device is currently open";
+		if(err_msg == NULL)
+			err_msg = "Device is currently open";
 		break;
 	default:
 		break;