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;