printk: ignore too long messages

[deliverable/linux.git] / kernel / printk / printk.c

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 99b7a2d87b6a99023474f207204c5e1f549313ee..8fbbab1771eb8567a7a2675dcd6ec8afca14cb06 100644 (file)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -297,12 +297,20 @@ static u32 log_next(u32 idx)
        return idx + msg->len;
 }
 
-/* check whether there is enough free space for the given message */
-static int logbuf_has_space(u32 msg_size)
+/*
+ * Check whether there is enough free space for the given message.
+ *
+ * The same values of first_idx and next_idx mean that the buffer
+ * is either empty or full.
+ *
+ * If the buffer is empty, we must respect the position of the indexes.
+ * They cannot be reset to the beginning of the buffer.
+ */
+static int logbuf_has_space(u32 msg_size, bool empty)
 {
        u32 free;
 
-       if (log_next_idx > log_first_idx)
+       if (log_next_idx > log_first_idx || empty)
                free = max(log_buf_len - log_next_idx, log_first_idx);
        else
                free = log_first_idx - log_next_idx;
@@ -314,15 +322,21 @@ static int logbuf_has_space(u32 msg_size)
        return free >= msg_size + sizeof(struct printk_log);
 }
 
-static void log_make_free_space(u32 msg_size)
+static int log_make_free_space(u32 msg_size)
 {
        while (log_first_seq < log_next_seq) {
-               if (logbuf_has_space(msg_size))
-                       return;
+               if (logbuf_has_space(msg_size, false))
+                       return 0;
                /* drop old messages until we have enough continuous space */
                log_first_idx = log_next(log_first_idx);
                log_first_seq++;
        }
+
+       /* sequence numbers are equal, so the log buffer is empty */
+       if (logbuf_has_space(msg_size, true))
+               return 0;
+
+       return -ENOMEM;
 }
 
 /* insert record into the buffer, discard old ones, update heads */
@@ -339,7 +353,9 @@ static void log_store(int facility, int level,
        pad_len = (-size) & (LOG_ALIGN - 1);
        size += pad_len;
 
-       log_make_free_space(size);
+       /* if message does not fit empty log buffer, ignore it */
+       if (log_make_free_space(size))
+               return;
 
        if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
                /*