1 files changed, 121 insertions, 38 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index ac4bc9e79465..50c96b5651b6 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -216,6 +216,7 @@ struct log {
  */
 static DEFINE_RAW_SPINLOCK(logbuf_lock);
 
+#ifdef CONFIG_PRINTK
 /* the next printk record to read by syslog(READ) or /proc/kmsg */
 static u64 syslog_seq;
 static u32 syslog_idx;
@@ -228,14 +229,19 @@ static u32 log_first_idx;
 
 /* index and sequence number of the next record to store in the buffer */
 static u64 log_next_seq;
-#ifdef CONFIG_PRINTK
 static u32 log_next_idx;
 
+/* the next printk record to write to the console */
+static u64 console_seq;
+static u32 console_idx;
+static enum log_flags console_prev;
+
 /* the next printk record to read after the last 'clear' command */
 static u64 clear_seq;
 static u32 clear_idx;
 
-#define LOG_LINE_MAX 1024
+#define PREFIX_MAX              32
+#define LOG_LINE_MAX            1024 - PREFIX_MAX
 
 /* record buffer */
 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
@@ -360,6 +366,7 @@ static void log_store(int facility, int level,
 struct devkmsg_user {
         u64 seq;
         u32 idx;
+        enum log_flags prev;
         struct mutex lock;
         char buf[8192];
 };
@@ -425,6 +432,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
         struct log *msg;
         u64 ts_usec;
         size_t i;
+        char cont = '-';
         size_t len;
         ssize_t ret;
 
@@ -462,8 +470,25 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
         msg = log_from_idx(user->idx);
         ts_usec = msg->ts_nsec;
         do_div(ts_usec, 1000);
-        len = sprintf(user->buf, "%u,%llu,%llu;",
-                      (msg->facility << 3) | msg->level, user->seq, ts_usec);
+
+        /*
+         * If we couldn't merge continuation line fragments during the print,
+         * export the stored flags to allow an optional external merge of the
+         * records. Merging the records isn't always neccessarily correct, like
+         * when we hit a race during printing. In most cases though, it produces
+         * better readable output. 'c' in the record flags mark the first
+         * fragment of a line, '+' the following.
+         */
+        if (msg->flags & LOG_CONT && !(user->prev & LOG_CONT))
+                cont = 'c';
+        else if ((msg->flags & LOG_CONT) ||
+                 ((user->prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
+                cont = '+';
+
+        len = sprintf(user->buf, "%u,%llu,%llu,%c;",
+                      (msg->facility << 3) | msg->level,
+                      user->seq, ts_usec, cont);
+        user->prev = msg->flags;
 
         /* escape non-printable characters */
         for (i = 0; i < msg->text_len; i++) {
@@ -646,6 +671,15 @@ void log_buf_kexec_setup(void)
         VMCOREINFO_SYMBOL(log_buf_len);
         VMCOREINFO_SYMBOL(log_first_idx);
         VMCOREINFO_SYMBOL(log_next_idx);
+        /*
+         * Export struct log size and field offsets. User space tools can
+         * parse it and detect any changes to structure down the line.
+         */
+        VMCOREINFO_STRUCT_SIZE(log);
+        VMCOREINFO_OFFSET(log, ts_nsec);
+        VMCOREINFO_OFFSET(log, len);
+        VMCOREINFO_OFFSET(log, text_len);
+        VMCOREINFO_OFFSET(log, dict_len);
 }
 #endif
 
@@ -876,7 +910,7 @@ static size_t msg_print_text(const struct log *msg, enum log_flags prev,
 
                 if (buf) {
                         if (print_prefix(msg, syslog, NULL) +
-                            text_len + 1>= size - len)
+                            text_len + 1 >= size - len)
                                 break;
 
                         if (prefix)
@@ -907,7 +941,7 @@ static int syslog_print(char __user *buf, int size)
         struct log *msg;
         int len = 0;
 
-        text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
+        text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
         if (!text)
                 return -ENOMEM;
 
@@ -930,7 +964,8 @@ static int syslog_print(char __user *buf, int size)
 
                 skip = syslog_partial;
                 msg = log_from_idx(syslog_idx);
-                n = msg_print_text(msg, syslog_prev, true, text, LOG_LINE_MAX);
+                n = msg_print_text(msg, syslog_prev, true, text,
+                                   LOG_LINE_MAX + PREFIX_MAX);
                 if (n - syslog_partial <= size) {
                         /* message fits into buffer, move forward */
                         syslog_idx = log_next(syslog_idx);
@@ -969,7 +1004,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
         char *text;
         int len = 0;
 
-        text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
+        text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
         if (!text)
                 return -ENOMEM;
 
@@ -1022,7 +1057,8 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
                         struct log *msg = log_from_idx(idx);
                         int textlen;
 
-                        textlen = msg_print_text(msg, prev, true, text, LOG_LINE_MAX);
+                        textlen = msg_print_text(msg, prev, true, text,
+                                                 LOG_LINE_MAX + PREFIX_MAX);
                         if (textlen < 0) {
                                 len = textlen;
                                 break;
@@ -1349,20 +1385,36 @@ static struct cont {
         u64 ts_nsec;                    /* time of first print */
         u8 level;                       /* log level of first message */
         u8 facility;                    /* log level of first message */
+        enum log_flags flags;           /* prefix, newline flags */
         bool flushed:1;                 /* buffer sealed and committed */
 } cont;
 
-static void cont_flush(void)
+static void cont_flush(enum log_flags flags)
 {
         if (cont.flushed)
                 return;
         if (cont.len == 0)
                 return;
 
-        log_store(cont.facility, cont.level, LOG_NOCONS, cont.ts_nsec,
-                  NULL, 0, cont.buf, cont.len);
-
-        cont.flushed = true;
+        if (cont.cons) {
+                /*
+                 * If a fragment of this line was directly flushed to the
+                 * console; wait for the console to pick up the rest of the
+                 * line. LOG_NOCONS suppresses a duplicated output.
+                 */
+                log_store(cont.facility, cont.level, flags | LOG_NOCONS,
+                          cont.ts_nsec, NULL, 0, cont.buf, cont.len);
+                cont.flags = flags;
+                cont.flushed = true;
+        } else {
+                /*
+                 * If no fragment of this line ever reached the console,
+                 * just submit it to the store and free the buffer.
+                 */
+                log_store(cont.facility, cont.level, flags, 0,
+                          NULL, 0, cont.buf, cont.len);
+                cont.len = 0;
+        }
 }
 
 static bool cont_add(int facility, int level, const char *text, size_t len)
@@ -1371,7 +1423,8 @@ static bool cont_add(int facility, int level, const char *text, size_t len)
                 return false;
 
         if (cont.len + len > sizeof(cont.buf)) {
-                cont_flush();
+                /* the line gets too long, split it up in separate records */
+                cont_flush(LOG_CONT);
                 return false;
         }
 
@@ -1380,12 +1433,17 @@ static bool cont_add(int facility, int level, const char *text, size_t len)
                 cont.level = level;
                 cont.owner = current;
                 cont.ts_nsec = local_clock();
+                cont.flags = 0;
                 cont.cons = 0;
                 cont.flushed = false;
         }
 
         memcpy(cont.buf + cont.len, text, len);
         cont.len += len;
+
+        if (cont.len > (sizeof(cont.buf) * 80) / 100)
+                cont_flush(LOG_CONT);
+
         return true;
 }
 
@@ -1394,7 +1452,7 @@ static size_t cont_print_text(char *text, size_t size)
         size_t textlen = 0;
         size_t len;
 
-        if (cont.cons == 0) {
+        if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
                 textlen += print_time(cont.ts_nsec, text);
                 size -= textlen;
         }
@@ -1409,7 +1467,8 @@ static size_t cont_print_text(char *text, size_t size)
         }
 
         if (cont.flushed) {
-                text[textlen++] = '\n';
+                if (cont.flags & LOG_NEWLINE)
+                        text[textlen++] = '\n';
                 /* got everything, release buffer */
                 cont.len = 0;
         }
@@ -1507,7 +1566,7 @@ asmlinkage int vprintk_emit(int facility, int level,
                  * or another task also prints continuation lines.
                  */
                 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
-                        cont_flush();
+                        cont_flush(LOG_NEWLINE);
 
                 /* buffer line if possible, otherwise store it right away */
                 if (!cont_add(facility, level, text, text_len))
@@ -1525,7 +1584,7 @@ asmlinkage int vprintk_emit(int facility, int level,
                 if (cont.len && cont.owner == current) {
                         if (!(lflags & LOG_PREFIX))
                                 stored = cont_add(facility, level, text, text_len);
-                        cont_flush();
+                        cont_flush(LOG_NEWLINE);
                 }
 
                 if (!stored)
@@ -1616,9 +1675,20 @@ asmlinkage int printk(const char *fmt, ...)
 }
 EXPORT_SYMBOL(printk);
 
-#else
+#else /* CONFIG_PRINTK */
 
+#define LOG_LINE_MAX            0
+#define PREFIX_MAX              0
 #define LOG_LINE_MAX 0
+static u64 syslog_seq;
+static u32 syslog_idx;
+static u64 console_seq;
+static u32 console_idx;
+static enum log_flags syslog_prev;
+static u64 log_first_seq;
+static u32 log_first_idx;
+static u64 log_next_seq;
+static enum log_flags console_prev;
 static struct cont {
         size_t len;
         size_t cons;
@@ -1902,10 +1972,34 @@ void wake_up_klogd(void)
                 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
 }
 
-/* the next printk record to write to the console */
-static u64 console_seq;
-static u32 console_idx;
-static enum log_flags console_prev;
+static void console_cont_flush(char *text, size_t size)
+{
+        unsigned long flags;
+        size_t len;
+
+        raw_spin_lock_irqsave(&logbuf_lock, flags);
+
+        if (!cont.len)
+                goto out;
+
+        /*
+         * We still queue earlier records, likely because the console was
+         * busy. The earlier ones need to be printed before this one, we
+         * did not flush any fragment so far, so just let it queue up.
+         */
+        if (console_seq < log_next_seq && !cont.cons)
+                goto out;
+
+        len = cont_print_text(text, size);
+        raw_spin_unlock(&logbuf_lock);
+        stop_critical_timings();
+        call_console_drivers(cont.level, text, len);
+        start_critical_timings();
+        local_irq_restore(flags);
+        return;
+out:
+        raw_spin_unlock_irqrestore(&logbuf_lock, flags);
+}
 
 /**
  * console_unlock - unlock the console system
@@ -1923,7 +2017,7 @@ static enum log_flags console_prev;
  */
 void console_unlock(void)
 {
-        static char text[LOG_LINE_MAX];
+        static char text[LOG_LINE_MAX + PREFIX_MAX];
         static u64 seen_seq;
         unsigned long flags;
         bool wake_klogd = false;
@@ -1937,19 +2031,7 @@ void console_unlock(void)
         console_may_schedule = 0;
 
         /* flush buffered message fragment immediately to console */
-        raw_spin_lock_irqsave(&logbuf_lock, flags);
-        if (cont.len && (cont.cons < cont.len || cont.flushed)) {
-                size_t len;
-
-                len = cont_print_text(text, sizeof(text));
-                raw_spin_unlock(&logbuf_lock);
-                stop_critical_timings();
-                call_console_drivers(cont.level, text, len);
-                start_critical_timings();
-                local_irq_restore(flags);
-        } else
-                raw_spin_unlock_irqrestore(&logbuf_lock, flags);
-
+        console_cont_flush(text, sizeof(text));
 again:
         for (;;) {
                 struct log *msg;
@@ -1986,6 +2068,7 @@ skip:
                          * will properly dump everything later.
                          */
                         msg->flags &= ~LOG_NOCONS;
+                        console_prev = msg->flags;
                         goto skip;
                 }