[PATCH v3 4/5] xen/console: Provide timestamps as an offset since boot

[Andrew Cooper <andrew.cooper3@citrix.com>]

This adds a new "Linux style" console timestamp method, which is shorter and
more useful than the current date/time timestamps with single-second
granularity.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Keir Fraser <keir@xen.org>
CC: Jan Beulich <JBeulich@suse.com>
CC: Tim Deegan <tim@xen.org>
---
 docs/misc/xen-command-line.markdown |   15 +++++++--
 xen/drivers/char/console.c          |   58 +++++++++++++++++++++++++++++------
 2 files changed, 61 insertions(+), 12 deletions(-)

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index 15aa404..98c9e5e 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -275,11 +275,20 @@ cleared.  This allows a single port to be shared by two subsystems
 makes sense on its own.
 
 ### console\_timestamps
-> `= <boolean>`
+> `= none | date | boot`
 
-> Default: `false`
+> Default: `boot`
+
+Specify which timestamp format Xen should use for each console line.
+
+* `none`: No timestamps
+* `date`: Date and time information
+    * `[YYYY-MM-DD HH:MM:SS]`
+* `boot`: Seconds and microseconds since boot
+    * `[SSSSSS.uuuuuu]`
 
-Flag to indicate whether include a timestamp with each console line.
+For compatibility with the older boolean parameter, specifying
+`console_timestamps` alone will enable the `date` option.
 
 ### console\_to\_ring
 > `= <boolean>`
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 7d4383c..60461b9 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -49,8 +49,17 @@ static bool_t __read_mostly opt_console_to_ring;
 boolean_param("console_to_ring", opt_console_to_ring);
 
 /* console_timestamps: include a timestamp prefix on every Xen console line. */
-static bool_t __read_mostly opt_console_timestamps;
-boolean_param("console_timestamps", opt_console_timestamps);
+enum con_timestamp_mode
+{
+    TSM_NONE,          /* No timestamps */
+    TSM_DATE,          /* [YYYY-MM-DD HH:MM:SS] */
+    TSM_BOOT           /* [SSSSSS.uuuuuu] */
+};
+
+static enum con_timestamp_mode __read_mostly opt_con_timestamp_mode = TSM_BOOT;
+
+static void parse_console_timestamps(char *s);
+custom_param("console_timestamps", parse_console_timestamps);
 
 /* conring_size: allows a large console ring than default (16kB). */
 static uint32_t __initdata opt_conring_size;
@@ -546,23 +555,54 @@ static int printk_prefix_check(char *p, char **pp)
             ((loglvl < upper_thresh) && printk_ratelimit()));
 } 
 
+static void __init parse_console_timestamps(char *s)
+{
+    if ( *s == '\0' || /* Compat for old booleanparam() */
+         !strcmp(s, "date") )
+        opt_con_timestamp_mode = TSM_DATE;
+    else if ( !strcmp(s, "boot") )
+        opt_con_timestamp_mode = TSM_BOOT;
+    else if ( !strcmp(s, "none") )
+        opt_con_timestamp_mode = TSM_NONE;
+    else
+        printk(XENLOG_ERR "Unrecognised timestamp mode '%s'\n", s);
+}
+
 static void printk_start_of_line(const char *prefix)
 {
     struct tm tm;
     char tstr[32];
+    uint64_t sec, nsec;
 
     __putstr(prefix);
 
-    if ( !opt_console_timestamps )
-        return;
+    switch ( opt_con_timestamp_mode )
+    {
+    case TSM_DATE:
+        tm = wallclock_time();
+
+        if ( tm.tm_mday == 0 )
+            return;
+
+        if ( opt_con_timestamp_mode == TSM_DATE )
+            snprintf(tstr, sizeof(tstr), "[%04u-%02u-%02u %02u:%02u:%02u] ",
+                     1900 + tm.tm_year, tm.tm_mon + 1, tm.tm_mday,
+                     tm.tm_hour, tm.tm_min, tm.tm_sec);
+        break;
+
+    case TSM_BOOT:
+        sec = NOW();
+        nsec = do_div(sec, 1000000000);
 
-    tm = wallclock_time();
-    if ( tm.tm_mday == 0 )
+        snprintf(tstr, sizeof(tstr), "[%5"PRIu64".%06"PRIu64"] ",
+                 sec, nsec / 1000);
+        break;
+
+    case TSM_NONE:
+    default:
         return;
+    }
 
-    snprintf(tstr, sizeof(tstr), "[%04u-%02u-%02u %02u:%02u:%02u] ",
-             1900 + tm.tm_year, tm.tm_mon + 1, tm.tm_mday,
-             tm.tm_hour, tm.tm_min, tm.tm_sec);
     __putstr(tstr);
 }
 
-- 
1.7.10.4