Implement [v]printk_header() which takes @header argument and
automatically prints header in front of or indents multiline messages.
For example, if @header is "<7>ata1.00: " and the formatted message is
"<6>line0\nline1\n", the following gets written to the console.
<6>ata1.00: line0
<6>ata1.00 line1
As seen above if header ends with ':' followed by any number of
spaces, the colon is replaced with space from the second line. This
helps to distinguish where a multiline message begins when messages of
similar pattern repeats, for example...
ata8.00: cmd 60/80:20:e1:71:02/00:00:00:00:00/40 tag 4 ncq 65536 in
ata8.00 res 40/00:34:de:71:02/00:00:00:00:00/40 Emask 0x10 (ATA bus error)
ata8.00 status: { DRDY }
ata8.00: cmd 60/0e:28:d0:71:02/00:00:00:00:00/40 tag 5 ncq 7168 in
ata8.00 res 40/00:34:de:71:02/00:00:00:00:00/40 Emask 0x10 (ATA bus error)
ata8.00 status: { DRDY }
ata8.00: cmd 60/7f:38:61:72:02/00:00:00:00:00/40 tag 7 ncq 65024 in
ata8.00 res 40/00:34:de:71:02/00:00:00:00:00/40 Emask 0x10 (ATA bus error)
ata8.00 status: { DRDY }
Signed-off-by: Tejun Heo <htejun@xxxxxxxxx>
---
include/linux/kernel.h | 12 ++++++
kernel/printk.c | 95 +++++++++++++++++++++++++++++++++++++++++++++---
2 files changed, 102 insertions(+), 5 deletions(-)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 2df44e7..d885208 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -177,6 +177,10 @@ struct pid;
extern struct pid *session_of_pgrp(struct pid *pgrp);
#ifdef CONFIG_PRINTK
+asmlinkage int vprintk_header(const char *header, const char *fmt, va_list args)
+ __attribute__ ((format (printf, 2, 0)));
+asmlinkage int printk_header(const char *header, const char * fmt, ...)
+ __attribute__ ((format (printf, 2, 3))) __cold;
asmlinkage int vprintk(const char *fmt, va_list args)
__attribute__ ((format (printf, 1, 0)));
asmlinkage int printk(const char * fmt, ...)
@@ -192,6 +196,14 @@ extern int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst);
extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
unsigned int interval_msec);
#else
+static inline int vprintk_header(const char *header, const char *s, va_list args)
+ __attribute__ ((format (printf, 2, 0)));
+static inline int vprintk_header(const char *header, const char *s, va_list args)
+{ return 0; }
+static inline int printk_header(const char *header, const char *s, ...)
+ __attribute__ ((format (printf, 2, 3)));
+static inline int __cold printk_header(const char *header, const char *s, ...)
+{ return 0; }
static inline int vprintk(const char *s, va_list args)
__attribute__ ((format (printf, 1, 0)));
static inline int vprintk(const char *s, va_list args) { return 0; }
diff --git a/kernel/printk.c b/kernel/printk.c
index 2317ec8..2283a75 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -608,18 +608,75 @@ asmlinkage int printk(const char *fmt, ...)
int r;
va_start(args, fmt);
- r = vprintk(fmt, args);
+ r = vprintk_header(NULL, fmt, args);
va_end(args);
return r;
}
+EXPORT_SYMBOL(printk);
+
+asmlinkage int vprintk(const char *fmt, va_list args)
+{
+ return vprintk_header(NULL, fmt, args);
+}
+EXPORT_SYMBOL(vprintk);
+
+/**
+ * printk_header - print a kernel message with header
+ * @header: header string
+ * @fmt: format string
+ *
+ * This is printk() with a twist. @header points to string which will
+ * be used as message header. If @header is NULL, this function is
+ * identical to printk().
+ *
+ * @header may contain loglevel in front of it. Each new line
+ * including the first one in the message formatted from @fmt can also
+ * have loglevel. When both exist, the latter is used. In multiline
+ * messages, log level is inherited from the previous line if not
+ * explicitly specified.
+ *
+ * @header is printed when a new line starts. If @header ends with
+ * ':' followed by spaces, the colon is replaced with space from the
+ * second line.
+ *
+ * For example, if @header is "<7>ata1.00: " and the formatted message
+ * is "<6>line0\nline1\n<4>line2\nline3\n", the following gets written to
+ * the console.
+ *
+ * <6>ata1.00: line0
+ * <6>ata1.00 line1
+ * <4>ata1.00 line2
+ * <4>ata1.00 line3
+ */
+asmlinkage int printk_header(const char *header, const char *fmt, ...)
+{
+ va_list args;
+ int r;
+
+ va_start(args, fmt);
+ r = vprintk_header(header, fmt, args);
+ va_end(args);
+
+ return r;
+}
+EXPORT_SYMBOL(printk_header);
static int is_loglevel(const char *p)
{
return p[0] == '<' && p[1] >= '0' && p[1] <= '7' && p[2] == '>';
}
-asmlinkage int vprintk(const char *fmt, va_list args)
+/**
+ * vprintk_header - a variant of printk_header() which takes va_list argument
+ * @header: header string
+ * @fmt: format string
+ * @args: va_list to format @fmt
+ *
+ * This function is identical to printk_header() except that it takes
+ * va_list @args instead of variable argument list.
+ */
+asmlinkage int vprintk_header(const char *header, const char *fmt, va_list args)
{
/* cpu currently holding logbuf_lock */
static volatile unsigned int printk_cpu = UINT_MAX;
@@ -632,7 +689,8 @@ asmlinkage int vprintk(const char *fmt, va_list args)
int last_lv = default_message_loglevel;
unsigned long flags;
- int printed_len = 0;
+ const char *header_colon = NULL;
+ int printed_len = 0, printed_header = 0;
int this_cpu;
const char *p;
@@ -670,6 +728,20 @@ asmlinkage int vprintk(const char *fmt, va_list args)
strcpy(printk_buf, printk_recursion_bug_msg);
printed_len = sizeof(printk_recursion_bug_msg);
}
+
+ /* Parse header log level */
+ if (header) {
+ size_t len = strlen(header);
+
+ if (is_loglevel(header)) {
+ last_lv = header[1] - '0';
+ header += 3;
+ }
+
+ if (len >= 2 && !strcmp(header + len - 2, ": "))
+ header_colon = header + len - 2;
+ }
+
/* Emit the output into the temporary buffer */
printed_len += vsnprintf(printk_buf + printed_len,
PRINTK_BUF_LEN - printed_len, fmt, args);
@@ -718,6 +790,20 @@ asmlinkage int vprintk(const char *fmt, va_list args)
printed_len += tlen;
}
+ if (header) {
+ const char *h = header;
+
+ while (*h) {
+ if (!printed_header || h != header_colon)
+ emit_log_char(*h);
+ else
+ emit_log_char(' ');
+ h++;
+ printed_len++;
+ }
+ printed_header = 1;
+ }
+
last_lv = lv;
log_level_unknown = 0;
if (!*p)
@@ -769,8 +855,7 @@ out_restore_irqs:
preempt_enable();
return printed_len;
}
-EXPORT_SYMBOL(printk);
-EXPORT_SYMBOL(vprintk);
+EXPORT_SYMBOL(vprintk_header);
#else
--
1.5.2.4
-
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