[PATCH] printk: make line continuation not result in stray emergency errors

[Roland Hieber <r.hieber@pengutronix.de>]

The levels of pr_emerg() and pr_cont() are both set to 0. When pr_cont()
is used to continue a previous line, and colored console output is
enabled, this can result in garbled log messages being printed, e.g.:

    ERROR: HABv4: -------- HAB warning Event 0 --------
    ERROR: HABv4: event data:
    ERROR: HABv4:  dbEMERG:  00EMERG:  24EMERG:  42EMERG:   69EMERG:  30EMERG:  e1EMERG:  1d
    ERROR: HABv4:  00EMERG:  04EMERG:  00EMERG:  02EMERG:   40EMERG:  00EMERG:  36EMERG:  06
    ERROR: HABv4:  55EMERG:  55EMERG:  00EMERG:  03EMERG:   00EMERG:  00EMERG:  00EMERG:  00
    ERROR: HABv4:  00EMERG:  00EMERG:  00EMERG:  00EMERG:   00EMERG:  00EMERG:  00EMERG:  00
    ERROR: HABv4:  00EMERG:  00EMERG:  00EMERG:  01EMERG:
    ERROR: HABv4: Status: Operation completed with warning (0x69)

Note the additional "EMERG: " in front of each continuation, which is
inserted by pr_cont(buf) being expanded to pr_printk(0, buf). These
additional strings show up in deep red on the console (which is not
supported in Git commit messages…). One might argue that this is the
same color as the "ERROR: " prefix, but when pr_cont() is used with
pr_notice() and pr_warning(), which are printed in blue and yellow
respectively, at least then the change in color would lead to additional
confusion.

The log level argument to pr_printk is defined as int, so we can solve
this by defining the level for pr_cont() to -1, which is not used for
any loglevel:

    ERROR: HABv4: -------- HAB warning Event 0 --------
    ERROR: HABv4: event data:
    ERROR: HABv4:  db 00 24 42  69 30 e1 1d
    ERROR: HABv4:  00 04 00 02  40 00 36 06
    ERROR: HABv4:  55 55 00 03  00 00 00 00
    ERROR: HABv4:  00 00 00 00  00 00 00 00
    ERROR: HABv4:  00 00 00 01
    ERROR: HABv4: Status: Operation completed with warning (0x69)

Fixes: 0fcefdd9369050f35a88b41dcd42cc5a3c6c6b33 ("printk: Add pr_cont")
Fixes: ea0e077ed65a003e4d7a1e023aee38cbe2d14898 ("printk: Fix pr_cont")
Signed-off-by: Roland Hieber <r.hieber@pengutronix.de>
---
 include/printk.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/printk.h b/include/printk.h
index 4384fb85ea..858e800543 100644
--- a/include/printk.h
+++ b/include/printk.h
@@ -84,21 +84,21 @@ static inline int pr_print(int level, const char *format, ...)
 #define pr_emerg(fmt, arg...)	__pr_printk(0, pr_fmt(fmt), ##arg)
 #define pr_alert(fmt, arg...)	__pr_printk(1, pr_fmt(fmt), ##arg)
 #define pr_crit(fmt, arg...)	__pr_printk(2, pr_fmt(fmt), ##arg)
 #define pr_err(fmt, arg...)	__pr_printk(3, pr_fmt(fmt), ##arg)
 #define pr_warning(fmt, arg...)	__pr_printk(4, pr_fmt(fmt), ##arg)
 #define pr_notice(fmt, arg...)	__pr_printk(5, pr_fmt(fmt), ##arg)
 #define pr_info(fmt, arg...)	__pr_printk(6, pr_fmt(fmt), ##arg)
 #define pr_debug(fmt, arg...)	__pr_printk(7, pr_fmt(fmt), ##arg)
 #define debug(fmt, arg...)	__pr_printk(7, pr_fmt(fmt), ##arg)
 #define pr_vdebug(fmt, arg...)	__pr_printk(8, pr_fmt(fmt), ##arg)
-#define pr_cont(fmt, arg...)	__pr_printk(0, fmt, ##arg)
+#define pr_cont(fmt, arg...)	__pr_printk(-1, fmt, ##arg)
 
 #define printk_once(fmt, ...)					\
 ({								\
 	static bool __print_once	;			\
 								\
 	if (!__print_once) {					\
 		__print_once = true;				\
 		printk(fmt, ##__VA_ARGS__);			\
 	}							\
 })
-- 
2.19.1


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