Commit f7d4ca8b authored by Daniel Thompson's avatar Daniel Thompson Committed by Jason Wessel
Browse files

kdb: Avoid printing KERN_ levels to consoles 



Currently when kdb traps printk messages then the raw log level prefix
(consisting of '\001' followed by a numeral) does not get stripped off
before the message is issued to the various I/O handlers supported by
kdb. This causes annoying visual noise as well as causing problems
grepping for ^. It is also a change of behaviour compared to normal usage
of printk() usage. For example <SysRq>-h ends up with different output to
that of kdb's "sr h".

This patch addresses the problem by stripping log levels from messages
before they are issued to the I/O handlers. printk() which can also
act as an i/o handler in some cases is special cased; if the caller
provided a log level then the prefix will be preserved when sent to
printk().

The addition of non-printable characters to the output of kdb commands is a
regression, albeit and extremely elderly one, introduced by commit
04d2c8c8 ("printk: convert the format for KERN_<LEVEL> to a 2 byte
pattern"). Note also that this patch does *not* restore the original
behaviour from v3.5. Instead it makes printk() from within a kdb command
display the message without any prefix (i.e. like printk() normally does).

Signed-off-by: default avatarDaniel Thompson <daniel.thompson@linaro.org>
Cc: Joe Perches <joe@perches.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarJason Wessel <jason.wessel@windriver.com>
parent df0036d1

include/linux/kdb.h

+7 −1
Original line number Diff line number Diff line
@@ -156,8 +156,14 @@ typedef enum { 
	KDB_REASON_SYSTEM_NMI,	/* In NMI due to SYSTEM cmd; regs valid */

} kdb_reason_t;



enum kdb_msgsrc {

	KDB_MSGSRC_INTERNAL, /* direct call to kdb_printf() */

	KDB_MSGSRC_PRINTK, /* trapped from printk() */

};



extern int kdb_trap_printk;

extern __printf(1, 0) int vkdb_printf(const char *fmt, va_list args);

extern __printf(2, 0) int vkdb_printf(enum kdb_msgsrc src, const char *fmt,

				      va_list args);

extern __printf(1, 2) int kdb_printf(const char *, ...);

typedef __printf(1, 2) int (*kdb_printf_t)(const char *, ...);

kernel/debug/kdb/kdb_io.c

+13 −9
Original line number Diff line number Diff line
@@ -548,7 +548,7 @@ static int kdb_search_string(char *searched, char *searchfor) 
	return 0;

}



int vkdb_printf(const char *fmt, va_list ap)

int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap)

{

	int diag;

	int linecount;
@@ -691,19 +691,20 @@ kdb_printit: 
	 * Write to all consoles.

	 */

	retlen = strlen(kdb_buffer);

	cp = (char *) printk_skip_level(kdb_buffer);

	if (!dbg_kdb_mode && kgdb_connected) {

		gdbstub_msg_write(kdb_buffer, retlen);

		gdbstub_msg_write(cp, retlen - (cp - kdb_buffer));

	} else {

		if (dbg_io_ops && !dbg_io_ops->is_console) {

			len = retlen;

			cp = kdb_buffer;

			len = retlen - (cp - kdb_buffer);

			cp2 = cp;

			while (len--) {

				dbg_io_ops->write_char(*cp);

				cp++;

				dbg_io_ops->write_char(*cp2);

				cp2++;

			}

		}

		while (c) {

			c->write(c, kdb_buffer, retlen);

			c->write(c, cp, retlen - (cp - kdb_buffer));

			touch_nmi_watchdog();

			c = c->next;

		}
@@ -711,7 +712,10 @@ kdb_printit: 
	if (logging) {

		saved_loglevel = console_loglevel;

		console_loglevel = CONSOLE_LOGLEVEL_SILENT;

		printk(KERN_INFO "%s", kdb_buffer);

		if (printk_get_level(kdb_buffer) || src == KDB_MSGSRC_PRINTK)

			printk("%s", kdb_buffer);

		else

			pr_info("%s", kdb_buffer);

	}



	if (KDB_STATE(PAGER)) {
@@ -844,7 +848,7 @@ int kdb_printf(const char *fmt, ...) 
	int r;



	va_start(ap, fmt);

	r = vkdb_printf(fmt, ap);

	r = vkdb_printf(KDB_MSGSRC_INTERNAL, fmt, ap);

	va_end(ap);



	return r;

kernel/printk/printk.c

+1 −1
Original line number Diff line number Diff line
@@ -1811,7 +1811,7 @@ int vprintk_default(const char *fmt, va_list args) 


#ifdef CONFIG_KGDB_KDB

	if (unlikely(kdb_trap_printk)) {

		r = vkdb_printf(fmt, args);

		r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);

		return r;

	}

#endif

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