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

The addition of non-printable characters to the output of kdb commands is a
regression, albeit and extremely elderly one, introduced by commit

 ("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 <>
Cc: Joe Perches <>
Signed-off-by: default avatarJason Wessel <>
parent df0036d1
......@@ -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 *, ...);
......@@ -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--) {
while (c) {
c->write(c, kdb_buffer, retlen);
c->write(c, cp, retlen - (cp - kdb_buffer));
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);
pr_info("%s", kdb_buffer);
......@@ -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);
return r;
......@@ -1811,7 +1811,7 @@ int vprintk_default(const char *fmt, va_list args)
if (unlikely(kdb_trap_printk)) {
r = vkdb_printf(fmt, args);
r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
return r;
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