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 this 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 04d2c8c83d0e ("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: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com Cc: Joe Perches joe@perches.com Cc: stable@vger.kernel.org ---
Notes: This patch is tested both on arm (kgdboc=ttyAMA0) and x86_64 (kgdboc=kdb,ttyS0).
v2:
* Adopt printk_skip_level() to skip the header characters (Joe Perches).
* Update patch description to describe the addition of non-printable characters to kdb output as a regression and Cc: stable@ (Joe Perches).
kernel/debug/kdb/kdb_io.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index 7c70812caea5..f3982adf8695 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -691,19 +691,20 @@ kdb_printit: * Write to all consoles. */ retlen = strlen(kdb_buffer); + cp = 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 (cp == kdb_buffer) + printk(KERN_INFO "%s", kdb_buffer); + else + printk("%s", kdb_buffer); }
if (KDB_STATE(PAGER)) { -- 1.9.3