From: Christophe Leroy christophe.leroy@csgroup.eu
commit 7c6c86b36a36dd4a13d30bba07718e767aa2e7a1 upstream.
Since some time now, printk() adds carriage return, leading to unusable xmon output if there is no udbg backend available:
[ 54.288722] sysrq: Entering xmon [ 54.292209] Vector: 0 at [cace3d2c] [ 54.292274] pc: [ 54.292331] c0023650 [ 54.292468] : xmon+0x28/0x58 [ 54.292519] [ 54.292574] lr: [ 54.292630] c0023724 [ 54.292749] : sysrq_handle_xmon+0xa4/0xfc [ 54.292801] [ 54.292867] sp: cace3de8 [ 54.292931] msr: 9032 [ 54.292999] current = 0xc28d0000 [ 54.293072] pid = 377, comm = sh [ 54.293157] Linux version 5.10.0-rc6-s3k-dev-01364-gedf13f0ccd76-dirty (root@po17688vm.idsi0.si.c-s.fr) (powerpc64-linux-gcc (GCC) 10.1.0, GNU ld (GNU Binutils) 2.34) #4211 PREEMPT Fri Dec 4 09:32:11 UTC 2020 [ 54.293287] enter ? for help [ 54.293470] [cace3de8] [ 54.293532] c0023724 [ 54.293654] sysrq_handle_xmon+0xa4/0xfc [ 54.293711] (unreliable) ... [ 54.296002] [ 54.296159] --- Exception: c01 (System Call) at [ 54.296217] 0fd4e784 [ 54.296303] [ 54.296375] SP (7fca6ff0) is in userspace [ 54.296431] mon> [ 54.296484] <no input ...>
Use pr_cont() instead.
Fixes: 4bcc595ccd80 ("printk: reinstate KERN_CONT for printing continuation lines") Cc: stable@vger.kernel.org # v4.9+ Signed-off-by: Christophe Leroy christophe.leroy@csgroup.eu [mpe: Mention that it only happens when udbg is not available] Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/c8a6ec704416ecd5ff2bd26213c9bc026bdd19de.160707734... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/xmon/nonstdio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/powerpc/xmon/nonstdio.c +++ b/arch/powerpc/xmon/nonstdio.c @@ -182,7 +182,7 @@ void xmon_printf(const char *format, ...
if (n && rc == 0) { /* No udbg hooks, fallback to printk() - dangerous */ - printk("%s", xmon_outbuf); + pr_cont("%s", xmon_outbuf); } }