From: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxxxxxxx) (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@xxxxxxxxxxxxxxx # v4.9+
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
[mpe: Mention that it only happens when udbg is not available]
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/c8a6ec704416ecd5ff2bd26213c9bc026bdd19de.1607077340.git.christophe.leroy@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -178,7 +178,7 @@ 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);
}
}
