Add compat.linux.debug sysctl, to make it possible to silence down

the debug messages. While here, clean up some variable naming.

Reviewed by:	bcr (manpages), emaste
MFC after:	2 weeks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D25230

4 files changed, 13 insertions, 1 deletions

diff --git a/share/man/man4/linux.4 b/share/man/man4/linux.4
index 4703bdd3a21e..d865ce5476a5 100644
--- a/share/man/man4/linux.4
+++ b/share/man/man4/linux.4
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd June 10, 2020
+.Dd June 12, 2020
 .Dt LINUX 4
 .Os
 .Sh NAME
@@ -95,6 +95,10 @@ variables and
 .Xr loader 8
 tunables:
 .Bl -tag -width indent
+.It Va compat.linux.debug
+Enable debugging messages.
+Set to 0 to silence them.
+Defaults to 1.
 .It Va compat.linux.default_openfiles
 Default soft openfiles resource limit for Linux applications.
 Set to -1 to disable the limit.
diff --git a/sys/compat/linux/linux_mib.c b/sys/compat/linux/linux_mib.c
index 65ca97461b62..9815424aafa4 100644
--- a/sys/compat/linux/linux_mib.c
+++ b/sys/compat/linux/linux_mib.c
@@ -63,6 +63,10 @@ static unsigned linux_osd_jail_slot;
 SYSCTL_NODE(_compat, OID_AUTO, linux, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
     "Linux mode");
 
+int linux_debug = 1;
+SYSCTL_INT(_compat_linux, OID_AUTO, debug, CTLFLAG_RWTUN,
+    &linux_debug, 0, "Log warnings from linux(4); or 0 to disable");
+
 int linux_default_openfiles = 1024;
 SYSCTL_INT(_compat_linux, OID_AUTO, default_openfiles, CTLFLAG_RWTUN,
     &linux_default_openfiles, 0,
diff --git a/sys/compat/linux/linux_mib.h b/sys/compat/linux/linux_mib.h
index d7a13a456125..385ba2ab390f 100644
--- a/sys/compat/linux/linux_mib.h
+++ b/sys/compat/linux/linux_mib.h
@@ -62,6 +62,7 @@ int	linux_kernver(struct thread *td);
 
 #define	linux_use26(t)		(linux_kernver(t) >= LINUX_KERNVER_2006000)
 
+extern int linux_debug;
 extern int linux_default_openfiles;
 extern int linux_ignore_ip_recverr;
 extern int linux_preserve_vstatus;
diff --git a/sys/compat/linux/linux_util.c b/sys/compat/linux/linux_util.c
index 54769451d1e5..59fc844e1cbe 100644
--- a/sys/compat/linux/linux_util.c
+++ b/sys/compat/linux/linux_util.c
@@ -91,6 +91,9 @@ linux_msg(const struct thread *td, const char *fmt, ...)
 	va_list ap;
 	struct proc *p;
 
+	if (linux_debug == 0)
+		return;
+
 	p = td->td_proc;
 	printf("linux: pid %d (%s): ", (int)p->p_pid, p->p_comm);
 	va_start(ap, fmt);