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Date: Fri, 23 Jan 2015 12:37:15 -0600
From: Tom Zanussi <tom.zanussi@...ux.intel.com>
To: josh@...htriplett.org
Cc: linux-kernel@...r.kernel.org,
Tom Zanussi <tom.zanussi@...ux.intel.com>
Subject: [PATCH 09/10] drivers/char: Support compiling out /dev/kmsg
Some embedded systems with tightly controlled userspace have no use
for /dev/kmsg, and could benefit from the size savings gained by
omitting it. Add a new EMBEDDED config option to disable it.
bloat-o-meter (based on tinyconfig):
add/remove: 0/8 grow/shrink: 1/1 up/down: 92/-1538 (-1446)
function old new delta
do_syslog 1027 1119 +92
devkmsg_release 15 - -15
devlist 192 160 -32
devkmsg_poll 97 - -97
devkmsg_open 112 - -112
check_syslog_permissions 114 - -114
kmsg_fops 116 - -116
devkmsg_llseek 144 - -144
devkmsg_write 209 - -209
devkmsg_read 699 - -699
Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
---
drivers/char/Kconfig | 14 ++++++++++++++
drivers/char/mem.c | 2 +-
kernel/printk/printk.c | 2 ++
3 files changed, 17 insertions(+), 1 deletion(-)
diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 1af4551..25fe627 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -89,6 +89,20 @@ config DEVURANDOM
disabled on systems that will never use it in production,
such as many embedded systems. When in doubt, say "Y".
+config DEVKMSG
+ bool "/dev/kmsg virtual device support" if EMBEDDED
+ depends on DEVMEM_BASE && PRINTK
+ default y
+ help
+ Say Y here if you want to support the /dev/kmsg device. The
+ /dev/kmsg device provides access to the raw kernel message
+ ring buffer, and can be disabled on systems that will never
+ use it in production, such as many embedded systems. The
+ kernel log buffer is also accessible via the syslog() kernel
+ interface and userspace tools such as dmesg (using -S) can
+ be directed to use that interface instead. When in doubt,
+ say "Y".
+
config SGI_SNSC
bool "SGI Altix system controller communication support"
depends on (IA64_SGI_SN2 || IA64_GENERIC)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 5315f63..6cc26ea 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -832,7 +832,7 @@ static const struct memdev {
#ifdef CONFIG_DEVURANDOM
[9] = { "urandom", 0666, &urandom_fops, NULL },
#endif
-#ifdef CONFIG_PRINTK
+#ifdef CONFIG_DEVKMSG
[11] = { "kmsg", 0644, &kmsg_fops, NULL },
#endif
};
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 02d6b6d..fbd05d8 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -505,6 +505,7 @@ int check_syslog_permissions(int type, bool from_file)
return security_syslog(type);
}
+#ifdef CONFIG_DEVKMSG
/* /dev/kmsg - userspace message inject/listen interface */
struct devkmsg_user {
@@ -797,6 +798,7 @@ const struct file_operations kmsg_fops = {
.poll = devkmsg_poll,
.release = devkmsg_release,
};
+#endif
#ifdef CONFIG_KEXEC
/*
--
1.9.3
--
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