[RFC PATCH 2/4 V2] livedump: Add the new misc device "livedump"

[YOSHIDA Masanori]

Introduces the new misc device "livedump".
This device will be used as interface between livedump and user space.
Right now, the device only has empty ioctl operation.

***ATTENTION PLEASE***
I think debugfs is more suitable for this feature, but currently livedump
uses the misc device for simplicity. This will be fixed in the future.

Signed-off-by: YOSHIDA Masanori <masanori.yoshida.tv@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: Kevin Hilman <khilman@xxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
---

 arch/x86/Kconfig  |   15 ++++++++++
 kernel/Makefile   |    1 +
 kernel/livedump.c |   83 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 99 insertions(+), 0 deletions(-)
 create mode 100644 kernel/livedump.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c9866b0..4c97583 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1729,6 +1729,21 @@ config CMDLINE_OVERRIDE
 	  This is used to work around broken boot loaders.  This should
 	  be set to 'N' under normal conditions.
 
+config LIVEDUMP
+	bool "Live Dump support"
+	depends on X86_64
+	---help---
+	  Set this option to 'Y' to allow the kernel support to acquire
+	  a consistent snapshot of kernel space without stopping system.
+
+	  This feature regularly causes small overhead on kernel.
+
+	  Once this feature is initialized by its special ioctl, it
+	  allocates huge memory for itself and causes much more overhead
+	  on kernel.
+
+	  If in doubt, say N.
+
 endmenu
 
 config ARCH_ENABLE_MEMORY_HOTPLUG
diff --git a/kernel/Makefile b/kernel/Makefile
index cb41b95..f095e7a 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -106,6 +106,7 @@ obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
 obj-$(CONFIG_PADATA) += padata.o
 obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
 obj-$(CONFIG_JUMP_LABEL) += jump_label.o
+obj-$(CONFIG_LIVEDUMP) += livedump.o
 
 $(obj)/configs.o: $(obj)/config_data.h
 
diff --git a/kernel/livedump.c b/kernel/livedump.c
new file mode 100644
index 0000000..3103292
--- /dev/null
+++ b/kernel/livedump.c
@@ -0,0 +1,83 @@
+/* livedump.c - Live Dump's main
+ * Copyright (C) 2012 Hitachi, Ltd.
+ * Author: YOSHIDA Masanori <masanori.yoshida.tv@xxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA  02110-1301, USA.
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+
+#define DEVICE_NAME	"livedump"
+
+#define LIVEDUMP_IOC(x)	_IO(0xff, x)
+
+static long livedump_ioctl(
+		struct file *file, unsigned int cmd, unsigned long arg)
+{
+	switch (cmd) {
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+
+static int livedump_open(struct inode *inode, struct file *file)
+{
+	if (!try_module_get(THIS_MODULE))
+		return -ENOENT;
+	return 0;
+}
+
+static int livedump_release(struct inode *inode, struct file *file)
+{
+	module_put(THIS_MODULE);
+	return 0;
+}
+
+static const struct file_operations livedump_fops = {
+	.unlocked_ioctl = livedump_ioctl,
+	.open = livedump_open,
+	.release = livedump_release,
+};
+static struct miscdevice livedump_misc = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = DEVICE_NAME,
+	.fops = &livedump_fops,
+};
+
+static int livedump_module_init(void)
+{
+	int ret;
+
+	ret = misc_register(&livedump_misc);
+	if (WARN(ret,
+				"livedump: Failed to register livedump on misc device.\n"
+		))
+		return ret;
+
+	return 0;
+}
+module_init(livedump_module_init);
+
+static void livedump_module_exit(void)
+{
+	misc_deregister(&livedump_misc);
+}
+module_exit(livedump_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Livedump kernel module");

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