[PATCH v6 4/8] kmsg: add additional buffers support to memory class

Kazimierz Krosman
2016-02-24T11:53:40Z

From: Marcin Niesluchowski <m.niesluchow@samsung.com>

Memory class does not support additional kmsg buffers.

Add additional kmsg buffers support to:
* devnode() callback of "mem" class
* file operations of major "mem" character device

Signed-off-by: Marcin Niesluchowski <m.niesluchow@samsung.com>
Signed-off-by: Paul Osmialowski <p.osmialowsk@samsung.com>
[Rebased kmsg patch v5 on Linux 4.5-rc5]
Signed-off-by: Kazimierz Krosman <k.krosman@samsung.com>
---
drivers/char/mem.c | 27 ++++++++++++++++++++-------
include/linux/printk.h | 32 ++++++++++++++++++++++++++++++++
kernel/printk/kmsg.c | 42 ++++++++++++++++++++++++++++++++++++++++++
kernel/printk/printk.c | 1 +
kernel/printk/printk.h | 1 +
5 files changed, 96 insertions(+), 7 deletions(-)

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 4f6f94c..aa68923 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -799,9 +799,6 @@ static const struct memdev {
[7] = { "full", 0666, &full_fops, 0 },
[8] = { "random", 0666, &random_fops, 0 },
[9] = { "urandom", 0666, &urandom_fops, 0 },
-#ifdef CONFIG_PRINTK
- [11] = { "kmsg", 0644, &kmsg_fops, 0 },
-#endif
};

static int memory_open(struct inode *inode, struct file *filp)
@@ -811,7 +808,7 @@ static int memory_open(struct inode *inode, struct file *filp)

minor = iminor(inode);
if (minor >= ARRAY_SIZE(devlist))
- return -ENXIO;
+ return kmsg_memory_open(inode, filp);

dev = &devlist[minor];
if (!dev->fops)
@@ -833,16 +830,28 @@ static const struct file_operations memory_fops = {

static char *mem_devnode(struct device *dev, umode_t *mode)
{
- if (mode && devlist[MINOR(dev->devt)].mode)
- *mode = devlist[MINOR(dev->devt)].mode;
+ int minor = MINOR(dev->devt);
+
+ if (!mode)
+ goto out;
+
+ if (minor >= ARRAY_SIZE(devlist)) {
+ kmsg_mode(minor, mode);
+ goto out;
+ }
+
+ if (devlist[minor].mode)
+ *mode = devlist[minor].mode;
+out:
return NULL;
}

-static struct class *mem_class;
+struct class *mem_class;

static int __init chr_dev_init(void)
{
int minor;
+ struct device *kmsg;

if (register_chrdev(MEM_MAJOR, "mem", &memory_fops))
printk("unable to get major %d for memory devs\n", MEM_MAJOR);
@@ -866,6 +875,10 @@ static int __init chr_dev_init(void)
NULL, devlist[minor].name);
}

+ kmsg = init_kmsg(KMSG_MINOR, 0644);
+ if (IS_ERR(kmsg))
+ return PTR_ERR(kmsg);
+
return tty_init();
}

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 9ccbdf2..342e9d0 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -417,8 +417,40 @@ do { \
no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
#endif

+#define KMSG_MINOR 11
+
+struct file;
+struct inode;
+
+#ifdef CONFIG_PRINTK
+
+extern struct class *mem_class;
+
extern const struct file_operations kmsg_fops;

+extern struct device *init_kmsg(int minor, umode_t mode);
+extern int kmsg_memory_open(struct inode *inode, struct file *filp);
+extern int kmsg_mode(int minor, umode_t *mode);
+
+#else
+
+static inline struct device *init_kmsg(int minor, umode_t mode)
+{
+ return NULL;
+}
+
+static inline int kmsg_memory_open(struct inode *inode, struct file *filp)
+{
+ return -ENXIO;
+}
+
+static inline int kmsg_mode(int minor, umode_t *mode)
+{
+ return -ENXIO;
+}
+
+#endif
+
enum {
DUMP_PREFIX_NONE,
DUMP_PREFIX_ADDRESS,
diff --git a/kernel/printk/kmsg.c b/kernel/printk/kmsg.c
index dbb4a6b..b5e07ff 100644
--- a/kernel/printk/kmsg.c
+++ b/kernel/printk/kmsg.c
@@ -16,6 +16,9 @@
#include <linux/syslog.h>
#include <linux/uio.h>
#include <linux/wait.h>
+#include <linux/device.h>
+#include <linux/major.h>
+#include <linux/kdev_t.h>

#include <asm/uaccess.h>

@@ -386,6 +389,45 @@ const struct file_operations kmsg_fops = {
.release = devkmsg_release,
};

+/* Should be used for device registration */
+struct device *init_kmsg(int minor, umode_t mode)
+{
+ log_buf.minor = minor;
+ log_buf.mode = mode;
+ return device_create(mem_class, NULL, MKDEV(MEM_MAJOR, minor),
+ NULL, "kmsg");
+}
+
+int kmsg_memory_open(struct inode *inode, struct file *filp)
+{
+ filp->f_op = &kmsg_fops;
+
+ return kmsg_fops.open(inode, filp);
+}
+
+int kmsg_mode(int minor, umode_t *mode)
+{
+ int ret = -ENXIO;
+ struct log_buffer *log_b;
+
+ if (minor == log_buf.minor) {
+ *mode = log_buf.mode;
+ return 0;
+ }
+
+ rcu_read_lock();
+ list_for_each_entry_rcu(log_b, &log_buf.list, list) {
+ if (log_b->minor == minor) {
+ *mode = log_b->mode;
+ ret = 0;
+ break;
+ }
+ }
+ rcu_read_unlock();
+
+ return ret;
+}
+
static DEFINE_SPINLOCK(dump_list_lock);
static LIST_HEAD(dump_list);

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index b99403b..d8626ee 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -177,6 +177,7 @@ struct log_buffer log_buf = {
.next_idx = 0,
.clear_seq = 0,
.clear_idx = 0,
+ .mode = 0,
.minor = 0,
};

diff --git a/kernel/printk/printk.h b/kernel/printk/printk.h
index 4eefde5..e5c8a46 100644
--- a/kernel/printk/printk.h
+++ b/kernel/printk/printk.h
@@ -130,6 +130,7 @@ struct log_buffer {
u64 clear_seq;
u32 clear_idx;

+ int mode; /* mode of device */
int minor; /* minor representing buffer device */
#endif
};
--
1.9.1