From: Marcin Niesluchowski <m.niesluchow@xxxxxxxxxxx>
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@xxxxxxxxxxx>
---
drivers/char/mem.c | 27 ++++++++++++++++++++-------
include/linux/printk.h | 32 ++++++++++++++++++++++++++++++++
kernel/printk/printk.c | 43 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 95 insertions(+), 7 deletions(-)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 6b1721f..7d46234 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 9729565..67840e0 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
+struct file;
+struct inode;
+
+#ifdef CONFIG_PRINTK
+
+extern struct class *mem_class;
+
+#define KMSG_MINOR 11
+
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/printk.c b/kernel/printk/printk.c
index 0d4d726..3157239 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -46,6 +46,8 @@
#include <linux/utsname.h>
#include <linux/ctype.h>
#include <linux/uio.h>
+#include <linux/device.h>
+#include <linux/kdev_t.h>
#include <asm/uaccess.h>
@@ -253,6 +255,7 @@ struct log_buffer {
u64 next_seq;
#ifdef CONFIG_PRINTK
u32 next_idx; /* index of the next record to store */
+ int mode; /* mode of device */
int minor; /* minor representing buffer device */
#endif
};
@@ -295,6 +298,7 @@ static struct log_buffer log_buf = {
.first_idx = 0,
.next_seq = 0,
.next_idx = 0,
+ .mode = 0,
.minor = 0,
};
@@ -1216,6 +1220,45 @@ 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;
+}
+
#ifdef CONFIG_KEXEC_CORE
/*
* This appends the listed symbols to /proc/vmcore
--
1.9.1
--
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