From: Marcin Niesluchowski <m.niesluchow@xxxxxxxxxxx>
Additional kmsg buffers should be created and deleted dynamically.
Adding two functions
* kmsg_sys_buffer_add() creates additional kmsg buffer returning minor
* kmsg_sys_buffer_del() deletes one based on provided minor
Signed-off-by: Marcin Niesluchowski <m.niesluchow@xxxxxxxxxxx>
---
include/linux/printk.h | 9 ++++
kernel/printk/printk.c | 120 +++++++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 126 insertions(+), 3 deletions(-)
diff --git a/include/linux/printk.h b/include/linux/printk.h
index 67840e0..35111e8 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -431,6 +431,8 @@ 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);
+extern int kmsg_sys_buffer_add(size_t size, umode_t mode);
+extern void kmsg_sys_buffer_del(int minor);
#else
@@ -449,6 +451,13 @@ static inline int kmsg_mode(int minor, umode_t *mode)
return -ENXIO;
}
+static inline int kmsg_sys_buffer_add(size_t size, umode_t mode)
+{
+ return -ENXIO;
+}
+
+static inline void kmsg_sys_buffer_del(int minor) {}
+
#endif
enum {
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 3157239..aac7ce8 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -47,6 +47,8 @@
#include <linux/ctype.h>
#include <linux/uio.h>
#include <linux/device.h>
+#include <linux/slab.h>
+#include <linux/kref.h>
#include <linux/kdev_t.h>
#include <asm/uaccess.h>
@@ -242,6 +244,7 @@ struct log_buffer {
char *buf; /* cyclic log buffer */
u32 len; /* buffer length */
wait_queue_head_t wait; /* wait queue for kmsg buffer */
+ struct kref refcount; /* refcount for kmsg_sys buffers */
#endif
/*
* The lock protects kmsg buffer, indices, counters. This can be taken within
@@ -294,6 +297,7 @@ static struct log_buffer log_buf = {
.len = __LOG_BUF_K_LEN,
.lock = __RAW_SPIN_LOCK_UNLOCKED(log_buf.lock),
.wait = __WAIT_QUEUE_HEAD_INITIALIZER(log_buf.wait),
+ .refcount = { .refcount = { .counter = 0 } },
.first_seq = 0,
.first_idx = 0,
.next_seq = 0,
@@ -864,6 +868,15 @@ struct devkmsg_user {
char buf[CONSOLE_EXT_LOG_MAX];
};
+void log_buf_release(struct kref *ref)
+{
+ struct log_buffer *log_b = container_of(ref, struct log_buffer,
+ refcount);
+
+ kfree(log_b->buf);
+ kfree(log_b);
+}
+
static int kmsg_sys_write(int minor, int level, const char *fmt, ...)
{
va_list args;
@@ -971,8 +984,21 @@ static ssize_t kmsg_read(struct log_buffer *log_b, struct file *file,
}
raw_spin_unlock_irq(&log_b->lock);
- ret = wait_event_interruptible(log_b->wait,
- user->seq != log_b->next_seq);
+
+ if (log_b == &log_buf) {
+ ret = wait_event_interruptible(log_b->wait,
+ user->seq != log_b->next_seq);
+ } else {
+ rcu_read_unlock();
+ kref_get(&log_b->refcount);
+ ret = wait_event_interruptible(log_b->wait,
+ user->seq != log_b->next_seq);
+ if (log_b->minor == -1)
+ ret = -ENXIO;
+ if (kref_put(&log_b->refcount, log_buf_release))
+ ret = -ENXIO;
+ rcu_read_lock();
+ }
if (ret)
goto out;
raw_spin_lock_irq(&log_b->lock);
@@ -1142,8 +1168,14 @@ static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
rcu_read_lock();
list_for_each_entry_rcu(log_b, &log_buf.list, list) {
if (log_b->minor == minor) {
+ kref_get(&log_b->refcount);
+ rcu_read_unlock();
+
ret = kmsg_poll(log_b, file, wait);
- break;
+
+ if (kref_put(&log_b->refcount, log_buf_release))
+ return POLLERR|POLLNVAL;
+ return ret;
}
}
rcu_read_unlock();
@@ -1259,6 +1291,88 @@ int kmsg_mode(int minor, umode_t *mode)
return ret;
}
+static DEFINE_SPINLOCK(kmsg_sys_list_lock);
+
+int kmsg_sys_buffer_add(size_t size, umode_t mode)
+{
+ unsigned long flags;
+ int minor = log_buf.minor;
+ struct log_buffer *log_b;
+ struct log_buffer *log_b_new;
+
+ if (size < LOG_LINE_MAX + PREFIX_MAX)
+ return -EINVAL;
+
+ log_b_new = kzalloc(sizeof(struct log_buffer), GFP_KERNEL);
+ if (!log_b_new)
+ return -ENOMEM;
+
+ log_b_new->buf = kmalloc(size, GFP_KERNEL);
+ if (!log_b_new->buf) {
+ kfree(log_b_new);
+ return -ENOMEM;
+ }
+
+ log_b_new->len = size;
+ log_b_new->lock = __RAW_SPIN_LOCK_UNLOCKED(log_b_new->lock);
+ init_waitqueue_head(&log_b_new->wait);
+ kref_init(&log_b_new->refcount);
+ log_b_new->mode = mode;
+
+ kref_get(&log_b_new->refcount);
+
+ spin_lock_irqsave(&kmsg_sys_list_lock, flags);
+
+ list_for_each_entry(log_b, &log_buf.list, list) {
+ if (log_b->minor - minor > 1)
+ break;
+
+ minor = log_b->minor;
+ }
+
+ if (!(minor & MINORMASK)) {
+ kref_put(&log_b->refcount, log_buf_release);
+ spin_unlock_irqrestore(&kmsg_sys_list_lock, flags);
+ return -ERANGE;
+ }
+
+ minor += 1;
+ log_b_new->minor = minor;
+
+ list_add_tail_rcu(&log_b_new->list, &log_b->list);
+
+ spin_unlock_irqrestore(&kmsg_sys_list_lock, flags);
+
+ return minor;
+}
+
+void kmsg_sys_buffer_del(int minor)
+{
+ unsigned long flags;
+ struct log_buffer *log_b;
+
+ spin_lock_irqsave(&kmsg_sys_list_lock, flags);
+
+ list_for_each_entry(log_b, &log_buf.list, list) {
+ if (log_b->minor == minor)
+ break;
+ }
+
+ if (log_b == &log_buf) {
+ spin_unlock_irqrestore(&kmsg_sys_list_lock, flags);
+ return;
+ }
+
+ list_del_rcu(&log_b->list);
+
+ spin_unlock_irqrestore(&kmsg_sys_list_lock, flags);
+
+ log_b->minor = -1;
+ wake_up_interruptible(&log_b->wait);
+
+ kref_put(&log_b->refcount, log_buf_release);
+}
+
#ifdef CONFIG_KEXEC_CORE
/*
* This appends the listed symbols to /proc/vmcore
--
1.9.1
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