[PATCH] create /proc/kmsg, remove sys_syslog()-based

Back out the sys_syslog()-based printk-from-userspace and replace
it with Ben's /proc/kmsg version.

Requires a `mknod /dev/kmsg c 1 11'.

Documentation/devices.txt

@@ -97,6 +97,7 @@ Your cooperation is appreciated.
 		  8 = /dev/random	Nondeterministic random number gen.
 		  9 = /dev/urandom	Faster, less secure random number gen.
 		 10 = /dev/aio		Asyncronous I/O notification interface
+		 11 = /dev/kmsg		Writes to this come out as printk's
     block	RAM disk
 		  0 = /dev/ram0		First RAM disk
 		  1 = /dev/ram1		Second RAM disk

drivers/char/mem.c

@@ -598,6 +598,28 @@ static struct file_operations full_fops = {
 	.write		= write_full,
 };
 
+static ssize_t kmsg_write(struct file * file, const char * buf,
+			  size_t count, loff_t *ppos)
+{
+	char *tmp;
+	int ret;
+
+	tmp = kmalloc(count + 1, GFP_KERNEL);
+	if (tmp == NULL)
+		return -ENOMEM;
+	ret = -EFAULT;
+	if (!copy_from_user(tmp, buf, count)) {
+		tmp[count] = 0;
+		ret = printk("%s", tmp);
+	}
+	kfree(tmp);
+	return ret;
+}
+
+static struct file_operations kmsg_fops = {
+	write:		kmsg_write,
+};
+
 static int memory_open(struct inode * inode, struct file * filp)
 {
 	switch (minor(inode->i_rdev)) {
@@ -627,6 +649,9 @@ static int memory_open(struct inode * inode, struct file * filp)
 		case 9:
 			filp->f_op = &urandom_fops;
 			break;
+		case 11:
+			filp->f_op = &kmsg_fops;
+			break;
 		default:
 			return -ENXIO;
 	}
@@ -653,7 +678,8 @@ void __init memory_devfs_register (void)
 	{5, "zero",    S_IRUGO | S_IWUGO,           &zero_fops},
 	{7, "full",    S_IRUGO | S_IWUGO,           &full_fops},
 	{8, "random",  S_IRUGO | S_IWUSR,           &random_fops},
-	{9, "urandom", S_IRUGO | S_IWUSR,           &urandom_fops}
+	{9, "urandom", S_IRUGO | S_IWUSR,           &urandom_fops},
+	{11,"kmsg",    S_IRUGO | S_IWUSR,           &kmsg_fops},
     };
     int i;
 

kernel/printk.c

@@ -25,7 +25,6 @@
 #include <linux/module.h>
 #include <linux/interrupt.h>			/* For in_interrupt() */
 #include <linux/config.h>
-#include <linux/slab.h>
 #include <linux/delay.h>
 
 #include <asm/uaccess.h>
@@ -164,15 +163,12 @@ __setup("console=", console_setup);
  * 	7 -- Enable printk's to console
  *	8 -- Set level of messages printed to console
  *	9 -- Return number of unread characters in the log buffer
- *     10 -- Printk from userspace.  Includes loglevel.  Returns number of
- *           chars printed.
  */
 int do_syslog(int type, char * buf, int len)
 {
 	unsigned long i, j, limit, count;
 	int do_clear = 0;
 	char c;
-	char *lbuf = NULL;
 	int error = 0;
 
 	switch (type) {
@@ -287,23 +283,11 @@ int do_syslog(int type, char * buf, int len)
 		error = log_end - log_start;
 		spin_unlock_irq(&logbuf_lock);
 		break;
-	case 10:
-		lbuf = kmalloc(len + 1, GFP_KERNEL);
-		error = -ENOMEM;
-		if (lbuf == NULL)
-			break;
-		error = -EFAULT;
-		if (copy_from_user(lbuf, buf, len))
-			break;
-		lbuf[len] = '\0';
-		error = printk("%s", lbuf);
-		break;
 	default:
 		error = -EINVAL;
 		break;
 	}
 out:
-	kfree(lbuf);
 	return error;
 }