Re: [patch] printk from userspace

Benjamin LaHaise
2002-08-14T04:31:14Z

On Tue, Aug 13, 2002 at 09:26:45PM -0700, Linus Torvalds wrote:
> That said, I like the notion. I've always hated the fact that all the
> boot-time messages get lost, simply because syslogd hadn't started, and
> as a result things like fsck ran without any sign afterwards. The kernel
> log approach saves it all in one place.
>
> But /dev/console just sounds potentially _too_ noisy.

/dev/kmsg was another suggestion for the name. But please revert the
yet-another-syscall variant -- having a duplicate way for logging that
doesn't work with stdio just seems sick to me (sys_syslog should die).
Something like the following untested code is much better.

-ben
--
"You will be reincarnated as a toad; and you will be much happier."

diff -urN v2.5.31/drivers/char/mem.c foo/drivers/char/mem.c
--- v2.5.31/drivers/char/mem.c Fri Aug 2 11:41:29 2002
+++ foo/drivers/char/mem.c Wed Aug 14 00:34:33 2002
@@ -579,6 +579,24 @@
write: write_full,
};

+static ssize_t kmsg_write(struct file * file, const char * buf,
+ size_t count, loff_t *ppos)
+{
+ char tmp[1025];
+
+ if (count > 1024)
+ count = 1024;
+ if (copy_from_user(tmp, buf, count))
+ return -EFAULT;
+ tmp[count] = 0;
+ printk("%s", tmp);
+ return count;
+}
+
+static struct file_operations kmsg_fops = {
+ write: kmsg_write,
+};
+
static int memory_open(struct inode * inode, struct file * filp)
{
switch (minor(inode->i_rdev)) {
@@ -608,6 +626,9 @@
case 9:
filp->f_op = &urandom_fops;
break;
+ case 11:
+ filp->f_op = &kmsg_fops;
+ break;
default:
return -ENXIO;
}
@@ -634,7 +655,8 @@
{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;